Raymond

Hello friends,

just collected my '90 C2 from the workshop after some diagnostic work on a hot starting problem. I think there was some electrical work done..but can't be sure till monday.

On the drive back, I switched on the rear wiper (new blade)....it started to wipe but got jammed halfway because it couldn't clear the roof mounted rear spoiler. After that, I couldn't get the wiper to move at all (either by force, or with continued use of the swtich).

I found out also a little later that all interior lights would not light up. These are the two lights above the doors, as well as the glovebox light. What's more, each time I try to turn them on, the central warning light (the "!") on the speedo comes on. With the lights set to the "door open" mode, the warning light will come on when i open the door, and go off when I close the door. It also comes on and off when I open and close the glovebox. No warning light when I press the rear wiper switch though.

The car is otherwise fine....except for the hot starting.

Anyone have any clue what might have happened?
do the rear wiper and interior lights share the same fuse, and could I have blown the fuse when the wiper jammed?
Should the warning light come on for something as minor as interior lights?
Could these faults (wiper and interior lights) be unrelated, or caused by some 'wrong connections' during the electrical work?
Could it be a battery about to expire? (it's 2 years old now.

sorry for long post.

have a great weekend.

Raymond

horst

Raymond, I dont have the wiring diagram in front of me, but have a couple of general comments: My battery is an Interstate, 5 years old, and is fine (mabey, having said that it will die today) 2 years should be fine unless you have a problem with a short, alternator, etc. If you pop off the cover off the central electrics box that has the relays, etc. you will see inside the the cover a listing of all the fuses etc. There is also a slot where you can insert each fuse, and an LED wil light if it is ok. Check the fuses. Re the wiper: at the bottom of the arm is a cover which you can unsnap, and pivot up so you can use a wrench to take off the fastening nut (?13mm?) Take off the wiper arm, and mabey you can worry it loose. Try to sart the thing with the arm off, and see if the motor works as it should. I have noticed, that the wiper can jam itself if you pivot the arm up incorrectly, as when you are washing the car.

PH964

Hi Raymond,

My front wipers jammed the other day half way through a stroke. Turned out that the previous owner (or a garage) had used a wrongly rated fuse! Easy to fix.

Pretty dangerous for this to happen when driving in the outside lane in heavy rain on the M25 (London Motorway) though!!!

Rgds,
Peter 1990 C4

Stephen Smith

Hi Raymond
I think that the electrical circuitry is very complicated and your complaint has no real logic to it.
I would (telephone first and then) take it back to the guys who have just been working on your car and advise them of your problem.
If your wipers are stopping then maybe there is a shorting out in your electrical wiring.
Alternatively, there may be an incorrect fuse installed. A slight difference from the correct fuse may cause problems to occur.
It doesn't sound like your battery would be giving rise to the problems you are referring to unless you have an incorrectly specified battery, but you've had it for 2 years so it shouldn't be a problem.
A friend of mine has a 993 and his rear wiper had the same problem, shortly after I had to put in a new battery because we thought that the battery had naturally died. A week later the brand new battery was flat. He took his car into Porsche Australia and they said that there was a fuse or some other similar component which needed to be replaced. Thereafter no problems for 3 months now.
I guess the compensating factor is that the problem isn't big $ but I know it's annoying.
Regards
Stephen Smith
93 C2 Tip
YZF R1

Adrian

Dear Raymond,
The rear wiper fuse is number 28. I would suspect this is blown.
The interior lights are fuse 11, instruments and the central informer are on fuse 18.
Check all fuses. If all these have been blown I suspect you may have burned your central electric control which is contained within the central electric panel (fuse and relay box). 2 embedded ICs underneath.
The rear wiper motor is fuse is also used for the mirror adjustments and rear window demister.
Based on your comments I would take the 964 back to where the work was done and have them fix it.
Okay first thing to do with the hot engine start is replace relay R41. The DME and fuel pump relay.
If this fails top fix the problem look at the engine temp sensor. It may be open circuit or the wiring is damaged telling the DME that the engine is cold.
If the engine temp sensor is okay then you are looking at the idle control or speed valve. It may not be opening so you will not be getting the start schedule from the DME.
I assume (and this is dangerous I know) that the basics have been checked like, spark. The coils are known to overheat. DME relay and fuel supply problems go hand in hand.
Ciao,
Adrian
911C4

Raymond

Thank you Horst, Peter, Stephen, Adrian,

I brought the car back to the mechanic today for a quick look.

- The interior light problem turned out to be a fuse he forgot to replace. Put it back in and all is fine inside now. Interesting that the warning light ("!") should come on, as it would have had a non-technical person like me very worried that it was something dangerou$$. (e.g if I failed to notice there were no interior lights).

- The fuse for the rear wiper is fine. Put in a new fuse but it still refused to move. As a temporary fix, he unsnapped the bottom part as Horst described and put it to the correct position . He'll take a closer look at it when I send the car in next week.

- Quite pleased to hear that 2-5 years for a battery is quite ok.

