Triumph Repair: Car Running Rough: Advice, head gasket problem, triumph stag

Question
Dear Howard;

Thanks for your responses to my previous questions (TR7 related).  I have a question for you in regard to a 1973 Triumph Stag.  I know this is not a model you specialize in, however I believe the question is fairly general.

The car I am referring to belongs to a colleague and has sat for 3 years.  Recently, I offered to help this colleague get it started and running.  I had to replace the battery (would not hold a charge) and I got it running.

The car runs but not that well.  It has a rough idle.  When it comes off choke it wants to stop running, even at normal operating temperature.  I believe the fuel in the car is at least 3 years old.

I would like to get your advice on what checks (and in what order they need to be done) need to be accomplished in order to properly diagnose and correct this problem.  At this point I have not done any diagnosis at all.  All I've done is to get the car started up.

Thanks for all your help,
Matt

Answer
Hi Matt,

In the dealerships I worked in we often received cars that had been stored for different lengths of time and we had a needed procedure to follow.

Drain the fuel and blow out the fuel lines and put fresh gas in and in the case of SU carburetors we would clean them out too and confirm the free movement of the piston and put oil in the top pots. And then test fuel pressure (1.5 to 3 PSI on carburetor cars)

Then we run a compression test (throttles open) 125 PSI to 170 PSI. If any cylinder fell below that we would run a "WET" compression test. (about 4 or 5 squirts of engine oil in the plug hole and throttles open) the "Wet" test will be higher then a normal test but it must not be more than 10% to 15% higher. If it is, there is a ring failure. If it don't bring it up at all there is a valve problem. Sometimes two cylinders are low and next to each other and that can possibly be a head gasket problem. Compressed air into a cylinder test is then required.

We would do a rough preliminary test of the ignition by removing a spark plug (does not matter which one) and place it on it's wire and lay it on a metal part of the engine so we can see the spark. Then put your thumb over the plug hole and have someone spin the engine with the starter. The compression will make a "Pop" sound as it pushes your thumb off of the plug hole and you will see the spark that makes a "Click" sound. If the "Pop" seems to have caused the "Click" the ignition timing is close enough to start. (It does not mean it is exactly correct just close enough to start) The spark should be thick as a pencil lead and blue in color (not in bright sun light). If you get a "Pop - Click" or a "Click - Pop" the timing may be so far off that it will not start.

If it had been stored a long time (a year +) we would change oil and filter but other wise just check the level and color. If any sign of brown or tan It must be changed and the system pressurized to test for head gasket leakage. Brown or tan oil is a sign of coolant in the oil.

Change the coolant and check for external leakage.

Then we would charge the battery or replace it and start the engine and tune the carburetors and test the charging system and road test the car after checking brake and clutch fluids etc.

Many customers wanted us to shortcut that procedure but we learned the hard way to tell them to take it to someone else then.

Howard