500 SEC (126) Ignition Problem

[windycottage]

Hello All - I'm new to this so apologise in advance for any stupid mistakes. I've got an 1989 500 SEC thats been fine for the last three years but has developed an ignition problem (I guess - I'm no expert!). The car starts OK but after its been running for about half an hour the engine fails plus the whole ignition system. When it fails the car wont re-start (engine turns over but does not start), but if its left for about 30 mins it starts OK and runs again for about another half hour when the problem re-occurs! Sometimes if the car is run for a short time then switched off and left for 10 -15 mins it wont restart, but left for 30 mins or more its OK. MB diagnosed problem as ignition coil which has been replaced but has not solved problem. I've also had fuel pump relay and ECU replaced on advice of specialist but still problem persists! Any body got any ideas? Many thanks.

 

[television]

The crankshaft sensor can do this, you can measure it when good it is 1kohms

when bad measures near open circuit, this will stop all ignition circuits

 

[windycottage]

Many thanks - Will see if this helps.

 

[jibcl500]

Ignition module!!

jib

 

[windycottage]

Replaced the crankshaft sensor and this seems to have done the tick! Many thanks Television.