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MG MGA - My starter is dead!

This is actually a part 2 to the previous post 'Starter Ate may battery'.

Today I wanted to take my car to drive to work.
Since the last incident the started has been turning slowly even if the car eventually starts.
So I started this morning, and by the time I got to the street the I started to smell 'burn electrics' and the engine died. I tried to start it but nothing.

I thought the battery was died due to an internal short in the starter (as last time).
I tried to jump start it with another car without success. The starter would not even move.
A guy on the street suggested it could be the starter that 'froze up' so we tried taping it without success.

Now I need to check was is causing this.

I suspect that the starter pull switch may be arcing... since I don't see why the starter would be using the battery after starting.
Also I fear the starter brushes may be dead due to all of this.
Also in addition, after the second time, I suspect the battery may also be dead/deep cycled.

Any thoughts before I take the starter and switch apart would be highly appreciated.

Gonzalo Ramos


I think your initial analysis is pretty good. However, I would disconnect the battery and try charging it and seeing if it will hold a charge. If it isn't sealed, try adding some distilled water to it, you may be able to wake up the cells. If not, well, you'll need a new one.

I think it is likely that your starter is the culprit, not the switch. The starter needs good brushes (as you identified) and clean commutator poles, and good windings. Usually on non-working starters I'll disassemble it, polish the contacts and replace the brushes. Note that on the starter, unlike the generator, the commutator insulation should not be undercut. You can test the field coils with a battery and a 12v test light. If it lights they are good, if not, they are open. Then I try spinning it on a battery.

Hope this helps,
Dave Braun

You might try these two tests. Remove ground lead from the battery. Disconnect the wire to the starter from the starter switch. Using jumper cables, connect a battery to the starter (ground on the case, "hot" lead to the starter wire). If the starter doesn't turn it's probably bad. Next, with the power lead (fat brown wire) disconnected from the starter switch, put an ohm meter across the starter to switch measure the resistance. Should be infinite (open). Pull the starter switch closed. You should get zero ohms, or close to it. If you get a higher resistance you have a problem with the starter switch. I would not take the starter switch apart unless you just want to see how it failed. They are not really repairable although people have tried.
Good luck,
G T Foster

If the starter switch was delivering current to the starter, it would be turning and you would hear it. It would also engage the flywheel. It would be the last thing on my list, as they fail because they are worn out, not because they short.

Also your symptoms point to an ignition circuit issue, not a starter one.

You can see of there is an internal short by measuring if the switch has 12V on the starter side when it is in its normal (off) position. It should have 0V at rest, and 12V when you operate the switch.

To check your starter without removing it, try removing the plastic cap on the front end and see of it will turn with a spanner on the shaft.

dominic clancy

Hi Gonzalo,

Have you eliminated the starter failing to disengage from the ring gear.

Your symptoms sound like the motor could have been driving the starter motor. This would make the electric burning smell as the starter will become a generator.

Try removing the starter and giving a test run. Make sure there is no liquid lubricant on the bendix gear. it should be dry lubricated (if at all).
P Reardon

If a jump start will not turn over the engine, then most likely it is starter related. However it could be the starter switch. I have had one or two occasions where the pull knob on the dash did not return completely and the starter stayed energized.

One way to eliminate the starter switch as the cause, is to jump to the starter side of the switch, eliminating the switch. If the car still does not turn, then you know it is starter related, perhaps frozen, perhaps the bendix is stuck, perhaps faulty brushes or worse, burned out windings. Either way, the starter must be removed. Fortunately, starters are easy to repair and cheap to replace.
Chuck Schaefer

Thanks guys!
I did some of the trouble shooting today and this is what I found.

I isolated the starter switch and tested it. Seem to work fine. Zero resistance when closed, infinite when open.

I checked the terminal for grounding. The big terminal coming from the battery is open circuit to ground. This is normal as I have battery cut-off switch.

As an interesting thing I tested the continuity to the 'accessory terminal' (i.e. the one that goes into the control box). I found the was continuity to ground with around 500ohms. I suspect this may be normal as this could be dash accessories...? You comments welcome on this. I need to check the wiring diagram.

I isolated the starter motor. I checked the starter hot terminal and it is shorting to ground! i.e. there must be an internal short inside I suspect. Maybe a cable came loose?
voltmeter indicates zero resistance so I imagine this is not normal. I guess in a working starter there may be some continuity through the windings but would show a high resistance, right?

NOW, my question is...
Is it possible to take out the starter without removing the oil filter and making a subsequent mess?
I tried for 30mins all possible combinations and it won't come out. It seems to be too long to clear the oil filter as the drive spindle is rather long.

