Please help: 930 start / running issues

[LucaScali]

First let me congratulate the board on building the best Porsche community and reservoir of knowledge on the Internet. I've learned a lot on here and appreciate all the great posts.

Now my problem (930 3.3)...

Several months ago I started experiencing occasional sluggish cold starts in that the idle would dip below 950 rpm for the first few miles before building back up. Otherwise there were no starting or operating issues whatsoever. Over time this issue became more frequent and was eventually joined by some difficulty starting the car from time to time, mostly cold.

A couple months ago I came to a stop in a parking space and the engine sputtered and died. I went to restart it and it would catch and immediately die. After several attempts and some throttle, I got it to start, but it ran very, very rough and would not rev past about 4000 rpm. After a while I tried again, got the car started, gave it a little gas and everything smoothed out. Drove it 10 miles to my house without issue, only to have it die again after I made it back.

Since then the car has been extremely hard to start--hot or cold, requiring perfect timing of the throttle after letting it sit a while. If it's not executed perfectly that first or second attempt, it is almost impossible to get it started. Sometimes it will catch, but without some throttle the revs will drop until it stalls out.

Once it does start in earnest (meaning the revs build to the normal 950 idle) the car runs perfectly. I have tried to get it to stall once it's started, but have not been able to. I have taken several short, but spirited drives without issue. Again, once i get it started, there are absolutely no problems. It has not spontaneously died since the first day it happened.

I have reviewed the no-start checklist and tried the following so far:

1. Swapped the Permatune CDI for a Bosch: I popped the Bosch in yesterday. The car started right away after sitting for a few weeks and I thought the problem had been solved. Went for a nice drive, then parked it. Restarted a short while later--it ran rough (lot of popping) and required gas to keep it alive; sputtered and died. Unable to restart since despite several attempts.

2. Yellow relay replaced not long ago.

3. Green wire looks ok.

4. Fuel filter is relatively new (maybe 6k miles).

5. Fuses checked

6. Hoses all seem intact and secure.

7. No apparent issues w/ the fuel pumps.

8. Starter/alternator/battery fine.


Would appreciate your thoughts. In fact, it would be really great if someone in the DC area would be willing to come by and help me figure this out. Please let me know. Thanks in advance.

[Alan L]

Throttle plate safety switch?
AAR?
Faulty pump relay - needs both to run properly? Disconnect throttle plate switch and turn key on - check both pumps running before trying to start. (I had issues with intermittent relay - hard to track down).
Alan

[Alan L]

Originally Posted by Alan L

Throttle plate safety switch?
AAR?
Faulty pump relay - needs both to run properly? Disconnect throttle plate switch and turn key on - check both pumps running before trying to start. (I had issues with intermittent relay - hard to track down).
Alan

You may also need to check the cold pressure in your WUR - in case it is sticking and too low (Rich) at start up. Another possibility is the Cold Start Valve - since it seems OK once you get it fired up. Or does it do this when hot as well.
Alan

[Alan L]

I think you probably need to start a systematic search - checking your fuel pressure specs first - CP, Rest Pressure, Fuel Pressure etc. It sounds like a fuel issue.
Alan

[johanpor]

I tried to start my 930 today with no luck
Lots of battery but NO firing.

[johanpor]

Ran fine when I parked it about a month ago.
I use stabil in the fuel every winter and still on that tank of gas.

[johanpor]

I have suspicion of fuel pumps and coil, maybe even the fuel filter.
Checked distributor and cleaned rotor contact and cap contacts.

[johanpor]

Another thing that has changed in the last couple of years is that the fast cold idle doesn't work. It will sometimes rev to the cold level, 1300 RPM, when warm.??????

[mark houghton]

Originally Posted by johanpor

Another thing that has changed in the last couple of years is that the fast cold idle doesn't work. It will sometimes rev to the cold level, 1300 RPM, when warm.??????

When you say "when warm", do you mean when warm and you've shut here down for a few minutes to go into the store for a pack of smokes or a 6 pack of beer? If so, then probably your AAR is working correctly...the high idle after a hot shutdown of a few minutes is typical, as the AAR opens back up while the car sits for a few minutes.

So we're going to presume that the AAR isn't your cold start issue. Suspect the WUR/cold control pressure being perhaps too high...thus not a rich enough mixture to facilitate easy starting when cold. That, and as already mentioned, your thermotime switch/cold start valve may not be functioning and not squirting that extra fuel in the first couple seconds of cold cranking.

You should invest in the proper gauge setup to check all fuel pressures (system pressure, cold and warm control pressures...and while you're at it, the boost control pressure as well).