Was wondering if I could just unscrew the 16mm nut on the fuel filter, unhook it and turn the motor over to see if the pump is pumping gas to the filter. I need to see if the pump is out; or, does the system have to be pressurized for the pump to work? I changed the filter out as I thought no start problem may be a clogged filter, but the engine turns over strong but won't start. I see the good threads on replacing the fuel regulator and the admin's good threads on the rest of the ignition tests, but wonder if my shortcut above would eliminate a fuel pump replacement as I really don't want to drop the tank if I don't have to. Thanks! Terry

 

Not really a good way to test. Even if you do get fuel to come out when you turn the key on, that doesn't mean you are getting enough pressure. Then you'll just be stuck with a bunch of fuel sprayed all over the place.

First, determine if you pump even kicks on by listening for it. No noise, check the fuel pump relay (though I've yet to hear of one of those going bad). If it does kick in, check the fuel pressure.

Many, many threads cover this.

 

By the way your pump is electric so you don't have to crank the engine to get it to make a mess. AJBert's dead on about the other stuff. If your fuel guage works then the pump ground is probably good too but that's not 100%. There's a gazillion threads on fuel isssues on the forum. What are we working on? It would help to know.

 

He doesn't say what year the truck is but on mine the pump ground comes from a splice pack on the rear of the frame, fuel level sensor ground is supplied by the PCM so they wouldn't correlate. Your 94 might still have the analog gauge and frame/chassis ground but I'm not 100% on *that*. Buy or borrow a fuel pressure gauge and check it, if you're lacking 5psi of the minimum recommended you'll have start problems.

 

tks guys, I'll try fuel pressure...1999 v6 4.3l

 

RonJon, about the gas guage (digital) the grounds for both the pump and guage are on the same ground at the rear crossmember. I know. I changed the sender and the pump. Did look in the Factory Service Manual though just to verify. Ain't no biggie anyway.
Terbates, yes a fuel pressure test would do you good. So you have some kind of manual that tells you how to do the test? If not then there are about a thousandposts on the forum that'll tell you how.

 

To be honest, no I didn't check. I was home and too lazy 9:30 at night to go to work and look at the FSM to verify. <laughing> I usually verify, keep my mouth shut, or qualify it as a guess and I felt confident in my memory. (maybe I was thinking of the pressure sensor?) I figured all in the displayed info came over the class 2 network digitally so the return was a regulated one supplied by the PCM. And..... I was wrong! G105 (for the gauges), located on the rear of drivers side head near the knock sensor (on a 2000, 99 is similar I'm sure) The fuel level sensor ground *is* supplied by the PCM so I was half right at least. Terbates, above the posts is a link for "fuel system diagnosis", that'll tell you what you want to see and as Gimpy pointed out-*lots* of helpful posts here.

 

Apples and oranges I believe. 1994 vs 2000. Anyway Terbates, if you need help on the fuel pressure test let us know. RonJon probably has more current info since my Blazer is the last year of Gen 1s.