clarkinTulsa

Hello. I have a stock 95 Z28. Last week it wouldn't start.My buddy had a fuel pressure test guage and it didn't register any pressure when cranking so I started looking for a pump. I found one on Ebay ,Carter, at a good price (this thing is about to break me, rear end, transmission etc have gone out in the last couple of months). So I installed it and when I tried to start it it started after a couple of tries. Then it would only turn over. tried things for two days to get it running. The pressure on the new pump reads 45psi when priming then around 39 or 40 when cranking. The pressure bleeds of pretty fast which I know is a problem. I got it to start once the next day and drove it around the parking lot (all this is taking place at my work) for about 15 min while it was running I did not have the gauge on the port. While it was running it had a pronounced lug when the gas was quickly applied. Then it died and would not start. I pulled the tank again yesterday and inspected everything and put it back together once again. I tried to start it with no luck. Today after work I went out and it started and ran for a while, still with the pronounced lug. I did have the gauge on it today and while idling the psi was about 35. I performed the fuel pressure regulator test by removing the vacuum hose and the psi jumped up about 5 psi so that eliminates the regulator correct?? I am now convinced after reading about the subject on this forum that the pump check valve must be defective so tomorrow I am gonna go get one I found from the salvage that is guaranteed. If it doesn't fix the issue I can return it. I have read on this forum that the OEM is better than the ones sold at the parts stores. So after a week I am hoping I have this figured out. So what did I miss? Opinions please! I have no experience with this type of fuel injection technology. I have worked on lots of old schoolstuff. Thanks in advance for your assistance!!!

Kevin Blown 95 TA

I don't see any sense in installing a used fuel pump. You can get a good replacement here Auto Performance Engineering - Walbro fuel pumps and more

clarkinTulsa

Not not a very user friendly site. I need to get this thing running asap. So again did I miss anything? Thoughts, opinions?

clarkinTulsa

Apologies. I should have been more clear. I was referring to the pump website that was linked

Kevin Blown 95 TA

Sorry for the misunderstanding - I deleted my post. That site does have an LT1 secton listed under the GM section LT1 F-body and B-body fuel pump kit see if that helps ya out.

clarkinTulsa

So today after work I installed the pump assembly that I got from the salvage. The priming pressure was 49 so the pressure was better but it would not start.again the pressure did not hold after thieving of the key. tomorrow I plan to use parts of the old assembly to block the return line to see if it holds then. So is it possible that the fuel pressure regulator could be the culprit?

Injuneer

Rapid loss of pressure could be the FPR. Have you found any sign of fuel in the vacuum compensation line?

Next would be leaking injectors. Pull the rails up, injectors intact. Turn key to "run" to cycle the pump (do not turn to "start") and see if there is any evidence of drips from the injectors.

You mention "dropping the tank". Have you considered cutting a hatch to facilitate easier pump replacement?

If you look for another pump, try this:

RX-FLT1-FPKG-2

clarkinTulsa

thank you for the response. no there is no sign of fuel in the vacuum line. when I did have it running the other day at idle I unplugged the line and the fuel pressure went up about 5 pounds which is what I read it should be doing. so can it pass this test and still be bad?

clarkinTulsa

So I got to go back up to my work and tried to start it with some starting fluid but no luck. I had my son with me so I pulled off a plug wire to see if I could see spark jumping off it when I put a screwdriver in it and held it close to ground. I got no spark.... ugh... Any thoughts? This is really getting old!!! **Edit** I tried again with the starting fluid and it did try to start a couple of times so I know it is getting spark

clarkinTulsa

My latest test was plugging the fuel return line. The pressure shot up to 90PSI when the key was turned to the "prime" position. Then began falling. I am guessing this tells me I have a leaky injector. So I see four bolts on top of the injector rail. I am guessing this comes straight off? I also wonder if I should unplug the plug on the fuel return line and hook it back up normally as 90 PSI and 40 PSI is quite a difference. So test at 40 PSI?

clarkinTulsa

I went ahead and pulled the injector rail out and tested it with the normal return line intact. I primed the pump three times and saw no leaks. However I did notice the schrader valve leaking so I went ahead and pulled the rail all the way out so I could get to it. So I am still befuddled what is going on????? Help!

Kevin Blown 95 TA

Not sure pressure pressure bleeding down is your entire problem, but keep in mind that any tiny leak will drop hydraulic pressure a lot because fluid doesn't compress very much - so lose a tiny bit of volume, lose all your pressure. From the test you did, sounds like your regulator is working. FYI, I once had an aftermarket fuel pressure regulator that didn't hold pressure and my car always started fine, warm or cold, but I did have a good, strong pump, so it was able to prime the engine even if the pressure leaked down.

clarkinTulsa

Is the schraeder valve a special valve? I stopped at a parts store abs they did not carry it.

clarkinTulsa

So here's what I did today. Stopped and got a schraeder valve (from a AC kit), and some new O rings for the injectors. I installed the valve O rings and injectors buttened everything back up and tested the pressure. I still am losing pressure. The car still would not start. I tested the power to an injector and with the key turned onto the prime position I got a buzz from the tool I was using so it tested good. When the engine was cranked I did not get a buzz though so not sure if I should be but I think so. I did not see any leakage at the shraeder valve. By this time we were soaked and pretty cold. I performed one final test- the old screwdriver in the spark plug wire test and held it close to a ground source while cranking and I got no spark. Should this old school check work on the new technology??? I unplugged the battery to see if I could get something to reset overnight... I'm sick of this!!!

Injuneer

There is always 12V power on the pink wire to each injector with the key on. The PCM supplies a ground to fire the injector. To verify the injector is getting the ground you need a 'noid light that plugs onto the injector. You can also measure the resistance of each injector with the harness plug off, should be in the range of 12-15 ohms However, is an injector circuit is faulty, the PCM sets DTC 18.

Rapid fuel pressure bleeddown can also be due to a leaking line, including the line internal to the tank. It isn't unheard of to have a pinhole in the flex line that connects the pump to the top of the support assembly. Rapid pressure loss may cause hard starting, but shouldn't affect the way the engine runs once it starts, as long as the leak isn't large.

This brings us to the next question - and I reread your long first paragraph and didn't see an answer - have you scanned the PCM for codes? There are a couple that shut down the engine. Loss of low resolution signal from the optical cam position sensor in the distributor sets DTC 16, and the PCM shuts down the fuel system. This code does not turn on the SES light. Similarly, problems with the ignition control module (ICM) can shut down the engine, or cause stumbles and low power. Those codes do turn on the SES light.