944 Starting Problem

[thill944]

My car starts right up when I get in it in the morning. I drive to the store, shut if off, leave it for a while, then when I get back in and try to start it-it doesn't start. It turns over as normal but doesn't fire. I can wait a few minutes and then when I try and start it it fires right up. If I drive to work-turn it off-come back after work-it fires right up. Engine does not over heat. Seems to be something in the fuel system. Anyone had this problem before? It just started to do this on a regular basis a few days ago.

A couple of months ago I did pull my intake off, cleaned the injectors and Idle Stabilizer Valve, put new intake gaskets on, etc.

Fuel Regulator?
Fuel Filter?
Fuel Pump?
Damper?
Fuel Check Valve?
Fuel Pump Relay?
Something Else?

Thanks Terry

87 944 NA

[Outback Porsche]

Does the tacho bounce, wiggle, move in any way, when it doesn't want to start?

[drew1]

Might be check valve on pump, put a guage on fuel rail shut it off & check how long it takes for pressure to drop. Be careful & don't lose that ball under the nut.

[kmakovac]

I have the same problem,ocasionally after 30 min/ 1 hour don't runs up.
Cold-every time.
Stop-sometimes faulty.

DME relay!

When it's warm up don't close electic cyrquit every time,loss of power/voltage?
How i know?When i disconectid 02 sensor the cars run up every time!?!?!

So i take a look to the diagram: heating of 02 sensor and DME realey have gut the same input cyrquit.This is why with plug disconected it fire's up(rise voltage and DME/fuel pump starts)

Now is one year that i change the realey and don't have any problems.
(like you i try everything)

[daltonhiggins]

im having same problem im going to check fuel pump/injec relay let me kno if you have any luck

[JAXTURBO]

Originally Posted by drew1

Might be check valve on pump, put a guage on fuel rail shut it off & check how long it takes for pressure to drop. Be careful & don't lose that ball under the nut.

Plus one on the fuel pump check valve

[rayporsche]

It sounds like the DME Relay, to rule it out you might jump pin 2 and 4 which are 30 (12V) and 87b (fuel pump) and see how it goes, just a test, remember that when you do this the fuel pump will be running with or without the key.......you see where I'm going with this right?!! Good Luck..............

[kayw]

Hi,

It happened on my 944 too. I figured out the speed/reference sensor causing the trouble. Just unplug those sensor, cleaning, then it should solve the problem

Kay

[mfischer78223]

kayw,
whats the best way to clean these speed/reference sensors? I have the same starting issue with my 85. Will start when cold, run for a little while then park, come back later...no start. Have already replaced fuel relay...no change. Any help greatly appreciated.

[kayw]

HI,

It is simple. Just plug out the sensor (ref to Speed and Reference Sensors - Checking, Replacement, and Adjustment)

I clean by "contact cleaner" which is for cleaning electric parts. You probably see little rust and oil stick on the sensor. just clean. Plugin back to the car. That is.

Hope you solve the problem.

[rayporsche]

Sounds like a plan but then again how dirty they can be, do you have an oil leak in that area that bad ? the thing that you need to check for is their resistance values to find out if they are good......that been said there are so many variables such as their wiring harness, the connections and the wires itself, they must be thoroughly check, the resistance of the ignition coil must be check to see if it changes with temperature and some fuel components and things such as fuel pressure, fuel filter & pump, fuel pressure regulator and last but not least the fuel injectors for pulsation, their wiring insulation tends to crack up with the heat and years causing problems like the wires contacting and messing the continuity......and the list goes on and on but since you already ruled out the DME-Relay these other things could be the culprit of your problem or not. Good Luck !

[drew1]

Take that nut off of rhe fuel rail % don't lose the ball. Hook up a hose to it & a pressure guage. Start the car & shut off, watch the drop in the pressure guage.

[porschetub]

Hi ,yea I go with the non-return not holding residual fuel pressure,the car will start cold as it will be on fuel enrichment. One member mentioned the fuel pump relay ,this is a good point as they don't always fail totally,my experience has been with a non starting fuel pump which turned out to be a voltage supply of less than 12Vs to the pump ,good luck sorting it.