t1376gb

just got into a hard start condition. Just replaced fuel pump, check valve and hoses. They were dry rotted anyway.. still same issue. Last year new DME, pressure regulators, tune up and speed and ref sensors.

mrgreenjeans

Have you checked the condition of the coil ?

Do you have confidence in the wholesomeness of the ignition switch ( plastic assembly behind the key switch ). They are susceptible to age, heat, and cold.

And, how about the grounds ? They need to be good and clean including the battery cable. ( which also may be corroded inside the casing ).

Last thing: what about your fuel filter and the condition of those fuel injectors ? Have you any knowledge when and if they have ever been checked or replaced ?

And unless you replaced that reference sensor with a good, well respected unit and not something from URO, these may also be suspect. With proper gap, the sensor clean, and all wires free from dirt and oil, cracking, a Reference Sensor of reputable construction will last years. ( one of mine replaced when the car was but a year old, is still firing the juice 33 years on ). Bought over the counter from Porsche. The one it was built with failed as many did very early on. That was soon re-diagnosed and resolved by the supplier on many 944s.

Best wishes on the diagnosis and solving of these most irritating of problems.

t1376gb

1. I did check coil last year when I started this project. But will check it again. It does want to try to start each time I bump the key.
2. Battery was new last year and all connections clean and good.
3. Fuel filter was changed last year after draining gas tank and putting in new gas... Sat for 15yrs
4. Injectors are original. And could be possibly leaking down??? I Just made a fuel pressure connector and will check leak down fuel pressure running / at idle and after 20 min which should be 14.5 psi.
5. Need to recheck pressure regulator..although I replaced last year.
6. Ref sensor I believe for FTP. which was easiest to get when I started last year.

Thanks for your suggestions!!! ... I also have a very good shop that got me going last year with water pump/timing belts etc. I can talk to ...

thomasmryan

if the dme is not reading the proper temperature of the motor, it will try to fire and die as the mix is off. put your temp sensor on the stove and compare to the readings off clarks.

i have a later tank and there is a half a gallon of swill that can linger below the strainer.

marc abrams

FYI at idle fuel pressure should be 29 PSI
Also have someone crank it over while you watch the pressure gauge. I've seen hard starting from a slow build up of fuel pressure, yet able to develop full power after started.

ltusler

4. Injectors are original. And could be possibly leaking down??? I Just made a fuel pressure connector and will check leak down fuel pressure running / at idle and after 20 min which should be 14.5 psi.

So should it prsssure stay at 14.5, or should it go to 0 at some point?

marc abrams

I know when I changed the fuel filter on my car and lost the residual pressure I did have to crank it a bit before it started. My car sat for a month and started right up. So I would guess it can hold residual pressure for sometime.