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Re: NO POWER TO FUEL PUMP, RELAY WORKS FUSE GOOD
If you have put direct power to the fuel pump and it still wont work, then get an electrical test unit, test light, and ohmmeter, and check to see if there is a break in any of the wires, and that you have got a good ground connection from the ground feed. After confirming you have good connections, then it will be obvious that the fuel pump needs replacing.
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Are you getting the ignition activated voltage to the relay? If you are, and you can jump across the relay to turn on the pump, I would say your relay is defective. If you know the relay pins for the ignition input and ground, you should be able to test it outside its plug in socket. You should hear it click when +12V and ground are applied to the proper pins/connectors for the ignition voltage. An ohm meter could be put across the supply +12V and fuel pump pins/connectors to really check the operation. If you think your relay is good. I would start checking for a bad +12V connection for your ignition supply, as well as the +12V that is switched through the relay. And the grounds to all. Use some contact cleaner on relay pins and socket. Ignition switch contacts can cause issues too. If it stays broke at least it should be easier to find than something that is intermittent. Based on what you stated, most of your troubleshooting should be at the relay socket (knowing which connectors do what) to isolate the issue to the relay, your ignition voltage, or your fuel pump voltage. After that it is knowing which step to take next.
Did you check all the fuses? Sounds like you have no power to the fuel pump if you worked on it recently, make sure there is no ground wire unhooked. Any ground wire could cause this problem. Locate the fuel pump relay. Switch it with a known good relay.
Make sure you're getting power to the fuel pump after start up. GM cars provide power to the electric fuel pump via the starting circuit when cranking and switch to alternator/battery power via the fuse block and 12v relay with ignition on in run position. Check your fuse block (bad fuse; power not getting to part of fuse block) and fuel pump relay. Could also be plugged fuel filter, bad pump or ?. but not likely because you get fuel while cranking. Check for error codes in the engine control computer (GM OBDII) as well but that probably won't show anything. Good luck and good hunting. I had a similar problem with a Chev Astro. Turned out to be power not getting to one bank of the fuse block because of a burned junction terminal buried behind the battery under the hood. Get out the multimeter and start looking for failed electrical components or broken wires.
There is a red and white wire feeding the fuel pump relay from a 30 amp fuse. Both the shutdown relay and the fuel pump relay are grounded by the PCM, so if the fuel pump relay is grounded it should be "on" and providing a direct link from the pump to that fuse. You should have battery voltage on that 30 amp wire before the relay and then on the dark green and black wire going to the pump. If you don't have battery voltage coming from the 30 amp fuse, the problem could be before the fuse. That 30 amp fuse is hot all the time, so it is powered by a fuseable link coming off the battery.
you should be able to hear the pump run inside the fuel tank. on the firewall there is a relay under the black cover on the passengers side, thats the fuel pump relay. the ORANGE wire should have 12V, The wire going to the pump is GRAY and should have power when cranking. . theres also a 20 amp fuse there, make sure its good. If the gray wire has power, most likely the pump is bad. At the pump there is a BLACK wire that attaches to the frame near the left rear wheel, thats the ground for the pump make sure its good and tight.
If the fuse and relay is good, and there is power AT the pump, then the pump is bad. Fuel pump power goes through the oil pressure switch but only after engine is running. So there should be power to the pump for approx 2 seconds when you turn key on. There is a RED wire (prime, it will be a single wire poking out near relay) at the fuel pump relay, if you put 12V on that wire the pump should run, IF the wires and pump is good. The GRAY wire powers the pump.
ECM B fuse supplies a constant 12v hot at all times to the VCM/PCM and to the fuel pump relay. The fuse is blowing telling you that there is a short to ground somewhere. Try this, take the fuel pump relay out and put a new fuse in. If it doesn't blow put the relay back in and if it blows then try a new relay. The relay may be shorted to ground internaly. Other wise you'll have to trace the wires to the VCM and the pump relay to look for a chafed wire that's contacting metal. The wire coming from the ECM B fuse is orange and has a splice in it going to the pump relay and the VCM/PCM. Hope this helps.....Andrew