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MG Midget and Sprite Technical - Coil Questions

Hi all,

I'm new to the forum, midgets and cars in general so apolgies if (as i'm sure i will) i cover old ground here.

I recently bought a '76 1500 midget and it has been generally well behaved. Have had some problems with the ignition system but a recent service (which included replacing the fuel pump - as it was advised this was the route cause of the starting problems) seemed to have solved things.

However, I stalled in traffic after a long drive at the weekend and it won't restart. AA suggested the coil be replaced as there was almost no spark off the connectors.

In the hour or so preceeding the stall the engine occasionally started putting, especially when accelerating or decelerating.

I have a replacement coil and am planning to fit it tonight but was just wondering if this really is likely to be the problem?

How do coils die? if they 'fade out' it could i suppose explain difficulty in starting?

Like i say, i'm very much a beginner with all things mechanical, but i'm slowly learning so any advice would be appreciated!

Thanks,

Stuart
S Balkham

Hi Stuart,
While I can't help with this, I may be able to give moral support. Where about in London are you?
G Lazarus

Coils are generally more reliable than other parts of the ignition system, such as points, rotor arms, caps...

Coil is easy to check: uncouple the lead from coil to dissy at dissy end, and place near engine; crank engine over: should see a spark. If not, check points open/close.

If they do, and there's 12v on the coil +ve, it suggests the coil might be u/s.

You can always jury-rig new coil by connecting its terminals and check spark in same was as above. If no spark, there's something wrong with your low-tension side...

A
Anthony Cutler

Hi, Stuart. Is you car still fitted with a condenser? There have been cases of these failing as well, and I can speak as a victim... the result was non-starting when hot, and a weak yellow spark. Replacing the condenser proved to be the cure, but not long after that I replaced my points and condenser with a pertronix unit.

-:G:-
Gryf Ketcherside

It is possible for it to be the coil or it could be a number of other things. Generally testing the coil as per Ant's suggestions is good enough for me to assume the coil is fine.

As Gryf states extremely rarely the condensor can be at fault and I have to say this sounds like it could be a possibility but time will tell.

However what is important is certainly to repair one thing at once, all too often everything baring the back axle is changed at once and thus the owner ends up with no idea what the original problem was.

So let's know how the coil performs, then perhaps short of more info you ought to try the condensor. :)
Robert (Bob) Midget Turbo

Hi all,

Thank you for your various advice - i've only just had time today to get under the bonnet and try things out so apologies for not replying sooner.

Bad news though:coil replaced and still doesn't start.

Anthony: I tested as best i could - i'm on my own so can't turn the engine over and check for spark (although i will try and recruit an assistant to do this). I did check the voltage though: on the +ve side it is about 6v (and only just over 1v on the -ve side...).

Gryf: I changed the condensor only a month ago - do you think this could still be the issue?

The distributor parts seem clean and generally in good shape from a purely visual inspection.

I'm at a slight loss as to what to check next. Should i be looking at fuses at all?...

Any suggestions welcome!

Thanks in advance.

Stuart
S Balkham

6v at the (+) coil terminal should be correct with the ignition on...the '76 1500 had a resistor wire in line from the ignition switch to drop the voltage at the coil to around 6v. On cranking, there is another wire to the (+) coil terminal coming from the starter solenoid to provide full battery voltage when cranking.

Now, the coil you need for this system HAS to be one designed for external resistance...it's easy enough to check with a VOM. The coil for this system measuring from the (+) to (-) terminals will read around 1.5 ohm. A coil not designed for external resistance will read around 3.0 ohm.

Make sure you have the correct coil fitted!

When I first bought my '78 1500, it had the wrong coil & a very weak spark.

Also, the basics: it's just a good idea to give the engine a good tune up when newly acquired...cap, rotor, codenser, spark plugs, points if you have them & GOOD quality spark plug wires.

Not sure if this was any help...just some random thoughts.

Good Luck,
Dave :)
Dave Rhine ('78 1500)

Why did you change the condensor?

There are known issues with some current replacement ignition items, so you may have a duffer.

Do you still have the old one, assuming that it wasn't faulty?
Dave O'Neill 2

Stuart
There was a lot of discussion on the forum a while back about the quality of new condensers - i.e.new condensers failing.
I would 100% advocate Bob's advice. Only play around with one thing at a time, eg if you try another condenser and it still fails to start, put the old one back, as its unlikely 2 things failed simultaneously, but the 2nd one might be faulty and so you wont know where you are!
Graham M V

I quit with points & condensers over 20 years ago.

I've been converting over to Petronix products since then, they're about the only reliable ignition products I've been able to find in quite some time.

Here in the US, we had a trade agreement called NAFTA, basically what it did was send most of our manufacturing to Mexico & other similar, cheap labor countries. There was a point in time using Mexican made points & condensers, you would be LUCKY if you got 2 weeks sevice out of them.

I don't know where the current batch of tune up parts are being made, most likely China. I repaced a rotor last Fall & the engine wouldn't run...polished the old one & put it back in & no problems since.

So, I guess what I'm trying to say is: I'm an Old Fart & back in the day I would put in new parts & forgot about them, but these days, new parts sometimes cause more troubleshooting & agravation than the parts I just replaced, after all, it's brand new!

