Bosbury1

Been having an issue in the mornings having to use the poor man's prime method. So, I replaced the fuel pump with a Bosch pump replaced the fuel filter with a good quality Wix fuel filter. Replaced all the old stock plastic lines with new 3/8 and 5/16 hose. New connectors at the fuel rail used fuel injector clamps. Rebuilt my fuel injectors, replaced the pressure regulator. Same issue. When I use the poor man's prime method it starts right up and runs like a champ. Schrader valve possibility? Any thoughts?

exasemech

1) if the Schrader valve was leaking you would have a visible leak.
2) what do you mean when you said you rebuilt the injectors?

3)Have you confirmed, with a gauge, that the fuel pressure is leaking down?

My first guess, assuming the parts you replaced are ok, is leaking injector.

Bosbury1

I have confirmed with a gauge that the leak down is taking place. With respect to the injectors they are a secondary set I had (all OHM'ed out alright) removed the filter, pintel, and o-rings. Cleaned in a ultrasonic cleaner and then replaced with new parts. Thank you.

exasemech

Okay

Were the injectors you replaced the filters, etc the same injectors that were in there when the pressure was leaking down before you replaced the pump, lini etc?
The fuel is going somewhere. If you are convinced there are no external leaks that pretty much leaves it's leaking back into the tank or injectors.

Bosbury1

I replaced the old injectors with a rebuilt set (same injector number for both sets). Its strange having the same issue with new rebuilt injectors, fuel regulator, fuel pump, fuel filter, all soft line replaced. Clearly, there's a leak down happening. Thanks.

exasemech

It's not impossible that a hard line has rotted through somewhere, the thing is 30 years old. It wouldn't take much of a leakBut the fact that the pressure is as low as it is when you're running seems like pump. Did you replace the entire pump assembly or just the actual pump module?
I don't know where the check valve is in the 94 fuel system but there's gonna be àt least one.

Bosbury1

I replaced the Bosch fuel pump only in addition to the hose on the fuel pump located in the tank. The old Bosch unit replaced was about 6 years old. I cleaned all the steel lines do not see any leaks no smell of gas at all. I filled the Jeep up to full no leaks coming out of the gas tank gasket as well. I'm perplexed for sure.

exasemech

Okay
assuming the pressure regulator you put in is good .
I can see only 2 possibilities.
An injector is leaking down
OrIF there is a check valve on the pump on a 94. ( I don't know, someone else will need to help with that) and it didn't get replaced when you worked on the pump and is bad.

Other than those things I'm out of ideas.... but the fuel is going somewhere

lalo

...



That hose that you replaced
in the tank, on the FP,
might be split or
leaking.

lalo

Bosbury1

Just to confirm the following parts have been replaced Fuel Pump, Fuel Filter, All rubber hoses, all new hose clamps, new fuel rail steel connectors, new fuel regulator, rebuilt injectors. How would I determine if I have a leaky Injector? I OHM'ed out the injectors and all six replaced were within spec. Thanks.

Bosbury1

Going to give this a try. Pull the fuel rail, and put a piece of paper under each injector, then turn the key to prime the fuel pump. Any injectors leaking will drip. Will report back.

exasemech

​​​​​​1) you're injector test should work.no smoking. All the ohm measurement does is tell you if the coil is okay, it doesn't tell you if the valve/needle whatever is leaking.

2) Do me(us) a favor. Start a new thread asking if a 1994 4.0 xj has a check valve on the fuel pump assembly. I think if you ask in this thread it will be lost in the noise. I don't have a 94 shop manual.

Bosbury1

Just removed the fuel rail decompressed the fuel. Turned the ignition to on position no leaks let run for about 2 top 3 minutes. Interesting. Will start a new thread thanks Exasemech.

Bosbury1

I went ahead a ordered a replacement fuel pressure regulator thinking the one replaced the other day might be bad.

Bosbury1

Update... Replaced the fuel pressure regulator and used a larger O-ring installed about 07:00 a.m. this morning. Placed gauge on it for an hour dropped 2 lbs. Just got back from lunch about 10 minutes ago. After sitting 5+ hours it started right up. Either the fuel pump regulator or the o-ring was bad. Thanks for all your assistance. The issue seems to have remedied itself. Thanks again.