ATD Not Working? Troubleshooting Tips & Fixes

Hello!

The following problem is driving me to despair:
My car won't start. The starter motor is spinning normally, the tachometer shows the engine is turning, but it only starts after 15 or 20 attempts. However, once it does start, it runs smoothly and doesn't have any other problems.
The search function provided me with numerous descriptions of starting problems, where the engine would sputter and smoke afterwards, but nothing about the machine starting smoothly like a kitten. However, I now know that it doesn't need to be pre-warmed below 5°C.
Recently, a badger gnawed on the radiator hoses and the foam under the engine cover. Now I suspect it might have damaged a cable or hose that is essential for the starting process. However, I haven't found anything yet and I'm at a loss. I've only been a TDI driver for 2.5 months, and I'm not very familiar with the engine yet.

Therefore, I'd like to quickly ask a question: On the fresh air side, there's a small vacuum-operated diaphragm before the EGR valve, which rotates a shaft via a lever. Is that the shut-off valve?

Best regards,
Jörg

Search function -> Expert articles

Okay, I'm ready. Please provide the German text you want me to translate.

Let's check the error codes; maybe a badger has chewed through the cable of the crankshaft position sensor. Then you have to crank the engine for a while before it starts.

And yes, it's the shut-off valve.


CU Gremlin.

mcgyver2k wrote:

The starter motor is happily whirring, the tachometer indicates the engine is turning, but it only starts after 15 or 20 attempts. However, once it starts, it runs smoothly and doesn't have any further problems... Recently, a badger gnawed on the radiator hoses and the foam padding under the engine cover. Now, I suspect that it might have chewed through a cable or a hose that is essential for the starting process.

Have you been experiencing these problems since the weasel attack?
If so, Gremlins' suggestion (Hall sensor cable) is definitely a good tip.

You can probably check the cable yourself - if it is routed the same way as it is on my engine:

Remove the hood (bonnet) and, if necessary, the foam collar.

The cable emerges from the timing belt cover on the front of the engine, just below the head gasket, and runs (in a thin corrugated tube) underneath the glow plug connector strip to a 3-pin connector (black) on the transmission side of the engine. Behind the connector, it disappears into a thick cable harness after a few centimeters.
Check the entire cable length!

At the same time, you can check the cable to the OT sensor. There's a gray 3-pin connector on the black plug. Follow the cable towards the clutch bell or the main cable harness and check for any signs of damage or chewing.

If chewed, have the dispenser replaced .
While a cable break would immediately stop the motor completely, which doesn't seem to fit your described problem, who knows what might happen if moisture gets into the cable through a damaged spot and causes issues for a while without being noticed...?

The cables were exactly where Ulf described. I just checked both of them and couldn't see any signs of damage, at least not until the cable harness disappears into the engine bay. I'd need to take a look from underneath, but that's not ideal on the street. One of the corrugated tubes is slightly damaged by something, but the cable itself is fine.
"Now, it doesn't start at all. I noticed that at the beginning, when the ignition was on for a few seconds without attempting to start it, an electric motor would engage. The sound seemed to be coming from somewhere near or behind the battery. Now, there's absolutely nothing happening."

mcgyver2k wrote:

Meanwhile, it doesn't start at all anymore. I noticed that at the beginning, an electric motor would engage if the ignition was on for a few seconds and I hadn't attempted to start it. The sound seemed to come from somewhere near/behind the battery. Now, nothing happens at all.

That was probably the pre-lift pump in the tank (where is your battery located?).

If nothing else seems to be happening, check the cables around the engine control unit (if a raccoon has been gnawing on them, things will get interesting ).

I don't know where the engine control unit (ECU) is located in the Fabia... In the Polo, it's roughly above the clutch pedal, in the engine compartment (not in the expansion tank!).

Perhaps it wasn't the weasel at all, but rather that relay 109 is malfunctioning (which, given the symptoms you're describing, is certainly a possibility).

on the Fabia, on the driver's side, near the splash guard...

When I turn the ignition on, fuel immediately leaks from the disconnected fuel line. So, the fuel pump is working. The battery is located behind the headlight on the driver's side.
I've checked the wiring harness as much as I could.
Okay, I'm going to take a closer look at this from the bottom. If I don't find anything there, I'll move on to the 109. Behind the obscuring panel, I saw what looked like oversized fuses, but they're not easily accessible. Could one of those be the problem?

PS: The shut-off valve isn't moving when I try to start the engine. Where does the engine get its vacuum from before starting? Could the engine not starting be due to the vacuum pump, which might be overworking because of a damaged hose?

mcgyver2k wrote:

P.S.: The shut-off valve does not move when attempting to start. Where does the engine get the vacuum from before starting?

What purpose would negative pressure serve during startup?

The bypass valve is open and depressurized, and is only briefly closed when the system is shut down.

What does the error memory say?

CU Gremlin.

Okay, the computer says there's an OT (output transistor) issue, and the phase sensor isn't sending a signal. Since the cables are fine as far as I can see with a mirror and flashlight, the workshop should take a look at this now. I had problems with the tachometer signal some time ago. It seems like it was only temporarily fixed, because the mechanic told me earlier that a new, custom-made wiring harness will be made for the car. And they're doing that free of charge.

mcgyver2k wrote:

Okay, the computer says OT and the phase sender is not receiving a signal.

I'm now curious to know if the problems have "coincidentally" been occurring since the visit from the badger.

It seems it was just a matter of luck. I just received a call from the mechanic saying the car is running again. The problem seems to be somewhere in the old wiring harness. Further problems are not excluded until the complete replacement.