Don't assume anything just because it's new & was just replaced.

Ok, off my soap box now, good luck keeping these old cars running with the current parts supply.

Dave :(
Dave Rhine ('78 1500)

I second not fully trusting new parts especially stuff under the dissy cap

Try for rotor arm etc, here - http://www.distributordoctor.com/

It's very difficult to see problems on the dissy cap and rotor arm so bear that in mind - I've had a few dissy cap problems with various cars

Also ignition leads can be a problem and new good quality ones are so cheap for Midgets - again leads can throw up intermitent problems

Another thought - not trying to put you off only to consider - if it's not ignition then it's probably a fuel problem

If you could get another head and set of eyes under your bonnet it would probably help
Nigel Atkins

Hi Dave you say you had a trade agreement called NAFTA LOL

Yes the real name for it of course was the FREE MARKET!! That wonderful belief we seem to have that using it cures all ills!!

Dont laugh some people seriously believe that!! Did we just have a reccession?? Another great job!!
Bob Turbo Midget England

Going back to the original problem ...!

If the car is new to you - TRUST NOTHING that was told by the previous owner!

Start at the beginning, and work through all the parts of the engine - they are pretty easy, and there's plenty of people who will be able to show you things you need to know if you need it.

One thing at a time - but - do do everything over time. At the very least, at least you will then know for certain what has and hasn't been done.

Get the best quality parts you can.

Make sure the fuel you use is decent (it does make a difference - I know this to my cost, but at least mine doesn't pink anymore!!!)

Never ever ever ever trust anything that the AA et al say - they are mostly about 10 years old and have never seen a car they can't just put a computer in to to diagnose a problem. OK yes, that's a wide stereotype, but, pretty much on mark - just use them to bring the car home when they don't have whatever little thing it is you needed ...!

If you live not that far from Gary - take him up on any offer of a beer - at the end of the day - at least you can drown your sorrows! Otherwise - go to the next meeting at the ACE cafe - and meet many of the people who make witterings on here ;)

Good luck with your car - there's nothing better in the world than driving them :)
rachmacb

Thanks all and again, apologies for slow reply.
Well, it's still not starting and I'm a little stuck for ideas. I'm sure this is a poor way of working but I changed the coil and swapped points & condenser for electronic unit. Still nothing though. I have no spark from the lead from the coil to sissy on the engine when cranked so presumably the problem is still before the coil?

The obvious points - to me at least: battery def ok. There is plenty of fuel in the tank, although when it was in the garage a few months ago they changed the fuel pump citing this as the reason for non starting...

That's about where I am. Help! Really want to get her running again without resorting to the garage and parting with yet more cash... G Lazarus - I'm near Peckham if you want to take a look?...

Cheers all!
Stuart
S Balkham

Er, do you have a starter soloniod on the 1500? - connectons to and from it clean and tight (if you have one)?

do you have ballast restistor wire on your model? other will be able to advise on that

wires and connections to from ignition switch clen and secure?

coils when they go tend to drop engine power (I thinK)

just thought, don't dismiss it as with the other stuff you've done whilst it hasn't solved this problem it could help prevent future problems

- battery in good condition? check the look of the plates inside and water level is correct, fully charge the battery whilst it's disconnected

battery connections clean and secure? clean the inside surface of the connectors and the battery terminals and coat in copperease inside and out or cover in petrolum grease when refitted
Nigel Atkins

A quick & easy test: run a jumper wire straight from the battery positive terminal to the small positive terminal on the coil, if you get spark from the coil high tension lead, then the problem's in the positive wiring to the coil.

I'm sure it's something simple, you just need to find it & don't jump around, be methodical, test each circuit/component thoroughly before going on to the next item.

Follow these guides exactly & you should find the problem, if it's in the igntion system:

Here's a helpful link:
http://www.midgetregister.com/index.php?option=com_content&view=article&id=73&Itemid=66

And guide to electronic type set up:

Dave Rhine ('78 1500)

Hi All,

Just a quick update for you all. It's up and running again! A bit more fiddling with wiring to the coil and new electronic ignition and all seems fine. Starts on the button and seems to be running fine...
I can only assume it was the condensor failing as points and coil looked good. Will be interesting to see if the electronic ignition is more reliable now.

Thank you all for your help - this forum is a fantastic resoucre for amateurs like myself. Without you guys I would have lost confidence long ago. I'll be back when we hit the next problem no doubt!

Dave - the links to ignition info were especially useful. Thanks!

Cheers.

Stuart
S Balkham

You're welcome!

Years ago we could do a tune up & forget about it, but these days especially condensers & now rotors have been very troublesome...back in the day, electrical components were made in the UK & US and they were very reliable.

I quit with point & condenser ignitions over 20 years ago, when all I could get was Mexican made units that were sometimes good for only a couple weeks!

Hopefully these electronic units we're getting now weren't made in China, India or Mexico.

These inferior parts have caused me so many problems, both in my hobby (the little Spridget) & my work...well I won't get into all that, I could write pages & pages on that subject!

Good job & good luck!

Dave :)
Dave Rhine ('78 1500)

This thread was discussed between 20/07/2010 and 12/08/2010

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