Low vacuum rich mixture on 2.8L 86 XJ Cherokee--- solved
01-13-2004 | 04:07 PM
#1
Guest
Posts: n/a
Low vacuum rich mixture on 2.8L 86 XJ Cherokee--- solved
Found the cause of the paradox of rich mixture and low vacuum on my
2.8L.
Eventually I located a teeny pin hole in the deceleration valve which
caused the diaphragm not to uncover the orfice plate at high vacuum.
The decel valve only opens at normal to high vacuum. With the valve
malfunctioning the engine was trying to aspirate (into the 'E' port on
the Rochester vari-jet) carb solely through the pcv valve ---- not
enough air yielded rich burn, but with the valve not working: low
vacuum .... thus the paradox.
Other:
Stalling on left turn does NOT involve the carb float !!!!!!!!!!
Another anomaly also solved in the step by step search of the vacuum
problem (and a problem that has been posted here many many times):
Engine would stall when turning left (not right). The 'usual'
suggestion is to increase the float height in the carb ..... WRONG
WRONG WRONG as that will only cause the carb to dump gas into the
intake manifold when you shut down and totally flood it and you still
stall when turning left.
The solution is a freakin teeny pressure switch on the high pressure
side of power steering pump .... when the pump goes over pressure the
switch (also) energizes the throttle kicker. $30.00 new switch and I
can turn to left again!!!! You might want to remember this info for
those who have 2.8L engines that stall when turning left (not right).
Anyway thanks to all who posted suggestions even that your suggestions
didnt work, I thank all of you for your help...... At least the
discussions here are extremely helpful in sorting things out. At
least I learned that after 300K miles you should replace the *entire*
emissions control system components ... its a BIG PITA if you dont. Im
now back to full power and 23+ mpg for long haul runs at speed.
Im now planning to make at least 500,000 miles on this XJ Cherokee
beast (- currently doing a semi-frame-off restoration). Too bad
DaimlerC cant build a vehicle to that standard, or without costing
$100,000 across the parts counter !!!!!!!!
2.8L.
Eventually I located a teeny pin hole in the deceleration valve which
caused the diaphragm not to uncover the orfice plate at high vacuum.
The decel valve only opens at normal to high vacuum. With the valve
malfunctioning the engine was trying to aspirate (into the 'E' port on
the Rochester vari-jet) carb solely through the pcv valve ---- not
enough air yielded rich burn, but with the valve not working: low
vacuum .... thus the paradox.
Other:
Stalling on left turn does NOT involve the carb float !!!!!!!!!!
Another anomaly also solved in the step by step search of the vacuum
problem (and a problem that has been posted here many many times):
Engine would stall when turning left (not right). The 'usual'
suggestion is to increase the float height in the carb ..... WRONG
WRONG WRONG as that will only cause the carb to dump gas into the
intake manifold when you shut down and totally flood it and you still
stall when turning left.
The solution is a freakin teeny pressure switch on the high pressure
side of power steering pump .... when the pump goes over pressure the
switch (also) energizes the throttle kicker. $30.00 new switch and I
can turn to left again!!!! You might want to remember this info for
those who have 2.8L engines that stall when turning left (not right).
Anyway thanks to all who posted suggestions even that your suggestions
didnt work, I thank all of you for your help...... At least the
discussions here are extremely helpful in sorting things out. At
least I learned that after 300K miles you should replace the *entire*
emissions control system components ... its a BIG PITA if you dont. Im
now back to full power and 23+ mpg for long haul runs at speed.
Im now planning to make at least 500,000 miles on this XJ Cherokee
beast (- currently doing a semi-frame-off restoration). Too bad
DaimlerC cant build a vehicle to that standard, or without costing
$100,000 across the parts counter !!!!!!!!
01-13-2004 | 04:19 PM
#2
Guest
Posts: n/a
Re: Low vacuum rich mixture on 2.8L 86 XJ Cherokee--- solved
Thanks for the results!
Good info to know, hard crap to track down....
Mike
86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00
88 Cherokee 235 BFG AT's
Rich Hampel wrote:
>
> Found the cause of the paradox of rich mixture and low vacuum on my
> 2.8L.
> Eventually I located a teeny pin hole in the deceleration valve which
> caused the diaphragm not to uncover the orfice plate at high vacuum.
> The decel valve only opens at normal to high vacuum. With the valve
> malfunctioning the engine was trying to aspirate (into the 'E' port on
> the Rochester vari-jet) carb solely through the pcv valve ---- not
> enough air yielded rich burn, but with the valve not working: low
> vacuum .... thus the paradox.
>
> Other:
> Stalling on left turn does NOT involve the carb float !!!!!!!!!!
> Another anomaly also solved in the step by step search of the vacuum
> problem (and a problem that has been posted here many many times):
> Engine would stall when turning left (not right). The 'usual'
> suggestion is to increase the float height in the carb ..... WRONG
> WRONG WRONG as that will only cause the carb to dump gas into the
> intake manifold when you shut down and totally flood it and you still
> stall when turning left.
> The solution is a freakin teeny pressure switch on the high pressure
> side of power steering pump .... when the pump goes over pressure the
> switch (also) energizes the throttle kicker. $30.00 new switch and I
> can turn to left again!!!! You might want to remember this info for
> those who have 2.8L engines that stall when turning left (not right).
>
> Anyway thanks to all who posted suggestions even that your suggestions
> didnt work, I thank all of you for your help...... At least the
> discussions here are extremely helpful in sorting things out. At
> least I learned that after 300K miles you should replace the *entire*
> emissions control system components ... its a BIG PITA if you dont. Im
> now back to full power and 23+ mpg for long haul runs at speed.
