Steven Kemp

Fuel pump could it be intermittent? "87 944S,
52 psi fuel pressure. OK
1 quart flow rate in one minute. OK

Symptoms:
Hard start (8 crank cycles) after sitting, no gas. checked plugs - clean burn.
Ran perfectly when started and at many full throttle situations. Normal easy restart within one Hour; progressively harder as time increased.

Tests: Fuel draining out/back?
Ran fuel pump to prime; started in three cranks ( fuel injectors not primed due to air lock. (DME relay - 87b to 30 jumper)

New check valve on fuel Pump. What do you think? could it still be fuel pump? Something else?

951and944S

Sounds like drain back.

Had a buddy go through 3-4 check valves on a 968.

Have you ever left the gauge hooked up and checked pressure in 5-10 minute intervals over a period of time compared to what psi you have right after killing the engine...?

I guess the impeller could slip on the motor shaft but it seems problem would get progressively worse as the fit between the two would get worse each time it happens.

T

PaulD_944S2

The DME temperature sensor in the front of the engine block can also produce hard starts, and it gets harder to start as the engine gets colder. Just a thought. If you decide to replace it, check the contacts and try cleaning/reseating the connector several times to make sure there's a good connection.

You have 52 psi fuel pressure, but you didn't specify under what conditions.
How well does the fuel pressure hold after shutting the engine off?

Steven Kemp

Thanks Paul and 951. have not checked the DME temp sensor yet.

Know what the ambient ohm reading is?
Will check the Technik.

Cold: Thinking back, it was always much harder to start in colder rainy weather. Let you know.

porscharu

After running the car and letting it sit for a couple minutes pull the vacuum lines from the regulator and dampener. See if there is any fuel in either.

bkrantz

I had occasional and intermittent starting problems that I traced to the flywheel sensors.