Fuel problem

JDCHEVYGUY

MEMBER
1993 GMC JIMMY
6 CYL
4WD
AUTOMATIC

I have a 1993 gmc jimmy with a 4.3 vortec when it sits over night I have trouble starting it, I checked the fuel pressure and its 56 but when the pump turns off it drops to 20 but if I give it a shot of ether it will fire up and run fine, if it is warmed up it will fire up right away

Thursday, January 6th, 2011 AT 9:08 PM

3 Replies

WRENCHTECH

MECHANIC
20,761 POSTS

It sounds like you have a fuel pressure problem. 56 is barely enough for this engine.

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Thursday, January 6th, 2011 AT 9:17 PM

WRENCHTECH

MECHANIC
20,761 POSTS

It appears you have a fuel pressure problem. This engine should shoot up over 60 PSI before it starts and it very pressure sensitive. You need to find out where that pressure is going. Get a helper and see if you can immediately pinch off the feed line as soon as it builds pressure and see if it holds then. If it does, then the pump is bad. If it still doesn't, then you have a problem under the intake, possibly a regulator.

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Thursday, January 6th, 2011 AT 9:20 PM

JDL

MECHANIC
16,098 POSTS

If this has the spider fuel system, the fuel poppets may need cleaning? That fuel spec you listed, is that key on engine off or engine running?

With engine running, fuel gage hooked up, quickly open the throttle and watch the pressure, should approach 64 psi, if it doesn't, replace cpi system, so says Mitchell?

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Thursday, January 6th, 2011 AT 9:32 PM