Hi, first time poster here. I'll try to keep it short. I have a 99 zr2, all at once it wouldn't start, cranks over but will not start. Will run putting fuel in the tb. Dropped tank, took out pump assembly, removed pump motor, hooked to 12v and motor runs. Engine compartment fuse is good. Checked harness at tank, short pulse of 12v. Hooked motor to harness, had a buddy turn the key on and pump barely runs, I mean barely. I don't know what else to check, or do I just replace the pump motor and quit thinking to much? Thanks

 

Check your fuel pressure using the valve in the engine compartment and a fuel pressure tester, you can rent one from advance auto parts or any loaner tool program store. These trucks are VERY picky about certain things, fuel pressure is one of those things, you could have 52psi up there but it wouldn't be enough. these trucks like to see 58-65 psi.

My truck gave me no warning AT ALL, i drove it somewhere one day, shut it off, and when i went to leave BOOM no fuel pump, no noise, nothing. Just broken.

I recommend replacing the pump (if needed) with ONLY a Delphi or ACDelco....Any other brands and you're just asking to have to do it again in a few months to a year (if the pump you get even works AT ALL out of the box if you don't go with either brand).

I also recommend replacing the pump and sender as a unit, however that's just my preference, why drop the tank twice if the fuel gauge stops working in a month or two.

If you click the link in my signature there's a tech article section, you will find testing procedures for the fuel system in there.

 

sounds to me like pump is shot...it seems you found everything else to be in order.
and you stated it would run with fuel directly added...so looks like pump is at fault.

 

I agree with that, but I'm a stickler, test test and test again. Because if it's not the pump and you (with all good intentions) said it is, well he's gonna be pissed at you for diagnosing improperly

 

A fuel pressure test will tell us everything if its fuel related...


Do it before spending money. If its below 60 psi at key on,and doesnt stay above 55 for 10 min,its the pump.

 

Check volt at pump connected and running. should be over 11 volts TO FRAME, Check neg wire to pump TO FRAME with motor running. should be less than .5 volts
If grd {black} is over .5v, remove and relocate G402 on top crossmember above differential to bared metal rear of crossmember.
If your FP connector is 2x2 pin, it either is now, or will be, bad.

 

Thanks for the info, the general vibe I'm getting here is that it is the pump. I don't get pissed very easy and will not in this situation. If I do have good pressure and it still will not start, what are my options?

 

Fuel line clogged, clogged fuel filter, things of that nature.

 

That's the problem with that knee jerk FP problem response.
I gave you specifics. IT may be bad connection it was for me. And several other people on here. One fix does not fit all.
I now have a perfectly good Delphi FP sitting in my garage. It has 107K on it. But I damn well replced it with a Delphi, costing me 359 for essentially a new connector but I aint sorry.
The problem was in the trucks 2x2 connector. That's why they were replaced. That's why all the 2x2 AC Delco available are NOS, discontinued stock
.Problem being you cant check that 2x2 connector without tearing it apart. G402 ground probs also show up in weird rear light problems, Fuel level probs and intermittent evap codes. Any or all.

If you have good pressure, good leakdown, and crank and still good pressure and it wont start then Fuel pressure or filter is NOT the start problem.
If the pump sound good connected directly to 12v but anemic and tired when connected to harness then you will not have good fuel pressure within the 2 seconds priming time and probably never.

 

Yeah.. there are two styles: the factory 2x2 and the 'Oopps we FU - AGAIN" 1x4 that comes with every over the counter replacement..
- disclainer: Ford does it too. For years you couldnt buy an alternator that didnt come with a new connector to wire in.

Rockauto still caries the replacement 2x2 pigtail for the harness though I think it may be a clearance item too.
And checking the voltage on those pins without the pump hooked up and running wont work. Because there has to be current flow for a voltage drop to show up