Rover V8 Starter Motor Wiring

[Riley RMF]

I'd expected this to be simple, but I'm either doing something stupid or something is broken.

It's a new starter motor on a reconditioned engine...



...but it's been sitting around for 5 years waiting until I have time. Which is now.

It's a special for which I'm putting together my own wiring loom, so nothing to refer back to by way of existing wiring. I'm using a 12 volt coil, so no ballast resistor to confuse the picture, and a Powerspark distributor.

I had expected that the solenoid terminal to the left would be the big red cable from the battery, and earth through the chassis. That surely has to be right, but I'm currently questioning my powers of coherent thought.

There are no markings as far as I can see on the solenoid to indicate what's what, but I think I'm right in believing that the terminal at 6 o'clock is raised to live to activate the solenoid? I currently have this lashed up to a simple push button for the starter. I'm just looking to get the engine turning over at this stage.

I believe the terminal at 12 o'clock goes to the ballast resistor, but because I'm not using that I don't need to connect this one. Do I have that right?

End result is a big fat nothing when I press the starter button.

My next step at diagnostic was to remove the battery cable from the 3 o'clock terminal and touch it on the 6 o'clock one, expecting to hear a cheerful clunking sound as the solenoid does it's thing, but nothing.

Not wanting to break anything and running out of time today, thought I'd stop and ask.

Anybody able to help me out on this?

Thanks

Phill

[DaveEFI]

The large terminal goes direct to the battery +12v.
The small one is the solenoid connection - goes to the starter switch, normally via a relay. (the solenoid takes more current than most switches can manage - hence the relay.
.

[Richard P6]

I take it that you have a good earth from the battery to the chassis, and also from the chassis to the engine.

If you have, then you can test it by connecting the large red cable to the left hand terminal as you say, then carefully short out the terminal to the one at 6 o'clock with a hefty screwdriver. That should spin the motor.

The smaller one at the top is designed to give a ballasted coil the full 12V to help start it, and normally goes to the coil, to bypass the resistor. You don't need it.

Richard

[Riley RMF]

That's great guys - thanks

Phill

[Riley RMF]

Battery fully charged and bolted the earth cable onto the engine, battery live to the big solenoid terminal.

No other electrics active.

Nice big screwdriver to bridge the battery live with the small 6 o'clock spade terminal.

Not a dicky bird....

Supposed to be a new unit...

Take the starter motor off and test it on the bench?

Could it be a faulty solenoid?

Maybe I broke it?

[DaveEFI]

Do you get a spark when doing this? If so, the solenoid may just be stuck.

[Richard P6]

I would take it off and give it a good once over. Check everything moves as it should, check the starter pinion moves out to engage with the starter ring. If the solenoid had a bit of rust in it, just moving it in and out by hand a few times, could well loosen it up.

If it is just the solenoid sticking, you may be able to tap it with a small hammer to free it off (Not whack it with a lump hammer )

[DaveEFI]

I've seen a few corroded solenoid armatures. The ones I've seen were copper plated over the magnetic core - and the plating had failed, allowing the core to rust.

With the starter off, you should be able to move the pinion in and out by hand.

After a couple of starter failures over the years on my SD1, I've fitted a Hi-Torque geared one. It certainly seems to spin the engine over quicker on a cold day.

[Riley RMF]

Hi guys,

Had it out and tested. Definitely an electrical fault in the solenoid. The metal core moves easily. Tested for switching when the core is pushed firmly home and that's fine. Starter motor spins when I touch positive on the 3 o'clock terminal with the solenoid off. Plus a shower of sparks of course.

Doesn't seem to be a way to take the solenoid apart without destroying it so I guess I'm looking for a Prestolite solenoid replacement, or I buy a Bosch one and hope I can swap the core for the original Prestolite one. The Prestolite has a nail-head type design on the mechanical linkage rather than the Bosch square loop design.

Don't really want to have to buy a whole new starter motor...

[scudderfish]

I've got an SD1 starter sat on my garage floor getting in the way. Yours if you can collect.

Regards,
David

[scudderfish]

Ah, just seen in your profile where you are

[Riley RMF]

Yeah - it can have its drawbacks. We have some nice country roads though

Thanks though David

[DaveEFI]

Can you get at the ends of the solenoid coil wires? Could be just a poor connection. Coil will only measure a few ohms on a DVM.

[Riley RMF]

Far as I can see the solenoid is a sealed unit. You can see in the pic up above that the innards are held in place by the edge of the can being turned over all around. Don't see any way in other than a tin opener. Currently doing some searches on how to mend...

[Riley RMF]

Sitting on a train watching how-to videos on youtube. This one is quite a useful tip for where you have burned out contacts, but it needs the original solenoid working to do the mechanicals...

https://www.youtube.com/watch?v=8n2eOwhG1gU

Although maybe this isn't such a good idea because the starter motor will be spinning before the gear has engaged?