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MG Midget and Sprite Technical - stupid mistake

last night i left my ignition on by mistake.this morning the coil was red hot and the car wouldnt start.i left it a couple of hours then tried it and it started fine.however now the ignition light is playing silly buggers.its glowing very lightly when i drive it.also sometimes when i turn the ignition on the light does not come on(but it still starts ok).any idea what iv done? its a 1500. also the battery is now only putting out 12v even when the cars running.iv driven it about 50 miles today so it shoud be fully charged.thanks.
roy j

Sounds like the regulator in the alternator is "not very good"

Just confirm are you only seeing 12 volts when the engine is running? if so then either change the alternator or if it is possible change the regulator pack at the rear of it, this is sometimes possible

I personally would also change the coil to be on the safe side.
Bob Turbo Midget England

yep its only given out 12v when tested at the battery.iv just went to start it and the engine wouldnt turn over,it was as if it was tight or the battery is dead.a battery given out 12v should still turn the engine over shouldnt it? i left it 10mins then tried it again and it started 1st time. could it have damaged the stater solenoid so its only working when it feels like it? thanks
roy j

Leaving the ign 'on' can only damage things in-circuit.

There can be no damage to the solenoid... the white/red wire is only in-circuit when the key is turned against the spring.

Some parts of the alternator regulator pack always have 12v from the battery (big brown wire connected from alt to soloenoid post to battery). Other parts will see 12v when ignition is switched on. I must say that I wouldn't expect this to cause a problem... but it's possible (so I agree with Bob!). If you can only see 12v with engine running (say) at 1500rpm, then sounds like it's been damaged.

fuel pump... the SU will run until the float chambers are full and then 'stall' in the normal manner.

Elec gauges/instruments... should not be damaged; it's no difference to them if engine running or not (rev couner should read zero, having said that).

Coil... well if the engine came to a stop with the points open (which is less likley than closed) then the coil wouldn't have any current through it. Mostly the points are closed when engine stationary, and so the coil has current flow for 100% instead of (guess?) 75% of the time. This is the reason why the coil is hotter when ign left on compared with normal running. It's hard to know what damage has taken place inside; normally, it's full of oil and this would prevent local heating and damage. But deterioration of the windings may have taken place such that a fail is only round the corner (or in-between junctions on your next motoway journey). So, as Bob says, better to replace it.

Agreed with Bob twice today; so by way of atonement: *always* time the engine *static*. (That feels better!)

A

Anthony Cutler

Yeap I've done this once

It was last year but with seemingly no adverse effects however just in case I swapped the (sports) coil that was only about 18 months old for a new one

I gave the coil to a mate and he put it on his car with no problems (always my luck)

You could look at it this way - you've possibly highlighed problems that would have appeared a bit later anyway and a new coil is only £13-£20 - whilstle "always look on the . . ."
Nigel Atkins

You SILLY boy - said with her best Capn Mannering voice :)!
rachmacb

so a new coil it is then. any ideas on why the ignition light has stopped coming on when i turn the key.the car starts but the light doesnt always come on. the annoying thing is the coil and alternater have only been on the car for a few 1000 miles. what volt should i see at the battery at 1500rpm?
roy j

rach beleive me i called myself a darn sight worse that that as 6am this morning.
roy j

When running the alternator should show between 13.5 and 14.5 ish volts (all cars are slightly different)

As the light works and hasn't blown the bulb, which it shouldn't, the fault is still in the alternator diode pack

Early types need a replacement alternator, some later types can have the regulator packs replaced instead

The advice you have already had is on the ball

Coil likely to have been damaged when allowed to get red hot if the cooling oil level is down, a replacement is better than a breakdown
bill sdgpm

Mine read 12.7 yesterday evening when being "inspected", but, is going like a bomb!
rachmacb

it could be part of alternator kaput but it may be worth checking -

bulb

connections are clean and secure to bulb and in alternator plug (brown/yellow wire)

and perhaps white wire(s) connection on ignition

ETA: I see my slow typing has left me behind again and I was going to guess at 13.5 volts but it would have been just that

loose/dirty connection on alternator can cause intermitent red light
Nigel Atkins

A new sports coil could be the first step in an incramental improved ignition system next is slighty widened gap on new plugs

