[vwdaun]

For some time, I've had starting issues with my '81 S. Symptoms:
Cold start:
Cranks, fires, dies almost immediately unless you feather the throttle. After 30-ish seconds it may hold an idle, but the idle will then continue to drop from a normal 950 rpm to 400-500. Once the car reaches normal operating temp, it idles just fine.
Warm start:
Cranks, fires, dies almost immediately like the cold start unless feathering the throttle. It will then go through a period of a minute or so that it just won't idle, but then after that all is well.
I ran all the fuel pressure tests on it today (per the Bosch fuel injection book) and everything checks out as perfectly normal. The only other thing I've done is replace the aux. air regulator with a used one of unknown condition.
Anybody have some good solid ideas on where I should go from here? (I am *not* Megasquirting this car, it is staying stock, including the doggy 1.7 engine.)

 

[veetarded]

Re: Starting issue is getting old... ideas? (vwdaun)

Bad ISV? Oh wait, maybe you should try airplane parts.

 

[cholland_]

FV-QR

Actually, my car has had very similar symptoms lately.
In for suggestions.

 

[power_house]

Re: FV-QR (cholland_)

i would say cold start valve but if it does it while warm that kind of throws a wrench in things. have you checked for vacuum leaks?

 

[xenergy_one]

Re: Starting issue is getting old... ideas? (vwdaun)

My 81 had a lot of cold start problems when I first got it.
1. My biggest problem was a vacuum leak at the injectors. I had to replace my seals and shrouds to fix it. This was causing both cold and hot start issues. You can spray some carb cleaner along the injectors to test this. If your idle changes = bad seals.
2. Using the carb cleaner, I also found a leak at my idle screw which I solved with a simple o-ring.
3. My other major problem was some fine rust build up in my WUR. I just disconnected fuel lines from it and blew it out with carb cleaner. This made a big difference in cold starts.
4. I also had a leaky fuel accumulator which caused both hot and cold start problems by allowing vapor form in my fuel lines.
5. Lastly, I had a bad fuel check valve which gave me the same symptoms as problem #4.

 

[Sciroccoracer7]

I would check and make sure your thermal time switch is functioning properly (bently should have test procedure), and the I would check to see if your frequency valve is working. Also make sure your oxy sensor is cycling correctly.

 

[kerensky]

Re: (Sciroccoracer7)

Quote, originally posted by Sciroccoracer7 »

I would check and make sure your thermal time switch is functioning properly (bently should have test procedure), and the I would check to see if your frequency valve is working. Also make sure your oxy sensor is cycling correctly.

Common problem in all flavors of CIS. After you test the thermo-time switch per the Bentley, and assuming you have no vacuum leaks (put your finger over the idle air screw - often that o-ring is bad. Open vacuum leak directly into the throttle body is bad, mmmm-kay?) then my favorite suspect is the coolant temperature sensor. Replace it with a *new Bosch* unit. Do not go cheap and get the FLAPS variety.
Good luck!

 

[Calimus]

Re: (kerensky)

Everyone's giving some excellent things to look at.
My contribution would be to check the cold start injector to make sure it's not continuing to spray after it should shut off.
The Aux air regulator caused some issues with my wifes cabby when I first rebuilt the car. Even after I replaced it. Turned out, it was the electrical connector to it that was faulty (harness side). The wire had broken inside the connector, check yours with a volt meter.

 

[TooClutchVW]

Re: Starting issue is getting old... ideas? (veetarded)

Quote, originally posted by veetarded »

Bad ISV?

x2 spray some cleaner in there and if that doesnt work then its probably the thermotime switch