TDI Starting Problems: Troubleshooting & Solutions

Hi,
Perhaps this is a silly question, as it might be quite simple.
If I want to spin up a TDI engine using the starter motor, but without it actually starting, how can I achieve that?
Surely, we need to prevent anything from being injected, right?
Is there any connector (e.g., for the fuel injector pump) that can be unplugged?
Is this an Audi A3 with a 1.9L TDI engine and 110 horsepower?
Best regards,
Roland
P.S.:
During a compression test, the starter motor is also used to turn the engine over without the engine actually starting.

It would be a good idea to disconnect the pump connector. Alternatively, you can remove the 109 relay. This will cut power to the engine control unit, and the pump will also no longer be activated.

Hello Matthes,

First of all, thank you for the quick response!

Sure, here is the translation of the text from German to English:

'Two more questions:'

1. The engine won't mind, right? (I'm not planning to run it for long, just about 20 revolutions.)

2. How do I find the relay? Or the pump connector?

Best regards, Roland.

The engine is robust. It doesn't care. If you pull out the pump connector, you'll get an error in the engine control unit. However, that error will disappear after 50 engine starts.
The pump connector is located near the pump and has 9 or 10 pins.
You need to remove the engine cover to see it better.

Das Relais ist unterhalb vom Lenkrad links hinter der Schalttafel. That's the spot.
for most of the relays in your A3.
Hi Mattes,

Just as easily, and probably without any errors, you can remove the retaining plug by unscrewing or pulling it out.

m,

Hi,
This is not my work, but rather that of a colleague.

So, a relay would be simpler because you wouldn't have to remove the motor cover, and your fingers would stay clean, right? And if the control unit doesn't get any power, it won't register any error codes, right?
And in that case, nothing can happen to the engine, right?

Best regards, Roland.

You actually have less access to the relay. The pump connector is easier. The shut-off valve would also be an option. However, on some TDI engines, it's encapsulated and difficult to reach. It's not just plugged in anymore; it's usually screwed in.

Hello RoBro!

I came up with the following idea to test my starter motor. Disconnect the plug from the starter's magnetic switch, connect a cable with a 6.3 mm flat connector to the wire, and hold the other end against the positive terminal of the battery. The ignition should be off, and the transmission must be definitely in neutral. Otherwise, you might run over yourself.

It worked well afterwards. Due to the sparking at the positive terminal (due to the high inductance of the magnetic contactor), I added an extra nut to the threaded bolt of the terminal.

RoBro wrote:

1. The engine won't mind, right? (I don't want to do it for long, just about 20 revolutions). Best regards, Roland

Just as bad as every start. I would limit the attempts to about 10 seconds, with cooling phases in between. In the 4-cylinder engine, the starter motor has a power consumption of approximately 2000 W (with a power loss of about 300W!) and is not designed for continuous operation (no cooling measures).

Regards,
mcgregg

Well, for me, as an electrician, it's probably easier to find a relay than a fuel injection pump...

The idea of connecting the starter motor to the battery is also a good one.

Best regards, Roland.

Hi,

Please only disconnect the plugs when the ignition is switched off.

Best regards, Rainer.

Well, I think the idea of using a trigger switch is the best one.
We'll probably have to start looking for the magnetic switch on Monday.
If anyone can provide navigation assistance, they are welcome to do so.
Regards,
Roland.