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Triumph Repair/1956 Triumph TR3 will not run


Car was running great three weeks ago.  Two weeks ago started to feel a
miss when driving. One week ago when driving started to all of a sudden
stop and start while under power. Questioned if I would make it home.
Then this weekend could hardly drive it around the block. Same problem but getting worst.

We checked the spark plugs.  They were a little dark but all 4 were firing. Checked the dwell and it was ok.  When we had it running a lot of black smoke coming out of the tail pipe.

Hi Mike,

I worked in the dealerships for several years and we worked out a diagnosis procedure because we needed a 100% fix rate as we worked on commission only.

Symptoms can sometimes lead you to a fix but for the most part they are useless other then tell you you need to test the car.

There are only three systems that make all gasoline engines run and you MUST find the system that failed first. The systems are Compression, Fire and Fuel and they MUST be tested in that order. You do need a few tools but none are expensive.

First is compression. Remove all 4 plugs and remove the wires off of the negative side of the coil. Be sure to hold the throttle open when doing the compression test. You need to see 125 PSI to 170 PSI on all four cylinders with little difference between cylinders. If you don't have that it is no use proceeding.

If you do and only if you do, you can then check "Fire" (ignition). You don't need expensive equipment to test ignition. You already have the plugs out so plug each plug on to it's wire and lay each plug on a metal part of the engine and reconnect the negative wire on the coil. Now turn the key to IGN (not Start) and use the remote starter button on the starter solenoid to spin the engine over and watch all the plugs spark. (not in bright sun light) You should see a blue spark and it must be thick as a pensil lead on each of the four plugs. At this time you should look closely at the inside of the distributor cap for any signs of carbon tracking. Also look at the rotor too. Now remove the coil wire from the cap and hold it about 1/8 inch from the center of the rotor to see if you can jump a spark to the center of the rotor. If you can it is bad and that most likely is the problem. You should file the points and chack the gap (.012" to .015").

If the spark at the plugs is thin as a hair and colored Yellow or orange, then it is a weak spark and will not fire at all under the pressure of compression. If you have that put your thumb over #1 plug hole and run the starter again while watching #1 plug fire. The compression will blow your thumb off of the plug hole with a "Pop" sound. At the same time the #1 plug will spark with a "Click". It should seem as though the "Pop" caused the "Click". If it seemes as though it is a "Pop-click" or a "Click-Pop" then the timing is probably off far enough that it will not start. If you have that you can put the plugs back in and turn off the key. And proceed to "Fuel"

To test fuel you can spray a little "Starting Fluid" into both carbureotrs and try to start the engine. If it starts but will not keep running unles you keep spraying then it is for sure a Fuel problem and the first test is to test the fuel pump by removing the line form the carburetor and place it into a can or jar and spin the engine to see the volume of fuel. It should pump fuel in strong spurts. If you have a fuel pressure gauge you can put it on the line and test the fuel pressure. It needs to be from 1.5 PSI to 3 PSI.
If fuel supply is ok you need to connect the fuel line back up to the carbureotrs and remove the tops of both float chambers to see if they are about one third to a half full. This tells you the foalt needles are allowing the fuel into the float chambers. At this time you should take a shop rag and soak the fuel out of the float chamber or use a suction bulb if you have one. You are looking to see that there is no water in the botom of the float chambers. If all this it correct so far remove the air filters and replace the tops of the float chambers and reach in the throught of each carburetor and lift the piston to the top and let it drop and it should hit bottom with a "Clunk". If all of this so far is correct then have someone spin the engine over while you place your hand over the open throught of each carburetor to feel the vacuum on your hand. If you don't feel the vacuum then you need to look at the ends of the intake manifold to see if the freeze plugs are still in place.

Let me know,


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Howard M. Fitzcharles III


Triumph TR-4 up & Spitfire, and Engine theory


Dealership line mechanic on MG, Triumph, Jaguar for 15 years, Instructor in commercial mechanics school 2 yr. Product information manager for piston and valve manufacture, Instructor & hotline answer man for import car parts importer 15 yrs.

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