suddenly starter motor wont engage

[2V8s]

Hi all,

having just got my 960 24v estate MOTd, the next time I went to use it, turn the key and nothing. It not the battery - thats fine and also I tried fully charging it - no difference.

I read somewhere else about dodgy ignition barrel - well that was already replaced once and also if I put the headlights on, they turn off when the key goes from pos 2 to start position so I figure that's fine?

The only sign of something going to be amiss was the day I took it to the MOT, when I started it initially there was a delay of a second or so when nothing happened and then it started as normal although the starter motor sounded a little sluggish.

Could it be the starter motor? do they suddenly fail in this way? Or could it be something else?

Im feeling a bit gutted because this has always been such a reliable car, dont recall there ever being a time it has failed to start (even when the fuel pump was playing up)

thanks

Aaron

[Laird Scooby]

Is it manual or auto? First thing i'd check is that the exciter/trigger wire (usually white/red) hasn't come off the starter terminal.

[aardvarkash10]

Highly unlikely the wire has fallen off. However, if you can see the starter motor (not sure of layout on that engine), try this:

1. With the vehicle in neutral or park, have someone hold the key in the start position.
   
2. Assuming the engine is not cranking, rap the starter motor itself with a hammer (via a drift or similar if you cant reach it easily).
   
3. If the starter springs into life, you have identified the problem - worn out brushes in the starter motor itself.

[cheshired5]

Originally Posted by aardvarkash10

Highly unlikely the wire has fallen off. However, if you can see the starter motor (not sure of layout on that engine), try this:

1. With the vehicle in neutral or park, have someone hold the key in the start position.
   
2. Assuming the engine is not cranking, rap the starter motor itself with a hammer (via a drift or similar if you cant reach it easily).
   
3. If the starter springs into life, you have identified the problem - worn out brushes in the starter motor itself.

Not necessarily. In this scenario the problem could just as easily be a sticking solenoid.

Originally Posted by Laird Scooby

Quick way to check for that is a jump lead fromthe bellhousing as near to the starter as possible to the battery -ve terminal.

..... or voltage test between the starter motor body and vehicle chassis/battery negative during cranking.
There'll be an over spec voltage drop reading if the earth strap is defective.

[Laird Scooby]

Originally Posted by cheshired5

..... or voltage test between the starter motor body and vehicle chassis/battery negative during cranking.
There'll be an over spec voltage drop reading if the earth strap is defective.

The jump lead does that and proves the starter at the same time if it is an earth strap fault.

[cheshired5]

Originally Posted by Laird Scooby

The jump lead does that and proves the starter at the same time if it is an earth strap fault.

Agreed but the jump lead trick is only good to identify that one fault but if you guess right first time, it's all good.
Using a multimeter to measure voltage drop on the live and ground side will identify many more potential faults though so a combination of methods is always handy.

[aardvarkash10]

Originally Posted by cheshired5

Not necessarily. In this scenario the problem could just as easily be a sticking solenoid.

Well, in over 15 years of working in the industry as an auto-electrician, I never encountered a solenoid that was sticky. I encountered plenty of solenoids that wouldn't engage because the motor brushes were worn out (remember - the solenoid pull-in winding earths through the starter motor so worn brushes means no earth circuit).

There could always be a first time though.

[Laird Scooby]

Originally Posted by aardvarkash10

Well, in over 15 years of working in the industry as an auto-electrician, I never encountered a solenoid that was sticky.

In that case Ash, either you missed them for whatever reason or the climate in NZ reduces the risk of it happening.

It's a common enough occurrence here, usually a gummy residue on the plunger causes the sticking and it works both ways as well - it can hold the starter pinion in once the key has been released, as well as preventing the plunger sliding towards the contacts and mechanically pre-engaging the drive pinion before completing the circuit to the starter motor and switching to the hold-in coil from the pull-in coil.

Usually cleaning the plunger with brake or carb cleaner/thinners restores normal operation.

[cheshired5]

Originally Posted by aardvarkash10

Well, in over 15 years of working in the industry as an auto-electrician, I never encountered a solenoid that was sticky. I encountered plenty of solenoids that wouldn't engage because the motor brushes were worn out (remember - the solenoid pull-in winding earths through the starter motor so worn brushes means no earth circuit).

There could always be a first time though.

A solenoid can easily stick if moisture causes corrosion.
It depends on climate, starter location and starter design. Certainly not impossible.

The solenoid is grounded through the body of the starter and the brushes play no part in this.
This can easily be shown by connecting a 12v feed to the solenoid ignition switch and grounding the solenoid body.
You could have badly worn brushes or no brushes at all in the starter yet still engage the solenoid.

[Laird Scooby]

Originally Posted by Laird Scooby

Is it manual or auto? First thing i'd check is that the exciter/trigger wire (usually white/red) hasn't come off the starter terminal.

What i forgot to say earlier is if it's auto, try holding the key in the start position and moving the gear lever through the entire range of movement (P to 1 and back again) several times and listen to see if the starter engages in N or P or tries to.

Could simply be a worn inhibitor switch or even just dirty contacts.

Still worth checking the exciter wire, if it's where it should be, not broken, clean and tight connection, give Ash's idea a try.

Also worth checking the relays are all pushed fully home in the electrical box behind the ashtray and/or under the bonnet depending on which model you've got - a loose start relay will also cause this problem.