QuestionI was given a '77 MG Midget as a gift from my dads friend. It was running good up utill about 2 days ago. The engine starts but not right away. It takes a few minutes and it will stall at random times. I can drive it for an hour or just a few minutes but stalls when I come to a stop. I'm not a master mechanic, so I'm a bit stumped on what *I* could do.
If its of any relevance, I accidentally ran out of gas the day before the issues started and assumed the fuel filter/pump got clogged with gunk so I replaced it but the stalling issue is still there.
AnswerHi Miguel,
There are hundreds of things that can make an engine stall or quit at random times. It is impossible to guess which one or more then one that does it. However, there is a method to pin point what is causing it.
First you need to clear your mind of what it may be and start testing. There are only three things that can make an engine quit. Compression, Fire or fuel so you need to get the problem down to which of the three sections it is in.
You can forget compression for now because if you loose compression it will not return.
So now it is in Fire (ignition) or fuel. You said it "Stalls" when you come to a stop. So it does not quit while running down the road but only when you stop?
Now you need a couple of tools that are not expensive. A timing light and a vacuum gauge that has a fuel pressure section. You will also need a "T" fitting and some fuel hose and some clamps. Be sure to put clamps at every joint!!!!
Connect the timing light to the coil wire not a spark plug wire. Then tape or rubber band the trigger down so the light flashes all the time. Run the wires out form under the hood (being careful not to let the hood cut the wires) and place the timing light under a wiper arm so you can see the flash of the light while driving. Now remove the fuel hose from the carburetor and install the "T" in the line and attach a hose to the "T" and run it out from under the hood again protecting the hose so it does not get cut by the hood and place the vacuum gauge that has a section for fuel pressure on it, under the other wiper arm so you can watch fuel pressure while you drive. You should see from 1.5 PSI to 3 PSI at all times. And you should see a very fast light flash all the time that the engine is turning.
You need to watch the fuel pressure at the time of a stall. If the fuel pressure is above 1.5 just as it stalls then you know it is not the fuel pump, lines or tank. This does not eliminate the carburetor as a cause but will eliminate the fuel supply.
The timing light is harder to spot because you need to spot if the light goes out first or the engine stops rotating first. (It is less likely to be ignition because the ignition tends to fail more often under load (acceleration and speed then at idle)
If the fuel pressure was ok at a stall then you need to look at the carburetor as a cause and since it is a Stromberg you will have to remove it to take the float chamber off and check the float needle and seat and the float level. And look for trash or water in the float chamber. You also need to remove the top pot and examine the diaphragm for any holes.
Let me know.
Howard
