Non-start issue

Q

The other halves pride and joy is her 2006 Mercedes 350 SLK with 38,000 miles. She has owned it for over 10 years. It is in excellent condition probably due to fact it remains in the garage for 11 months of the year and is only ever allowed out in fine weather and then only when the sun is melting the tarmac.

During the ‘lay-up’ months it is garaged and constantly on a CTEK smart battery charger. I start the engine every three to four weeks and allow it to warm-up to normal temperature, about 30 minutes of running.

It always bursts in to life first time and for 10 years we have never had any issues with the car – until now.

I tried to start it as normal but engine would not turn over. Battery is in excellent condition. Full set of instrument lights illuminate on the dash but when key turned further to the start position – silence! No ‘clicking’ sound from starter solenoid. Gear selector is definitely in ‘Park’. It would appear no power is getting to the starter as there is just silence when the key is turned to the start position – as if some ‘isolator’ is in play.

I have ensured gear selector is definitely in Park. Put headlights on – turned key to start position and no dimming of lights. Battery is definitely fine – 12.7 volts on voltmeter.

Checked the 15-amp fuse that was referred to in the manual as Starter (M1). Not sure what M1 stands for. Starter relay in fusebox replaced with new relay – still no starter action. Put a voltmeter across the solenoid terminal to earth on starter motor – then had someone turn the key to start position – no voltage showing on meter.

Replaced battery with a guaranteed good one just to eliminate my battery as the possible cause – no difference – still no turn-over.

Any ideas or suggestions as to what the cause of this ‘non-starting’ could be would be greatly appreciated.

As I mentioned previously, car has always started first time, so it’s not as if it has been getting progressively harder to start or shown any signs of hesitancy to turn over, so I’m baffled as to what has caused this sudden problem. Just confirming when I say nonstarting, I mean it’s not even turning-over.

Jim Harrower

A

Having carried out a test to ensure no current is reaching the starter motor and with the ignition appearing to operate correctly, I would suspect the most likely cause of your problems would be that the starter relay has failed. But you have also checked this. You have not mentioned if you have ensured that the relay does have a feed from the fusebox, and if not already done it would be worth ensuring this is the case.

If you did have access to diagnosis equipment a problem in this area may show up as a fault code P0615 or P0616 and that may help narrow down the source of the problem.

The relay trigger is fed from the engine control module and if no feed to the relay is present it may suggest a control module failure in which case getting this tested by either ECU Testing or Bbareman may be the best option.

It may also be worth making a good check to ensure no connection problems are present on either the multiplugs or the earth points.