Let me know your thoughts, I will continue the task next week.
Gonzalo Ramos

You are right - the starter will not clear the oil filter - that has to come off first - at least your steering column is out the way on the other side!!
Cam Cunningham

And now the stupid question:
how much oil will come out when I remove the filter?
More than the content of the filter?
Just want to make sure I am prepared....
Gonzalo Ramos

Hi there
You will only drain oil filter and some. El motor is series of el magnets, that is the nature of the beast,you will always have continuity to ground on any el motor. Disconect the starter an use jumper cables directly on starter and see if it will turn.


The starter motor can draw 100 amps or so when free spinning with no load, more like 200 amps when cranking the engine, and possibly closer to 300 amps under stall conditions (pinion gear jammed on a worn ring gear). To do this the starter motor internal resistance is VERY low, something like 1/25th of an ohm, 0.040-ohms. 40 milli-ohms. This low resistance may not register on a typical cheap hand held ohm meter, so it appears to be a dead short to ground when it really isn't.

However, .... It is possible for the cable connection post to get shorted to ground if the insulator pieces around that stud are damaged or degraded. To check for this condition (without disassembling the starter) you need an ohm meter that will measure in the very low range of the normal internal resistance of the starter motor 0 to 100 mili-ohm (0 to 1/10th ohm) meter range.

There are some other applications for an ohm meter that will measure similarly low resistance. For instance, distributor contact points should be very near zero resistance when closed. Anything like 1/4 ohm (250-milli-ohm) is too much resistance and will cause voltage drop and contact heating. Also wiring harness to chassis grounding connections, and any other electrical connector, should have less than 1/4 ohm resistance. The real killer would be 1/4 ohm resistance in any battery cable connection where it is needing to carry 200 amps at low voltage.
Barney Gaylord

Ok, so I gather that my started may not be shorted.
I do however suspect that the gear may have been jammed.

Also upon inspection it did look like the gear is a bit worn, but don't know what is acceptable. This may be causing the issue as it may be remaining engaged...

I am going to have a look at all the cable connections to see if there are any high-resistance points. Including the connection to the battery.
Thanks Barney for the clarification. I don't think I have a multimeter that is that sensitive, so no way for me to test it.

Is there any other way of testing the starter while still on the engine? If I energize it, it will crank the engine. I guess there is no way of testing it without load, right?
Gonzalo Ramos

Barney is correct the typical motor resistance is something less than 0.1 ohms. To measure a resistance as small as this a meter with a wheatstone bridge is required and is a specialized bit of kit that is well out of the reach of the ome mechanic

You will notice that your meter leads will have more resistance than this. :)

Ohms law is always your friend when you need to work out resistive values

If the starter could draw 240amps then volts divided by amps equals resistance

I make that 0.05 ohms :)
Robert (Bob) Midget Turbo

More to it than that. When talking about 240 amps there is some internal resistance in the battery that will drop the output voltage some, like maybe 11 volts vs. 12.6 open circuit voltage. Battery resistance is about an order of magnitude less than starter resistance, but any battery cable connection could have much higher resistance.

If the starter pinion gear gets jammed tooth crest to tooth crest on the ring gear it can totally freeze any forward rotation of starter AND the engine. Turn headlights on and try the starter. If the lights do not dim and it doesn't crank, then there is no current going through the starter, look for a loose cable connection. If the lights go dim the starter is drawing lots of current, and if not turning then it is jammed.

If you put it in gear for a push start it can skid the rear tires without turning the engine. The immediate cure for this is to put it in top gear and roll the car backward to rotate the engine backward and free the starter pinion. This may get you running, but it will happen again, and it will only get worst and happen more frequently with time. The permanent fix is to replace the starter ring gear, which requires removal of the engine for service to the flywheel. See here:
Barney Gaylord

Now you scared me Barney! I was not feeling like a BBQ nor taking the enginenout of the car.
I will inspect the ring gear and see what I find.
Could it also be the starter pinion that is worn?

I just took the battery out and it reads 12.46V. I am charging it now.

When cranking the starter there was a lot of current bing delivered to the starter as the light dim and even the fuel gauge goes down.

My conclusion is that the starter was probably jammed but I Ned to find out why it was slow cranking in first place.
Gonzalo Ramos

Didn't know you were an electrical engineer Barney

There are a number of other issues than simple ohms law of course but those simply confuse simple issues.
Robert (Bob) Midget Turbo


Could you get away with replacing the original stater with a modern geared stater without changing the ring-gear? The modern ones appear to engage the ring-gear from the front while the Bendix on the original starter engages from the rear.
David Werblow

Yes. (Maybe). If you don't mind the work to R&R the engine, a ring gear is cheaper than a gear reduction starter (and you likely only do it once in the life of any singe car). A badly worn ring gear will not mend itself. However, the gear reduction starter will engage the ring gear from the opposite side (less worn there). The gear reduction starter is also the pre-engage type with a big solenoid that throws the pinion gear into engagement with the ring gear before applying rotational torque. This process usually succeeds even with a badly worn ring gear.

