QuestionI had my 69 MGB tuned up, new plugs, wires, oil and filter, condenser, points, rotor and distributor cap. I picked it up from the shop and it ran great. I drove it for about 1.5 hours at 45mph with no problems. All of a sudden it began to run rough, back fire etc.. It went downhill quickly and after a few minutes of that it hardly ran at all.
I can get it to start but it won't run on it's own, lots of backfiring and no power when I give it the gas.
Any ideas as to where to begin? Any advice is greatly appreciated.
Thanks-Ian
AnswerHi Ian,
The problem may or may not had anything to do with the previous work done but you need to start from scratch and test.
Compression test first to confirm the engine is not the cause. (be sure to hold the throttles open during the test)
Check for a good fuel supply from the fuel pump to the carburetors.
Remove the cap and rotor and turn the engine by hand or a good method I used was to remove the plugs and put the car in 4th gear and roll the car as you examine the points with a strong light to see if the points are opening about the same on each of the four cam lobes. Set the point gap if it does not look correct (.015") clean the contacts with Emory paper or a points file and clean afterwards with a small piece of cardboard. (like a piece of match cover)
Examine the inside of the distributor cap with a strong light looking for carbon tracking. Put the rotor back on the shaft and remove the coil wire from the cap and hold it about 1/16th to 1/8th inch from the rotor and have someone spin the starter to try to jump a spark to the center of the rotor. If you can jump a spark to the rotor, it is definitely bad.
Backfiring and running poorly is a sign of an ignition problem but the compression and fuel supply needs to be done first.
Let me know,
Howard
