me61ic

Hi there, I have a problem with a 1992 964 turbo 3.3. The car starts perfectly fine when cold, but after driving for some 30 mins or more, if I stop and try to restart it will start again, but if I leave for 15-30 mins it will not start again until it cools down. I have red many threads with similar problems were they say the problem is a bad fuel accumulator, but when trying to diagnose my problem before doing the searches, I tried removing the king connector from the distribuitor to see if it was a gas problem or an electrical problem and I could not see any spark coming out of the cable close to the distribuitor.

What do you guys think? What can cause the same symptoms as a bad fuel accumulator but in the electrical side? Or can it be that I am having two problems together???

Thanks in advance

fritz k.

I have no clue what a king connector is but this can also be an electrical fault, e.g. there are two small relays in the turbo switchgear that sometimes, even intermittently, fail.
So it makes sense to check whether fuel or sparks are missing.

If the fault occurs, remove a spark plug connector, install a spare spark plug and put it to ground. A strong ignition spark must be visible when turning the starter.

The fuel pressure accumulator must have a residual pressure of at least 1.4 bar 20 minutes after the fuel pumps have been switched off. The measurement is made at the WUR, which requires a manometer with the appropriate fittings.
If the pressure is not maintained, the pressure accumulator does not necessarily have to be the cause. The pressure is also lost if the injectors are leaking, and the car will not start because there is fuel in the cylinders.

Fritz

997 tt/rs

check if it will start on a hot engine with gas pressed to the floor?

911 2

be careful you dont blow the EZL when taking out spark plugs and cranking the engine, see what the manual says as the EZL can blow for eg when removing ignition leads and only one or two plugs present eg when doing a compression test and then trying to turn over the engine

ianbsears

Does it crank and won't fire or is it totally dead? I had issues with more than a normal amount of cranking (took 7-10 seconds to fire when hot) and ended up replacing the accumulator, 1 fuel pump (rear), cleaned and tested the injectors - all of which made an improvement. Disconnecting the O2 sensor seams to have helped as well. My car sat for 10+ years before I owned it.

Nyx

As 9112 said, do not look for spark that way. The capacitive discharge system can be damaged when open circuited.


here is a cheat sheet I made for my 92 sensor testing.

however I would be more inclined to think you have a fuel issue.

me61ic

I already tried, no, it does not start, cranks but does not even try to start

me61ic

Don’t know what the EZL is, but did not know I can break something, I have always tested for spark this way, removing what I thought was called “king connector” (just made a quick translation) from the distribuitor (the center raised connector that comes from the coil) when I do that to my 964 C2 I can see very noticeable sparks when cranking, I thought I could see the same in the 964 turbo, but that is not the case, even when cold that the engine starts with no problem I cannot see any spark from that connector when close to the distribuitor, in fact it even starts when close to its connection (using pliers) point without being attached.

so I guess the problem must be the fuel accumulator, will try replacing it.

Thanks everybody

Nyx

I would say that isn’t your problem. The fuel accumulator would charge after a long crank and you’d sputter to life.


just measure residue pressure to confirm it’s function?


I would say it is fine if it starts cold. It won’t just magically build pressure while getting cool.

911 2

Its possible you have already blown your ignition coil, does it still start when cold, if it does then the coil will most likely be fine.
I learnt this the hard way when doing a compression test on a mercedes which run same set up as the Porsche, luckily I did not fry the EZL, if you burn the EZL you are in trouble as they are no longer available, only option, would then possibly be, a conversion to efi, which isnt going to be cheap.
Test the coil with an ohm meter if the car is not starting at all

ianbsears

I agree with @Nyx . The accumulator is there to regulate pressure in the system and prevent fuel from going back to the fuel pump or tank. Even if it is not working correctly you would eventually pump enough fuel in the system to get a start.

You could also check the DME relay.

Nyx

Don’t look too hard for the DME relay


CIS Turbos don’t have one


you have a turbo control module under the driver seat. Move the seat fully forward and you can access the connectors. (It’s the smaller module) It controls the fuel pump relay and a few other bits. You can jumper pin 9/11 to run the fuel pumps (I don’t think the German engineers did that by accident! ) or jumper the relay in the funk.


Critical path now is - Does it start at all- even stone cold?

me61ic

I can hear fuel pumps working perfectly both cold or hot.

It does start cold and drives perfectly with the same symptoms as when I started the thread, starts and drives well, but after driving it (getting to driving temperature) if I stop for longer than 10-15 mins it won’t start again until it cools down.

I thought it was a spark problem because I was checking for spark the same way I have always done in all my cars, removing the cable that comes from the coil into the distribuitor, when I did that in my other 964 in the primary distribuitor, I could see a clear bright spark, but in this 964 turbo I cannot see spark either cold or warm, there must be one as the car starts fine when cold or not after 15 mins hot, it is just that I do not see the spark as clear as I see it in my 964 C2. Now you guys told me it is not safe for the car to look for a spark that way, I will have to go through the more difficult process of having a spare spark plug and removing the cable from one of the spark plugs in the car to check, I have always done it the other way just for simplicity.

Scott Dunavant

There are 3 temp sending units. i just replaced the 4th going to the gauge... just right on the fan. The 90 degree temp advances the ignition and so on.
They are located in a triangle pattern. The left one is expensive. Coils do fail under load or heat. Those 4 items are a must before replacing the EZ69.

fritz k.

me61sc, you're on the right track, check first whether there is a spark or not. Getting a replacement spark plug is easy and there's access to a spark plug cap on the left-hand engine side.

You can also ground a wire somewhere that you wrap around the spark plug thread, that might be easier than putting it on ground. Keep in mind that you need someone to turn the key in the ignition.

Fritz