944 Starting problems
Having 944 starting problems, but only when engine is warmed up. Here is an email I sent to Vertex parts but did not get a reply to. Please advise which part (s) I need to fix this annoying problem. Many thanks, drparr.
Re: 1984 Porsche 944
Engine WP022294ZEN465584
Body WP0AA0945EN465584
Attention: Vertex 944 Specialist / Engine Sensor Specialist
Dear Vertex,
Received the new radiator you expressed down to me and installed it. New radiator is working great- cooling engine just fine. Engine temp gauge on dash in normal operating range.
Now, here is the problem. On the weekend before you shipped my new radiator, my 944 engine overheated for about 5 to 10 minutes but I did not notice that till I got home. This was due to the old radiator having a bad leak and most of my coolant leaked out while driving. I was driving for maybe 5 to 10 minutes with an engine temp. gauge on the dash showing overheating (into the overheating zone) before I got home and noticed the leak. I estimate this amount of time because I started the car cold and drove for about 20 minutes (normally takes about 10 minutes for engine to heat up to where engine temp gauge goes to right past the middle).
So the situation is that the engine ran really hot for about 5 to 10 minutes.
1) I checked the oil- it was down a quart and I topped it up. Now I check the oil level periodically and it is perfect- it is not burning or losing any oil.
2) The car starts beautifully in the morning when I go to work. Engine compression is good, oil pressure is good and normal on gauge as it is running.
3) The car starts beautifully after I let it sit for about 2 hours and it cools down completely and I need to drive it again.
4) The car starts ok if I do a short 5 minute hop to the grocery store, park it for a minute and then start it up to go back home. (the dash engine temp gauge can be in the middle or almost middle position).
5) The new radiator is cooling the car great. The engine runs beautiful and smooth. I can drive the car for an unlimited time and the cooling and engine is running great. The dash gauge showing engine temp stays in the normal operating range the entire time, a little to the right just past middle. The cooling fans cycle on and off as required normally.
6) The starter and alternator and battery is great. They crank the engine perfectly and the battery is like new and the alternator is charging perfectly.
7) The spark plugs are great- they are new Bosch Platinums installed 3 months ago. The car runs great, accelerating smoothly and powerfully- everything normal in the ride.
8) HOWEVER, if I run the car for say 15 minutes or longer (the dash gauge showing engine temp is in the normal operating range, tilted towards the right just past middle), park it, shut it down and THEN try to get in and start it again to go somewhere else, THE CAR ENGINE WILL NOT START. The starter turns the engine great, the battery is great but some sensor is not allowing air or gas or some combination to get to the engine to fire. The engine cranks and turns beautifully but it will not fire. I can crank that engine repeatedly for 30 seconds at a time and it turns beautifully but will not start. (I can press the gas pedal down while cranking and same thing- will not start). I literally have to wait about 1 hour to let the engine cool down (the dash gauge shows the engine temp in the far left area warm-up range) and then it will start again beautifully. (I do not smell any gas leak or anything when I am cranking the hot engine- it turns over great and sparks but just will not start).
So a little elimination first before we decide what it could be:
A) Battery, Alternator, Starter, Spark Plugs, Engine Compression, Thermostat: No, it is not the battery, not the alternator, not the starter, not the ignition, not the spark plugs, not the engine compression. It is also not the thermostat because the engine temp gauge is in normal range after long driving and I checked under the hood- the overflow tank is taking up the expansion (I can see more coolant in the overflow tank after a long drive as is expected. The level is higher (max. mark) than when I check it before going for a drive (min. mark) ). So that means the thermostat is opening and coolant is circulating through the engine.
B) Distributor cap, Rotor, Ignition wire: Can’t be as the car does start when it is COLD and it runs smooth and does not misfire when it is just started or when it has been running hot for a long time.
C) Fuel pump or fuel pump fuse: No because the car does start when it is COLD and it does run once it is started.
D) Fuel Injector: I don’t think it is the fuel injector as again the car does start when cold and the engine does run well, not poorly- it has great acceleration and instant pick-up- very responsive.
E) Idle speed regulator: It can’t be that because the car starts and idles beautifully, cold or hot.
F) Ignition DME Unit: can’t be that because the car sparks and starts and it never misfires.
G) Ignition Coil: not that because the spark is good. The car starts great when cold and runs great.
So now we are left with the following possibilities and I need your help to decide which one it is:
1) Auxiliary Air Valve- would this cause erratic fuel injection ONLY WHEN HOT and cause the 944 to not start when HOT? (It starts great when cold and runs great though).
2) Fuel Pressure Dampner- could this be the part preventing the 944 from starting when HOT?
3) Fuel Pressure Regulator- Could this be the part not allowing the 944 to start when HOT?
4) Air Flow Meter- Could this be the part not sending enough air to start the car when it is HOT?
So which one could it be? Which one could have been damaged by overheating and now is malfunctioning? Remember that everything worked beautifully BEFORE this overheating incident I had so it has to be related to that overheating incident.
Appreciate your time and any advice you can email me back with so that I can order the faulty part from you and replace it. Anxious to hear from you about this problem as it is a drag not to be able to stop and do errands with the car- as it is I can only drive to work in morning and then drive home at night. Hoping you had another client with the same bad experience of his 944 overheating and damaging some part so he cannot start it when HOT and you can share the experience with me.
Best Regards,
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