Crank sensor problems???

[Adz The Rat 0]

Was going back home after a gettin a curry yesterday and the C just decided to cut out.

Tried to start it, starter was spinning fast enough but engine wouldnt start.

First thoughts was something had got damp.

Left it for a while, kept trying but no luck.

So rang AA, man came in van and checked few things.

He said he thinks it is a crank sensor problem, ecu is getting power but its not telling engine to fire???

 

So towed it to work and left it there overnite.

Got to it this morning and it started first time, has been fine all day.

Anyone had similar problem to this???

[Bruno 4]

You need to get a VAG COM on this. The error message will be there. The AA man is probably right. A catastrophic loss of engine power is likely to be either:

- the ECU relay

- the Pump relay

- the ECU itself

- the crank sensor

- the cam sensor (although this will tend to allow you to run but it may cause the engine to flop about and hunt)

- the ignition switch failing.

 

If you dont get an error code, then I would look at the ignition switch first. You may need to wiggle it in its housing to get the engine to start. Its unlikely, that it is the problem cos the AA guy found power on the ECU, but it can happen.

[CorradoVR6-Turbo 0]

as above but do you have an alarm fitted?

[Reggit 0]

I used to have this fault, but with a very random cure - so may just be unique to mine.

 

The car would spin over but not fire as you described. I found that pulling relay 99 and replacing it would allow the car to start. It would then behave fine for weeks before acting up again.

 

Relay 99 is for the wipers and not related to the engine, the car will happily run without it fitted. I figured that I may have had a loose connection on the rear of the fuse panel and by fiddling with the relay was allowing the panel to flex and contact to be made. I never found out for certain though as the fault just went away!

 

It would play up only when the interior was humid or damp. Dunno if this is any help to you.

[Critical_Mass 10]

When i had this problem, again the car would turn over but not fire, RAC said it was the crank sensor. Replaced that and still no joy, ended up replacing ignition switch after advise on here and it started first time.

[dr_mat 0]

Note that the ECU will ALWAYS report "Crank Sensor: No Signal" when the engine is not turning over. You cannot diagnose a failed crank sensor from that.

Check the basics. Do you have fuel. Do you have spark. Does the immobiliser work. Wiggle ignition leads around, check fuses etc ..

[Kevin Bacon 5]

Motronic needs an absolutely perfect power supply or it's schitt at starting.

 

Reggit - nail on the head. Starting problems can sometimes be traced to the X relay having a bad contact. There's a technical bulletin on the net somewhere about some VR6s with dodgy X relays.