yes once the car is on it runs perfectly no problem at all not even in idling, even if i turn it off for a few hours it turns back on as if no problem unless its left for over 5 hours or so.
If that turns out the be the culprit . . . I highly encourage you to be an entire fuel pump and sending unit assembly. Do NOT buy just the pump, and reuse the old sending unit and sock. You might regret that
i already bought a full fuel pump assembly a few month back just incase. i will try a new relay tomorrow if that doesn’t fix it then in goes the new assembly.
Removing a fuel tank on an S-10 Blazer is actually quite difficult, versus a Silverado of same vintage, and that’s if you’re using a hoist. Can’t imagine how much harder it would be with jack stands . . .
Clearly you won’t drop the tank unless it’s nearly empty
You’ll have a helper
And you have a spare car to drive, in case something goes wrong
Why is almost everyone ignoring the OPs statement that if he hooks 12volts to a wire under the hood, the car starts and runs normally. How can it be a fuel pump problem???
The fuel pump runs and the car “starts as if nothing is wrong” when he hooks up 12V to the fuel pump via a wire under the hood. This suggests power is not getting to the FP via its normal route: that would include the ignition switch, the FP relay, possibly a computer, oil pressure switch, etc., etc.
Agree but if it is the anti drain back, energizing the pump full time may be enough to provide pressure to run where just the few seconds of the pump running when the key is turned on may not be enough to do it. So it may be just a false flag.
That means your fuel pump is OK. Instead of connecting that wire, try the key dance: turn key to Run (not all the way to Start. The FP should run for a couple seconds then turn off. You may hear it. Turn key to Off, then to Run and pause a couple seconds for the FP to run again. Each time it runs it brings fuel and fuel pressure to the engine. After a few steps of this “dance” turn the key all the way to Start.
I have had to do this a few times on my 1999 Honda Civic, especially when the fuel level is low and the temperature has dropped. As Tester opined above, it’s probably the anti-drainback valve in the fuel pump assembly allowing fuel pressure to drop; could also be a leaking injector or fuel pressure regulator. If the key dance works, that’s easier than any repair!
the key dance didn’t work. i have a new injector assembly with new fuel regulator. its either the pump is weak which i still dint have time to borrow a pressure tester should be tested. and the relay. i will bypass the relay tomorrow morning if this works then i need a new relay if not will test the pump pressure.
The normal starting sequence doesn’t cause the pump to run 30 seconds or more before beginning cranking. I’m presuming the OP"s test-wire-jumping method allows the pump to run for a good amount of time before they get back in the car and crank the engine. That time could be allowing the pump enough time to build the fuel pressure to the proper level to start the engine. While it seems unlikely the pump’s basic function is the problem, the clues are consistent w/ a faulty check valve. Since the check valve is part of the pump ass’y … well you get the idea.
OP could have a fuel pressure hold-test performed to explore this possibility.
Thank you everyone for your help it turned out to be the valve in the pump assembly its not holding fuel and its taking alot off effort for the pump to pump fuel all the way from zero to injectors i changed entire assembly and all is well now
