MG Car Repair: Midget 1500 rough running & starting when cold, compression gauge, combustion chamber

Question
Howard,

I have been driving a 76 Midget 1500 with no problems.  Recently she has had trouble starting when cold, and the last couple of days I have noticed she seems to misfire at low revs but runs fine when the throttle is opened further.  No fault at all when the engine is hot.  Thought I heard a slight exhaust noise, but now can't.
Any ideas please?
Martin

Answer
Hi Martin,
Your symptoms only narrow the problem down to several hundred possible things so you must do some testing to narrow the problem to a smaller area.
Any time I received a car with those type of symptoms I had to follow a procedure of tests. Even though it may be something simple you have to follow the procedure.

First you must confirm that the combustion chamber is sound. It is a simple test, just run a compression test on each cylinder. It is easy to do and a compression gauge is not expensive. Most any auto parts store have them, even Wall Mart. Be sure to hold the throttle open during the test and first remove the wires off of the (+) side of the coil. Also, be sure to spin the engine over at least 4 or 5 revolutions on each cylinder. Write down the results and let me know.

Ignition problems can cause your symptoms except most ignition problem are most noticable under load or at high RPM. Not at idle and low RPM. There are a few things you can do here. Clean the spark plugs (or replace them) and set the timing axactly to factory specs.

It is no use doing anything with the carburetor untill the first things are completed sucessfully because the carburetor is adjusted by the responce to a carburetor test and if anything is wrong in compression or ignition timing you will get a false responce and thus make wrong adjustments.

Complete the first items and I will tell you how to proceed.
Let me know,
Howard