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MG Midget and Sprite Technical - What have I done?

Whilst replacing the clutch master cylinder (don't ask) yesterday I inadvertently touched a live terminal on the solenoid with a spanner and it sparked.

When starting the engine later, at first it just clicked but then started normally.
Today again a click followed by normal starting. Until now. Now is just a click. It won't start.

I've tried tapping the starter motor and rocking it in gear but to no effect.
Have I burnt out the solenoid or starter motor?
Where do you suggest should I start?
Thanks
Jeremy MkIII

Chris,
you've provided a perfect example of "have a go myself, make mistakes, and learn from them."

I feel so superior as it's a mistaken I'd never make, oh no. 😁
Nigel Atkins

Jeremy,
clicking sounds like solenoid (if not flat battery).

If you wanted to you could check by connecting from battery to starter to test starter but be aware that could be 200 amps you're playing with. For the price I'd just gamble you've 'jeremied' the starter solenoid and just replace it.

On mine it was a 12mm spanner (or whatever that is in BA spanners?) on the solenoid nuts as I learnt to my surprise yesterday when replacing battery cables (couldn't remember sorting different spanners when I fitted it).

Lesson - disconnect battery - both sides - before playing with the bigger sparks, whilst the battery is off recharge, or top up.

There are 3 and 4 posts solenoids, you want 3 for 1275 and the parts quality as usual can vary so check the rivets are tight on them.

BTW - if you touch the body with a spanner from the live battery post clamp nut you can take a chunk out of the spanner, which is why I now use a 4" adjustable spanner with the handle well wrapped in old insulating tape that remained stuck on unlike the rubbish now.

Nigel Atkins

Jeremy, start by recharging the battery, if you have a charger. It may be that in accidentally shorting the solenoid you have discharged an already marginal battery so it is now struggling to spin the starter motor after those couple of extra starts. I think it unlikely that you have caused any permanent damage to the solenoid, or anything else.

Another test would be to use jump leads off another car, and check that with the added battery boost, it then starts normally.
GuyW

Thanks Nigel,

Battery is fine so immediate thought was solenoid - is there a test to check it's functioning?

Just checked the wiring, all seems ok and it's started several times in succession so not sure what it is!

Would like to sort it as it saps confidence in using it until I know it's resolved.

Guy, crossed postings. Thanks I'll check its charge and see what it's reading. No harm in charging it so will do that too. Good to know there's little likelihood in any permanent damage.
I dug out the original solenoid which has the push button in the middle so may clean that up and refit it, it makes tappet adjustment a bit easier IIRC.

It celebrated its 50th Birthday last week so want to get it running well and back out on the road, been too long in hibernation.
Jeremy MkIII

ETA: I took a long time to do this post so some bits are already covered, but twice is better than not at all (I hope).

Do you mean it now starts or did start but now doesn't?

Have you checked the solenoid is well screwed together, and down (solenoid earthing), and you've not knocked it?

Thoughts for now.
For testing solenoid (and other) you could get a meter out and look for voltage drops in situ/use but I'm not a fan as you need a reliable meter and reliable tests which can have you reaching into awkward places and needs a second person really to turn the key. Those more confident (i.e. know a lot more than me about the subject) will disagree and say how easy it is so I'll leave that to them.

Actually I'm with Guy on battery charging, I've heard so many times the battery is good when it anit. A long slow low charge not this modern stuff of quick and shallow. It costs next to nothing, leaving overnight now and you'll be asleep for most of it anyway. By morning you should know how good your battery charge is.

If you check it before you go to bed and it's fully charged (to a slow charger or proper battery tester then fine). You always want your battery fully charged if investigating starting and/or electrical issues.

Next is battery posts, battery cable clamps, all main cables and earths and their connections all in good condition, clean, secure and protected. You want all this regardless of the problem or resolve.

I'm totally with you in that I hate a car I'm not confident will start, hence my vigilance to battery and connections.

So check battery and connections (always first), if still problems check solenoid if you can, if not for the money just replace it as you have a known working spare. As you start to take the existing one out Sod's Law you'll see the problem and refit it. 😁
Nigel Atkins

Assuming your car is negative earth, which a MKIII should be....

I can suggest some basic tests.
Set your multimeter to A or amps. Most multimeters are okay up to 10A,but check first. Take care to have the test wires in the correct holes.
Disconnect the negative cable from the battery and connect the meter between the negative cable end and the negative battery pole. Ideally you should see no current draw, but possibly a small draw if there is a dash clock or radio still in circuit. If you see (say) a couple of amps there is a leak somewhere.
Probably either the solenoid or the starter. Both are notorious for leaking.
Disconnect the big cable from the solenoid that goes to the starter. Then connect the meter between the solenoid pole you took the cable off and the battery negative.
If you see the same draw it's likely the solenoid is leaky. Depending on where you touched the spanner it's possible you might have burned a conductive path through the solenoid which is drawing enough current to flatten the battery but not to turn the motor. There should be no current measurable there unless someone turns the key
Please remember to take precautions like disconnecting the battery live between testing because the potential for unplanned fireworks is considerable.
I have seen a small car battery explode when accidentally short circuited - the energy contained is absolutely awesome. Seriously, be careful.
If you survive these tests let us know what you found please.
(Kidding. You'll be fine) 😉
Greybeard