This is only worth while if the rest is in good condition such as -

points (better still electronic)

dissy cap http://www.distributordoctor.com/

rotor arm http://www.distributordoctor.com/

good quality ignition leads

all with a well serviced car with give better mpg and/or respnse (depends how you drive)
Nigel Atkins

LOL - reckon from what he's said - he drives like the proverbial "bat out of hell"!!!!
rachmacb

fast driver all the more reason for good ignition system Rach :)

sorry in my last but one post I missed out a word again - I meant it's probably the alternator (or part of) that's the problem but it still migh be worth checking the other things

I was trying to do two things at once - both badly
Nigel Atkins

LOL - that is true .....!

I'm thinking of an electronic one - but - like everything else, can't decide ........
rachmacb

Roy

Your car is a 1500 and as such uses a ballasted coil, please be careful when you purchase a new one to ensure you buy the correct spec
See here for clarification and testing to ensure it is a ballasted installation
http://starturl.com/kkgfw
Bob Turbo Midget England

Id be SO fearful of the wiring?

I cant belive the wiring didnt catch fire with it in the "on" position over night.

Im wondering if there WAS a simi melt down inside the loom under the dash and some of the wires are grounding out causing a drain on the battry

seriously keep a "ABC" fire extinguisher close by in the car, Make sure you got full coverage insurance that covers everything...dont tell them about this, and disconnect the battry at the end of each day till its sorted

Prop
Prop

good point by Bob - I was on a 1275 forgot your is a 1500 (despite checking your profile - old age has me firmly in its grip now)
Nigel Atkins

I should have said some 1500 have ballasted ignition so please chech as described if you are not sure.

There should be no reason why any wiring has melted? the wiring is designed to take the current of any circuit on the car.

Leaving the ignition switched on with the points closed will definately flatten the battery and make the coil extremely hot but the wiring should not be a problem

Exactly why the alternator has failed at the same time is a bit of a mystery but could simply have been a coincidence, however the test you have done confirms the alternator is faulty. It could equally be the straw that broke the camels back
Robert (Bob) Midget Turbo

all this becouse of a stupid mistake.and yes rach i do tend to make the wheels go as fast as they can.it makes me smile.lol. recken im gona have to order a new alternater,coil then.bugger!! prop im well covered with insurance and iv got 3 fire extinguishers in the garage and 1 in my kitchen(sort of a thing with me).
roy j

bob after checking that link it seems i do have the ballasted coil. useful link that,thanks.
roy j

What year is the car?
Robert (Bob) Midget Turbo

bob its a 1977 on an R.
roy j

Roy and I have been chasing this through on his car, and it is actually a 78 wiring loom in there!

There's a small wire from the centre of the solenoid to the + side of the coil, and it's broken away from solenoid. Process of elimination I *think* this supplies 12v to the coil when the starter's engaged, which then drops off again when it's released.

I think Roy's alternator is charging 'cos he drove out to mine today in it! He has to jump start it early in the morning when it's cold, after that it starts OK but crucially doesn't fire *until he lets go the starter switch*.

So....taking our supposition further, if he just attached the broken wire to the downstream HT lead it should do the job, yeah?

No steer on how that affects the charging light, but at least it should avoid the cost of alternator and solenoid. Roy's going to try it tomoz, and hopefully will report back.
Max max-at-midgetmax-dot-com

max.it was good to meet you and put a face to your name,thanks for your time this morning.after i left it ran fine as far as devizes then died.when i took a voltage reading the battery was only reading 9v, i suspect the battery was fully charged when i left home and was running ok at yours as it had a charged battery but "ran out of electric" on the way back home.so i suspect the alternator is a deadun.the AA man was as much use as a kick in the nuts as in his words "i dont understand these old vintage cars".hmm i reckon il be cancelling my AA cover.iv put the battery on charge and will test it again in the morning.
roy j

OK, so scrap para 3 from my posting above!
Max max-at-midgetmax-dot-com

Excluding the use of electric motors like windscreen wipers a good battery should run for a good while when fully charged this time of year

So once, or even before, you've sorted your present problem I'd possibly think about buying a new good quality battery

AA - well that's progess . . . best I not say more on that subject
Nigel Atkins

I assume that, even though it's a later wiring loom, that there isn't something "going dead" in there - or earthing and dropping the power in the battery?

