81 Diesel Rabbit

[81VWDIESELRABBIT]

I need help!!!! Alright I bought my first diesel, an 81 diesel rabbit. Started and ran fine right away. Drove it for a couple months and then the gravity valve broke while driving. Didn't think much of it, couldn't find anything on it so just left it. Drove it one day when it was raining. Next day went to start it and wouldn't fire. Would water have gotren into the system? It Would puff blue smoke every once in a while when cranking. Replaced Glow plugs and relay. Replaced Air and fuel filter. Still nothing.
Sat for a couple more months. Tried starteing it up, didnt sound like it was getting fuel. Towed it, and kicked it into gear, and would run until you let off the throttle. Towed a little more, got it to start and run for a bit but then died. Tried starting it with the key and got it to fire up, but would die at low rpms. Started it, kept it throttled up, cracked open injectors one at a time until fuel started out. Then I thought maybe to remove the broken Gravity Valve and just connect the two hoses and got a vented gas cap. Do I need to cap the hoses? When priming it at the pump, it will start only once in a while but still see air bubbles right in the line from filter to the pump. Any ideas? Anything will help! Thanks!

[82vdub]

Welcome to the forum. What is a gravity valve?

I think you need to start to look at various systems and rule them out of the starting issue or keep them in the starting issue, depending on the results of your tests. For example, if you have a working block heater system, plugging that in for (say) 4 hours will have the car "think" it is a warm/hot engine and a warm diesel will start much easier. The results of that will tell you if the glow plug system is working or not. If it fires right up, it's likely glow plug related.

Also, rigging up a bottle of fuel with an inline filter, gravity fed, to the injector pump will tell you if you may have a fuel delivery issue with the fuel line/tank system etc on the chassis of the vehicle. Once again, if the vehicle starts right up, you have a fuel delivery issue on the chassis of the vehicle. If it does not, you still may have a fuel issue, but it's not located anywhere but on the engine.

Have you checked the injector pump timing to see if that's on?

You basically half a system and test, and see which half failed the test to tell you which half to focus on next. Also, if you have not purchased a Bentley repair manual, it's worth it's weight in time and parts replacement money as it will tell you a whole lot about these engines.

[81VWDIESELRABBIT]

A gravity valvle, is a check valve that connects two fuel lines, not sure which ones exactly, and is basically there just for when the car would flip over. It's located inside the back passenger side wheel well. I am going to try the test ideas you provided me and see if I can figure this out.. Thanks a lot!

[Fatmobile]

If the gravity valve is closed; no air can enter the tank.
As fuel is being pulled from the tank, no air takes it's place.
It can build up enough vacuum to collapse the tank.

Look underneath.
Does it look like someone jacked your car up using the tank?