Triumph Repair: Cut out at 3000 rpm under load, fuel pressure gauge, triumph spitfire

Question
Howard

I have a 1979 triumph spitfire and been having a few problems. The car runs and starts fine, it will run all day just sitting there but when i put it under a load and usually around 3000rpm 2nd 3rd and 4th gear it will cut out,chug sometime even die, this usually happens when the car is warmed up. I have replaced the fuel filters,fuel pump,cap,rotor,spark plugs,plugs,coil and the manifold was changed with a header and it is still doing the same problem. if you could help me out that would great.
thanks Adam

Answer
Hi Adam,
It is no use replacing parts until you know what is wrong. The ONLY way you will know what is wrong is testing.

All engines only require 3 items to run, compression, fire and fuel with conditions on each.
If your symptom is that if you accelerate slowly up to 3000 RPM on the road and the engine just seems to level off and not go any faster and if you back off a little it seems to run at a lower throttle setting then you should first check exhaust back pressure. If it has a bolt in CAT just loosen the joint at the front of the CAT so that you have about at least a half inch gap. this is a loud exhaust noise but you only need to make one quick run to see if it is the problem.
If it is not then you need to test ignition and fuel supply and that is easy to do. connect a timing light to the coil wire (not a plug wire) and run the light out form under the hood and place the light under a wiper arm so you can see the flash of the light when driving. Tape the trigger down of the light so it flashes all the time and if it is a bright sunny day you may have to tape a piece of cardboard over the light on the windshield so you can see the flash.
This will monitor the primary ignition when the engine quits.
Also, Put a "T" in the fuel line just at the carburetor and run a long piece of hose out from under the hood and a fuel pressure gauge and place the gauge under the other wiper arm so you can see what the fuel pressure is at the time of failure. (be sure to put clamps on all the hose joints). Fuel pressure should be from 1.5 to 3 PSI.
These tests MUST be done at the time of failure not when the engine is running good.
Howard