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73-87 Chevy _ GMC Trucks => Fuel Systems and Drivability => Topic started by: waldosx5 on March 09, 2015, 05:57:35 pm
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I have a 1987 Chevy Pickup, 350 TBI. This weekend I replaced the fuel pump and the sending unit. After the install the truck ran great. I took it out for a ride that night with no problems. Today(2 days later) I went to crank it and I could no hear the pump. I checked and no gas was coming from injectors. I went and bought a new relay to see it that was the problem. If anyone has an idea throw it my way. This is going to be my son's first truck and he bugging the crap out of me to fix it. Thanks
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Did you check the fuse? Check the associated wiring? If it put a jumper wire to the red pigtail on the fuel pump relay to B+ does it run?
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Thanks for the help. Where is the fuse located?
and I hate to sound stupid but does B+ mean Positive Battery Terminal?
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and I hate to sound stupid but does B+ mean Positive Battery Terminal?
Yes
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Thanks again, I will try that and let you know the outcome but where is the fuse located for the fuel pump?
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afaik no "fuel pump fuse" but the ecm controls the fuel pump and if the ecm fuse either one is blown the pump wont work. but the main one that goes to the pump is "ecm B"
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The fuse is marked ECM B.
A failed fuel pump oil pressure switch will kill fuel pump voltage.
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Fuel pump circuit (http://www.73-87chevytrucks.com/techinfo/7387CKMans//Fuel_Emissions/X8736_1987_GMC_Light_Duty_Truck_Fuel_and_Emissions_Including_Driveability.pdf#page=94)
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ok here's what happened. I did the jumper test and nothing happened, I checked the fuses and they were all good. I went to crank it and the battery was dead(the key was left on all night)so I charged it. after charging I tried cranking it and it ran *great*. Now my question is, How charged does the battery have to be to run the fuel pump. It is a refurbished battery and it is about a year old, should I just break down and get a new one or do you think it may be something else?
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have you checked/cleaned all your ground wires? in my experience if the battery has any juice at all it will power the fuel sending unit.
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have you checked/cleaned all your ground wires? in my experience if the battery has any juice at all it will power the fuel sending unit.
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i wouldnt think it would take too much energy to at least turn the pump. BUT it might not have been enough pressure to do anything.
do you hear the pump when you first turn the key "on"
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I do not hear the pump and when I checked the voltage going to the pump i got nothing. I just bought a new relay and i cleaned all the grounds. This is killing me!!!
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dual tanks?
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Yes but only one is hooked up (like that when I got it) the one tank bypasses the switch and is straight line to throttle bottle and the switch inside the cab is hard wired. It has been running for years like that.
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make sure that 12 volts are arriving at the fuel pump relay on the orange wire.
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ok here's what happened. I did the jumper test and nothing happened, I checked the fuses and they were all good. I went to crank it and the battery was dead(the key was left on all night)so I charged it. after charging I tried cranking it and it ran *great*. Now my question is, How charged does the battery have to be to run the fuel pump. It is a refurbished battery and it is about a year old, should I just break down and get a new one or do you think it may be something else?
what happens now if you jump the 3" red wire
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I checked the wire and I get 12.2v going to the relay. I have two brand new relays and I'm having the same problem with each. What could be between the relay and the fuel pump that could be preventing power getting to the fuel pump?
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again I'm sorry for being ignorant but what is the 3" red wire. I jumped from the orange to red and nothing happened.
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the 3" red wire will be part of the pigtail that plugs into the fuel pump relay. look at the pigtail and you will see a 3" wire with a female spade end (do not unhook it from the relay) apply B+ to this wire it should energize the pump.
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when my 91 was acting up i was having the same problem and the relay wouldnt power the pump unless you gave it b+. my problem turned out to be my fuel tank switch. i would check those wires just to make sure nothing has come loose