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MG Car Repair/Ignition Light comes on and off

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Question
It started a few days ago, and then got worse. I start the car fine, its then the ignition light comes on and then the car stalls.

The other day i got in the car for going to work, and it had a hard time starting. Which i thought wried as it never has done it before. But when i was going home after work the issue was worse, the car started jumping everytime the light came on (every time i change gear in fact it comes on). I went round a corner and got into 3rd and that was it. It had stalled on me whilst driving.

Got green flag to take me and the car home, which is very helpful. But then we tested it, the battery is fine, the alternator charges the battery (we did this very quickly as it was hard to keep her alive for long, and she just wanted to stall as soon as we had her running).

I have even checked the ignition barrel, and when i played around with some wires it started fine but as soon as i went in gear it stalled.

Any ideas on whats wrong?

Answer
Hi Chris.  This is a tricky one because it could be so many things. The fault sounds electrical.

A red ignition light coming on usually means the alternator has an internal fault or the fanbelt is slipping, but neither of these would cause the engine to stop.  

I don't know the make, model or year of your car which complicates things a bit.  I will assume it is an MGB or a Midget.  

If this is a 1976-80 car then I would be suspicious of the ignition relay near the fusebox.  (You can recognise it because it has two white/brown wires going to different terminals).  I have heard several reports of these failing recently.  If the relay drops out, the power is cut to the coil, the engine dies and the ignition warning light comes on.  Try replacing the relay before you do anything else.  If that doesn't fix it then try the following:

The fact that it happens when you change gear might be down to the engine rocking so an ignition wire breaks contact.  Check the White/Black wire on the side of the distributor.  If the insulation is hard and cracking, replace that section of wire.  

Do you still have the original points ignition?  If so, is the points gap correct?  It may have closed up as the heel of the points wears.  New sets of points do not seem to be made of durable plastic nowadays.  

Finally, there is a thin copper earthing wire inside the distributor that can fray or even break.  If that wire is just touching the base plate it could be producing a random misfire or engine stoppage.

Let me know what you find.  

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Barrie Jones

Expertise

MG Sports Cars from 1949 to 1980 - Including MGB, MGBGT V8, TF1500, TF, TD and modern Midgets. I also specialise in SU carburettors, Lucas wiring, suspension, steering & brakes.

Experience

I have owned my 1955 TF1500 since 1966. Technical specialist for the TD and TF with the MG Car Club T Register. Also owned 20 MGBs and currently own an MGBGT V8. Written 3 books on MGs and produced a DVD on how to strip and rebuild the TD/TF gearbox.

Organizations
MG Car Club.

Publications
Barrie's Notes on the 1953-55 MG TF (author). /=====/ Barrie's Notes on the MGB (author). /=====/ Barrie's Notes on the MGB GT V8 (author). /=====/ The Essential Buyer's Guide to the MG TD, TF and TF1500. (author)

Education/Credentials
M Phil, C Eng, BSc (Eng).

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