> Im now planning to make at least 500,000 miles on this XJ Cherokee
> beast (- currently doing a semi-frame-off restoration). Too bad
> DaimlerC cant build a vehicle to that standard, or without costing
> $100,000 across the parts counter !!!!!!!!
Good info to know, hard crap to track down....
Mike
86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00
88 Cherokee 235 BFG AT's
Rich Hampel wrote:
>
> Found the cause of the paradox of rich mixture and low vacuum on my
> 2.8L.
> Eventually I located a teeny pin hole in the deceleration valve which
> caused the diaphragm not to uncover the orfice plate at high vacuum.
> The decel valve only opens at normal to high vacuum. With the valve
> malfunctioning the engine was trying to aspirate (into the 'E' port on
> the Rochester vari-jet) carb solely through the pcv valve ---- not
> enough air yielded rich burn, but with the valve not working: low
> vacuum .... thus the paradox.
>
> Other:
> Stalling on left turn does NOT involve the carb float !!!!!!!!!!
> Another anomaly also solved in the step by step search of the vacuum
> problem (and a problem that has been posted here many many times):
> Engine would stall when turning left (not right). The 'usual'
> suggestion is to increase the float height in the carb ..... WRONG
> WRONG WRONG as that will only cause the carb to dump gas into the
> intake manifold when you shut down and totally flood it and you still
> stall when turning left.
> The solution is a freakin teeny pressure switch on the high pressure
> side of power steering pump .... when the pump goes over pressure the
> switch (also) energizes the throttle kicker. $30.00 new switch and I
> can turn to left again!!!! You might want to remember this info for
> those who have 2.8L engines that stall when turning left (not right).
>
> Anyway thanks to all who posted suggestions even that your suggestions
> didnt work, I thank all of you for your help...... At least the
> discussions here are extremely helpful in sorting things out. At
> least I learned that after 300K miles you should replace the *entire*
> emissions control system components ... its a BIG PITA if you dont. Im
> now back to full power and 23+ mpg for long haul runs at speed.
> Im now planning to make at least 500,000 miles on this XJ Cherokee
> beast (- currently doing a semi-frame-off restoration). Too bad
> DaimlerC cant build a vehicle to that standard, or without costing
> $100,000 across the parts counter !!!!!!!!
01-13-2004 | 04:19 PM
#3
Guest
Posts: n/a
Re: Low vacuum rich mixture on 2.8L 86 XJ Cherokee--- solved
Thanks for the results!
Good info to know, hard crap to track down....
Mike
86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00
88 Cherokee 235 BFG AT's
Rich Hampel wrote:
>
> Found the cause of the paradox of rich mixture and low vacuum on my
> 2.8L.
> Eventually I located a teeny pin hole in the deceleration valve which
> caused the diaphragm not to uncover the orfice plate at high vacuum.
> The decel valve only opens at normal to high vacuum. With the valve
> malfunctioning the engine was trying to aspirate (into the 'E' port on
> the Rochester vari-jet) carb solely through the pcv valve ---- not
> enough air yielded rich burn, but with the valve not working: low
> vacuum .... thus the paradox.
>
> Other:
> Stalling on left turn does NOT involve the carb float !!!!!!!!!!
> Another anomaly also solved in the step by step search of the vacuum
> problem (and a problem that has been posted here many many times):
> Engine would stall when turning left (not right). The 'usual'
> suggestion is to increase the float height in the carb ..... WRONG
> WRONG WRONG as that will only cause the carb to dump gas into the
> intake manifold when you shut down and totally flood it and you still
> stall when turning left.
> The solution is a freakin teeny pressure switch on the high pressure
> side of power steering pump .... when the pump goes over pressure the
> switch (also) energizes the throttle kicker. $30.00 new switch and I
> can turn to left again!!!! You might want to remember this info for
> those who have 2.8L engines that stall when turning left (not right).
>
> Anyway thanks to all who posted suggestions even that your suggestions
> didnt work, I thank all of you for your help...... At least the
> discussions here are extremely helpful in sorting things out. At
> least I learned that after 300K miles you should replace the *entire*
> emissions control system components ... its a BIG PITA if you dont. Im
> now back to full power and 23+ mpg for long haul runs at speed.
> Im now planning to make at least 500,000 miles on this XJ Cherokee
> beast (- currently doing a semi-frame-off restoration). Too bad
> DaimlerC cant build a vehicle to that standard, or without costing
> $100,000 across the parts counter !!!!!!!!
Good info to know, hard crap to track down....
Mike
86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00
88 Cherokee 235 BFG AT's
Rich Hampel wrote:
>
> Found the cause of the paradox of rich mixture and low vacuum on my
> 2.8L.
> Eventually I located a teeny pin hole in the deceleration valve which
> caused the diaphragm not to uncover the orfice plate at high vacuum.
> The decel valve only opens at normal to high vacuum. With the valve
> malfunctioning the engine was trying to aspirate (into the 'E' port on
> the Rochester vari-jet) carb solely through the pcv valve ---- not
> enough air yielded rich burn, but with the valve not working: low
> vacuum .... thus the paradox.
>
> Other:
> Stalling on left turn does NOT involve the carb float !!!!!!!!!!
> Another anomaly also solved in the step by step search of the vacuum
> problem (and a problem that has been posted here many many times):
> Engine would stall when turning left (not right). The 'usual'
> suggestion is to increase the float height in the carb ..... WRONG
> WRONG WRONG as that will only cause the carb to dump gas into the
> intake manifold when you shut down and totally flood it and you still
> stall when turning left.
