SuperSport88

Okay, I have a 95 Z with some minor bolt ons. A few weeks back I posted the symptoms of the car cranking but not firing after sitting for a few hours. Well found out that with the pump primed and shrader valve depressed = no fuel. SO i replaced the pump with a Granatelli 255lph which i hear is just a walbro pump with the name rubbed off. Well the car ran great for a few weeks until today while driving to work the car just chocked itself out. Felt like i was in too low a gear for a slight hill then when I down shifted, pushing the gas did nothing. Car cranked forever but doesnt start again. SO i had the car towed home, checked for gas at the s. valve and nothing. Before tearing the pump apart (which i can plainly hear prime) i decided to change the fuel filter once more to make sure that it wasnt a junky clogged up one. Changed that and now i can get fuel to squirt out of the shrader valve. The car will start for literally a second and die. It does this all before anyone can blip the throttle by pedal or at the motor. Heres the real questions:

1.) IF the pump was a dudd, would it still sound normal and prime itself for 3-5 seconds and stop???

2.) Could it be a bad regulator even though the vacuum lines arent soaked with fuel???

3.) Bad ICM??

I'm all out of ideas. It seems like those who tear the **** outta cars have their's run fine and those who baby and take EXCELLENT care of them have them give them problems (ME). That is all.

cehan

Get a fuel pressure test gauge and connect it at the test port. As best as I can remember on mine, when it first primes, the pressure goes up to about 25 psi.

SuperSport88

Another question for you folks: Should I even mess with the hassle of sending this one back, receiving another since it has a warranty, and waiting for them to give me a refund or should I bite the bullet and just get a genuine gm pump and call it a day???

SuperSport88

Hooked up a fuel pressure guage and when primed the needle doesn't even budge. Verified that the guage works by checking it on my father's silverado and another buddys car. Ordered another pump, a gm one this time. Any suggestions as to why it wouldn't be the pump?

Injuneer

Should produce at least 40psi when it primes. May drop off rapidly when the pump shuts off (not good), or it may hold that pressure and bleed off slowly (good).

Are you sure you got all the hoses securely connected to the new pump?

Cobra2k7

I just dealt with this issue. Priming the pump ignition on only, nothing. Primed it 6 times, barely got 7 psi and it drops rapidly. I changed the pump yesterday and found the hose between the pump and hard steel lines, had a hole in it from rubbing against something. I probably could of just changed the hose and been fine, but i figured since i was in there id change out everything. Resealed the bucket and ran my wiring harness(racetronix kit) and now she fires up first crank and holds pressure properly.

SuperSport88

Cobra- That is exactly what happened. The line from the pump to the sending unit had the outer shell of the line all ripped to shreds (none actually torn off though) and a tiny hole in the line. Ran to Autozone and got a high pressure fuel line hose and hooked it back up and cut it to fit better and she fired right up. Thankfully that was all the problem was, knock on wood. The pump is quieter now and sounds like its running much better and easier. Gonna hook up the pressure guage again tomorrow to verify the pressure is in the desired range. One last question: Even though it was only a short time period, the pump should still be fine am I correct??? Thanks for all the help and opinions everyone.

Injuneer

What would have damaged the pump? It was pumping fuel. The fuel just happened to be flowing out the hose instead of toward the engine.

SuperSport88

Thanks for all the help and support so far. I have some bad news tonight thought. I went to the test and tune at the local track and ran into some problems still. The car seems to be very weak and doesnt even wanns spin the tires when mashing the throttle. Used to just light em up. At the track it would severly bog down and seemed to misout or choke out, but heres the catch. Ive had to replace an opti so I know what that feels like when it breaks up. This just felt like it had power for a second, then lost it, then got it back, etc. Too tired tonight but will check fuel pressure and plugs tomorrow. After replacing the fuel line the car ran extremely rich and poured black smoke, even when just free revving in the driveway. ALso, the car seems to have to be cranked alot longer. I'm leaning towards the plugs becoming fouled up but, as always, I am looking for the guiding light and knowledge of others to fix the beast. Thanks.

