Golf III TDI Starting Problems: 1996, 1Z Engine

Hello TDI experts,

My Golf has been starting very poorly for the past three days. It only starts with full throttle and about 5 seconds of cranking, and it doesn't matter if the engine is cold or warm. This problem appeared suddenly, overnight. When it does start, there are no other issues, and I haven't noticed any loss of power. I've also tried a different relay (relay 109).

Do you have any ideas?

Thank you.

Daniel.

What does the error memory say?
Have you checked the lower timing belt pulley? Perhaps the screw is loose, and your injection timing is no longer correct.

Thank you for your quick response.
I went to the workshop, and they read the error codes and connected a diagnostic tool.
I believe that the emission values are within acceptable limits.
They also tested the battery, starter, and generator.

Could the throttle valve in the intake manifold be defective?

Best regards, Daniel.

I've checked again, and I've discovered an air bubble between the diesel filter and the fuel injection pump. How do I get it out?

Best regards, Daniel.

Hi Daniel,

"Your fuel system is drawing in air somewhere. Have it checked for leaks. Possibly, a seal between the pump and the fuel line has become damaged. It doesn't necessarily have to be diesel leaking out, but air could be getting sucked in! Also, check the fuel filter; I once had one that cracked, and air got in."
When the engine is running, the air automatically escapes, and the system self-bleeds.

Quote:

Could the throttle valve in the intake manifold be defective?

I am not familiar with a throttle valve in the intake manifold of the 1Z engine.

Hi,
I followed your advice and replaced the diesel filter, but unfortunately, that wasn't the problem. Then I checked the diesel lines in the engine compartment with a 'leak detection spray,' but I didn't find anything.

A friend mentioned something about a diesel pre-heater and said it might be the cause, possibly because it's leaking.

Do you think that's possible, or can you think of any other reasons?

Best regards, Daniel.

The 'diesel pre-heater' is the valve that sits on the diesel filter; it's the (usually) white part to which the diesel return line and the hose back to the tank are connected. Normally, when changing the diesel filter, you only remove the clip, detach the part, and reattach it to the new filter.

Sometimes things break, develop a crack, or something similar. The part itself costs just under €12.

Hello,

The small diverter valve located at the top of the diesel filter, used for preheating, has one or two seals that are prone to failure if the connected hoses move too much due to vibration.
With my last diesel filter, there were even 2 new sealing rings included. Installed -> no more bubbles in the line to the fuel injection pump.
The leak was minimal and not noticeable.

Best regards, Rainer.

Thanks for the tip, I'll try replacing it and see if it gets better.

Best regards, Daniel.