> The solution is a freakin teeny pressure switch on the high pressure
> side of power steering pump .... when the pump goes over pressure the
> switch (also) energizes the throttle kicker. $30.00 new switch and I
> can turn to left again!!!! You might want to remember this info for
> those who have 2.8L engines that stall when turning left (not right).
>
> Anyway thanks to all who posted suggestions even that your suggestions
> didnt work, I thank all of you for your help...... At least the
> discussions here are extremely helpful in sorting things out. At
> least I learned that after 300K miles you should replace the *entire*
> emissions control system components ... its a BIG PITA if you dont. Im
> now back to full power and 23+ mpg for long haul runs at speed.
> Im now planning to make at least 500,000 miles on this XJ Cherokee
> beast (- currently doing a semi-frame-off restoration). Too bad
> DaimlerC cant build a vehicle to that standard, or without costing
> $100,000 across the parts counter !!!!!!!!
01-13-2004 | 04:19 PM
#4
Guest
Posts: n/a
Re: Low vacuum rich mixture on 2.8L 86 XJ Cherokee--- solved
Thanks for the results!
Good info to know, hard crap to track down....
Mike
86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00
88 Cherokee 235 BFG AT's
Rich Hampel wrote:
>
> Found the cause of the paradox of rich mixture and low vacuum on my
> 2.8L.
> Eventually I located a teeny pin hole in the deceleration valve which
> caused the diaphragm not to uncover the orfice plate at high vacuum.
> The decel valve only opens at normal to high vacuum. With the valve
> malfunctioning the engine was trying to aspirate (into the 'E' port on
> the Rochester vari-jet) carb solely through the pcv valve ---- not
> enough air yielded rich burn, but with the valve not working: low
> vacuum .... thus the paradox.
>
> Other:
> Stalling on left turn does NOT involve the carb float !!!!!!!!!!
> Another anomaly also solved in the step by step search of the vacuum
> problem (and a problem that has been posted here many many times):
> Engine would stall when turning left (not right). The 'usual'
> suggestion is to increase the float height in the carb ..... WRONG
> WRONG WRONG as that will only cause the carb to dump gas into the
> intake manifold when you shut down and totally flood it and you still
> stall when turning left.
> The solution is a freakin teeny pressure switch on the high pressure
> side of power steering pump .... when the pump goes over pressure the
> switch (also) energizes the throttle kicker. $30.00 new switch and I
> can turn to left again!!!! You might want to remember this info for
> those who have 2.8L engines that stall when turning left (not right).
>
> Anyway thanks to all who posted suggestions even that your suggestions
> didnt work, I thank all of you for your help...... At least the
> discussions here are extremely helpful in sorting things out. At
> least I learned that after 300K miles you should replace the *entire*
> emissions control system components ... its a BIG PITA if you dont. Im
> now back to full power and 23+ mpg for long haul runs at speed.
> Im now planning to make at least 500,000 miles on this XJ Cherokee
> beast (- currently doing a semi-frame-off restoration). Too bad
> DaimlerC cant build a vehicle to that standard, or without costing
> $100,000 across the parts counter !!!!!!!!
Good info to know, hard crap to track down....
Mike
86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00
88 Cherokee 235 BFG AT's
Rich Hampel wrote:
>
> Found the cause of the paradox of rich mixture and low vacuum on my
> 2.8L.
> Eventually I located a teeny pin hole in the deceleration valve which
> caused the diaphragm not to uncover the orfice plate at high vacuum.
> The decel valve only opens at normal to high vacuum. With the valve
> malfunctioning the engine was trying to aspirate (into the 'E' port on
> the Rochester vari-jet) carb solely through the pcv valve ---- not
> enough air yielded rich burn, but with the valve not working: low
> vacuum .... thus the paradox.
>
> Other:
> Stalling on left turn does NOT involve the carb float !!!!!!!!!!
> Another anomaly also solved in the step by step search of the vacuum
> problem (and a problem that has been posted here many many times):
> Engine would stall when turning left (not right). The 'usual'
> suggestion is to increase the float height in the carb ..... WRONG
> WRONG WRONG as that will only cause the carb to dump gas into the
> intake manifold when you shut down and totally flood it and you still
> stall when turning left.
> The solution is a freakin teeny pressure switch on the high pressure
> side of power steering pump .... when the pump goes over pressure the
> switch (also) energizes the throttle kicker. $30.00 new switch and I
> can turn to left again!!!! You might want to remember this info for
> those who have 2.8L engines that stall when turning left (not right).
>
> Anyway thanks to all who posted suggestions even that your suggestions
> didnt work, I thank all of you for your help...... At least the
> discussions here are extremely helpful in sorting things out. At
> least I learned that after 300K miles you should replace the *entire*
> emissions control system components ... its a BIG PITA if you dont. Im
> now back to full power and 23+ mpg for long haul runs at speed.
> Im now planning to make at least 500,000 miles on this XJ Cherokee
> beast (- currently doing a semi-frame-off restoration). Too bad
> DaimlerC cant build a vehicle to that standard, or without costing
> $100,000 across the parts counter !!!!!!!!
01-13-2004 | 06:02 PM
#5
Guest
Posts: n/a
Re: Low vacuum rich mixture on 2.8L 86 XJ Cherokee--- solved
You mean there's another person with the 2.8L GM engine, Chevrolet
won't even put it in their cars?
