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MG MGA - Starter problem---or Gremlin?

My starter suddenly got very weak and would barely turn the engine. It acted like a very weak battery. I checked battery voltage ---12.7v, and 11.5v while starting. I checked all 12v connections, ground, etc. and all were fine. I directly connected the battery to the starter via jumpers (12v and Ground)-- and same thing, very difficult, slow, or stalled starter motor. The starter, brushes and commutator had been checked and cleaned last spring. I figured I was ready to replace the starter.

As a final last check, I tried it again and suddenly it speeded up a little-----, and then ran at its previous full speed and starting strength. Now I cant get it to do anything wrong.

A couple days prior to this experience I had changed the Polarity of the car to Negative Ground but cant see how this would have precipitated the problem. Is it a coincidence or is there a reason for this.

I plan on another inspection of the brushes, etc.

Damn Lucas gremlin is testing me------is he waiting for a really bad time to reappear?

Jim
Jim Ferguson

I had exactly the same symptoms and it turned ot to be somewhere in the battery cable to terminal connectors or conectors to posts. I cleaned and retightened them all and it has been fine ever since.

Neil
Neil McGurk

Jim,
If the problem re-occurrs, use jumper cables to apply votage directly to the starter. If it turns properly it's in the wiring. Did you check the braided ground wire connections at the motor mount? These are critical. I'm betting its a connection somewhere. However, motor brushes have been know to hang up on occassion.
Good luck,
GTF
G T Foster

Jim,
On additonal thought. Check the starter switch (contact block). I was having a similar problem on a recently purchase car. I discovered the terminals on the start switch were moving in the plasic insulator. A good spare starter contact fixed the problem.

GTF
G T Foster

And again, bypassing the starter switch with jumper cables is a good way to test whether the switch a causing the problem or not....is the symptom is present.

OK, I'm done.....:)

GTF
G T Foster

Hi Jim. I had a similar strange problem on my starter a while back and found the lower screw holding the backplate of the motor was sheared. This meant the brushes where out of alignment and would fail to turn the motor very well. After removing the motor, drilling out the sheared bolt and fiting a new one all was well (but I lost count of the times I swore at it in between!!).
Neil
Neil Purves

GTF
I did thr jumper cable thing, and it was still slow. It is working fine for now.........

Jim
Jim Ferguson

Jim, did you attach the jumper cable to the battery terminal connectors or directly to the battery? I still have two six volt batteries and when I checked with the jumper cables I attached them to earth and on the 12v hot terminal connector. I still had the starter problem and pulled the starter and replaced with a spare, same problem. The bad connection was somewhere between that hot connector and earth. But I only found that out after I removed, cleaned and refitted all the cables, connectors and terminals. As I said this gave the same intermittent problem you had.
Neil McGurk

Jim the most common problems in the electrics are bad earths [ grounds] It's always advisable to start with the basics before proceeding to the exotics. Bad earths will produce all sorts of "gremlins". Starter motor problems are either lack of current flow or too much current draw ie,. a faulty starter. From memory from an earlier life. current draw should be approx. 150 amps. Remember electron flow is negative to positive , not as per conventional wireing schematics. That's why the earth connections are of equal importance if not more.
S Sherry

Jim,

Is the battery voltage drop different now that it is working? A 1.5 volt drop during cranking suggests your starter is pulling some power yet not exceeding your battery's available amperage.

If the voltage drop is higher now, then the issue is/was an intermittant/dirty connection. The added resistance was limiting the starter's ability to draw current. Although uncommon, dirty connections can "self-heal" although the miracles seldom last.

If the voltage drop is lower now, then the issue is probably mechanical. Culprits could include the switch, starter bushings, and starter fasteners. If the "no start" was with a hot engine and the later "good start" is cold, I'd suspect bushings. Otherwise a missalignment due to loose/broken bolts is binding things up.

When checking starter voltage, check from the main starter electrical lug to the starter housing. This eliminates all connections from the test path.

I keep a spray bottle of baking soda in water and a can of motorcycle chain lube around for routine battery cable maintenance. The soda eats the corrosion and the chain lube wicks into the connection, displacing water and gunk.

Hope this helps,
Bill

Bill Eastman

Bill

The voltage is the same when it isn't working and when it is (within 0.2v).

I inspected the brushes and found all free to move and the comuntator looked fine. I did notice a burnt smell when I removed the inspection band.

I sprayed it with electrical motor/contact cleaner, let it dry, and did a 10 second starter test with the ignition off. It did fine for about 7 seconds and then slowed to a near stop and started smoking.

I am replacing the starter tomorrow. Fortunately I have a spare. Maybe when I get the old one off I can figure out what all went wrong and see if it is repairable.

Jim
Jim Ferguson

I have had to clean and protect the ground connection from the batteries to the chassis in the battery area behind the seats several times in the 40+ years that I have owned my A. The connection from the batteries, through the frame and to the engine block are critical for good starter performance, as well as keeping the Prince at bay with the other electrical devices. Replacing the cables and connectors every decade or so makes for good starts and bright lights too. For the battery area; clean the metal and connections bright, de-grease, make attachments with new hardware and washers, paint several coats of rust proof paint to seal both sides of the hardware. Clean all contact surfaces for the engine braided cable, the MGA engine is self rustproofing.
Fuzz
Russ Carnes

This thread was discussed between 18/08/2008 and 20/08/2008

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