M40 not Cranking.

[m_jermyn]

Gday boys and girls.


Got me a little M40 thats not cranking over on the key but all electrics are working such as headlights, radio, washer jets ect ect.

I am able to clutch start the car however.... I think the starter has shit it self.

I have bridged pins 11 and 14 on the diagnostic plug and I can here the starter move just a little click but it wont make it spin.


Whats next?

Mike

[Billwill]

You can short out the two large lugs....one has the braided wire that goes direct into the starter motor and the other goes direct to the battery/alternator.
This should spin the starter motor like crazy but will not engage the flywheel.

Then short the small lug that should have a Black/Yellow wire on it to the large lug with the battery/alternator leads on.
This should produce a loud "click" as the solenoid engages and the engine should turn over....if you get the loud click but nothing else then the solenoid is shot.

Of course the first thing to do is make sure your battery connections are clean and tight, the negative battery lead going to chassis is clean and tight and the grounding strap connecting the engine to the chassis is clean and tight on both ends.

[m_jermyn]

Picture of the wiring on the starter.....











When I bridge the -Neg to +Pos with a screw drive I get a single click.


When I bridge Yellow/black to +pos I get a single click.

Same as I bridge pic11 and 14 in the diagnostic plug.

[Billwill]

The cable you marked as "negative braided cable" is actually the input to the starter motor itself; the other side of the starter motor goes to ground on the motor body itself.

This "braided" wire should be insulated from the starter motor body....your picture looks like the insulation is a bit ragged?

When you bridge that braided cable to the thick positive cable you should be applying +12 volts straight to the starter motor and you would expect it to run continously but without engaging the flywheel....this is what the large contact inside the solenoid normally does but at the same time the solenoid swings out the small pinion gear to engage the flywheel.

So either the starter motor is not grounded properly ie. the grounding cable going from engine to chassis is not working properly or the starter motor is not bolted cleanly to the bellhousing or the negative lead of the battery is not going to the chassis properly or your starter motor is burnt out.

Or the "braided" cable is shorting directly to the starter motor housing.

Try use the black portion of a jumper cable to connect the negative side of the battery onto a good clean bolt on the engine itself...preferably the mounting point of the engine grounding cable....you should find this on the drivers side of the engine under the exhaust pipes on the M40, or clamp this jumper lead direct onto the body of the starter motor. Then see what happens if you bridge the Black/Yellow wire to + 12 volts.

[m_jermyn]

Ok so I put a jumper lead from the negative on the battery to the engine lify hook turned the key and the car started.....


So its a earthing problem then.... But where are they on the m40?


Thanks so much

[Speedtouch]

Usually, the engine-to-body earth straps run from the engine block to one of the chassis rails.

[Brianmoooore]

Engine mounting arm and chassis rail in the case of the M40. It's possible for the poor connection to be between the alloy arm and the iron bock, as well as at each end of the strap itself.