God Bless America, ßill O|||||||O
mailto:-------------------- http://www.----------.com/
Rich Hampel wrote:
>
> Found the cause of the paradox of rich mixture and low vacuum on my
> 2.8L.
> Eventually I located a teeny pin hole in the deceleration valve which
> caused the diaphragm not to uncover the orfice plate at high vacuum.
> The decel valve only opens at normal to high vacuum. With the valve
> malfunctioning the engine was trying to aspirate (into the 'E' port on
> the Rochester vari-jet) carb solely through the pcv valve ---- not
> enough air yielded rich burn, but with the valve not working: low
> vacuum .... thus the paradox.
>
> Other:
> Stalling on left turn does NOT involve the carb float !!!!!!!!!!
> Another anomaly also solved in the step by step search of the vacuum
> problem (and a problem that has been posted here many many times):
> Engine would stall when turning left (not right). The 'usual'
> suggestion is to increase the float height in the carb ..... WRONG
> WRONG WRONG as that will only cause the carb to dump gas into the
> intake manifold when you shut down and totally flood it and you still
> stall when turning left.
> The solution is a freakin teeny pressure switch on the high pressure
> side of power steering pump .... when the pump goes over pressure the
> switch (also) energizes the throttle kicker. $30.00 new switch and I
> can turn to left again!!!! You might want to remember this info for
> those who have 2.8L engines that stall when turning left (not right).
>
> Anyway thanks to all who posted suggestions even that your suggestions
> didnt work, I thank all of you for your help...... At least the
> discussions here are extremely helpful in sorting things out. At
> least I learned that after 300K miles you should replace the *entire*
> emissions control system components ... its a BIG PITA if you dont. Im
> now back to full power and 23+ mpg for long haul runs at speed.
> Im now planning to make at least 500,000 miles on this XJ Cherokee
> beast (- currently doing a semi-frame-off restoration). Too bad
> DaimlerC cant build a vehicle to that standard, or without costing
> $100,000 across the parts counter !!!!!!!!
won't even put it in their cars?
God Bless America, ßill O|||||||O
mailto:-------------------- http://www.----------.com/
Rich Hampel wrote:
>
> Found the cause of the paradox of rich mixture and low vacuum on my
> 2.8L.
> Eventually I located a teeny pin hole in the deceleration valve which
> caused the diaphragm not to uncover the orfice plate at high vacuum.
> The decel valve only opens at normal to high vacuum. With the valve
> malfunctioning the engine was trying to aspirate (into the 'E' port on
> the Rochester vari-jet) carb solely through the pcv valve ---- not
> enough air yielded rich burn, but with the valve not working: low
> vacuum .... thus the paradox.
>
> Other:
> Stalling on left turn does NOT involve the carb float !!!!!!!!!!
> Another anomaly also solved in the step by step search of the vacuum
> problem (and a problem that has been posted here many many times):
> Engine would stall when turning left (not right). The 'usual'
> suggestion is to increase the float height in the carb ..... WRONG
> WRONG WRONG as that will only cause the carb to dump gas into the
> intake manifold when you shut down and totally flood it and you still
> stall when turning left.
> The solution is a freakin teeny pressure switch on the high pressure
> side of power steering pump .... when the pump goes over pressure the
> switch (also) energizes the throttle kicker. $30.00 new switch and I
> can turn to left again!!!! You might want to remember this info for
> those who have 2.8L engines that stall when turning left (not right).
>
> Anyway thanks to all who posted suggestions even that your suggestions
> didnt work, I thank all of you for your help...... At least the
> discussions here are extremely helpful in sorting things out. At
> least I learned that after 300K miles you should replace the *entire*
> emissions control system components ... its a BIG PITA if you dont. Im
> now back to full power and 23+ mpg for long haul runs at speed.
> Im now planning to make at least 500,000 miles on this XJ Cherokee
> beast (- currently doing a semi-frame-off restoration). Too bad
> DaimlerC cant build a vehicle to that standard, or without costing
> $100,000 across the parts counter !!!!!!!!
01-13-2004 | 06:02 PM
#6
Guest
Posts: n/a
Re: Low vacuum rich mixture on 2.8L 86 XJ Cherokee--- solved
You mean there's another person with the 2.8L GM engine, Chevrolet
won't even put it in their cars?
God Bless America, ßill O|||||||O
mailto:-------------------- http://www.----------.com/
Rich Hampel wrote:
>
> Found the cause of the paradox of rich mixture and low vacuum on my
> 2.8L.
> Eventually I located a teeny pin hole in the deceleration valve which
> caused the diaphragm not to uncover the orfice plate at high vacuum.
> The decel valve only opens at normal to high vacuum. With the valve
> malfunctioning the engine was trying to aspirate (into the 'E' port on
> the Rochester vari-jet) carb solely through the pcv valve ---- not
> enough air yielded rich burn, but with the valve not working: low
> vacuum .... thus the paradox.
>
> Other:
> Stalling on left turn does NOT involve the carb float !!!!!!!!!!
> Another anomaly also solved in the step by step search of the vacuum
> problem (and a problem that has been posted here many many times):
> Engine would stall when turning left (not right). The 'usual'
> suggestion is to increase the float height in the carb ..... WRONG
> WRONG WRONG as that will only cause the carb to dump gas into the
> intake manifold when you shut down and totally flood it and you still
> stall when turning left.
> The solution is a freakin teeny pressure switch on the high pressure
> side of power steering pump .... when the pump goes over pressure the
> switch (also) energizes the throttle kicker. $30.00 new switch and I
> can turn to left again!!!! You might want to remember this info for
> those who have 2.8L engines that stall when turning left (not right).
