QuestionHave replaced the fuel pump my 97 S-10 4x4 pu.
Had it started once but now will not start.
Pump runs for 2-3 sec. then shuts off. Can't
get any fuel to come out the schrader valve
at eng. Can get stream of fuel to flow at
pump outlet, looks heathly but I do not know
the pressure. Eng. will fire with starting
fluid so ing. system is working. Can you tell
me what to check next or what to look for. I
replaced the pump only in the modular unit...
not the complete assembly. Thank you for any
help you can give me. I cut a hole in pu box
so pump unit is still very accessable.
AnswerHello Craig,
Unique idea, cutting that hole. Wish GM would do that.
Sounds like your pump is acting like it is supposed to do when the key is turned on. Due to lack of a crank signal, it stops after that time.
If you want to check for power at the pump, connect a test light, and see if it stays running while you are cranking the engine.
If not, there is a crank sensor that sends a signal to the computer, which in turn operates the fuel pump relay, running the pump.
I assume you have checked the fuses. You can also check for battery voltage to the injectors. When the key is in run, there should be power to one wire of each injector, and as the engine is cranked, the power should pulse. A noid light is used to check that.
As for the fuel pressure, if you have throttle body injection, which looks a lot like a carburetor but has two injectors in the top, then the pressure should be 13 PSI. Other types of injection require more, some around 45, but I think you probably have TBI.
There is a fuel pressure regulator in the TBI unit, and pinching the return line from it can be used to test it, to see if it is returning too much fuel.
Then, there is the filter, which should be under the truck, along the frame. Remove it, and connect a gauge to the line from the tank if you don't have access to a fuel pressure tester. You could also teat back at the tank unit since you have access there. You can use a jumper wire at the fuel pump fuse, to jump battery voltage to it, and make the pump run while testing pressure.
I don't know why you changed the pump, but I was going to replace a pump one time that was running, but my pressure wasn't high enough. Upon removing the pump, I wanted to see what the deal was, so submerged it in a bucket of diesel fuel,(much safer than messing with a bucket of gasoline, and sparking jumper wires). With the pump running, it pumped up a storm, but when I restricted the end of the tube, that little hose where the pump connects to the tank unit, was split, and would spray fuel out inside the tank. I connected my pressure tester, and it did it at exactly the pressure I had observed, which was 7 PSI. Everything over 7 just sprayed inside the tank.
Replaced that little hose, and saved $60.00. Worth thinking about. Did you replace that little piece, or just use the old one?
PS. The normal method is unbolting the bed and two guys lifting it and moving it to the rear a couple feet.
Van
