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99 GMC Jimmy Starting issue

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28 Jun 2019 19:15 #31176 by Mort
99 GMC Jimmy Starting issue was created by Mort
Working on a 99 GMC Jimmy 4.3 4WD did an engine swap on the jimmy got everything back together tried to start it and it cranks but doesn't start, however if I put fuel down the intake and crank it it will start and run. It is not throwing any codes so I am sort of at a loss as to wear to start the troubleshooting Any ideas out there?

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28 Jun 2019 19:29 #31177 by Cheryl
Replied by Cheryl on topic 99 GMC Jimmy Starting issue
You have fuel pressure??

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28 Jun 2019 20:41 #31183 by Mort
Replied by Mort on topic 99 GMC Jimmy Starting issue
I haven't put a gage to it. I am thinking the fuel pump was the culprit, but wouldn't it throw a code for low fuel pressure

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28 Jun 2019 20:50 #31184 by Cheryl
Replied by Cheryl on topic 99 GMC Jimmy Starting issue
Doubt it. It’s to old for that

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28 Jun 2019 21:17 #31189 by Mort
Replied by Mort on topic 99 GMC Jimmy Starting issue
I'll check the fuel pressure when I get home Sunday

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28 Jun 2019 21:55 #31192 by Cheryl
Replied by Cheryl on topic 99 GMC Jimmy Starting issue
Might check the grounds. Is the frame grounded? Cause if not the pump won’t have a ground

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30 Jun 2019 15:04 #31247 by Mort
Replied by Mort on topic 99 GMC Jimmy Starting issue
Ok Turning the switch to the on position, fuel pressure is 55 psi. when cranking it drops to 40 psi. I can zero it out and turn the switch on and it jumps to 55 psi So to me this indicates the fuel pump is working. Shut the switch off and it starts to drop off. Am I correct in assuming this indicates a bad fuel regulator?

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30 Jun 2019 17:08 #31250 by Cheryl
Replied by Cheryl on topic 99 GMC Jimmy Starting issue
That cranking pressure is way to low. The popper valves won’t open on the injectors.

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30 Jun 2019 21:26 #31270 by Mort
Replied by Mort on topic 99 GMC Jimmy Starting issue
If my gauge is is showing 55 psi with the switch on but drops off when cranking is that not indicative of a bad fuel regulator?? The battery is new and my customer says there is a new fuel pump in the tank.

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30 Jun 2019 22:03 #31272 by jreardon
Replied by jreardon on topic 99 GMC Jimmy Starting issue
Fuel Pressure is low. Is your the SFI or CSI (spider injectors) ? Pinch off the return line switch key to on position and see if pump is strong enough to push the psi roughly 80-90 psi. If this pump passes this test, then change the regulator. Don't forget to change out the fuel filter while you're there.


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01 Jul 2019 05:15 #31284 by Mort
Replied by Mort on topic 99 GMC Jimmy Starting issue
Thank you for that info. I was looking for a way to check the Regulator and couldn't find it in my manual..

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