My 1997 Pontiac Firebird Transam Ram-Air with 169K miles is becoming hard to start. It used to start right up with the first key-switch. Now, if the gas level in the tank is below 75% it will not start on the key-switch. However, it would now normally start right up on the second key-switch. However, very recently the car is now needing the third key-switch to start with lower gas levels in the tank. I MAY be noticing a difference in starting reliability with change in temperature. Lower temperatures seem to increase the frequency of starting on the first or second key-switch. Higher temperatures seem to require the third key-switch to start.
This slow to start behavior manifests its self after the car has rested for about an hour or longer.
A friend checked a fuel check-valve immediately behind the engine when the. However, he found fuel there.
The local GM dealership claimed they could not find the problem and suggested a new car battery and then a tune-up for $1K.
I suspect the problem is a fuel pump in the fuel-tank or associated seal degrading.
Any ideas on the actual cause of the observed behavior?
The next time you go to start the engine, turn the ignition switch on so the dash lights come on for a couple of seconds and then turn ignition switch off. Repeat this a half dozen times and then try starting the engine. If the engine starts right up, the problem is with the anti drain-back valve on the fuel pump assembly.
I agree with Tester’s, well, test. Doing the on-off a few times builds up fuel supply and pressure. One other possible malfunction would be a leaking injector. That could give a too-rich condition for a couple seconds, which could mean the engine would not start up quite as quickly as it used to.
But many of us used to be/still are dealership mechanics
I was, for a long time, until I got a better offer turning wrenches for “the city”
There’s got to be at least 1 experienced and competent mechanic at a dealer. A big problem, as I see it, is that the customer usually doesn’t know who the job is getting assigned to.
Concur w/ @WheresRick, to get to the bottom of this without going on a parts swapping adventure, the first thing is to ask your mechanic to check the fuel pressure at the injector rail. Ask them also to check that the pressure varies with applied intake manifold vacuum, like it should. They may have to connect a pressure guage and leave it connected, checking it immediately after stopping after a drive, then again in an hour after it has been parked. Mechanics will sometimes run the fuel pressure guage to a point where it is visible through a window while driving. (There’s always a fire and explosion hazard when messing w/the fuel system, so take the necessary precautions.) I expect you’ll find the fuel pressure is drooping. You could also look at the fuel pressure regulator for any signs of leaks, especially if there is gasoline in the vacuum line, that’s usually a sign the regulator diaphram is leaking.