Car not turning over - intermittent

[GordyB]

OK, not sure if this is electrical or mechanical. About 1 in 20 times you go to start the car it just turns over for a fraction of a second then everything stops. You have to turn the key back to the off position and restart. It always starts second time you try when this has happened - until this week. At the last service the "specialist" said it was to do with the immobiliser. I only have 1 key so when it happens there's not a lot I can do other than try again.

To me its acting like an old car of mine did from the 70's when the windings on the starter motor were on the way out and about 1 in 10 times starting it, the starter motor would stop in the position with the issue and it wouldn't turn the next time you try.

This week it's got worse. Took 8 attempts in the petrol station this morning with a queue behind me. Drove straight home and tried it another 5 times and can't get it to not work!!!

Any suggestions where to try looking first would be appreciated.

 

[m7m]

From experience I had with previous cars (ones I had before the Merc), the first things to check will be the condition of the distributer cap and the spark plugs.

 

[richard]

Any suggestions where to try looking first would be appreciated.

What car ?

The "newer" ones the starter motor operation is controller from the engine management system, which is how it does "one touch" start, i.e just flick to 'start' and it will keep running the starter motor until it is started.

You could put a meter on the starter motor power contact and ground and see if power is making it to the starter motor in this "failure" mode, if there is power and its not turning then i'd suggest a new starter motor, if there is no power then something more complex/awkward no doubt

R

 

[EDZ649]

It could be as simple as a worn ignition switch. I have this problem on my partners A140, was a real pain, gradually got worse until one day it wouldn't start at all. A new switch sorted it out

 

[GordyB]

Sorry, 1999 CLK cabrio

Worn switch sounds a possible cause from the way it's acting.

 

[jonnyboy]

Also check things like earth straps

 

[219]

Wouldn't do any harm to keep a large hammer in the boot until this is diagnosed .

It does sound as if the switch is a likely contender , but if you do get another episode of repeated failures - giving the starter motor a sound 'whack' might just do the trick : in which case you'll have identified the problem . As Jonnyboy says , worth checking the electrical connections to the motor , the grounding of the motor to the engine , and the earth return circuit to the body .

 

[markmifsud]

does the rev counter flick up a few 1000 on the display ? This could be a dry ring gear. I have heard of a few like this where the only repair was a liberal greasing of the ring gear

 

[BlackC55]

It take it it is a 320.

This is a common issue and it needs the ring gear and starter lubricating with special grease (that I have)

 

[Doug_]

Is this a straight forward job or labour intensive? The reason i ask is because it is an intermittent fault on my CLK320.

Thanks
Doug

 

[markmifsud]

where are you doug? might be worth a trip to portsmouth (blackc55) to get the job done properly.

 

[Doug_]

I'm quite a distance away in the East Midlands, north of Nottingham, so it would depend on length of job/ cost and mileage as opposed to stealer charges.

 

[BlackC55]

A dealer will charge about 2-3 hours labour.

I only charge 1 hour as I have done many many before a can do it quickly.

 

[GordyB]

Hi BlackC55 , yes it's a 320 !!! I'm even further away than Doug - will this be commonly known about at independant garages if it's a known problem?

Doug - where are you as I'm about an hour'ish north of Nottingham, sounds like we could do with finding someone close by with the knowledge BlackC55 has........

 

[darylyoung]

if your mechanically min ded at all you could do it yourself there was an article in the mb club gazette a month or so ago where they cleaned the ring gear i think through an apperture in the bell housing or they may have removed the starter motor its the rust on the ring gear what causes the fault.

 

[74merc]

if your mechanically min ded at all you could do it yourself there was an article in the mb club gazette a month or so ago where they cleaned the ring gear i think through an apperture in the bell housing or they may have removed the starter motor its the rust on the ring gear what causes the fault.

I think the engine was running and they removed the rust from the ring gear with sandpaper. Sounds like a job for a pro!

 

[Doug_]

Doug - where are you as I'm about an hour'ish north of Nottingham, sounds like we could do with finding someone close by with the knowledge BlackC55 has........

I have by chance found an indie in Nottingham, they come well recommended, so as i am due an A service in about 1300 miles i will check them out. I expect to have the service done sometime in April. They have quoted about £150 for the A service and approx £180 to change garbox oil and filter. Do these prices sound reasonable?

Doug