QuestionQUESTION: Hello Howard,
I have recently been asked to fix a 1979 MG Midget with approx. 60k original miles on it the car used to be a nice car I am sure until it was taken to a guy who was paid to fix it and didnt. I was told that it always cranked but would not start, which it still does. this guy has obviously started with the most least likely area and then continued on for 2 yrs and still does not run. So this is why I was asked to check it out and get it running. This is my first MG experience not to bad so far just in need of a little help, (I generally work with newer VW cars.
First I charged the battery and found a wiring diagram in a manual put all the wires that were disconnected back to where they go to my best knowledge. I checked for spark and no spark was present so then I checked for power to the primary side of the ignition coil and I had battery voltage there 12.4 volts with key on. then i checked the negative terminal of the primary side with the key on there is 12.4 volts there too. dont know if this is normal with electronic ignition should it change from power to ground depending on where the reluctor wheel is located.if i disconnect the negative terminal wire at the coil then it seems like it turns to a ground. I suspect that I have a bad pickup coil in the distributor but am not for sure. Does this sound right?, since I have power to the coil. The three pin connector to the distributor has 12.4 volts at 2 of the terminals and approx. 3v-4v at the other terminal I am guessing that this connector only goes to the pick up coil. Is there a Ignition module? No right. If you could give me any input I would greatly appreciate it. I read your responce to a prevous problem someone was having where they had an MG with a points distributor instead.
ANSWER: Hi Bradley,
If you have the same voltage at the (+) and (-) side of the coil no matter where the reluctor is then the module is bad if the air gap is correct (about .012" to .015")and the wiring is correct.
Disconnect the three wires and turn the key on and test each wire. The white wire should have power with the key on and so should the white w/blue tracer and the white with black should go to the (-) terminal of the coil.
If it is wired correctly the white w/blue tracer wire goes to a drive resistor and the white wire should go directly to a power wire.
On the coil you should have two white w/black tracer wires on the (-) side of the coil, one goes to the tach and the other goes to the dist. On the (+) side of the coil you should have two white w/light green tracer wires, one goes to the starter solenoid and the other goes to a resistor wire from the ignition switch.
The original Lucas electronic ignition failed often which prompted several aftermarket companies into producing their own ignition system. Many MGB owners just put in the older pointed distributors when the original system failed.
Other than high energy electronic ignition systems like MSD and others, you may not find any advantages of electronic ignition systems over the Kettering ignition system on an MGB.
Electronic ignition systems on late model cars today are far different and have many features needed on cars today. But what was available on the MGB was mostly more trouble than it was worth.
Howard
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QUESTION: Hello again,
Well the day after I emailed you I went ahead and purchased a aftermarket pick-up coil because all the wiring checked like i thought it should. You confirmed it.
It is an upgrade that is available through a place in lenexa,ks and installed it then cranked the engine over and spark was present to the plugs. Thanks for the input.
So now I have spark, but do not have fuel I checked to see if any fuel was in the tank and there was not I can smell a faint odor of bad gas when cranking it but no gas going to lines so I went and got 5 gallonsof fresh fuel put in tank and cranked it over still nothing in lines so I suspect that the fuel pump had gas that sit in it for 2yrs plus and dried out/ corroded the fuel pump diaphram and anything else in the carb. that came in contact with fuel. I had a friend crank the engine as I sprayed small amounts of starting fluid into the intake tube and it acted as it wanted to start but didnt. It was back firing slightly through the intake which makes me believe that the prevous guy that worked on it may have crossed the ignition leads or put the dist. in incorrectly.
The first thing I am going to do is get fuel to the engine then I will try to sort out the timing. If you have anymore input I would greatly appreciate it.
Thank you so much,
Brad Heuer
AnswerYour welcome Brad, the 79 Midget engine is a Triumph Spitfire engine and uses a mechanical fuel pump and sitting for years will make the diaphragm harden and since the spring in the pump is the only thing that pushes fuel to the carb (the operating lever only retracts the spring)it can not move the hardened diaphragm. Plus the valves in the pump will probably be stuck closed and not release.
If you have a fuel filter on between the pump and the carb, you should replace it and if there is not one on the car you should put one on in between the pump and the carb. Use a metal filter NOT a plastic one. Remove the line at the pump and lower it into a can so as to drain some of your fresh fuel onto a can to flush any loose trash out.
Howard