Other arguments for and against: Gear reduction starter is more likely to start the car in very cold weather. Gear reduction starters have a reputation (sometimes) for early failure. Genuine Denso starters are supposed to be pretty good. The Chinese made look-alikes can be pretty bad.
Barney Gaylord

Well, I charge the battery and reinstalled it in the car.
I checked all the connections and made sure the earth an starter connections were solid.

When I push the starter button some sparks come our from the back of the starter + smoke. It does eventually turn VEEEEERY slowly and the is a component on the end cap that glows 'red-hot'.
The smoke it produces is what I call 'electrical fire burnt plastic smell'.

So my conclusion is that the started has burnt out and/or is shorting inside.

I checked the ring gear and it has virtually no wear on it so I think I am on the clear about that.

I still take the starter apart and inspect but I suspect I will need a new one.

Anyone has a spare one they want to sell?
Otherwise I am going to check in the usual places and ebay. I've the sell for around $100.

Hopefully this will be the end of the problems! ; )
Gonzalo Ramos

Try They list a Beck Arnley remanufactured starter for 55.32 shipped (incl core deposit). If you send them back the core, you'll get 13 back. That is ~42 plus shipping cost of the core.

However, don't overlook your local auto stores. Advance Auto shows the reman'd starter for 44.99 + core + ship to home. Total around 69.00 (-13 for the core) Some auto stores have free shipping from the warehouse to their store. You could do a swap there and not have the expense to ship the core back.

For a final cost of around 50.00, I wouldn't bother with a used one. But that's just me.
Chuck Schaefer

The common fault is broken insulator pieces where the power stud goes through the end plate. Quite often all you need is to slip a couple bits of nylon or phenolic bushing or washer in there and it's good to go.
Barney Gaylord

You might also consider taking is to an automotive electrical repair shop. We have one locally with an older guy who loves repairing old starters and generators.
G T Foster

Gonzalo, I think Barney is right on the button. I too have had that piece of insulation fail, it will give all the symtoms you have mentioned earlier including a temporary (or permanent) welding together of your starter switch contacts.
Lindsay Sampford

I guess sometimes it may makes more sense to get a new one to avoid further issues.

I will however take it apart and inspect. Will post some pics if I find something interesting. ; )

The RockAuto deal looks great.
I was not able to find the same price on the Advanced auto Part website. It shows around $159.
I guess the shipping will cost more than the core fee...
Gonzalo Ramos

I took the starter out and it is bad condition inside.
There is a lot of rust and it seems like one of the brush springs made contact on the casing. Then the phenolic washers that isolate the brush support frame melted and are shorting.

So the problem has been identified.
Although I could try to fix it I am going for the easier option and just ordered on from JC Whiney for $38 plus $8 shipping.
For that price I don't want to take the risk that is shorts again.
Gonzalo Ramos

Gonzalo, I have never had much luck with bargain price starters. I just wonder how good of a starter can you get for $38 bucks.
I'm just saying....
Richard Taylor TD3983

JC Whitney IMHO ranks with the Checker, Autozone and Advance. Their target market is the DIYS, price is everything buyer. Bosch sells with 2 year unlimited mileage warrantee for $49.98. Simple part with a simple price.
R J Brown

I purchased a starter from Advance for a 91 Firebird I drove for several years, not an easy car to crawl under and work on. It never did sound quiet right from the moment I put it on. It lasted about 6 months and sure it had the lifetime warranty but I decided I wasn't willing to change the starter every 6 months. Since Advance would only replace and not refund I ate the price of that starter and purchased a new one from Pontiac for about 3 times the Advance price, and that was the last time I messed with the starter.
Richard Taylor TD3983

I just wanted to report that I received the starter from JC whitney and it looks pretty good.
It does not look exactly the same on the back but look good quality.
In any case it took me only 15min to install. + 15mins for the oil filter.

What a difference! as soon as I pushed the starter it cranks with a LOOOOOOOT of speed.
My MGA is back!! ; )

I spend some hours on the weekend cleaning the MGA ready to drive the hell out of it.
I will post some pics soon as it is looking as good as it will ever will.
Gonzalo Ramos

Question is what do should I do with the old starter core? It is an original LUCAS one.

Any suggestions?
Gonzalo Ramos

This thread was discussed between 15/04/2011 and 02/05/2011

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