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Triumph Repair/79 Spitfire overdrive issue


Good evening:

Last weekend I purchased the Spitfire and ironically, when I was taking it to a mechanic for an inspection, the car let out these two large bangs (in overdrive) and stopped running. There were electrical issues I already noted (brake lights, gas/temp gauge, turn indicator). Could this be related, or  I looking at a whole new engine?


Hi Zack,

Your symptoms of large bangs and it stops running does not tell you anything except that it has stopped running. An engine that has stopepd running is one of the easiest to diagnose for a mechanic (or an individual) But it does require some testing.

All engines only require 3 items to run and they are Compression, Fire and Fuel with conditions on each. They MUST be tested in that order and nothing skipped. It also requires a few tools that are not expensive too. A compression gauge, vacuum gauge (with a section on the gauge for fuel pressure), a 12v test light and a set of hand tools.

"Compression" -- Remove all four spark plugs and put the car in 4th gear (hand brake off) and roll the car and watch the front pulleys to confirm that the drive train is free turning. Take it out of gear if the engine does rotate ok and remove the white wire/s off of the coil and see if the startermotor spins the engine over. If it does, check the compression on each cylinder with the throttle open and be sure to let the engine rotate at least 5 or 6 revolutions. The compression must read at least 135 PSI to 170 PSI on each cylinder with little difference between cylinders.
It must pass these tests for you to proceed as it is a waste of time to go on unless it passes these tests.

"Fire" (Ignition) While the plugs are still out put each spark plug on it's plug wire and plug the white wire/s back on to the coil. Turn the Ignition switch to "ON" (not start) and take the 12v test light and confirm that you have power to the coil.

If everything passes up to this point let me know and I will give you the next set of tests. If it does not pass these tests let me know and I will give you the tests to see why it didn't pass.


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Howard M. Fitzcharles III


Triumph TR-4 up & Spitfire, and Engine theory


Dealership line mechanic on MG, Triumph, Jaguar for 15 years, Instructor in commercial mechanics school 2 yr. Product information manager for piston and valve manufacture, Instructor & hotline answer man for import car parts importer 15 yrs.

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Import Car magazine

ASE Master Auto with L-1 certification up to 2000

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