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no fuel pump when cold


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I have a problem with cold starting. So this weeken I put a fuel pressure guage on it and here is what I discovered.

With it stone cold and key on no fuel pressure and pump not running.

Crank for about 5 seconds and fuel pressure will come up and car will start.

All the rest of the day I started it 3 or 4 times and when I turned the key on pressure would come up and car would start fine.

This morning agian no fuel untill I cranked on it for a while.

Fuse looks good and I swaped out the pump relay with the horn relay and it didn't make any difference.

Any thoughts?

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It sounds like the fuel pump is not receiving the 12V signal when the key is torned to "ON". There is a redundant 12V feed to the pump from the oil pressure sensor. When the engine has adequate oil pressure, the fuel pump will receive 12V from that circuit. That explains why the engine starts after 5 sec. of cranking.

You really need the wiring diagram to trace the wires and monitor the voltages at various points in the fuel pump circuit to effectively troubleshoot the problem.

'93 Fleetwood Brougham
'05 Deville
'04 Deville
2013 Silverado Z71

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