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MG MGA - Starter solenoid short

I have a '57 MGA with a pull starter switch linked to a pre-engaged starter in a 72 18V engine with pertronix Flame Thrower ignition, 12V generator neg ground system with an in dash amp meter and electronic fuel pump.
I had previously noted that the old pull starter switch needed replacement and received one from Moss. Just before making the change, I pulled the starter, heard a click, the engine started but then died within seconds. Pulling the starter again resulted in nothing.
I installed the new pull starter from Moss.
Noting that it was the same as the item Barney had had problems with, was aware that it may be bad. Pulled and nothing. Check with a meter and there was closure, lights remain bright, horn works, fuel pump clicks but no gas is pumped, fuel gauge reads half tank, amp meter reads two amp draw (normal for just the fuel pump) but nothing from the starter.
I assume that I will need a new solenoid for the starter but am concerned that there might be something else that might allow the Lucas smoke to escape somewhere.
Any suggestions welcome.
Bayard DeNoie

Bayard

Odd. With the pre-engaged starter set-up the notorious starter switch only transmits a very small load to operate the starter solenoid. It slides the starter cog forward to engage the flywheel. Once engaged, high energy current direct from the battery spins the motor, bypassing the starter switch. It sounds very much like you have wrong wiring through the switch.

With my pre-engaged set-up I have the heavy duty battery cable, heavy duty starter cable and power feed cable all on one terminal; and the starter solenoid cable only on the other.

Steve
Steve Gyles

HI Steve,
Thanks for your response. I noticed that when I pulled on the old starter it drew the battery cables toward the metal case. My major concern is with the very real possibility that pulling on the starter shorted the positive lead from the battery and amp meter wire with the negative grounded case. When I mentioned closure on the new switch, it was with a multi meter and not via the amp meter. The amp meter shows nothing when I pull on the switch.

I have seen Barney G's diagram for the small load set up but I fear it was not originally set up that way 17 years ago. Will definitely employ when I replace the solenoid. Right now I'm just searching for shorts.
Bayard DeNoie

Bayard,
if your car already has a pre-engaged starter motor fitted then you probably already know that it is wired completely differently to the standard MGA starter.

Your starter should have the battery connected directly to it and the output of your starter switch (when you pull it) just sends a low amperage current to the small solenoid terminal on the motor to trigger the motor.

Also your amp meter is not connected through the starter circuit and so it only shows the amperage flowing through thr ignition circuit.

Once you have double checked all your starter and ignition cicuits I would then take the starter motor out and have it and its solenoid checked.

Also, electronic ignition is really sensitive to being short circuited or if the generators voltage output is too high.
So I would check to see if it is still working.

Cheers
Colyn
Colyn Firth

Hi Colyn,
Thank you for your reply. Unfortunately I did run, back in 1966, a white wire directly from the starter switch to the amp meter to track draw on the very old 1500 starter motor and never needed to switch it out until today.
I do keep a module for the ignition and a dizzy with the old points system as well but cannot figure why the pump ticks but doesn't push fuel.
I do at times long for the simplicity of the old MG but once I figure this all out, I'll still love it.
Bayard DeNoie

After metering every possible connection, I am happy to say that the only short went to the solenoid which I will replace.
The odd fuel issue seems to have been a wire worn to a single strand so it had power to tick but not enough to to push fuel.
Anyone have experience with pulling a pre-engaged starter from a MGA?
Bayard DeNoie

I have been looking at fitting a pre-engaged starter to my 18V engine in my MGA instead of the standard inertia starter motor.
Although they are a a bit bulkier than the std starter, they obviously do fit this engine.

It looks to me that I would have to remove the oil filter to gain enough working space to get a pre-engaged starter into position.

Probably fitting an inverted oil filter conversion would help.

Can you let me know which type and model of starter motor you are using Bayard?
Cheers
Colyn
Colyn Firth

Colyn

Not that bulky. This is mine: http://www.mgaroadster.co.uk/hi_torque_starter_motor.htm

Do LHD cars have the same issue as RHD with starter motor removal? i.e. no obstruction caused by steering column.

Steve

Steve Gyles

Modern pre engaged starters are much smaller and lighter than the original ones.
Chris at Octarine Services

Dear all,
Thanks for your assist - I spoke with Moss Guru Kelvin Dodd who walked me through the porocess and recommended the modern version both smaller and lighte than the original. I also like the way he recommended running the battery cable and starter cable together and adding a small wire from the other Lucar connector direct to the other side of the starter switch (see Barney's wiring diagram).
A little scary but now it kicks right over and just purrrrrs
Thanks again!
Bayard DeNoie

Glad it's now sorted out Bayard and that it was only the solenoid.
If it had been my car I would have burnt out the electronic ignition and the fuel pump at the same time😁.

It's strange how your fuel pump developed a problem at the same time just to complicate things.

If you made a note of the starter motor make and model, could you let us know as I may well change mine to a similar one.

Cheers
Colyn
Colyn Firth

Hi Colyn,
We live in the boondocks so it's not unusual to roll over downed branches after a nasty storm ( which we did have recently) so
I' m hanging on to that as a possibility for how two failures happened at opposite ends of the car at the same time (?). Just glad it all came about in my garage and not on the open road.
I will give you any specifics I can upon my return from Easter holiday on Tuesday or Wednesday.
Best Regards
Bayard
Bayard DeNoie

Hi Colyn,
There were no markings on the new starter so I assume it was either made for or by Moss. But I did get a picture before the swap and as you can see the new motor is less than half the size of the old and less than half the weight.
In order to remove the old motor I had to remove the oil cooler hose, the dizzy, the coil, the oil filter etc - the new motor would have just slipped out.


Bayard DeNoie

This thread was discussed between 11/04/2017 and 19/04/2017

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