C 180 Sport bump only?

[Dave mac]

Hi all been driving myself mad....C180 sport...1998...petrol...wont start with key

Had pal with "star" check key and immobilizer all good
will bump start... but wont start from key
Starter is getting main feed and feed from ignition
Changed starter relay just in case
checked all earths and live feeds but still no luck

anyone please?

 

[martyz]

If you have +12v to the starter motor,and a start signal then your problem is -12v,check all earths,suspect engine strap.force an earth on to starter motor with a jump lead from motor to known good earth to confirm.

 

[Dave mac]

If you have +12v to the starter motor,and a start signal then your problem is -12v,check all earths,suspect engine strap.force an earth on to starter motor with a jump lead from motor to known good earth to confirm.

Already used extra long jump leads from battery to starter live and earth. Cheers

 

[E55BOF]

Did you use one of the jump leads to earth the starter motor to the battery?

If you have +12v at the starter live terminal and the ignition feed, and the starter motor casing is earthed, but the starter motor does not turn, then either the starter motor solenoid or the starter motor itself is U/S. Have you considered these as possibilities?

 

[Dave mac]

Did you use one of the jump leads to earth the starter motor to the battery?

If you have +12v at the starter live terminal and the ignition feed, and the starter motor casing is earthed, but the starter motor does not turn, then either the starter motor solenoid or the starter motor itself is U/S. Have you considered these as possibilities?

Hi thank you for your input.... I've also used my probe on the starter ( ignition wire ) and the starter jumps into life and turns the engine over no problem.... When I turn the key I do get a "klick" as if the starter had a blank spot but as I said with the probe there's no problem. So might thoughts are, there's nothing wrong with the starter. I've also replaced the starter relay with a new one from Merc. And a new battery in the boot (trunk). .... :-(

 

[Dave mac]

Did you use one of the jump leads to earth the starter motor to the battery?

If you have +12v at the starter live terminal and the ignition feed, and the starter motor casing is earthed, but the starter motor does not turn, then either the starter motor solenoid or the starter motor itself is U/S. Have you considered these as possibilities?

The jump cables were from battery terminals in boot directly to starter. Which in my eyes rules out bad earth or poor live feed

 

[E55BOF]

If the starter turns over when you energise it by feeding 12V to the switched (should be) live feed from the ignition, then it should be serviceable. Is the click you hear the starter solenoid, or the starter relay, or (unlikely) the starter motor turning a fraction?

 

[Dave mac]

The klick is the starter turning ... Enough to make the fan move 1/8th. Unless the amps through the ignition wire aren't enough? But then my probe is only about 15 amps...

 

[E55BOF]

It doesn't take much current to energise the starter solenoid - much less than 15 amps, I would have thought. If the starter motor cranks normally (when you put 12V to the ignition live feed) with a jump-lead supply direct to its live terminal, then the cause of the problem is either that the in-car high-current connection from the battery is breaking down under load, or the engine earth strap connection is breaking down under load, or the solenoid is failing to stay engaged, or the connection within the solenoid is breaking down under load.

Most likely causes are the high-current connection from the battery to the starter motor, or the engine earth strap. Check for resistance within the cables, and clean all the connections back to bright metal and make sure they are good and tight.

Hang on - just reread. If the starter motor turns over OK when you apply 12V direct to its ignition live terminal, using the car's normal wiring (i.e. without using the jump leads between it and the battery), then the problem lies in the ignition live feed. Does the terminal get hot when you try to start the car?

 

[Dave mac]

That's very interesting thank you .... I shall look and get back to you.

 

[Dave mac]

Well ok... There's barley 1 volt reaching the starter motor... Traced the wire back to fuse box in engine bay (the one that holds starter relay(which I replaced)) a purple wire... Getting erratic voltage reading from the terminal in the fuse box ... So now I'm going from ignition back in direction of said fuse box .... The saga continues......