Starter Solenoid

Wed May 16, 2012 2:08 pm

I've got problems at the moment with the IS not starting. I can hear the starter motor spinning but it sounds like it is not engaging and actually cranking the engine over.

So I assume it must be an issue with the solenoid not engaging? I have tried starting via the key/shorting pins 11 & 14 and the same thing happens.

There look to be 3 connections to the solenoid itself - two smaller wires and one thicker one. Are the two smaller ones just for the solenoid? As next test, is to see if it that is actually getting power i guess?

thanks,

Wed May 16, 2012 2:40 pm

If the solenoid was faulty, the starter motor wouldn't turn at all! All it is is a large relay that takes the low current from the ignition switch as you turn the key and switches a large current direct from the battery to the motor.

It is more likely to be a sticking bendix on the starter motor - as they spin, it gets thrown into the flywheel teeth.

Or it may be that your battery is not powerful enough to operate it properly - try recharging it and having another go.

Also try hitting the starter motor with a hammer, which sometimes frees them off.

Failing that, you may need to remove the starter motor to see what's what.

Wed May 16, 2012 3:34 pm

These starter motors do not use a centrifugal Bendix that shoots out as the motor spins...the solenoid when it engages also slides the pinion wheel outwards on a spline on the starter motor to engage it into the flywheel.

So it could be possible that the small pinion gear is worn or is not extending all the way out or the teeth on the small gear are not meshing with the flywheel teeth due to a loose starter motor or worn teeth somewhere.

Are you sure you have the wires connected properly to the solenoid?

The one large stud has the flexible braided wire going directly into the starter motor...nothing else should be on this stud.
The second large stud has a thick black wire going direct to the positive terminal of the battery.

Then there is a black/yellow wire that should get +12 volts on it from the ignition key when it is turned to Start...this wire goes on to one of the smaller terminals to energise the solenoid.
If you have this wire on the correct terminal then you should hear the solenoid "click".

The other thin wire is black/green and goes to the other small terminal...this drops the unloader relays K5/K7 to drop power to the air-con, heated seats, electric mirrors etc. when starting.

You can get this action of the starter motor spinning but not engaging if the black/yellow wire is connected to the large stud with the braided wire thus directly supplying power to the starter when ignition is turned on.

You can also get this action if you have connected your black/yellow wire onto the small connector that should be for the unloader circuit...this is the most likely scenario. Leave the black/green wire off for the time being and try the black/yellow wire on each of the small terminals on the solenoid.

You can try move the flywheel to a different position by bumping the car while in gear.

As stated above..you may need to remove the starter motor to see what is going on!

Wed May 16, 2012 4:19 pm

sarkie83 wrote:I've got problems at the moment with the IS not starting. I can hear the starter motor spinning but it sounds like it is not engaging and actually cranking the engine over.

Maybe it's a stupid suggestion, but is the starter belt too slack / split/actually turning?

Edit: Ignore me I've just learnt the difference between the starter motor and water pump!!!

Wed May 16, 2012 4:38 pm

milescook wrote: starter belt?

What's that then?

Ben

Wed May 16, 2012 4:40 pm

Err, this is where I delete my original post! There's a belt driven mechanism near the alternator, I assumed it was the starter motor? On my 320 at least... off to check the wiki!

Edit: I'm an idiot - please ignore!

Wed May 16, 2012 4:43 pm

Starter motor is at the back of the engine and has a toothed wheel which engages with the toothed ring on the flywheel.

Ben

Wed May 16, 2012 4:52 pm

Hide your shame, I haven't written the Starter part of the wiki yet ;)

As others have chimed in, the Starter motor is very much an all-in-one unit with only three wires going in, so if you can hear it spinning up the motor's not turning, it's either not got enough juice or it's a duff unit.