Whats up guys/girls, got an 00 4.0 XJ. Ive been having trouble with the jeep vapor locking, if im driving around town and shut it off ill go to restart it like 1-30min and it will vapor lock, it will fire but runs like shit, usually misfires, and a rough idle for maybe 30 secs tops than it is fine. Jeep has a 195 t-stat and runs at that, fresh anti freeze, rad isnt clogged that i can see, good air filter, new CPS, new coil pack, plugs, boots, etc. (i take care of it lol) it is driving me nuts why its doing it though?! any ideas? boths fans work also. thanks!
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Vapor Lock?
- Thread starter Spokes
- Start date
Oatmeal
NAXJA Forum User
- Location
- Cedar City, UT
sneakyjap96
NAXJA Forum User
- Location
- modesto
Cayse the fuel lines are hot causing the fuel to turn to a vapor normally happens with a bad fuel return an or weak pump
sneakyjap96
NAXJA Forum User
- Location
- modesto
To chexk the regulator and or pump gotta use a fuel gauge on the fuel rail an turn the key let it prime its self an see how high the psi gets an check specs that will test the pump. Then let it sit it shouldnt bleed down if it does the regulator is stuck or bad
Flyfisher
NAXJA Forum User
- Location
- Billings, Montana
I agree with the weak fuel pump answer. With the fuel being at 30-50 psi, it takes a LOT of heat to turn it into vapor.
sneakyjap96
NAXJA Forum User
- Location
- modesto
Yes but if its bleeding back to the tank it will vapor lock very easily
- Location
- In the islands
I do not think fuel presure have any thing to do with what you are experiencing. And OH, by-the-way, the 2000 XJ like my 1996 XJ do not have a fuel return line. Neither does it have an external fuel regulator. The regulator is a part of the pump which is inside the fuel tank.
I too like so many others on this forum have had that same problems which plagued us for many years,...and yes, it is vapor lock. The summer in South Florida was especially brutal untill I installed a temperature switch in the cooling system and hot wired it that the problem seem to be abated. This switch caused the fans to run wether I am in the XJ or not untill the temperature dropped. The secondary benefit is that it moved the hot air out of the engine compartment thus cooling the manifolds and fuel line. Since then I cannot recall having a problem with vapor lock. The original fuel pump is still in use and put out 50 PSI of pressure.
I too like so many others on this forum have had that same problems which plagued us for many years,...and yes, it is vapor lock. The summer in South Florida was especially brutal untill I installed a temperature switch in the cooling system and hot wired it that the problem seem to be abated. This switch caused the fans to run wether I am in the XJ or not untill the temperature dropped. The secondary benefit is that it moved the hot air out of the engine compartment thus cooling the manifolds and fuel line. Since then I cannot recall having a problem with vapor lock. The original fuel pump is still in use and put out 50 PSI of pressure.
got more info on the fan? and where u ran the lines?
CharlesS
NAXJA Forum User
- Location
- Quezon Province, Philippines
More testing is needed to rule out these problems...
My thoughts on this problem would be dirty fuel injectors bleeding thru which depressurizes the fuel rail adding fuel into the combustion chamber. This is why when the engine is started it takes longer to start and idles rough for a while until the combustion chamber warms up and vaporizes the raw fuel....
My thoughts on this problem would be dirty fuel injectors bleeding thru which depressurizes the fuel rail adding fuel into the combustion chamber. This is why when the engine is started it takes longer to start and idles rough for a while until the combustion chamber warms up and vaporizes the raw fuel....
Oatmeal
NAXJA Forum User
- Location
- Cedar City, UT
Well.........I replaced the pump and the problem went away.
Also, depressing the schrader valve (bleeder) on the fuel rail, reveled very low pressure.
So.........?
Hans
Also, depressing the schrader valve (bleeder) on the fuel rail, reveled very low pressure.
So.........?
Hans
this could be, im sure there the OE injectors and with 175K im sure they could use a replacing lol
i checked my fuel rail about a month ago and it had great PSI so i would rule out the pump problem too.
- Location
- In the islands
The fans I am using are the Derale duals with a total output of 4,000 CFM from Summit racing with a temperature switch in the cooling system wired directly to the battery which in turn triggered a relay to run the fans. Those fans are power hungry so an up-graded alternator is a must. I also had to modify one fan housing to fit around the steering gear. I installed these early 2003 and have no regrets so far,....well one thing. The AW4 seem to run hotter than when the mechanical fan was being used.
http://www.summitracing.com/parts/der-16928