I know it's like a really simple question - but, you know what it's like when you're looking for something - it's easy to miss the obvious!
rachmacb

rach i dont think there is,iv looked at and tested everything i can see.i think im going to have to just get a new alternator and try that. i just went out and put the charged battery on the car and it started 1st time.i think at some point il take it for a drive then check the voltage when i get back and see if its dropped.i started the car up with the alternator unplugged and put the tester on the termanals on the alternator and there is no voltage coming out at all.iv been quoted £47 for a new alternator from mike rolls so its not as bad as i thought.
roy j

I for one am always interested in the outcome of these things to learn from so please let us (me) know how you get on

If you're not used to prices of parts for Spridgets you'll find most are less than you expect
Nigel Atkins

Is your engine earth strap in good condition.
Guy Weller

LOL - remind me of that in a few days time when I double check it all - again :)

Glad that it's sorted and you'll be back out soon
rachmacb

You've still got that "mystery" lead on the solonoid to sort out Roy. I still reckon attach it to the starter-side HT lead and it'll start like a good 'un.
Max max-at-midgetmax-dot-com

max il try that in the morning when the batterys charged up.i put a tester on it when the engine was running and its putting out a constant 9v. im unsure if its surposed to or not? when the engines of the wire is dead.
roy j

Did you look at our website for a desription of the ballasted coil Roy?

If I understand correctly you have 9 volts on the running feed to the coil? that should be correct for a balkasted coil. And as said originally please put a new alternator on. The one you have is b*ggered!

The only other possible scenario that can cause the Alternator to not charge is as Guy rightly notes a bad engine earth.
Bob Turbo Midget England

Can anyone shed light on that extra wire onto the coil from the solenoid? It goes onto the + side where the main ignition wire goes. Does it, as we surmise, provide a burst of 12V to get the car to start when the solenoid is activated? Will it cause harm to attach it to the starter output wire?

If all else fails Roy you'll have to buy a suitable solenoid as well...it's definitely broken and if it can't be bodged as we discussed - ahem, creatively repaired - then there's no other way round it!

Suggestion - wire up an mp3 player to your door courtesy light awitch that shouts "HAVE YOU TURNED THE IGNITION OFF?" every time you leave the car. RAOFLMAO.

Max max-at-midgetmax-dot-com

Bob i looked on the link you sent me and it is a ballasted coil for sure.Max iv decided to stop being a tight git and am going down to mike rolls next week to collect a new starter solenoid and alternator. and as for the bodge you suggested im a firm beleaver that if it works then it NOT a bodge,its just a re-design.Lol. your mp3 idea ant such a bad idea.i might wire up a 12v buzzer to the ignition light so it buzzs when the ignition light is on.
roy j

Max i just tried the car and it started 1st turn with out using that wire. however when i touched it to the starter out put the engine stopped.its starting fine now iv charged the battery up.
roy j

No it can not work in the modified arrangement suggested by Max. Because when the starter is NOT engaged the power to the coil would be then trying to turn the starter motor. It could even burn your ignition wiring out so please do not use it.

If the solenoid is faulty 99 times out of 100 the engine will start fine simply using the 9 volts from the ballasted supply The extra power from the solenoid generally only helps in the middle of winter or when the battery is going flat.

I once had a mtero that the soleniod was faulty and did not give boost voltage on start up. I overcame this by fitting a "HOT" switch to the coil in place of the solenoid voltage. In essence the switch put 12 volts direct from the battery to the coil positive for easy start, then after start up I simply turned off the switch. You would not believe hoew many times I forgot to switch it off!!!! I would only find that out when I turn off the ignition switch and the engine would remain active!! LOL
Bob Turbo Midget England

>>Can anyone shed light on that extra wire onto the coil from the solenoid? It goes onto the + side where the main ignition wire goes. Does it, as we surmise, provide a burst of 12V to get the car to start when the solenoid is activated?

Max - you are spot on.

>>Max i just tried the car and it started 1st turn with out using that wire. however when i touched it to the starter out put the engine stopped

Roy - Your car will start whether this wire is connected or not; the idea of this wire is your 6v coil gets a full 12v blast when cranking (or whatever voltage the batetry can give during cranking...) to aid starting under cold conditions.

