Manager Forum

I have this 1995 Chevy Lumina, 4 door sedan with a 3.1L engine. Customer can start engine first thing in the morning, go where they want to, come out, the engine may start or it may not start. But if it starts, it will run only a few seconds and then shut off. When I press the fuel pressure test port shrader valve, there is pressurized air there and if I depress the shrader valve while the engine is cranked over, the air will come out and then the gas. Once there is fuel there, then the engine will start and run fine till the next time you shut it off and want to start it. If you get home, let it sit overnight, the engine will start fine then. The issue seems to be a hot restart and, as mentioned, there is air at the fuel pressure test port. Where is the air coming from and what can I do for it. Otherwise, the engine runs fine, excellent fuel economy and no check engine light. By the way, KOEO & KOER fuel pressure is within specs when tested.

Similar issue sorta..had a 92 Camaro that would int start. Run good other times not so good. Had air in lines at times. Found a crack in the rubber line on the pump up to the fitting on the hanger. Replaced the pump and hose.

Just have to find were the air is coming from. Id suggest removing the pump and leak testing the system.

If air can get in, fuel can get out - right? or not?

I have seen it not leak out before. I have seen the tiny hoses on Ford 7.3L have dry cracks and somehow suck air in but not leak fuel out. Diesels do not like air. It may be tough to find. It could even be a broken hose between the pump and sender maybe. Good luck.

Is there any way that the fuel pressure regulator could be the culprit?

Just a thought. Because as of today (and we don't know for how long) the fuel pressure is down to 27psi with the engine running and MOD says the fuel pressure spec is 41-47 psi.

Could be I think it is part of the pump or sender. I would try to spate it from t he system and see if the pressure still bleeds off. I would bet its the hose between the pump and sender but that's my best guess.

Sorry for the late reply. A few things here, #1, is the hissing at the vale air coming out or a vacuum being released? I've had symptoms like this and the vents are plugged causing a vacuum lock when valve is depressed it relieves it and then allows fuel to flow. #2, a leak inside the tank may allow air into lines and show no leak. I've run into many air issues where air is sucked in prior to pump and shows no external sign of leakage. #3, the low fuel pressure may be a sign of a vent issue as well, if symptom can be duplicated remove fuel cap and see if pressure climbs back up. The issue may be a fuel cap vent. #4, a stuck pressure regulator should cause a pressure drop to zero after key is turned off, regulator is on the rail. #5, I've had regulators leak fuel into intake through the vacuum line that attaches to it and although it's never happened to me air being introduced into fuel system through that hose is possible I guess. On the subject of the pressure regulator, it's highly possible that there will be a deposit of rust and other debris inside the fuel rail near where it attaches. I have had the pleasure of it coming loose and plugging an injector or two. This led to another Kiser Shop Rule of rail replacement if any deposit is present. #5, plugged pump socks will cause a pressure loss as well. I usually find if the sock is plugged and there is more than just a bit of metal filings inside tank the pump is compromised and is on the way out. I warn customer of that and will not warranty any of the work I'm doing to the fuel system. #6, by now I've either succeeded in replacing the fuel filter either by getting lucky and having it come off without major incident or there are pieces of line in the trash and new attachments on the filter. Being in the snow and salt belt I've grown accustomed to a fair amount of collateral damage such as filler tubes, tank straps, exhaust issues and brake lines near the filter starting to leak because they moved while filter and filter lines were being fought with. Good luck and I hope all this was helpful.

What are the chances of there being a vapor lock and the gas boils in the fuel rail after the engine is shut off? This problem surfaced late last summer, as ambient temperature got colder there was no issue until it got hot again this summer. So here we are again with this problem.

In theory is sounds like it could happen but I still would try driving it around with the gas cap off.