Intermittant Electrical Fault

[Glyncon]

My 2004 2l HDi SX has a major problem which the local garage seem unable to clear. The engine runs normally but if I have been running for an hour or so and switch off it will not re start. Engine temp is normal and once cold it will start. Diagnostics indicate a defective Cam sensor but this has been replaced to no effect. The garage has wiggled wires, used contact cleaner on ECU plugs/sockets but its made no difference. Dignostics does sometimes indicate other problems such as crank sensor and occasionally the rev counter stops working. This nightmare has been ongoing for 2 weeks with no solution in sight. Has anyone experienced similar problems????

[iannez]

i would have gone for cam or crank sensor. the fault would have been cam and crank synchronization. sounds like they have fitted the wrong one.

[Glyncon]

C8 will not now start at all. towed to garage where diagnostics indicate just the Cam sensor as faulty. How does this sensor work? what is it looking for? Is there any voltage to it? Is there any way of testing it? I'm told that it is only used to check the cam position prior to starting and is not in use when the engine is running. True or false?

[Glyncon]

Fault eventually determined to be an occasional voltage spike on the 4.7v suppy from the ECU to the camshaft sensor. Amazed that there is no protection against this and that the official answer is to replace the ECU at a cost of around GBP700. A simple solution was to fit a 5 volt zener diode across the supply to the sensor - any spike will cause the diode to conduct and take the spike out. No recurring problems in the 3 months since this was done.

[techbod]

very interesting :rolleyes: that sort of fault is very rare with the ECU they are very well protected against surge