MG Car Repair/1972 mg midget question
QUESTION: hi, I have a 1972 mg midget that is not sparking. I really don't know much about the car and was wondering what my problem could be?
ANSWER: Hi Avery.
I assume that you have the original ignition setup with a distributor that has points inside it. There are some basic tests that you can do with the car parked on a patch of level ground, so long as you have a few tools such as a screwdriver and a set of feeler gauges.
1) Undo the two clips holding the distributor cap onto the top of the distributor and lift the cap off without undoing any of the high tension leads. Put the gear lever in top gear, then push the car forward whilst watching the points. They should open and close as the 4-lobed cam rotates. If they do not open, then the points gap must be adjusted using a 0.015 inch (0.4 mm) feeler gauge and a medium sized flat bladed screwdriver. If you do not know how to do this, get back to me and I will describe it in more detail. When you have finished, push the car forward a bit more so that the points are closed and put the gear lever back into neutral.
2) I have heard reports of a bad batch of rotor arms. To test yours, pull the middle HT lead from the distributor cap and hold the lead over the rotor arm so the metal part is about 1mm above the rotor arm. Do not hold the metal part or you may get a shock from it. Turn the ignition on but do NOT start the engine. Now flick the points open with the finger of your other hand. You should NOT see a spark between the metal end of the HT lead and the metal part of the rotor arm. If there IS a spark, then your rotor arm is faulty and you need a new one.
3) Now hold the metal end over one of the cylinder head studs and flick the points open. You should see a spark this time. If there is no spark, then you may have a faulty coil.
Clip everything back together again and hopefully the engine will now start.
Let me know how you get on.
---------- FOLLOW-UP ----------
QUESTION: So we tried all of your tests and they all came up good but we were still getting no spark, we are thinking that we need a new distributor cap and rotor. Do you know if there is any thing that would be in the clutch that isn't working to stop it from sparking?
No, Avery. There is nothing in the clutch mechanism that would affect the ignition system.
The good news is that you have a spark coming out of the centre HT wire that goes from the coil to the distributor. If you still have no spark at the spark plugs, then that narrows down the problem a lot.
I recommend that you inspect the inside of the distributor cap. In the centre there should be a spring-loaded carbon brush sticking out. Make sure it is clean and that it springs back out smoothly when you push it into its hole. If you have any doubts about it, replace the cap with a new one. They are not expensive.
Whilst you are doing that, for a little more money you could replace all 3 parts (distributor cap, points and condenser).
The only other item that sometimes causes problems is the spark plug wires. We call them HT leads in the UK. They come as a set of 5, one for each plug and a 5th one that goes between the centre contact and the coil. However, I don't think this is your problem.
Let me know how you get on.