87 911 starting problem

[umedawy]

I am having trouble starting my 1987 911. It has been sitting for awhile and now it starts then dies and I am unable to start it and there is a strong fuel smell. If I let it sit for a day it does the same thing but once it fires up it dies and will not start until I let it sit for awhile or it cranks until the battery gets weak. I swapped the DME relay with one that was new but on joy. I do not understand why it would fire up them not continue to run and fail to start again without sitting for awhile. It reminds me of a flooded engine. Is it possible that the injectors are stuck? Any help is appreciated. I guess it is obvious that I do not know much about Porsche's and am old school carburetor type of guy and maybe it is a mistake for me to get into Porsche's which is over my head. Does anyone have any suggestions?

[Quicksilver]

A leaky injector could cause a bit of trouble. There is a check valve in the injector system to retain pressure at the injectors to help the car start immediately. The fuel pump does not start until the DME detects that the engine is spinning so that would cause an unacceptable delay in startup. You could detect this by hooking up a pressure gauge to the fuel rail test port (rear drivers corner of the engine) and see if it holds pressure over night.

I don't see that your symptoms would be caused by an injector leaking to cause a pre-start flooded condition. Once the engine fired you would be fine but that isn't what you are seeing. It sounds like it is flooding once it starts running. First thought I have is if the pressure regulator is bad causing way to much pressure at the injectors. They way to check that is to also hook up a pressure gauge to the test port on the right injector rail.

That is a just a good starting point...

[rick-l]

By your description (fuel smell) it sounds like the spark disappears. Do you have any way to verify that?

Are your coil and distributor in good condition?

Do you have a friend you could put your DME into his car to test.

[ischmitz]

A stuck injector is unlikely. It would make raw fuel drip out of the exhaust. Ask me how I know. As Rick stated start with the simple things: Caps, rotor, ignition wires.

The 3.2 has a transistorized Ignition controlled by the DME. The coil get's +12 Volts just like a Kettering ignition on one side and the points are replaced by the DME. The DME takes care of dwell and timing by grounding the coil and then opening the "contact" (power transistor) to generate the spark All electronic parts including the power transistor are inside the DME.