SuperSport88

Thought of a few more facts and questions. I just checked the plugs and they look brand new. My pressure guage is at my g-pa's, but when depressing the shrader valve I could hear air escaping follow by a tiny trickle of fuel. So i tore the pump out again. The bucket's sealant failed some. About have the distance around of the bucket wasn't sealed to the lid anymore. HOW much of a problem is this??? Does it have to be totally sealed or just enough to keep em together. The second part is that the new high pressure fuel line was still intact, but it also had a few air pockets between the inner and outter layers. This is what I assume led to destruction of the first line rupture.

If NEITHER of these things has much to do with the pressure in the lines and i can plainly hear the pump priming, but with no pressure, could the pump actually be bad if it still ran enough to get me home from the track??? Or should I try a new regulator ???? Even if the vacuum line isnt soaked with gas could the regulator be bad enough to cause a hard start but let it run enough to drive around but not be able to go WOT ???

As always, any suggestions and opinions welcomed.

Injuneer

If the hose was leaking when you shut the engine down, the fuel pressure was low and the PCM would have raised the long term fuel corrections to increase the injector pulse width. When you started it back up (unless you pulled the power to the PCM at some point) with the replaced hose, it would have been using those elevated long terms to fuel the engine, and it would have run pig rich until the PCM could reduce the long terms.

Even though you bought a high pressure fuel hose, is it rated for exposure to gasoline on both sides - inside and outside of the hose? It sounds like the fuel vapor is destroying the structure of the new hose?

If it sucking air, there's something wrong on the inlet side of the pump. Once its run for a couple minutes, all the air should be out of the rails.

Run it on the road with the fuel pressure gauge taped to the windshield, so you can observe how the pressure responds under load. If you have access to scanning software, a check of the long term fuel corrections will tell you if you are having fuel delivery problems.

Is your pressure regulator stock, or aftermarket?

SuperSport88

Thanks for all the help Injuneer. After fixing the fuel line the first time, it ran really rich and felt low on power, so after getting back to the house I unhooked the negative terminal on the battery to reset the pcm. This really helped the car. My G-pa was out of town so i didn't have access to his guage yesterday but the car ran good all the several times I took it out, so thats why I took it to the track.Once there, it seemed to run like it did before I unhooked the battery, but with the sort of miss I described earlier. I will put it all back together and as long as it starts I will hook the guage up and take her for a spin.

My fuel pressure regulator is the stock unit from 95. I know kind of think with all this help that maybe it went back and lets all the pressure bleed back super quick. The funny thing is thought that the vacuum line isnt soaked with gas. Guess time will tell.

SuperSport88

Finally got a guage hooked up to the s. valve. When primed, it read ~40-42 psi, but bleeds off within a minute to about 26-28psi. Once running, it reads around 40 also but when revving it goes up a tad but back down to a little below idle pressure. With the fpr vacuum line off, the psi went to about 48-50, which is normal from what I've read. SO, I've concluded its not a pump, fuel filter, or regulator problem and is likely a leaky/bad injector letting the pressure escape. Gonna pull the rails in a bit and see if any leak with KOEO. If any of my logic seems wrong or if any other opinions arise, they are most welcomed. Thanks.

SuperSport88

Pulled the rails and no leaks whatsoever. Now the pressure stays at 40-41, but decreases to about 35 when revving, but the engine sounds like it has a slight misfire, enough where I didn't wanna take a trip around the block. Gonna pull all the plugs and check em. Any ideas???

'94 Bad A Z28

A failing pump does this. Your FP should not drop when you hit the gas... especially on a all motor car, there is no reason for this other than a weak FP. My FP barely blips down 1-2psi and instantly back up when I spray the car. The only reason for this "blip" in FP is because another fuel line is opening up and needs to be pressurized.