>
> Anyway thanks to all who posted suggestions even that your suggestions
> didnt work, I thank all of you for your help...... At least the
> discussions here are extremely helpful in sorting things out. At
> least I learned that after 300K miles you should replace the *entire*
> emissions control system components ... its a BIG PITA if you dont. Im
> now back to full power and 23+ mpg for long haul runs at speed.
> Im now planning to make at least 500,000 miles on this XJ Cherokee
> beast (- currently doing a semi-frame-off restoration). Too bad
> DaimlerC cant build a vehicle to that standard, or without costing
> $100,000 across the parts counter !!!!!!!!
won't even put it in their cars?
God Bless America, ßill O|||||||O
mailto:-------------------- http://www.----------.com/
Rich Hampel wrote:
>
> Found the cause of the paradox of rich mixture and low vacuum on my
> 2.8L.
> Eventually I located a teeny pin hole in the deceleration valve which
> caused the diaphragm not to uncover the orfice plate at high vacuum.
> The decel valve only opens at normal to high vacuum. With the valve
> malfunctioning the engine was trying to aspirate (into the 'E' port on
> the Rochester vari-jet) carb solely through the pcv valve ---- not
> enough air yielded rich burn, but with the valve not working: low
> vacuum .... thus the paradox.
>
> Other:
> Stalling on left turn does NOT involve the carb float !!!!!!!!!!
> Another anomaly also solved in the step by step search of the vacuum
> problem (and a problem that has been posted here many many times):
> Engine would stall when turning left (not right). The 'usual'
> suggestion is to increase the float height in the carb ..... WRONG
> WRONG WRONG as that will only cause the carb to dump gas into the
> intake manifold when you shut down and totally flood it and you still
> stall when turning left.
> The solution is a freakin teeny pressure switch on the high pressure
> side of power steering pump .... when the pump goes over pressure the
> switch (also) energizes the throttle kicker. $30.00 new switch and I
> can turn to left again!!!! You might want to remember this info for
> those who have 2.8L engines that stall when turning left (not right).
>
> Anyway thanks to all who posted suggestions even that your suggestions
> didnt work, I thank all of you for your help...... At least the
> discussions here are extremely helpful in sorting things out. At
> least I learned that after 300K miles you should replace the *entire*
> emissions control system components ... its a BIG PITA if you dont. Im
> now back to full power and 23+ mpg for long haul runs at speed.
> Im now planning to make at least 500,000 miles on this XJ Cherokee
> beast (- currently doing a semi-frame-off restoration). Too bad
> DaimlerC cant build a vehicle to that standard, or without costing
> $100,000 across the parts counter !!!!!!!!
01-13-2004 | 06:02 PM
#7
Guest
Posts: n/a
Re: Low vacuum rich mixture on 2.8L 86 XJ Cherokee--- solved
You mean there's another person with the 2.8L GM engine, Chevrolet
won't even put it in their cars?
God Bless America, ßill O|||||||O
mailto:-------------------- http://www.----------.com/
Rich Hampel wrote:
>
> Found the cause of the paradox of rich mixture and low vacuum on my
> 2.8L.
> Eventually I located a teeny pin hole in the deceleration valve which
> caused the diaphragm not to uncover the orfice plate at high vacuum.
> The decel valve only opens at normal to high vacuum. With the valve
> malfunctioning the engine was trying to aspirate (into the 'E' port on
> the Rochester vari-jet) carb solely through the pcv valve ---- not
> enough air yielded rich burn, but with the valve not working: low
> vacuum .... thus the paradox.
>
> Other:
> Stalling on left turn does NOT involve the carb float !!!!!!!!!!
> Another anomaly also solved in the step by step search of the vacuum
> problem (and a problem that has been posted here many many times):
> Engine would stall when turning left (not right). The 'usual'
> suggestion is to increase the float height in the carb ..... WRONG
> WRONG WRONG as that will only cause the carb to dump gas into the
> intake manifold when you shut down and totally flood it and you still
> stall when turning left.
> The solution is a freakin teeny pressure switch on the high pressure
> side of power steering pump .... when the pump goes over pressure the
> switch (also) energizes the throttle kicker. $30.00 new switch and I
> can turn to left again!!!! You might want to remember this info for
> those who have 2.8L engines that stall when turning left (not right).
>
> Anyway thanks to all who posted suggestions even that your suggestions
> didnt work, I thank all of you for your help...... At least the
> discussions here are extremely helpful in sorting things out. At
> least I learned that after 300K miles you should replace the *entire*
> emissions control system components ... its a BIG PITA if you dont. Im
> now back to full power and 23+ mpg for long haul runs at speed.
> Im now planning to make at least 500,000 miles on this XJ Cherokee
> beast (- currently doing a semi-frame-off restoration). Too bad
> DaimlerC cant build a vehicle to that standard, or without costing
> $100,000 across the parts counter !!!!!!!!
won't even put it in their cars?
God Bless America, ßill O|||||||O
mailto:-------------------- http://www.----------.com/
Rich Hampel wrote:
>
> Found the cause of the paradox of rich mixture and low vacuum on my
> 2.8L.
> Eventually I located a teeny pin hole in the deceleration valve which
> caused the diaphragm not to uncover the orfice plate at high vacuum.
> The decel valve only opens at normal to high vacuum. With the valve
> malfunctioning the engine was trying to aspirate (into the 'E' port on
> the Rochester vari-jet) carb solely through the pcv valve ---- not
> enough air yielded rich burn, but with the valve not working: low
> vacuum .... thus the paradox.
