944 random non-start

[houseguy4]

I'm not a mechanic, I just like driving my Porsches! So I need advice from all you pros!
'85.5 944 Every once in a while, the car won't start. It cranks just fine. Once started it runs just fine. I can drive it to the store and come back out to a no-start. Try and try, and eventually it HAPPENS to start. This used to occur rarely and it SEEMS to be getting worse, like 50% of the time.
I've been able to start by:
-spraying starter fluid (ether) Not desirable, only the very last resort. I was stuck in a parking lot at night.
-my European import mechanic (not a Porsche specialist) checked it - hard to diagnose sporadic problems - and guessed/recommended changing the "crankshaft sensor" and the "engine speed sensor" for $650. I cannot find these parts by these names on Pelican.
-a few times when it would not start, thinking about sensors, I cranked it BRIEFLY while in gear, moving the car a few inches and it started. Did I activate or move the sensors?
-the last 2 times this week, I tromped on the gas pedal about five times like starting an old truck and it started right up!
Any suggestions?

As a thank you - here's a fun pic of my car
One snowfall while I was in the office:

[porschetub]

Check your battery and all connections first but it appears you may have issues with your throttle position switch or air flow meter .
If your car starts your sensors are ok.
Go to Clarks Garage and have a look @ fixes then ask on this site for shops with 944 repair skills in your home town.

[JRMock]

There is a DME/Fuel pump relay that are common failures on these cars. Most of us carry a spare in the glove compartment. Car will turn over, but will not fire. Easy to replace.

Pressing the gas pedal on these cars only opens the throttle body, does not pump gas.


See the shop manual section of Clarks Garage for more info.

http://www.clarks-garage.com/shop-manual/

Good luck
JM

[AKCJ]

A few ideas:

1. If the car doesn't crank very well you may just have a low or weak battery or bad connections.
2. A common problem is the speed and reference sensors or the connections to them. Do a search - there is tons of info on them. These are what your mechanic was referring to.
3. The DME relay is almost always suspect as mentioned above. Get one and change it out just in case that is the problem. If not, then you needed a spare anyway.
4. This doesn't seem like an AFM problem to me but it wouldn't hurt to read up on it.
5. It's possible there is a fuel problem. Best to confirm that you have fuel pressure at the fuel rail but at least confirm that the fuel pump starts when you try to start.
6. Wouldn't hurt to look at the ignition system. Spark plugs, wires, cap, rotor, coil.

Good Luck

[houseguy4]

Thanks for the great replies!
To clarify: battery and cranking are strong.
I printed out some info from Clark's - great site and a blessing to guys like me! Thanks for the referalls!
AKCJ - so my snowy picture looks like a light dusting to you in Fairbanks! -22 tonight!

[ballysdad]

Agree on dme relay you need a spare anyway.
When your car will not start check to see if you have tach bounce when you try and crank. If you do not check your reference sensors. I would check the condition of reference sensor plugs. If car wont start jiggle connections and see if it starts.