diesel engine

My 1995 Audi 2.5 tdi also does that.

When it is cold, the glow plugs will be activated, and the engine starts without problem, even down to -20°C. When it is between +10 -

A VAG mechanic told me to try by disconnecting the temp sensor controlling the glow plugs, which makes the controller believe it is very cold, and this method works fine.

I have not been able to find out the nominal temp/resistance of the sensor, and I haven't gotten around to replace it yet. If the engine doesn't start after cranking for 45s, then I disconnect the plug and it will start immediately.

Before I knew this trick I had it flatbedded once, and have drained the battery fully a few times.

The problem has gotten worse over the years. It now has about 285'km on the odo and it has begun consuming some oil, about a liter in 5'km, which isn't too bad. The injection pump is also leaking slightly, and nothing has ever been done to the injectors or pump.

A very simple solution would be to add a manual switch inside that disconnects the temp sensor, but that feels like a bad solution.

Thomas

This is mostly speculation based on observing my old VW diesel that did exactly this as it got older. The problem traced to a bad starter motor. I had to glow it every time until the starter was changed.

To start a diesel, it has to be cranked at a certain relatively fast RPM. When the engine is hot, everything tends to seal better, which increases compression a little making it harder to crank. If you use the glow plugs, the extra heating in the cylinders gets the fuel to the flash point sooner.

I think your starter is getting tired and spinning too slowly (and probably drawing too much current while its doing it).

That might in fact be the problem.

Lately it has occasionally failed to engage the gears properly, and it might be an indication that entire starter is shot.

These aren't cheap... I checked at a non-VAG parts dealer, and it is the equivalent of US $520 for an exchange unit...

Thanks!

Thomas

Could it be something as basic as a dud battery or bad battery connection?

Henry

No, the battery, which was about two years old, was replaced about a month ago as the starter wouldn't turn over fast enough, and my intelligent charger couldn't charge it fully.

This morning I had real problems with the starter gear cutting out. I bought a used starter and I'm on my way to the garage to replace it.

Thomas