Fuel Pump Has No power in a 1990 Chevy Suburban 5.7L Fuel Injected (K) motor?

Question

I just replaced fuel pump, sending unit, filter, relay, and fuel line. Took truck for a short drive then died. After 2 minutes truck restarted and continued home and let run. Died after 5 minutes. The relay has power, and put 12 volts to new pump and old, they work. I am absolutely positive that there is no fuse for the pump and can't figure out why. When using a scanner it asks me to test the G (bottom left) terminal of the diagnostic socket, but there is no wire lead in the socket. I am starting to think maybe the computer's bad but I'm not sure. There are no trouble codes either. Has anyone run into a similar problem or have a suggestion on what to do next? This problem seems to come and go beacuse this is the original complaint, but in the begining I had power to the pump and now I do not. Any help or suggestions would be greatly Appreciated. - Thanks

If there is a fuse for the fuel pump it's not labled as it is in my 89 Camaro. My father who's been a mechanic for over 30 years also told me there was a fuse until he looked for himself.

I've already tested the tan and white wire(fuel pump) And the female harness is new(came with sending unit). There are alot of inline fuses in the engine compartment. But how would you explain this only happeneing sometimes? A bad fuse wouldn't work at all.

Answer 1

Talor245 is wrong your computer does not control the pressure that comes out of the pump. the fuel pump puts out a constant pressure wich is the regulated by a vacuum pressure regulator when vacuum is high the regulator lowers the pressure going to the fuel rail the injectors are hooked to because the vehicle would be at a lower rpm or load an would not need the pressure at this time. When you step on the gas throttle the engine loses the vacuum it had and then the regulator redirects more of the pressure to the fuel rail so the truck can get as much fuel as possible out of the injectors. He is right that the computer controls how much fuel the vehicle get by pulsing the fuel injectors in millisecond incraments. The more fuel the vehicle needs the longer the pulse are and the higher the fuel pressure will be. Not all regulators work this exact way some work on back pressure and have pressure on either side of them. They will be set up that as long as x amoun of pressure is on the side of the fuel rail it will dump the excss fuel back in the fuel tank if the pressur drops below the desired pressure it will allow a valve to open up and allow more fuel to come in wich will increase the amount of fuel pressure because fuel will come in quicker than it leaves.

The rest of the answers you recieved were all right on the money. If you cannot find this problem I would suggest taking a test light and hooking it up the positive wire back at the fuel pump connector and the other to the ground side of fuel pump connector while the pump is still plugged in (it has to be plugged in so the vehicle will run you should still be able to see the light light up though). Then I would take a different test light at the same time and hook it up to the control side of your relay that would be the side that your ECM engine control module would control. again hook it up just like the fuel pump not in line but parallel make sure where you hook it is before the relay and not after hook one wire directly to the wire going to the relay and the other to ground of the vehicle you may have to get jumper wires to do these test. After I hooked up these two test lights then I would hook another up to the controled side of my relay. I would hook it up one end to the power supply side of the relay and the other to the bodies ground. With these three lights hooked up you should be able to start the vehicle up and watch these lights and see wich light goes out first. If the light that is hooked up to the ecm goes out first you know that either the ecm is faulty or you have some kind of connection problem probably due to corrosion or a stretched out female terminal. If the other lights go out first you will know that there is a problem in the controlled side of the circuit and you will want to look at all the ful length of the wire it is connected to before and after the relay if the light goes off before the relay mostlikely it is a faulty problem from the power source to the relay if it goes off after the relay most like it is after the relay assuming that the relay control cicuit is fine. The reason It is important to know what light goes off first is once the vehicle has quit running the computer will shut off the fuel pump after two seconds of vehicles engine has stopped turning. Remember electricity always follows the path of least resistance If it can go directly to ground without going through the fuel pump or whatever it is supposed to be powering up then it will. It could be a wire that has rubbed through and every once in a wile it hits the frame and grouns out or it could be when the vehicle gets hot the resistance in one of the connectors for the wiring harness builds up resistance and uses up an excessive amount of electricity there and robs to much power to let the motor run.

Answer 2

dodge man is right, there is a fuse, it may be in the fuse box, or it could be an inline fuse beside the fuel pump relay. The oil pressure switch is in the circuit, but it shouldn't shut the engine down. Check for 12 volts at the tan and white wire in the pump power feed harness where it connects to the pump harness, you may have a bad connection at the terminal(the female terminal is prone to getting deformed and will cause an open circuit) then check the ground wire that goes to the truck frame. When checking for power at the T-W wire just touch your test light gently to the terminal and have someone turn the key on, the computer will only power this wire for a few seconds, then it will be dead.

Answer 3

1990 Chevy Suburban

Answer 4

check under hood there are fuses in engine compartment its possible that it is the oil pressure sending unit it WILL shut off the fuel pump ive personaly had this problem in a work truck and it left me on the side of the road would run fine just as yours then stop you could try one i dont recall it being real costly good luck its hard when it works ''some times''

Answer 5

i own a repair shop,and there is a fuse for the fuel pump is located in the fuse box for it,,i have one now working on it and its a 91 model,and it does have a fuse for the fuel pump on it,,just look real good in the fuse panel and you will see it there I'm redoing one for a customer ,And i have ran across this problem before on them,,good luck i hope this help,s.

Answer 6

possibly oil pressure switch, if im thinking right the oil pressure switch will shut down the fuel pump if the pressure gets low.

Answer 7

the computer would be a good guess it controls the amount of fuel and pressure . if you compare the price of a car computer to a PC you would think that for the price the computer in your car could tell you more all it does is monitor your car systems and it cost more than a desk top computer