1993 Jeep Cherokee Help with fuel pressure

TRUSOLDIER626

MEMBER
1993 JEEP CHEROKEE
6 CYL
4WD
AUTOMATIC
200,000 MILES

Ok my inline 6 want to crap it starts fine. But as soon as it starts it dies runs for 2 seconds then dies or Idles really rough then dies. Best I can figure it does so untell it uses up the fuel pressure. So far I have changed:
fuel pump
fuel filter
idle air control valve
trottle position sensor
o2 sensor
fuel pressure regulator
coolent temp sensor
fuel lines

so far im up to 500 in parts.
I hooked up a pressure guage to the fuel line and before parts it was about 31psi before start then would drop to 15 after start and then just kept falling tell it died. Now that I changed the fuel pump its worse.
the only differance the fuel pump made is now my fuel guage doesn't work.
I have no idea where to go next. Any ideas? Would like it running by work in 2 days.

4 Replies

RASMATAZ

MECHANIC
75,992 POSTS

When the pump is turned off or stops running, the system should hold residual pressure for several minutes (look up the specs to see how much pressure drop is allowed over a given period of time). If pressure drops quickly, the vehicle may have a leaky fuel line, a leaky fuel pump check valve, a leaky fuel pressure regulator or one or more leaky fuel injectors. Low residual fuel pressure can cause hard starting and vapor lock during hot weather.

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Thursday, March 26th, 2009 AT 3:31 AM

TRUSOLDIER626

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8 POSTS

So with what u have said ive done all but the injectors. It is also sucking in alot of air more then it used to. And it is also backfireing if u hit the throttle and let it go it backfires in the intake not sure if this helps. But it build pressure at start then slowly goes down

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Thursday, March 26th, 2009 AT 2:22 PM

FDTRACTOR

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2 POSTS

I was wondering if you got it fixed. I cant figure out whats wrong with mine but it sounds like the same thing.

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Sunday, April 12th, 2009 AT 9:29 PM

TRUSOLDIER626

MEMBER
8 POSTS

Yes I did track down my problem. The problem was a little ceramic box on the driveside quarter panel under the hood it only has 2 wires to it I cut them and connected them together and it works just fine. I belive the box was the fuel pump shutoff switch. (Used if in a wreck it auto kills engine) but I wired the 2 wires together and after 600 in parts that I didnt need it was that little box. Hope u get yours running.

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Thursday, April 16th, 2009 AT 10:10 PM