AFN won't start: Troubleshooting guide

My 1997 A4 drove about 150 meters, but it didn't respond well to the accelerator. When I pressed the clutch at the intersection, it stalled, and it hasn't started since. I've already checked relay 219 (replaced it), and fuel is being supplied, which I confirmed by checking the return line at the fuel filter. About two weeks ago, I had the same problem, and it turned out to be a faulty relay for the fuel pump/injection pump. Now I'm a bit at a loss... or did I perhaps buy a defective relay? Is there a way to test it?

I am grateful for any help.

Hi,

Have you ever measured the voltage at the output terminal?
To test whether the pump is actually working, you can loosen the retaining nuts on each nozzle individually, wrap them in a cloth, and then play the organ to see if anything reaches the nozzles.

Okay, thanks for your tips.
I have board voltage at the starter } when turning on the ignition, but only for about one second. I tried bridging it, but it still doesn't start. Regarding the injectors, I can say that there is definitely voltage reaching them. The glow plugs should also be working; I tested that by disconnecting the temperature sensor, but without success. }

Could the starter motor be rotating at too low a speed?

No, it's turning normally like always. It's probably not the immobilizer, or at least the warning light goes out after about five seconds... I'm pretty clueless right now and don't want to have to call the police again. Does anyone have any other ideas?

Hmm... Have you actually measured to see if there's any voltage reaching the motor shaft? It could also be a faulty ignition switch, or maybe it's the relay 109 again...
Okay, I'm going to assume for now that all the fuses are in good condition and free of oxidation.

Best regards,
Dirk.

Hmmmm...

'When you turn the ignition key, does the preheating indicator light up briefly? It should illuminate for a moment. If not, then either the ignition switch, a fuse, or the darn relay 109 is faulty.'

I'm ruling out a faulty water pump. If that were the problem, the engine would at least briefly start and then immediately stall.

something else,

'Are the timing marks aligned? If the timing chain has skipped a tooth for any reason, the engine won't start.'

Okay, all contacts are fine. The preheating indicator turns on and off after about a second, as usual for these temperatures. The ignition coil is also okay. I've already replaced the relay, but in my car, it's the 219 model, not the 109 model!

so, all contacts are okay, the preheating indicator turns off after about a second as usual at these temperatures, the ZR is also okay, I already replaced the relay, but in my case it's the 219 model, not the 109 model!

If everything is okay, then it will start!

How did you check the valve timing?

I followed the instructions... I jacked up the front of the car, adjusted the timing to the crankshaft and camshaft, removed the injector and looked inside, and it also appeared to be at TDC. The end of the story: I had it towed away .
I'll let you know when I find out what it is. Thanks to everyone for your support!

I followed the instructions... I jacked up the front of the car, adjusted the timing to the crankshaft and camshaft, removed the injector and looked inside, and it also appeared to be at TDC. The end of the story: I had it towed away .
I will let you know when I know what it is. To everyone, thank you very much for your support!


hähh ??? It's about the position of the crankshaft and camshaft relative to each other when it comes to the timing, and the ESP as well! And that's what you should be checking. You can see if the piston is at TDC or not, but you can't see if the valves are in the correct position, or if the fuel injection pump is working at the right time to do what it's supposed to do... !!!

Okay, the friendly staff said: 'The coolant temperature sensor and the parking brake sensor are defective (according to the diagnostic scan) but we don't have those parts in stock.' I'll try to find those parts and maybe install them myself?

Well... you mentioned earlier that fuel reaches the injectors. So, it probably can't be the fuel shut-off valve. I think the error might have been caused by your measurements. Maybe you disconnected some connectors. And I find it hard to believe that it wouldn't even start in the summer if the coolant temperature sensor is defective...
It's probably best to check out joergs' tips again. They sounded quite plausible...
Best regards,
Dirk.

Okay, so the friendly people just told me that the car started perfectly this morning, and they think the problem might be with the starter motor. I'm starting to get confused. Just a small note: apparently, there was a tuning box installed in the car until about a month ago. Could that be related?

Okay, this is getting too confusing for me now!

I don't think there were any errors stored. The engine started, and then... and then... it should have been running! But it wasn't! And now it's running, but the mechanic is saying something is wrong? Sorry, but something doesn't add up here! Either your information about the tests performed is incorrect (like the valve timing), or you're being misled!

I certainly can't imagine that, given your detailed explanations and all the successful tests, the diesel engine wouldn't have started!