Mercedes: Mercedes E280 (94) wont start, mercedes e280, crankshaft sensor

Question
I own a 1994 Mercedes e280 and it wont start.  The air pressure sensor and the crankshaft sensor have both been replaced.  The AA came and said there is no spark and he suspects wiring loom fault.  Quote: 'Non spark.  No switching at coils.'  Sometimes the car starts and other times it does not.  When it does start it runs perfectly but when I stop and go to restart it might or might not start.  Apart from wiring loom is there any other possible cause?

Answer
Hello Lawrence,
Of the ignition receives on voltage then you may have a bad fuse or bad connection. The other possibility is the ignition switch. If you have the codes checked, it may tell you where in lies the fault. I had similar problems with my 420sel and had to replace the electrical part of the switch to cure the issues.
On my car the switch in on the dash not in the column so I had to drop the steering column to get to the switch. This was quite time consuming, as I had to crawl under the dash and take loose considerable stuff and remove the instrument display. The dealer would probably charge 600.00 USD or here for such a job.
I bought the electrical that is attached on the back of the key/tumbler section with serews for about 40.00 on ebay.

Good Luck
Rob