mk3 gti cutting out

[mk3mark]

hello all..first time forum user here!
I bought a 96 gti 3 weeks ago. I was happy with the car until it cut out 3 days ago. I got it back to the garage.started fine after a few minutes but cut out again,as if i turned off the ignition. fuel pump runs but no spark.replaced the coil,fuel pump relay and ecm relay,but no change. Then i turned to the forums. It appears a lot of these mk3's give the same problem,but i havnt found a solid answer to the problem.
Today i checked was there a signal to the crank sensor when the car wouldnt fire..no signal. I also chcked the hall sender and got the same thing.neither show a trace on a scope when the car is in this non starting mode..but after a few minutes the car starts and both show a pattern.
I opened up the ecu. All terminals look very clean,no sign of any sort of damage.
Im truely baffled at this stage...can anybody help me out??

[boneybradley]

time to connect vag-com and see what errors it reports

[mk3mark]

I have had the vw 5051 plugged to it and got a code for the hall sender.
I checked for power supplies to the ecu today,both present when running,cranking and also when the car cuts out..but still no signal from the crank sensor or hall sender..and both have a supply and earth.
Its starting to look like an ecu.my guess is something is overheating in the unit.
any more advice for me??

[boneybradley]

check the wiring for the hall sender....they become brittle and cause issues!

[robiwill]

clean the throttle body out as these can cause faults too and replace the crank sensor if the ecu return relay didnt cure it, also worth checking the coil as these can also cause the car to cut out

[trigolf]

I agree with Bony - check condition of wiring loom to crank sensor, its hard to see properly as its largely hidden from view. The loom insulation breaks down with heat from the engine block and you can end up with the sensor signal being shorted against the block. I had this problem with my Golf and when the garage showed me the state of the loom I couldn'nt believe it, It was bare wire in places !