97 C/K No power to fuel pump...
ibbygibbie
08-11-2007, 04:45 PM
I have checked all fuses and relays and I am stuck....I have no power getting back to the fuel pump...I pulled the relay under hood in the fuse box and am getting power to just one post...Was running fine and then tried to start and just cranks...What am I missing....What color wire should have power running back to the fuel pump(there are three)....Thanks
J-Ri
08-11-2007, 09:57 PM
I have checked all fuses and relays and I am stuck....I have no power getting back to the fuel pump...I pulled the relay under hood in the fuse box and am getting power to just one post...Was running fine and then tried to start and just cranks...What am I missing....What color wire should have power running back to the fuel pump(there are three)....Thanks
the relay should have power to two terminals. One should always have power, one should have power when the computer wants the pump to run (priming and cranking/running). The pump will run for about two seconds after turning the key on, then shuts off. Have someone crank the truck for you and check for power to the other terminals with a voltmeter. Using a test light can overload the output from the computer. Check the other two terminals for continuity with ground. They should be zero ohms.
A quick check for a bad fuel pump is to pound on the bottom of the tank with a deadblow hammer or a rubber mallet while cranking. If it starts then, the problem is either a bad fuel pump or a loose wire on top of the tank.
the relay should have power to two terminals. One should always have power, one should have power when the computer wants the pump to run (priming and cranking/running). The pump will run for about two seconds after turning the key on, then shuts off. Have someone crank the truck for you and check for power to the other terminals with a voltmeter. Using a test light can overload the output from the computer. Check the other two terminals for continuity with ground. They should be zero ohms.
A quick check for a bad fuel pump is to pound on the bottom of the tank with a deadblow hammer or a rubber mallet while cranking. If it starts then, the problem is either a bad fuel pump or a loose wire on top of the tank.
ibbygibbie
08-12-2007, 12:19 AM
Thanks I will check for the power next....I have had to do the ol beat the fuel tank to my sisters suburban before...Of the the three wires leading back to the pump the center(purple I think) wire was showing some power but very weak...If I don't show power during or after cranking is there a module or ecm I need to trace down...Thanks again...
777stickman
08-12-2007, 11:32 AM
The Grey wire is the one that should have power on it at the fuel pump plug. The black wire is ground and the purple wire is the fuel guage signal.
At the relay socket the power you're getting is from the ECM B fuse. Pull the relay and turn it over so you can see the pins. Look for the numbers 87 & 30 (very small numbers). Match those up to the socket. #87 should be where you have the constant power. Put a jumper between 87 & 30 and you should have power on the grey wire at the pump.
The relay control circuit comes from the VCM. Pin #85 is control power and #86 is control ground.
At the relay socket the power you're getting is from the ECM B fuse. Pull the relay and turn it over so you can see the pins. Look for the numbers 87 & 30 (very small numbers). Match those up to the socket. #87 should be where you have the constant power. Put a jumper between 87 & 30 and you should have power on the grey wire at the pump.
The relay control circuit comes from the VCM. Pin #85 is control power and #86 is control ground.
4 wheler
09-14-2007, 10:50 PM
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Hey man I may have your trouble solved. I have a 97 C/K 2500 Chyene HD and I had the same issues your talking about.
Drop your fuel tank and pull the pump assembly then unplug the pump wire plug from the housing connector to see if the metal prongs are burnt. If so this may be the culprit. I don't know if you can just replace this contact, I just replace the pump assembly, fuel rely,fuel filter and the pump so all would be new. It has run like a top since I did this work and there have been no starting issues either.
Also remember to change you fuel filter when you do this. I had a pump to burn out due to an old filter about 3 years ago. Go figure
I shopped around and found every thing (fuel pump, pump assembly, fuel filter and fuel rely) in the area of $ 300.00 bucks. I choose not to use mechanics.
Good luck to ya.
4 wheler
Hey man I may have your trouble solved. I have a 97 C/K 2500 Chyene HD and I had the same issues your talking about.
Drop your fuel tank and pull the pump assembly then unplug the pump wire plug from the housing connector to see if the metal prongs are burnt. If so this may be the culprit. I don't know if you can just replace this contact, I just replace the pump assembly, fuel rely,fuel filter and the pump so all would be new. It has run like a top since I did this work and there have been no starting issues either.
Also remember to change you fuel filter when you do this. I had a pump to burn out due to an old filter about 3 years ago. Go figure
I shopped around and found every thing (fuel pump, pump assembly, fuel filter and fuel rely) in the area of $ 300.00 bucks. I choose not to use mechanics.
Good luck to ya.
4 wheler
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