meissen

Hey guys,

Having a hard time believing it's the fuel pump, just wanted to see if anyone could think of something we didn't think of in the PCM that might be stopping the car from starting.

Fuel pump doesn't prime. I can faintly hear the click of the relay on the driver's side with the kick panel still in place. My dad measured voltage at the fuel pump connection on the rear end and he said that it's getting the 12v switched source and it's getting the 12v constant. Everything on the plug going from the body to the fuel pump seems to be OK with the voltmeter.

Is there anything with the PCM that would give power to the fuel pump but still not allow the fuel to get there? It sounds pretty stupid asking it I'm just having a damned hard time believing that we drove the car into the garage, put it up on ramps, dropped the engine out, rebuilt the engine, put it back in, and of all things the fuel pump - one of the parts we never touched - is now completely dead... but hey, weirder things have happened.

What do you guys think?

meissen

And second question - if the pump is bad, is it OK to buy the high pressure walbro 340 for a completely stock setup? Found a good deal on one.

tom2

You would only have voltage back at the tank for a couple seconds after key on, then nothing until the engine is running. You sure you're checking the right wire?

meissen

Well, I'm going off what my dad told me he did. He said that the fuel pump plug had 3 wires. He measured and ensured the ground was good and then tapped the wire that the service manual said was the power wire. He said he was able to measure 12v when the pump "should be priming" and that it did 'turn off' when it would have stopped priming. I think he said he had 12v when he was cranking or that he was able to get a 12v constant measurement as if it was "on" at some point too...

mcssmostwanted

i was there when we measured the voltage upon cranking we had proper voltage.. either there is no power getting to the pump or we figure the pump is bad im going to grab a harness from a work camaro and see if we can get that one to turn the pump on and off.

moparman

You need to test for pressue at the Schrader valve on the fuel rail on the back of the intake.

bw_hunter

There is a priming connector under the hood. Go to shoebox's page to find it. When this is engaged, there is voltage tot he pump. Voltage at the pump connector, with no pump sounds, indicates a failed pump. If you have pump sounds, measure the pump pressure at the underhood schrader valve as suggested above.

To tell the truth, it does sound like a bad pump.....

meissen

Yeah, it's gotta be a bad pump then. My dad said he measured voltage at the prime connector and it measured 12v. No sense in measuring pressure at the schraeder valve - I opened it up and there's not an ounce of gas at the valve, didn't even feel pressurized when I pushed down on the valve using one of those valve stem removal tools.

Crazy that it just took a dump like that with no warnings. Of course we weren't measuring fuel pressure, but the car was running fine before the lifter collapsed and we pulled the engine out to replace the lifters. Ah well, time to suck it up and get to cutting.

moparman

The fuel pump on my car failed without warning.

mcssmostwanted

yea it has good ground and voltage... damn pump time for a walbro 340

97FormulaWS-6

They can and do fail without warning... and with it sitting and not moving for a while while you were rebuilding the car; I can believe it.

jsetzer

Yep I've killed a couple of pumps.

The test port is a good way to check though. Just jumper 12v to it and if the pump ain't running...

mcssmostwanted

I wonder why they fail like that... I had my car down for almost 1 1/2 years and the SOB worked fine.. silly pumps..

meissen

We're only talking a couple months at the very most, though... we just dropped the engine out, replaced lifters, put some headers on, put 'er back in the car. Cars sit longer during the winter months around here.

I'm a little confused on that. My dad measured the jumper with a voltmeter and it registers 12v on the volt meter. If you then supply an already hot [powered] wire with 12v straight from the battery, what good is that doing?

meissen

Well, I'm happy to report that my dad swapped my bad stock v6 pump into his car and it fired right up. The pump loses PSI as RPMs go up when I was using it on my LT1 with 30lb injectors, so we're just using it to make sure it was the pump that was bad. Hoping that the PSI loss will be slightly less with the stock injectors but I vaguely remember that the injectors don't have much of an influence on the PSI.

Funny story, though - my dad and I are firm believers in the trap door method after replacing my pump in my Camaro. So he gets the carpet pulled back and low and behold he's not the first cat to be staring at the trunk with a cutoff wheel in his hands. Someone did a 3-sided trap door and then bent the metal over to replace the fuel pump. Then when they were done with the swap, they folded the metal back into place and FIBERGLASSED over the trap door. Since they couldn't even do the trap door correctly, I'm guessing they bought some cheap chinese off-brand POS pump.

Well, then my dad wanted to test the pump. So he rigged some jumper cables to the battery and gave the pump 12v. It made a grumble and then stopped. So he did it again and it made a louder grumble and then stopped. Did it a third time and with a "whoosh" it started spinning and working. Needless to say, he's not putting it back in...