5.7 1996 new fuel pump won't start

[Rynkinasz]

Ok...so for the last month my truck has been starting hard. Mechanic said it sounded like fuel pressure regulator and I didn't have time so I had him put it in. Ran better for a couple of days and started acting up again. Took it back to mechanic and it was giving a lean fuel code. Checked fuel pressure and it was at like 20psi. He said pump was bad. I just changed the pump and it started immediately and ran fine. An hour later I had to go outside so I figured I'd try to start it again. Nothing. Fuel pressure at 0. Pump will not kick on. I've tried running a ground to the black wire straight from the battery. I've tried jumping the fuel pump relay (87 and 30 I believe). Pump did not kick on. Will start and sputter on starting fluid. I have an MAF code, but I wonder if that comes on because I tried unplugging it to get it to start. Also getting both lean fuel codes and I've had the cam/crank code for 5 years. Anything?

[Jsdirt]

Sounds like you may have a wiring issue to the pump. These can be a real PITA to diagnose and find, even for some seasoned techs. MAF code was probably set by cranking with it unplugged.

 

You need to be SUPER careful jumping relays - if the wrong pins were jumped, even momentarily, you WILL fry the driver in the PCM in the blink of an eye. I've nearly done that myself a time or 2 - caught myself before I did any damage, thankfully. It's easy to do without realizing it, because as you pull the relay to look at what pins are what, you're looking at a mirror image of the pin layout in the box - everything is backwards! Best way to jump it is with a test light - that way if you accidentally hit the wrong pins, the chances of frying the driver go way down. I still mark the relay with a white paint pen at the proper terminals, flip it back over like I'm going to install it, then mark the 2 corresponding female terminals in the box.

 

Best to have 2 people troubleshooting these. One can turn the key, the other can listen for the relay "click" - the click just means the control side is probably good - the relay can still be bad, even though it clicks. Next step would be to test for 12v at the relay. If there's no power there, that needs to be fixed, or the pump won't run. If that all checks out, you'll need to check for power and ground at the pump connector.

 

Keep in mind that these days it's entirely possible to get a bad "new" pump, right out of the box. Yours may have failed after the initial run. Might not be the case, but something to keep in mind when troubleshooting.

[Silverado4x4]

+1 Don't go out and buy a cheap pump or reman as they are hit and miss on them working. Trust me stick with the original new AC fuel pump. If seen people cheap out with aftermarket pumps and some work for a while and some don't work at all.

[Jsdirt]

These days you get the same odds, even with OE stuff. Seems the stuff they sell us after the initial sale is further down on the quality chain from the original parts, unfortunately.

 

I see parts straight from GM that say "Made in China" on the label more and more these days.

[Dnt]