>
> Other:
> Stalling on left turn does NOT involve the carb float !!!!!!!!!!
> Another anomaly also solved in the step by step search of the vacuum
> problem (and a problem that has been posted here many many times):
> Engine would stall when turning left (not right). The 'usual'
> suggestion is to increase the float height in the carb ..... WRONG
> WRONG WRONG as that will only cause the carb to dump gas into the
> intake manifold when you shut down and totally flood it and you still
> stall when turning left.
> The solution is a freakin teeny pressure switch on the high pressure
> side of power steering pump .... when the pump goes over pressure the
> switch (also) energizes the throttle kicker. $30.00 new switch and I
> can turn to left again!!!! You might want to remember this info for
> those who have 2.8L engines that stall when turning left (not right).
>
> Anyway thanks to all who posted suggestions even that your suggestions
> didnt work, I thank all of you for your help...... At least the
> discussions here are extremely helpful in sorting things out. At
> least I learned that after 300K miles you should replace the *entire*
> emissions control system components ... its a BIG PITA if you dont. Im
> now back to full power and 23+ mpg for long haul runs at speed.
> Im now planning to make at least 500,000 miles on this XJ Cherokee
> beast (- currently doing a semi-frame-off restoration). Too bad
> DaimlerC cant build a vehicle to that standard, or without costing
> $100,000 across the parts counter !!!!!!!!
01-13-2004 | 07:50 PM
#8
Guest
Posts: n/a
Re: Low vacuum rich mixture on 2.8L 86 XJ Cherokee--- solved
LOL I guess I am another one. I ended up with this combination from an
auction. I was able to get almost 200,000 miles out of it until it finally
gave up the ghost two weeks ago.
"L.W. (ßill) ------ III" <----------@***.net> wrote in message
news:40046B04.C03AD94C@***.net...
> You mean there's another person with the 2.8L GM engine, Chevrolet
> won't even put it in their cars?
> God Bless America, ßill O|||||||O
> mailto:-------------------- http://www.----------.com/
>
> Rich Hampel wrote:
> >
> > Found the cause of the paradox of rich mixture and low vacuum on my
> > 2.8L.
> > Eventually I located a teeny pin hole in the deceleration valve which
> > caused the diaphragm not to uncover the orfice plate at high vacuum.
> > The decel valve only opens at normal to high vacuum. With the valve
> > malfunctioning the engine was trying to aspirate (into the 'E' port on
> > the Rochester vari-jet) carb solely through the pcv valve ---- not
> > enough air yielded rich burn, but with the valve not working: low
> > vacuum .... thus the paradox.
> >
> > Other:
> > Stalling on left turn does NOT involve the carb float !!!!!!!!!!
> > Another anomaly also solved in the step by step search of the vacuum
> > problem (and a problem that has been posted here many many times):
> > Engine would stall when turning left (not right). The 'usual'
> > suggestion is to increase the float height in the carb ..... WRONG
> > WRONG WRONG as that will only cause the carb to dump gas into the
> > intake manifold when you shut down and totally flood it and you still
> > stall when turning left.
> > The solution is a freakin teeny pressure switch on the high pressure
> > side of power steering pump .... when the pump goes over pressure the
> > switch (also) energizes the throttle kicker. $30.00 new switch and I
> > can turn to left again!!!! You might want to remember this info for
> > those who have 2.8L engines that stall when turning left (not right).
> >
> > Anyway thanks to all who posted suggestions even that your suggestions
> > didnt work, I thank all of you for your help...... At least the
> > discussions here are extremely helpful in sorting things out. At
> > least I learned that after 300K miles you should replace the *entire*
> > emissions control system components ... its a BIG PITA if you dont. Im
> > now back to full power and 23+ mpg for long haul runs at speed.
> > Im now planning to make at least 500,000 miles on this XJ Cherokee
> > beast (- currently doing a semi-frame-off restoration). Too bad
> > DaimlerC cant build a vehicle to that standard, or without costing
> > $100,000 across the parts counter !!!!!!!!
auction. I was able to get almost 200,000 miles out of it until it finally
gave up the ghost two weeks ago.
"L.W. (ßill) ------ III" <----------@***.net> wrote in message
news:40046B04.C03AD94C@***.net...
> You mean there's another person with the 2.8L GM engine, Chevrolet
> won't even put it in their cars?
> God Bless America, ßill O|||||||O
> mailto:-------------------- http://www.----------.com/
>
> Rich Hampel wrote:
> >
> > Found the cause of the paradox of rich mixture and low vacuum on my
> > 2.8L.
> > Eventually I located a teeny pin hole in the deceleration valve which
> > caused the diaphragm not to uncover the orfice plate at high vacuum.
> > The decel valve only opens at normal to high vacuum. With the valve
> > malfunctioning the engine was trying to aspirate (into the 'E' port on
> > the Rochester vari-jet) carb solely through the pcv valve ---- not
> > enough air yielded rich burn, but with the valve not working: low
> > vacuum .... thus the paradox.
> >
> > Other:
> > Stalling on left turn does NOT involve the carb float !!!!!!!!!!
> > Another anomaly also solved in the step by step search of the vacuum
> > problem (and a problem that has been posted here many many times):
> > Engine would stall when turning left (not right). The 'usual'
> > suggestion is to increase the float height in the carb ..... WRONG
> > WRONG WRONG as that will only cause the carb to dump gas into the
> > intake manifold when you shut down and totally flood it and you still
> > stall when turning left.
