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Fuel Delivery Issue Challenge #730100
November 27th 2017 10:13 pm
November 27th 2017 10:13 pm
Joined: Nov 2017
Posts: 3
Campbell CA
I
Icechopper Offline OP
stranger
Icechopper  Offline OP
stranger
I
Joined: Nov 2017
Posts: 3
Campbell CA
I have a 92 G30 van w/5.7L and A/T with 24k miles. Started the ole heap up a couple of weeks ago and the motor shut down after after 20 seconds of so. Tried it again, same thing. I dove into the fuel pump (FP) system, replaced the fuel filter and the FP relay, same results (actually timed the 20 second run with a stop watch). I assumed the FP was failing, so I dropped the tank and replaced the FP. Fuel tank was very clean, no obvious issues with anything that I saw in there. Started the motor, off again in 20 seconds. Oil pressure switch (OPS)? Did that too. So now I have my propeller hat on with voltage meter and test light. All fuses are sound, good fuel in the tank, recent tune up, cold beer still in the refrigerator, etc... Checked voltage at the relay plug, found 12+ V to the E terminal (gray wire) once the ignition is turned on. The proper voltage stays on for 20 seconds. The engine will start and run, but only for 20 seconds.
I then jumped 12V battery to the "E" terminal, the motor starts and runs indefinitely. One more tidbit, if I jump voltage to the orange wire of the relay plug (plug A or C terminal) the engine will continue to run as well, but if i pull the OPS plug, the motor quits (affirming that the OPS is working.

I'm getting advise from the gray-haired mechanics to look at the PCM since I've replaced everything else in the system. Does anyone have any experience with this problem? I can't think of anything else but I suspect something is telling the PCM to cut power to the FP? Any thoughts?

Re: Fuel Delivery Issue Challenge [Re: Icechopper] #730103
November 27th 2017 10:46 pm
November 27th 2017 10:46 pm
Joined: Nov 2013
Posts: 963
West Texas
W
Wedgy Offline
old hand
Wedgy  Offline
old hand
W
Joined: Nov 2013
Posts: 963
West Texas
Hi icechopper, Welcome to the site!

Sissy used to be a failure analysis engineer. Heat and vibration are the enemy of electronic circuitry. Chevy FSM may help with diagnosis. But not the easiest thing to do, darn it. Sounds reasonable, a short in the PCM. Especially if the voltage signal to the FP relay is cutting off. Good Hunting!

Re: Fuel Delivery Issue Challenge [Re: Icechopper] #730351
December 04th 2017 8:46 pm
December 04th 2017 8:46 pm
Joined: Dec 2017
Posts: 21
AZ
J
Jay85128 Offline
stranger
Jay85128  Offline
stranger
J
Joined: Dec 2017
Posts: 21
AZ
Hi, I do not reply to very many posts concerning repairs, and I am far from a professional. I certainly do not know your vehicle, but if you have a factory security system like the GM pass key system I think it is called (with the resistor chip in the key) you might want to check that system. I have read where on various systems a vehicle will start, but if it does not receive the proper signal from the key it will shut down the vehicle. I may be totally off base and I apologize if I am. I had a similar problem and thought I would share my thoughts.

Re: Fuel Delivery Issue Challenge [Re: Jay85128] #730973
December 20th 2017 2:46 pm
December 20th 2017 2:46 pm
Joined: Nov 2017
Posts: 3
Campbell CA
I
Icechopper Offline OP
stranger
Icechopper  Offline OP
stranger
I
Joined: Nov 2017
Posts: 3
Campbell CA
Just a bit of feedback on this issue. I purchased a cable identifier device from Harbor Freight that sends a current through a specific wire that can be tracked by a "tone" sounding wand. I traced the orange wire from the FP relay plug up to the bulkhead connections to the fuse block. I separated the three wire harness plugs from the fuse block and found the issue. Apparently, when this van was covered into an ADA vehicle, the electrical cable connections for the wheel chair lift was placed directly above the wire harness / fuse block connections on the firewall. The installers used some kind of asphalt product, like a roofing shingle, to separate the additional electrical block from the wire harness connectors. Unfortunately, the heat produced inside the engine compartment was too great for the asphalt product and it decomposed. A thick tarry substance permeated the wire harness connections, including the metal prongs and plugs of the fuse block. UGLY! Not much to be learned here, except the cheap cable tracer is worth the $30 I spent at Harbor Freight.

The fix: I'm soaking the connectors in kerosene to de-gunk them. Apparently, some of the wires overheated due to the reduced conductivity of the site, discoloring the insulation of a few wires adjacent to the plug. The power supply to the FP appears to be the only one that has lost conductivity. Going to buy a junkyard wire harness, cut the plug off of it and pull out each wire and check conductivity. I expect to splice a few wires and replace the good ones in the clean or new plastic.


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