So... there's an extra connection on the 1500 solenoid for this, and it's important that it's wired the right way or you can short out the coil supply (which sounds like what is happening).

The white/red from the ignition goes to the spade that controls the solenoid (same as 1275); then the wire from the coil +ve that provides the 'extra' volts goes to the a connector that's shorted with the battery supply and starter motor when the solenoid moves; this connector is not connected to anything when the starter is at rest.

HTH

A
Anthony Cutler

a couple of you have said about testing the engine earth strap. iv looked and looked and cant see anything that looks like it could be it. can someone help an idiot out and post a photo or a description and location of where it is on a 1500 please.
roy j

I am not sure where it is on a 1500 but it should be a heavy gauge wire/cable bolted to either side of the rubber on the engine mount.

Do not get bogged down with this Roy as it is unlikely to be the case baering in mind your engine starter motor happily turns the engine. If the strap/earth was loose then you expect the engine starter motor to be intermitant. However worth a simple look and check.
Bob Turbo Midget England

bob im just intrested in where it is. iv ordered a new alternator and starter solenoid as its cheap enough to replace them as a precaution.im still kicking myself for leaving the ignition on in the 1st place.
roy j

On the 1500 I think it is attached to one of the gearbox belhousing bolts, but that may not be right.

The reason I suggested the earth strap is because it is easy to check and a little while ago I had a battery that wouldn't charge up sufficiently. The engine span OK but it only fired as a "last gasp" as I turned the starter switch to off. I suspect that the starter was taking all of the available current. The alternator showed a low output and the battery about 9.5volts. The earth strap was attached firmly at both ends but heavily corroded in the middle and down to about 25% of the strands.
Guy Weller

could i check that by putting a jump lead from the engine to the body?
roy j

Yep a heavy jump lead would confirm the check mate.

I once used that technique to find hat actually it was the alternator making a very poor earth to the engine that was in fact the fault on the alternator. So you should also try connecting the jump lead to the alternator body as well.
Robert (Bob) Midget Turbo

il try that in the morning then.gota be worth trying.
roy j

Earth strap on 1500 comes off the front engine plat and attaches to one of the steering rack mounts - well it does on mine!

Les
l snowdon

Ant, thanks for confirming that the wire works like I think, Bob thanks for confirming the bodge doesn't work like I think. I didn't delve any further into it 'cos I was in my work clothes and I'm sure customers are quite capable of getting oil on their racewear without my help!
Max max-at-midgetmax-dot-com

by Max """Can anyone shed light on that extra wire onto the coil from the solenoid? It goes onto the + side where the main ignition wire goes. Does it, as we surmise, provide a burst of 12V to get the car to start when the solenoid is activated? Will it cause harm to attach it to the starter output wire?"""



Max I was refering to your suggestion of taking a wire from the starter side of the solenoid and linking this to the positive of the coil ""Will it cause harm to attach it to the starter output wire?""" (you obviously thought that when the starter solenoid was energised that this wire would put 12 volts to the coil on start up. Indeed it would but consider what happens when the solenoid de energises and the coil is then energised by the resistor wire. At this point you have power from the resistor wire to the coil (Small wire) this is also connected via your suggested mod to the solenoid and onto the starter motor. This wire will then be "Trying to turn the starter motor!!!) It obviously will not for 2 reasons 1 the voltage will be too low and secondly the "Capacity" of the wire will prevent enough energy from getting to the starter (in laymans terms) What will happen however is that in a short amount of time the wire will melt and catch fire and it will stop the engine which if I understand correctly happened when Roy tried it. Fortunately he did not connect it for long enough to damage anything! :)
Suprised Ant did not question that? very suprised!!
Bob Turbo Midget England

Hi Bob

There's a ton of background I could have written on the seemingly simple 'extra wire'; I just had to draw a line somewhere, since it takes time to write it, and I'm never sure similarly that everyone finds the time or the motivation to read long posts.

BTW I did mention that connecting the extra to the wrong terminal at the solenoid end would short out the coil supply.

Any road... we're all in agreement for a change!

A
Anthony Cutler

This thread was discussed between 12/07/2010 and 16/07/2010

MG Midget and Sprite Technical index

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