The point about using jump leads from another car is that it leaves everything else unchanged, so if it starts then all of those other possibilities; starter, cabling, solenoid, connectors, battery posts and ignition switch are all passed as ok. The only uncertainty might be the starter itself which might spin better with a higher voltage from the mothership car if its running at the time. Or a faulty battery which is why you additionally try a recharge of that.
GuyW

The battery was momentarily shorted, no big deal so long as it was momentary. Everyone's done that. It may need a boost charge. But do carry out Grey's tests as well to check for leakage.
Bill Bretherton

Thanks all,

will try Guy's idea as I have a charged spare battery handy.
Then if I've taken my brave pills and am wearing big boy's trousers, will have a go at Grey's suggestion.
Bill, will charge as you and Guy have suggested and charge the battery. Didn't appreciate it could discharge the battery.
Nigel, good advice so will take your suggestions and work through them, thanks.
Jeremy MkIII

Jeremy,
do keep checking your multimeter before and after each test against a known consistent good reading especially if using a modern cheap digital one otherwise you might be chasing a testing equipment fault and never find it on the car!

I always test testing equipment (and often the tester, especially if it's me) as many years ago I was looking for a leak of a different sort and in the process buggered my feet up for a few days (cobbled cellar) to discover it was the testing equipment at fault - and me assuming it was good without further investigating.

And the time when someone assured me "it's off" and it wasn't, now I double-check myself what I'd already checked as I can't trust myself either. If something can be removed to make something safe I remove it and keep it with so there's no mistakes or misunderstandings.
Nigel Atkins

What happens if you reach into the bonnet and press the button on the solenoid? Assuming you've got a button, my car is the same year as yours and I have but not sure it was original.

Check very carefully that the car is in neutral before trying this, otherwise it will jump forward and may even start. You don't want to be run over by your own vehicle!

I would guess no harm done by a quick spark test, suspect a connection is not clean or tight.

p.s. You didn't loosen or disconnect the earth strap underneath did you?
AdrianR

Thanks Adrian,

the original solenoid did have that starter button (and is being cleaned up atm) but the replacement hasn't.

Of course it's behaved itself perfectly since; starting first time every time. The battery is showing 12.95 volts so isn't at the very top of it's game.

Will print out Grey's instructions and have a careful go at the testing he describes.

Anyone doing anything for Drive It Day on Sunday?
Jeremy MkIII

Jeremy,
12.95v (subject to accuracy of meter) would be very high. You need to leave it a good while between charging the battery and taking a working reading. Try taking another reading if you've been starting the car since the last reading, if it's still around 12.95v then something's not right with something, unlikely to be the battery as it only handles what it's given.

The starter buttons were on the earlier cars and not later cars but I can't remember when the change was.

I was thinking of voltage loss for testing but if the car is starting fine why bother looking for trouble that isn't there, there'll usually be plenty more to look for very soon.
Nigel Atkins

As Nigel says you need to allow the surface charge to dissipate after charging (either with a charger or from the alternator while driving) before measuring battery voltage. About half an hour, say.
The other thing is that measuring unloaded voltage doesn't tell you much that's useful other than that your meter is doing something.
Voltage drop under load is a much more useful bit of knowledge.
If you're going to go testing make sure you have everything possible switched off first, to eliminate loads. The main reason I mention it is that the boot light is a bit a bugger for staying lit and of course you can't tell with the boot closed. I took the bulb out of mine long ago.
Just a thought...
Greybeard

Thanks again.
Just tested the battery after overnight storage without charging and it's 12.87v so it looks ok?
Put an LED in the boot light Grey, just in case as you say, you can't check it with the boot lid closed :)
Jeremy MkIII

Jeremy,
assuming your meter is reasonably accurate that is a very good high reading. Most say 12.6v-12.8v for a fully charged battery but you can get 12.9v.

I'm charging a neighbour's battery that I'm sure many modern chargers would reject as dodo reading so I'll see tomorrow if my old 4 amp analogue charger and old Carcoon (Accumate) 4 step LED charger have pulled it up. It might take the full two days to get it fully back then I'll check it holds that charge and doesn't fall over with real life use (as a drain test). I find using either or both of these chargers on a battery much more reliable than the modern chargers my mates and neighbours use. Very low, slow, long recharging suits batteries that have been drained in the same fashion.
Nigel Atkins

To check the boot light: set your smartphone camera to video and record, place it in the boot facing upwards and close the boot.

Open the boot and play back the video to see if the light really does go out.
Philip Sellen

Nice on Philip, had not thought of that use for a phone Will try it out.
There must be other old car uses for all this technology we have at our fingertips and take for granted.
Jeremy MkIII

What ever happened to climbing in the boot at night to check - oh, yer, I got too old and too fat - but most of you lot have grandkids and great-grandkids, put them to use, save the "smart" phone battery! (it needs all the help it can get).
Nigel Atkins

This thread was discussed between 18/04/2021 and 24/04/2021

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