1990 Passat won't start second time

Question

I have 1990 VW passat B3 1.6 liter 53 kw gasoline, single point injection.

I had some problems with starting ignition. Also Engine would stop working when I pressed on gas or spontaneously after few minutes of running on idle. I changed fuel filter and fuel pump and problem with engine shutting down on gas went away.

Now I have another problem. I can start engine only first time. If I stop it I can not start the engine immediately after the first attempt. I have to wait somewhere around 30 minutes and only then the engine would start again only for one time.

Also I notices that there is a lot of condensate being emitted through exhaust.

Any ideas how to fix this?

Answer 1

This sounds like temperature sensor problem. The ECU thinks the engine is always cold, and is trying to start a warm engine like it would start a cold engine. When you wait 30 minutes, the engine has had a chance to become slightly colder, and therefore, the cold engine start procedure works.

Do note that the ECU temperature sensor can be different from the temperature sensor that controls the temperature gauge on the dashboard. So, even though you see from the temperature gauge that the engine is warm, the ECU can still think it's cold.

On such an old car, there may not even be a trouble code for faulty temperature sensor, or if there is, the ECU may be dumb enough not to realize the sensor is faulty when it shows continuously cold engine.

Edit: Oh, and do check for the simple things, too. I had an occasional starting problem on my 1989 Opel Vectra and the cause was a bad ECU relay. I don't now recall the full details of the symptoms, but it wasn't clearly related to temperature.