1995 Buick Roadmaster LT-1. Overnight takes 15 seconds to start as gas draining from fuel rail. Runs good when it starts. Replaced fuel pump, fuel regulator, twice. First was mexico unit, second time with original equipment Delphi part. Not sure where to go from here. I know there have been problems with the fuel regulators, are they all bad? Can they be tested out of the car for bleed back? Jim
I believe the check valve is in the filter. Are you verifying this with a fuel pressure gauge? Your symptoms don't match your diagnosis
According to the manual the check valve is in the pump, but the fuel regulator can also bleed back gas to the tank. I see on the Chevy forums problems with the fuel regulators and having to replace bad ones multiple times.
Install a fuel pressure gauge, start the engine and shut it off. Carefully pinch off the supply line. They sell special plastic pinch off pliers for this or you can use needle nose vise grips covered with rubber fuel hose, but don't over tighten the pliers because you're pinching off a plastic line that you're really not supposed to do, but short of buying inline shut off valves. you don't have much choice. Pinch it off by the filter so that if the line fails, it won't spray fuel all over the engine an cause a fire, you can simply replace the end of the line with a repair kit. If the pressure still drops with the supply line pinched off, fuel is either going past the regulator or an injector is leaking. If this is the case, remove the pliers, start the engine, shut it off and pinch off the supply and return lines. If the pressure still bleeds off, an injector is leaking, if it doesn't, the regulator is faulty.
When you turn key on it should prime pump. I believe your looking in the wrong direction . Cold start needs to be richer. I would suggest a temp sensor. You really need a monitor that reads what the inputs are to ecm. . It can also be a hole after the mass air flow. Can even be a cam sensor, as it can run off crank but it has to learn from crank to ignore cam.
Thanks for the suggestions. It's definitely fuel related, fuel rail goes dry over-night. Changed the entire fuel pump assembly once and the fuel regulator twice. Checked temp sensor, in spec hot and cold. Looking at possibility of leaky injectors.
One leaky injector will do what you are saying. As mentioned is the initial cold start priming the pump? The pump should kick in for a few seconds even without oil pressure to pressurize the system. After a few seconds if the oil pressure doesn't build the pump will not continue to run. It sort of sounds like the initial prime isn't there and then the oil pressure builds while cranking and then the pump turns on.
Problem was an intermittent fuel pump relay, which I had changed, the mexico unit was bad, now have a Delco. As Mike said above, I looked at the Corvette website and found out the LT-1 has a fail safe mode when the fuel pump relay fails. The pump will start when oil pressure comes up and activates the oil pressure switch turning on the pump, take about 15 seconds to build up pressure and start the pump, making the long start.
