Chevrolet Repair Questions? Ask a Mechanic for Answers ASAP
There is a relay that turns the fuel pump on for a few seconds when the key is turned on then when the engine starts, the oil pump switch keeps power to the pump when the engine is running. Below is the circuit for the fuel pump, first make sure the fuse is good and then check for power at the pump when the key is turned on and the engine is cranking.
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So, first of all check with a 12 volt test light or voltmeter, the ECM B fuse 10a (hot at the time). If ok, then also make sure you have voltage at the orange wire at the relay. There is a prime connector, you could jump 12 volts to that to see if the fuel pump runs. It doesn't show the wire color but they are usually red. That would check out the relay and wiring to the pump.
If it runs when using the prime connector then the problem may be the ecm and/or wiring from it to the relay. Now remember, the fuel pump usually only comes on for a few seconds when the key is first turned to run, unless the engine is cranking and the oil pressure builds up enough to override the relay. So, have someone else turn the key to run and check for voltage along the dark green/white wire for 2 seconds. Also, check for voltage on the gray wire leading to the fuel pump if the relay is activating.
It appears as there are 3 of them. If any are the same part number you could swap with one and see if the fuel pump runs to quickly check if it's just the relay that is bad. From the diagram, the relay is on the far left looking at the bracket.
This vehicle only had two relay switches where the diagram showed three, but I changed it out and it now is running great.
Thanks very much for your help!