QuestionMy 1978 MGB has been breaking down on hills. The last time it died on a large hill and would not start, even tried starting fuel to see if it was fuel. Left it over night and started no problem next day.
It seems something is getting hot like coil then cools and starts
Hate to take long trips
Help
AnswerHi John,
The hardest fault to find is an intermittent problem, however to find a problem you must do the testing when it is in the failed mode. (not starting)
You can't rule a coil out but that is unlikely the problem as a coil does not know if you are climbing a hill or going down a flat road. The two main suspects are fuel supply and a partially stopped up exhaust system.
Both are easily tested. You need two tools however, a vacuum gauge and a fuel pressure gauge. Fortunately they are usually on the same gauge. Most vacuum gauges have a section for carburetor cars fuel pressure.
Since you tried starting fluid already test the vacuum first. Connect the vacuum gauge up to a vacuum port and run the hose out from under the hood and put the gauge under a wiper arm so you can monitor vacuum while driving. Then go find your hill and climb it and watch the gauge. All street engines should stay at least 5 in hg even at full throttle and full load.
If the vacuum continues to drop lower and lower as you climb the hill until it reads zero and the engine dies, you have a partially stopped up exhaust.
If you maintain vacuum on till it dies, that is not the problem. So you must do two things, first connect a "T" in the fuel line just before the carburetor and put a long hose on the "T" and run it out from under the hood and place the gauge under a wiper arm so you can monitor fuel pressure as it dies. If the pressure drops below 1.5 PSI before it dies you have a fuel supply problem. Fuel pump, fuel filter or fuel line or even the tank pick up. (Be sure you put clamps at all hose connections.)
If you maintain fuel pressure on till it dies put a timing light on the coil wire and tape the trigger down so it flashes all the time and run those wires out from under the hood and place the timing light under a wiper so you can see the flash of the light on till it dies. If you do this test in bright sun light you may have to tape a piece of cardboard over the light so as to shade it so you can see the flash. This tests the primary of the ignition system while under load.
I have had all three on at the same time when I had a car that would not fail in the shop but would under load on the road. It took too much time to do each test one at a time.
Howard