- Adrian - on the starting problem. I've read the posts and your technical advice on hot starts. Went through with my mechanic the areas that have been listed as possible culprits, but no luck so far. My idle control valve is new, as is my air flow meter, and cylinder head temperature sensor. They were showing strange symptoms, like CO levels going wrong after a few days (and stalling problems), 'total muscle failure' (caused by the idle control valve), and difficulty in adjusting the mixture to the correct level, and strange temperature readings. He's checked the fuel pressure, the relays and said they all seem ok.

-If I may stray a bit off topic, I'd like to describe how the starting problem began ....It began as an intermittent warm start problem (i.e. maybe 1 out of 20 warm starts would be difficult. By warm I mean if the car has been left to cool for about 1/2 - 1 hour), I had to crank for a very long time (about 5 - 10 secs) before the engine would fire. It then progressed to an perpetual warm start problem over a month or so. Now it has worsened (in about a month) to a problem even with cold starts. I need to crank for a long time and it will stumble to life, often with a puff of grey smoke (smells like unburnt petrol) that goes away after a few seconds. Hot starts (i.e. within 2 minutes of stopping the engine, whatever the engine temperature) have never been a problem.

- after ruling out the relays etc, we suspected the ECU. Thankfully ruled that out when we swopped ECUs with another car and the same problem was there. We then thought it could be the injectors, but inspected them and 'they looked OK'.

- Once started, the car runs smooth and powerful throughout the rev range. There is a slight noise that sounds a bit like 'pinking' or 'clicking' at a certain rev range between 2500 and 3500 rpm (only when engine is under load) but I've been reassured that it's nothing...all checks (exhaust etc) have not pinpointed the cause. Any chance it could be real pinking/detonation, and linked to the starting problem? (seemed to begin at about the same time if I recall correctly.)
I will send the car in for more diagnosis with new equipment (don't know what) next week...would appreciate any advice or other potential problem areas to look out for.

Thanks for reading this very long post! also my apologies for straying slightly off-topic. The problems I face with the above are really more irritations that real problems as the car is really really fantastic to drive.

Raymond

Adrian

Dear Raymond,
First of all. Relays always seem okay. I would advise replacing relay R41. You cannot really check this because the problem is so intermittant.
Burn´t fuel means too much fuel is getting through. CO2 levels could easily mean a failed O2 sensor or more likely somebody has been playing with the CO2 adjustment in the throttle body. Mess with this adjustment and you can end up in all kinds of trouble.
The kat can also cause these problems. Have you had it inspected.
Pinging, have you checked the knock sensors. They also can cause this problem. They have been known to go intermittant and retard your timing by up to 6 degrees on the crank,
Ciao,
Adrian
911C4

Raymond

Hi Adrian,

Thanks for the quick response.

Ok, will ask him to change R41 when it goes in next week.

Will also ask him to check the knock sensors...will faults in these sensors show up on 'advanced diagnostic equipment'? (he mentioned some new diagnostic equipment due to arrive from germany).

CO2 adjustments...are these the adjustments done on the air flow meter? I know some adjustments were done but don't know where.

My car is a non-cat version, without an O2 sensor. Cars sold in Singapore pre-91 did not require a cat, and most cars were sold without cats (from factory, not modified).

Raymond

Adrian

Dear Raymond,
Yes the knock sensors will show up if you hook up the Bosch hammer and do a diagnostic check. CO2 adjustments are manual in the throttle body. Instructions are found in the maint manual. Highly unrecommended for O2 sensor equipped 964s.
Make sure these people have the manual on hand when they do this work,
Ciao,
Adrian
911C4

PS: I suspect you are running rich. I am not experienced with 964s with option M150 installed as yours is. The hot starting maybe too much fuel wetting your spark plugs. I am guessing now.

Raymond

Dear Adrian, All,

Just a follow up on my starting problem.

Turns out the cause of all my starting troubles was a faulty fuel pressure regulator...had it changed (only about US$100 for the part, but US$150 for the labour!). It was apparently not able to hold the pressure (?) and deteriorated gradually and hence the cause of cold and warm starting.
In the course of changing the part, they found some parts related to the injectors that were cracked (potentially causing air leaks to the engine), as well as a fuel leak.

Had those all replaced and I am happy to report that my car now runs perfectly. (been like that for over a week now). It starts better than I can remember it ever starting...I just need to crank for about 1 or 2 seconds and it ALWAYS bursts to life as it should! Amazing stuff.

Thanks for the help and advice.

Raymond
90C2

p.s. Adrian, I think that means you were spot on when you said I was running rich and that fuel was wetting the spark plugs and causing black smoke on start up?

p.s2 As for the 'pinging', I can still hear it sometimes but have a suspicion it is probably a sound more related to the clutch/transmission. It only happens ocassionally, and only when in gear. Any thoughts on whether I could be right? (the sound can also be described as a little like 'clicking')I'll leave it alone for now because my mechanics advice it is not a problem at all. A few of them can't hear it at all!

horst

can anyone tell me just where the fuel pressure regulator lives? are we talking about the check valve that is part of the pump?