PTskater944

Every once in a while my car doesn't start up right away. It cranks, but i have to lay on the starter for a long time before it finally fires up. I noticed that sometimes I forget to roll my windows up before i turn the car off, so i turn the key to accesory power and I can hear this kind of electric humming noise from the back of my car, in the general area of where the fuel pump is (can't pinpoint exactly but what else could it be?). So maybed the fuel pump is pumping fuel into my engine while its off and i'm rolling my windows up, then after school when i go out to start it up it takes a while to burn off all that fuel. It also idles real low after it takes a long time to start up (because its too rich?) and also gives a tiny backfire when i shift from 1st to 2nd for the first time after starting it up (too rich?).

Please let me know if this is a pretty accurate guess, and if not, what could it be? In the meantime i'm going to just remember to put the windows up while the cars still running, but whats the long-term fix for this problem? Thanks.

User 41221

Feel free to drop by our next wrenching session at the KCWS, I think we can get you taken care of. Plus, it would be nice to meet up with another local 944 owner! Check out our website at KCWS.org.

You are correct, the sound you are hearing is your fuel pump.

Regards,

PTskater944

Thanks. I also just looked at clarks-garage, and read this:

Fuel System vapor lock can be caused by several things including a bad Fuel Pressure Regulator (FPR), bad fuel pump check valve, or leaking injectors. Any of these three will cause the fuel rail pressure to drop rapidly after shutdown. When this happens the heat from the engine causes the fuel remaining in the fuel rail to flash to vapor. This causes voiding in the fuel rail. During subsequent startups, it make take a long time cranking the engine or may take several attempts to get the engine to fire. This is due to the fact that the fuel pump may take some time after starting to clear the void and refill the fuel rail.
To determine if vapor lock is a potential cause, perform a fuel pressure and leakdown test (FUEL-01).

If the fuel system fails the leakdown test, determine the cause of the leakdown using FUEL-17.

Sounds a lot like whats happening to me. I'll have to look into that.

roadrunner

If you have the time, pull the spark plugs to see if they are wet with fuel before starting up. There will likely be a very heavy smell of fuel if the engine is flooded. As long as you are not getting fuel hydrolock while cranking, half throttle on hot starts usually helps get air into a flooded engine. If it shows no sign of flooding, priming the fuel pump 3-4 times before cranking may help minimize the voids in the fuel system.