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I had a similar problem with my '89. It turned out to be an intermittent ground on the internal wiring harness for the fuel pump/gas gauge assembly inside the tank. Over time, the 10% ethanol in the fuel attacked the insulation on the ground wire only causing it to swell and then burst. I replaced the in tank assembly with a new GM assembly rated for use with E85 fuel (which I don't use; but if it's okay to E85, then E10 shouldn't be a problem). That simple swap solved my problem.
Though I do not trust the car to drive it very much, wiring it back to stock seems to have fixed the problem. The pump has primed up every single time since then.
Well I spoke too soon, car died on me this morning as I was coming to a red light. It would not refire for a good 4-5 minutes.
So based on my prior troubleshooting it seems as if consistent voltage is not getting to the factory connector at the pump, unless this is an intermittent inside the pump wiring in the tank that didn't show its head before.
Where are the weak spots to look for the grounding out of the factory wiring?
30+ year old bulkhead and In-tank fuel pump wiring failures
This is why Racetronix is discontinuing our current PnP systems for the C4. There will be one kit which covers all C4 model years and includes our bulkhead wiring system as standard. In most cases these wiring components are compromised regardless of the miles on the vehicle. They were also never designed to support the power demands of today's high-flowing 255, 340 and 450LPH pumps which can draw 2-4 times that of a factory pump.
So now that I have their kit, I see it eliminates the EM/RFI filter, which I suppose is fine if newer pumps have that installed inside anyway.
The factory connection is pressed in from above into the hanger that holds the RFI filter, how best to replace that, and how is that extra ground best removed/re-attached with the new? Not a wiring guru. I guess I could butt splice.
The connector to the pump also has an extra ground coming out of the connector, to what?
After finally getting it all back together the rivet on the fuel guage sender came right off in my hands, I soldered that back on with 60/40 and the car runs again. Holding pressure pretty steady at 42psi.
