Intermittent starting problem

I have an intermittent starting problem with my 2001 Mercedes C240 auto with 85,000 miles. It seems similar to a situation with another reader in the October 2014 issue.

In my case, I replaced the fuel pump relay approximately six months ago. Prior to this, my car would not start and I had no fuel pressure at the injection rail, but after replacing the pump relay, things returned to normal. Then, over the past six weeks or so, upon switching on the ignition, I intermittently experience a situation where the engage starter motor ignition key position 3 appears to be dead and the gear change remains locked.

On further examination, I noticed that, with the ignition on and the key in position 2, where normally the LCD screen in the middle of the fascia shows zeros for mph, mpg and miles travelled, the zeros have been replaced by a row of dashes and that the gear position indicators – normally ‘S’ for summer and ‘P’ for park, are blank. After switching the ignition on and off several times, I eventually get the normal LCD display and the car starts and runs normally.

Normal starting may last for several days or I may have the non-start problem the next time I go for a drive. Over time the problem has become more frequent, so I am not keen on using the car in case it fails completely miles from home. John Wood There is a very common problem on the C240 which causes similar problems, although it is normally terminal and not intermittent. The cooling fan within the ECU housing fails and seizes up, causing a small 10A fuse to blow. As we do not often experience temperatures high enough to require the extra cooling delivered by this fan, it is generally accepted that disconnecting the fan and replacing the fuse is acceptable practice. The fuse and fan can be found within a small black box on the nearside inner wing. The cover is held on with four screws and should bear a sticker indicating that the workings below are connected to the air-conditioning unit.

Unfortunately, I do not believe this is the cause of your troubles. The problem you describe may be either a faulty ignition switch or that the transponder within the key is failing. If it is neither of these, the problem may lie within the gearbox electronics. I would start by checking the multi-plug connections