Starting Problems: Troubleshooting & Solutions

Hello everyone, I have a question for the group. Maybe someone here has experienced this problem and knows a solution...
I have a Volkswagen Passat 35i B4 TDI with 90 horsepower, manufactured in 1995. This car has 250,000 kilometers on the odometer and has generally been quite reliable.
"Recently, there have been problems starting the engine: The starter motor functions normally, but immediately after reaching the idle speed, the engine cuts out. So, it runs for a few cycles during the starting process, then the engine control unit apparently cuts off the fuel injection, the engine stops, and the electro-pneumatic converter for the wastegate control clicks... until you turn off the ignition and try again."

It initially happened sporadically, regardless of whether the engine was warm or cold, and could be resolved by disconnecting the connector from the torque converter and starting the engine once in normally aspirated mode. Therefore, I don't believe it's a real mechanical problem. For example, I drove 400 km on the highway normally, but then I couldn't start the car at the gas station. I followed the procedure and was able to continue driving normally... It seems like the engine control unit or the pump is requesting a failsafe mode or shutdown, but I don't know why.

If anyone can relate to the symptoms described, I would be grateful for any tips... I'm a student, and I would really like to avoid a visit to the workshop .

Dan.

Hello Dan,

The control unit writes error codes to the fault memory indicating what it doesn't like. For example, the WFS (likely referring to a specific system or component) doesn't like something.
Read the error codes.

Best regards, Rainer.

Hmm... Reading the error codes is always helpful, but right now, the thing won't even start, so I'd have to tow it to the nearest workshop.

"My concern is whether someone can diagnose the root cause based on the symptoms, because the error occurs quite unsystematically. And if everything works again after following the described procedure, it seems like the error in the control unit is somehow resolving itself... I had the error memory read about two months ago because my ABS wasn't working, and there were no other error messages at the time, even though the starting problems had already occurred occasionally."

You often hear about fuel pump relays failing... Does the engine control unit detect this and shut down, or would the engine only stall due to fuel starvation?

danbo wrote:

You often hear about the fuel pump relay, which is apparently prone to failure...

I'm familiar with this issue from relay 109, which is the relay for the control unit. You could check if all the solder joints are okay.

If you suspect it's a relay, then the connected components won't be receiving power. Try checking if the relays are actually switching.

Maybe you'll get lucky and it will start again. Not a member of the ADAC? I'll still try to read the error codes if possible.

If the part has an immobilizer, which I assume it does, there's a nearly 90% chance that the reading coil is damaged. This could be due to a faulty connection to the MSG (Main System Module) or a problem with the coil itself. Sometimes, a firm tap under the ignition switch can help, and the car might start on the next attempt. The only way to be sure is to read the error codes. Otherwise, remove the trim around the ignition switch and gently wiggle the ring while checking the wiring.

Hmm... that's a nice thought, and it's certainly possible... Does the car even start if there's no "clearance" from the WFS, or is the starter motor not connected to that?

The car definitely has an immobilizer, and the ignition switch was already broken when I bought it.
The described symptoms would then have been purely coincidental... it's possible.

"The car starts normally but then turns off after a very short time. This matches your description and isn't uncommon for a car of that age."

Okay... then the inevitable question : Can this be fixed, or do I have to take this thing to the workshop and have a new ignition switch installed? Actually, I don't care about the WFS (Wertfreisetzungssteuer), nobody is going to steal this car anyway...

...but the WFS (Warranty Fulfillment Service) is included in your insurance policy if you have comprehensive coverage.

m;

I have a partial casco insurance ... liability insurance is enough ... I just looked, and you can find locks with the control unit for the WFS, but do you have to "pair" them with the control unit, or can it be done without much effort ... (old out, new in, connect, done..)?

Only the WFS and MotorSTG need to be linked.

The reading head is replaceable.

m;