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MG Midget and Sprite Technical - Cutting out when driving?

Hi, I have a 1500 which when out on a run will cut out completely with no warning. This can happen at any time, although it first happened when i got to about 60mph. It doesn't seem to be fuel related, as it doesn't splutter, it just cuts dead.
I have checked the coil whilst the car is running and it shows anything from just over 6 volts down to about 3.8volts. Would this be the problem?
Thanks
Kevin
K Grice

Apologies, in my rush checking the voltage I measured the negative side of the coil not the positive. The positive actually reads 10.39v down to 7.59v and intermitently down as low as 1.5v.
Hope this is of help

Kevin
K Grice

Kevin - The problem really sounds like a flaky connection somewhere in the primary ignition circuit. See the article, Electrical Connection Preparation in the Other Tech Articles on my web site at: http://homepages.donobi.net/sufuelpumps/ and use those suggestions to redo all of the connections in you ignition systems. You might also want to chase the loss of voltage back along the line to the ignition switch and ultimately to the battery before you start redoing connections to save a bit of time and work. Look especially at the ignition switch as a possible source of voltage drop. Cheers - Dave
David DuBois

I've checked and cleaned what connections I can find. Now it will cut out while on tickover, I can start the car, let it idle for a few minutes at about 800rpm and then it cuts out. Its exactly like someone turns the ignition key off. Has anyone else experienced this problem?
Thanks
Kevin
K Grice

coil?
condenser?
David Smith

Condenser.

AndyB
a borris

Just changed the coil and now it ticks over ok. About to take it for a run, fingers crossed!

Thanks
K Grice

Good luck, Kevin. The condenser was mentioned above due to a spate of condenser failures over the last few years. I went through that little adventure myself, having the car die on the road several times, and throwing new parts at it with no avail. I never thought of the condenser, thinking that it was just a simple little capacitor, so what could go wrong? After yet another stall, I finally changed the thing and that completely cured the problem. But just to be on the safe side, I eventually replaced the points and condenser with a pertronix unit, and it hasn't missed a beat in years.

Best,

-:G:-
Gryf Ketcherside

Well i'm back, the car is as bad as ever! It drove 6 miles without any problems but then my luck changed. It started to cut out and would not start when bumped on the clutch. It eventually started after about 10 minutes, this happened at least 3 or 4 times. I think I've got a spare condensor, so i'll try that. What about a new ignition switch? Is there anyway to test the current one? This is driving me mad and on a nice sunny weekend too!
Kevin
K Grice

Kevin,

It can quite possibly be the ignition switch, I had to replace one on my frogeye, much easier than a 1500 IIRC as it sits in the middle of the dash. Can you reproduce the problem and check the ignition switch input and output when the problem occurs to see if you have 12V in and ? out.

BTW last autumn I was having frequent lighting of the ABS warning light on my VW Passat, the ignition switch failed mechanically and was replaced and the ABS problem has gone away.
David Billington

Kevin,
What does the tach do when this occurs? If the tach drops like a rock with the engine still being rotated by the wheels, it is in the primary ignition circuit (definitely try another condenser). If the tach continues to register, look elsewhere. I would suggest "hot-wiring" it, but I am not sure where to put the lead from the battery on your car. This would bypass the ignition switch and a lot of other suspects.
David "How many keys on your ring?" Lieb
David Lieb

thinking about it, perhaps you could carry a wire with clips on both ends and clip it from the battery + to the white wire at the fuse block when the problem occurs and see what effect it has.
David "I keep hitting 'submit' too soon..." Lieb
David Lieb

thanks, I have put in a new condensor. Yes the tacho drops to zero. I will take it for another drive and see what happens, if it does happen again i'll check the ignition switch.

Kevin
K Grice

Bear in mind that "new" does not necessarily equate to "good". Especially in parts for our Spridgets.

Depending on the vintage of your 1500, it might have 0, 1, or 2 ballast resistors with accompanying potential points of failure. Are you still using the original distributor? It could be going, too. Try the bypass wire next time it fails to eliminate the ignition switch as a suspect.
David "suspicious mind" Lieb
David Lieb

Hooray, I think I've cracked it. The replacement condensor seems to have done the trick. I did the same route and it didn't miss a beat. Only time will tell.
Mine is a 1976 1500 still with the original distributor.
This is the 3rd condensor replacement in the last year and this one is an 'old' one that I had as a spare. Does anybody know of a good source for condensors?
Thanks for all your help.
Kevin
K Grice

A "good source for condensors" or a "source for good condensors"? Best bet is to install a Pertronix conversion and eliminate points AND condensor like Gryf did.
David "or a 123/Mini" Lieb
David Lieb

I had just thought of replacing the points and condensor. What are the thoughts on the pertronix? I have also seen people mention the lumenition magnetronic system. Any pros & cons?

Kevin
K Grice

If the problem comes back again, it could be the earth flylead in the distributor is open circuit, they snap after many years of the distributor base plate rotating back and forth.

In that circumstance the base plate may be getting an intermittent earth through its slidy connection to the distributor body. Quick way to check it is to hook a finger under the lead and give a gentle tug and see if it comes apart.

Roly
Roly Alcock

Excuse my ignorance, but is that the small wire which is connected to the same screw as the condenser?
Thanks
Kevin
K Grice

Not sure with your dissy, Kevin, but it is a small braid from the body of the distributor to the moving plate on which the points are mounted. If it is bad, then the distributor is "grounding"("earthing"?) through the mechanical advance mechanism and that is not a good idea, ESPECIALLY if you convert to electronic.

There are multiple opinions on the electronics. I, personally, have had nothing but success with them. Others have had nothing but trouble.
David "still have points in the Bugeye" Lieb
David Lieb

Kevin,
fit an Aldon Ignitor module & you can forget about condensors & points for ever.
Brad (Sprite IV 1380)

This thread was discussed between 05/04/2009 and 14/04/2009

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