We are original owners of 1980 VW, 1.6 CIS fuel injection.
Starts OK when cold. Starts OK when warm. When warm, then left "off" for more than 20-minutes or so -- very difficult to restart unless gas pedal held to floor. Then finally starts starts but runs very roughly for 10 secs or so, then finally runs normally. Fuel consumption also higher than normal but passed emissions test OK.
Replaced plugs, points, condensor, reset timing, idle -- no changes. Replaced thermo switch & temp compensator but no change.
From reviewing diagrams, suspect fuel leak either at accumulator, check valve, lines, or injector regulator (would leak thru injector into manifold??). Don't smell any gas and car is garage kept.
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Hot starting problems are usually fuel related. When a hot engine is shut off, the temperature of the engine and everything on it continues to rise for awhile as the engine undergoes a period of "heat soak." This can cause fuel to boil inside the carburetor bowl, fuel lines and fuel filter. When you attempt to restart the engine, "vapor lock" obstructs the flow of fuel and the engine doesn't want to start.
This is much less of a problem on fuel injected engines because the fuel is usually under much higher pressure inside the injectors and fuel line. Even so, a fuel line routed near an exhaust manifold or a fuel rail that's exposed to a lot of heat may still suffer the same kind of problems.
Heat soak problems such as these can sometimes be cured by wrapping insulation around affected fuel lines, and/or installing an insulating spacer or heat shield under the carburetor.
This issue would not be timing, more likely something with the fuel control. The K jetronic fuel injection has several temprature sensitive controls, I suggest that you have a shop diagnose for you, as parts are expensive, so you want to replace only what is needed.
There are devices in the Bosch CIS-E system not functioning that may need replaced. Most commonly it would be the thermo-time switch. This switch is also a sensor telling the ECU whether your engine is cold or hot so it would compensate fuel delivery depending on temperature. An auxiliary air regulator also opens (more air) or closes (less air) dependent from the thermo-time switch signals. It's basically telling the ECU when it's a cold morning to supply a richer air/fuel mixture or not to when it's at operating temperature. There is also a cold start valve (fifth fuel injector) that could be sticking or leaking or simply not supplying fuel during cold start up. Again, this has a higher level of understanding and special VW tools to diagnose your fuel injection problem that should be left to a VW tech to work on. It could be dangerous because fuel is involved, a single spark from static electricity could ruin your day.
These CIS vehicle are tempermental. Best thing to do is change the air filter, clean air flow sensor plate(Spray gunout on a rag and lightly clean it ) Gun out throttle body and a slight idle adjustment. Finallyonce a month put some fuel injection cleaner in the tank. See how this works before we start testing items.
Ther are a few items that could be causing your problem. first there is a temp sensor that turns on a cold start valve to give it a shot of fuel to help start when cold. second of corse would be the cold start valve is bad, and not spraying like it should. And then you also have an item called an auxillary air valve that lets in more air durring start up that could be bad. and ect ect ect. The best thing to do would be to get a book called Bosh Fuel Injection & Engine Managment written by Charles Probst and published by Robert Bently. i got mine at Books a Million, but am sure you could order one on Ammazon. You have what is called a continuios fuel injection system CSI for short, and can be a bit of a bear to work on without any books. Once you read and understand what you have , the better of you will be. On the bright note, this is one of the most reliable type of injection systems on the market, and yours being an early year without any type of computer, is very easy to work on.
it starts from cold because the auto choke is on ,allowing a richer mixture ,try removing the sender unit in the tank and seeing if the connection from the pump to the outlet connection is ok or leaking causing a loss of fuel pressure