> > The solution is a freakin teeny pressure switch on the high pressure
> > side of power steering pump .... when the pump goes over pressure the
> > switch (also) energizes the throttle kicker. $30.00 new switch and I
> > can turn to left again!!!! You might want to remember this info for
> > those who have 2.8L engines that stall when turning left (not right).
> >
> > Anyway thanks to all who posted suggestions even that your suggestions
> > didnt work, I thank all of you for your help...... At least the
> > discussions here are extremely helpful in sorting things out. At
> > least I learned that after 300K miles you should replace the *entire*
> > emissions control system components ... its a BIG PITA if you dont. Im
> > now back to full power and 23+ mpg for long haul runs at speed.
> > Im now planning to make at least 500,000 miles on this XJ Cherokee
> > beast (- currently doing a semi-frame-off restoration). Too bad
> > DaimlerC cant build a vehicle to that standard, or without costing
> > $100,000 across the parts counter !!!!!!!!
01-13-2004 | 07:50 PM
#9
Guest
Posts: n/a
Re: Low vacuum rich mixture on 2.8L 86 XJ Cherokee--- solved
LOL I guess I am another one. I ended up with this combination from an
auction. I was able to get almost 200,000 miles out of it until it finally
gave up the ghost two weeks ago.
"L.W. (ßill) ------ III" <----------@***.net> wrote in message
news:40046B04.C03AD94C@***.net...
> You mean there's another person with the 2.8L GM engine, Chevrolet
> won't even put it in their cars?
> God Bless America, ßill O|||||||O
> mailto:-------------------- http://www.----------.com/
>
> Rich Hampel wrote:
> >
> > Found the cause of the paradox of rich mixture and low vacuum on my
> > 2.8L.
> > Eventually I located a teeny pin hole in the deceleration valve which
> > caused the diaphragm not to uncover the orfice plate at high vacuum.
> > The decel valve only opens at normal to high vacuum. With the valve
> > malfunctioning the engine was trying to aspirate (into the 'E' port on
> > the Rochester vari-jet) carb solely through the pcv valve ---- not
> > enough air yielded rich burn, but with the valve not working: low
> > vacuum .... thus the paradox.
> >
> > Other:
> > Stalling on left turn does NOT involve the carb float !!!!!!!!!!
> > Another anomaly also solved in the step by step search of the vacuum
> > problem (and a problem that has been posted here many many times):
> > Engine would stall when turning left (not right). The 'usual'
> > suggestion is to increase the float height in the carb ..... WRONG
> > WRONG WRONG as that will only cause the carb to dump gas into the
> > intake manifold when you shut down and totally flood it and you still
> > stall when turning left.
> > The solution is a freakin teeny pressure switch on the high pressure
> > side of power steering pump .... when the pump goes over pressure the
> > switch (also) energizes the throttle kicker. $30.00 new switch and I
> > can turn to left again!!!! You might want to remember this info for
> > those who have 2.8L engines that stall when turning left (not right).
> >
> > Anyway thanks to all who posted suggestions even that your suggestions
> > didnt work, I thank all of you for your help...... At least the
> > discussions here are extremely helpful in sorting things out. At
> > least I learned that after 300K miles you should replace the *entire*
> > emissions control system components ... its a BIG PITA if you dont. Im
> > now back to full power and 23+ mpg for long haul runs at speed.
> > Im now planning to make at least 500,000 miles on this XJ Cherokee
> > beast (- currently doing a semi-frame-off restoration). Too bad
> > DaimlerC cant build a vehicle to that standard, or without costing
> > $100,000 across the parts counter !!!!!!!!
auction. I was able to get almost 200,000 miles out of it until it finally
gave up the ghost two weeks ago.
"L.W. (ßill) ------ III" <----------@***.net> wrote in message
news:40046B04.C03AD94C@***.net...
> You mean there's another person with the 2.8L GM engine, Chevrolet
> won't even put it in their cars?
> God Bless America, ßill O|||||||O
> mailto:-------------------- http://www.----------.com/
>
> Rich Hampel wrote:
> >
> > Found the cause of the paradox of rich mixture and low vacuum on my
> > 2.8L.
> > Eventually I located a teeny pin hole in the deceleration valve which
> > caused the diaphragm not to uncover the orfice plate at high vacuum.
> > The decel valve only opens at normal to high vacuum. With the valve
> > malfunctioning the engine was trying to aspirate (into the 'E' port on
> > the Rochester vari-jet) carb solely through the pcv valve ---- not
> > enough air yielded rich burn, but with the valve not working: low
> > vacuum .... thus the paradox.
> >
> > Other:
> > Stalling on left turn does NOT involve the carb float !!!!!!!!!!
> > Another anomaly also solved in the step by step search of the vacuum
> > problem (and a problem that has been posted here many many times):
> > Engine would stall when turning left (not right). The 'usual'
> > suggestion is to increase the float height in the carb ..... WRONG
> > WRONG WRONG as that will only cause the carb to dump gas into the
> > intake manifold when you shut down and totally flood it and you still
> > stall when turning left.
> > The solution is a freakin teeny pressure switch on the high pressure
> > side of power steering pump .... when the pump goes over pressure the
> > switch (also) energizes the throttle kicker. $30.00 new switch and I
> > can turn to left again!!!! You might want to remember this info for
> > those who have 2.8L engines that stall when turning left (not right).
