QuestionHello. I just purchased a 1975 MG Midget with the 1500 engine that is stock besides the Holley single downdraft carb kit & manifold, header and electronic ignition kit already installed. It starts immediately, seemed to run fine for several miles and normally runs strong with no pulsing, backfiring or stalling.
I have driven it as far as 10-15 miles at a time and had no problems or indications of problems.
Last weekend I tried to drive it to another town 40 miles away and at about halfway the engine started cutting out or losing power. As though it was suddenly not getting enough gas or spark. I pulled over and checked under the hood expecting to see perhaps a loose or burnt coil wire or find the carb float bowls empty but this was not the case; everthing upon cursory check looked fine. I got back in and it immediately restarted and behaved normally. I turned around to take it back home and it ran fine for about 1/4 mile then began stalling out again, but I found that if I depressed the clutch the engine wasnt actually stalled, it just didnt have enough power to propel the car. It would idle, but had no power. This seemed to indicate a fuel delivery problem as opposed to an ignition problem to me so I began tapping the gas pedal and it began running with power on and off. Sometimes up to highway speed, then losing power and coasting for awhile, then back up to full power. And so on for the whole drive home. It seems important to me that the car never actually died, even when I came to a full stop at red lights or stop signs. It would just have extremely little power. (or maybe I was just lucky and it never hit when I was at a complete stop, I cannot be sure.)
I decided to go online and search for this issue and found a UK article explaining that the Midgets have heat issues. Apparently because the exhaust manifold/header are next to the intake and there is so little space that in extreme conditions or stop & go driving the heat may get to the carb and fuel line and boil or evaporate the gas prematurely. This seemed feasable because it was almost 100 degrees outside the day this happened. I am in north Texas and this is not uncommon this time of year. They advised that a heat shield might help this and that some models even had a little fan, (odd). Article is here: http://www.mgcars.org.uk/cgi-bin/gen5?runprog=mgoc&a=&p=emg/petrolclassicmg1.htm...
I kept searching for other issues and found this website and found several related articles but none discussing heat as an issue. I read most related articles up to page 10. I am prepared to buy a vacuum gauge and fuel pressure gauge and check exhaust backpressure as you have advised several times to other posters, but didnt see any info about what to do when I get the results.
Any ideas on what this issue is and how to correct it? Or at least where to look beyond checking pressures?
Thanks, Will
AnswerHi Will,
I learned working in dealerships that you should never look for what is wrong. Because that item is numbered in the hundreds or even thousands. Instead, run tests to isolate the problem into a smaller and smaller area. I am always surprised what I find but I always find the problem that way.
All gasoline engines only require 3 things to run so test to see which one or more of the 3 is missing. Tests must be done while in the failed mode. It is no use testing an engine that runs good.
Since the problem is not present in the shop you need to test on the road while it is failing.
Put a fuel pressure gauge under a wiper arm and run the car until it has the problem. This covers fuel supply. Do the same with a timing light on the COIL wire. (You may have to tape a piece of cardboard to cover the end of the timing light so the sun light don't prevent you from monitoring the flash of the light when the car starts failing. (this covers fire)
If you read the one I wrote about testing for exhaust back pressure, do the same with the gauge.
let me know,
Howard