> >
> > Anyway thanks to all who posted suggestions even that your suggestions
> > didnt work, I thank all of you for your help...... At least the
> > discussions here are extremely helpful in sorting things out. At
> > least I learned that after 300K miles you should replace the *entire*
> > emissions control system components ... its a BIG PITA if you dont. Im
> > now back to full power and 23+ mpg for long haul runs at speed.
> > Im now planning to make at least 500,000 miles on this XJ Cherokee
> > beast (- currently doing a semi-frame-off restoration). Too bad
> > DaimlerC cant build a vehicle to that standard, or without costing
> > $100,000 across the parts counter !!!!!!!!
01-13-2004 | 07:50 PM
#10
Guest
Posts: n/a
Re: Low vacuum rich mixture on 2.8L 86 XJ Cherokee--- solved
LOL I guess I am another one. I ended up with this combination from an
auction. I was able to get almost 200,000 miles out of it until it finally
gave up the ghost two weeks ago.
"L.W. (ßill) ------ III" <----------@***.net> wrote in message
news:40046B04.C03AD94C@***.net...
> You mean there's another person with the 2.8L GM engine, Chevrolet
> won't even put it in their cars?
> God Bless America, ßill O|||||||O
> mailto:-------------------- http://www.----------.com/
>
> Rich Hampel wrote:
> >
> > Found the cause of the paradox of rich mixture and low vacuum on my
> > 2.8L.
> > Eventually I located a teeny pin hole in the deceleration valve which
> > caused the diaphragm not to uncover the orfice plate at high vacuum.
> > The decel valve only opens at normal to high vacuum. With the valve
> > malfunctioning the engine was trying to aspirate (into the 'E' port on
> > the Rochester vari-jet) carb solely through the pcv valve ---- not
> > enough air yielded rich burn, but with the valve not working: low
> > vacuum .... thus the paradox.
> >
> > Other:
> > Stalling on left turn does NOT involve the carb float !!!!!!!!!!
> > Another anomaly also solved in the step by step search of the vacuum
> > problem (and a problem that has been posted here many many times):
> > Engine would stall when turning left (not right). The 'usual'
> > suggestion is to increase the float height in the carb ..... WRONG
> > WRONG WRONG as that will only cause the carb to dump gas into the
> > intake manifold when you shut down and totally flood it and you still
> > stall when turning left.
> > The solution is a freakin teeny pressure switch on the high pressure
> > side of power steering pump .... when the pump goes over pressure the
> > switch (also) energizes the throttle kicker. $30.00 new switch and I
> > can turn to left again!!!! You might want to remember this info for
> > those who have 2.8L engines that stall when turning left (not right).
> >
> > Anyway thanks to all who posted suggestions even that your suggestions
> > didnt work, I thank all of you for your help...... At least the
> > discussions here are extremely helpful in sorting things out. At
> > least I learned that after 300K miles you should replace the *entire*
> > emissions control system components ... its a BIG PITA if you dont. Im
> > now back to full power and 23+ mpg for long haul runs at speed.
> > Im now planning to make at least 500,000 miles on this XJ Cherokee
> > beast (- currently doing a semi-frame-off restoration). Too bad
> > DaimlerC cant build a vehicle to that standard, or without costing
> > $100,000 across the parts counter !!!!!!!!
auction. I was able to get almost 200,000 miles out of it until it finally
gave up the ghost two weeks ago.
"L.W. (ßill) ------ III" <----------@***.net> wrote in message
news:40046B04.C03AD94C@***.net...
> You mean there's another person with the 2.8L GM engine, Chevrolet
> won't even put it in their cars?
> God Bless America, ßill O|||||||O
> mailto:-------------------- http://www.----------.com/
>
> Rich Hampel wrote:
> >
> > Found the cause of the paradox of rich mixture and low vacuum on my
> > 2.8L.
> > Eventually I located a teeny pin hole in the deceleration valve which
> > caused the diaphragm not to uncover the orfice plate at high vacuum.
> > The decel valve only opens at normal to high vacuum. With the valve
> > malfunctioning the engine was trying to aspirate (into the 'E' port on
> > the Rochester vari-jet) carb solely through the pcv valve ---- not
> > enough air yielded rich burn, but with the valve not working: low
> > vacuum .... thus the paradox.
> >
> > Other:
> > Stalling on left turn does NOT involve the carb float !!!!!!!!!!
> > Another anomaly also solved in the step by step search of the vacuum
> > problem (and a problem that has been posted here many many times):
> > Engine would stall when turning left (not right). The 'usual'
> > suggestion is to increase the float height in the carb ..... WRONG
> > WRONG WRONG as that will only cause the carb to dump gas into the
> > intake manifold when you shut down and totally flood it and you still
> > stall when turning left.
> > The solution is a freakin teeny pressure switch on the high pressure
> > side of power steering pump .... when the pump goes over pressure the
> > switch (also) energizes the throttle kicker. $30.00 new switch and I
> > can turn to left again!!!! You might want to remember this info for
> > those who have 2.8L engines that stall when turning left (not right).
> >
> > Anyway thanks to all who posted suggestions even that your suggestions
> > didnt work, I thank all of you for your help...... At least the
> > discussions here are extremely helpful in sorting things out. At
> > least I learned that after 300K miles you should replace the *entire*
> > emissions control system components ... its a BIG PITA if you dont. Im
> > now back to full power and 23+ mpg for long haul runs at speed.
> > Im now planning to make at least 500,000 miles on this XJ Cherokee
> > beast (- currently doing a semi-frame-off restoration). Too bad
> > DaimlerC cant build a vehicle to that standard, or without costing
> > $100,000 across the parts counter !!!!!!!!