My 1952 XK120 OTS runs fine for approximately 15-20 minutes and then sputters and stalls. After it sits for awhile I can start it up again and it runs fine for another 15-20 minutes and repeats the process. The car has 85,000 miles, rebuilt cylinder head, Pertronix electronic ignition system, a new Pertronix Flamethrower coil 40.000 volts, 3.0 ohms with Pertronix ignition wires. The car was running fine and then suddenly started the sputtering and stalling as explained above. Once it stops running the engine turns over with no attempt to start. Does anyone have any ideas. It’s very baffling.
First I would check the fuel level in your carbs when it dies and won’t start just to confirm it’s not a fuel pump issue. Then pull the coil wire fron the distributor and check for spark. The problem sounds exactly like a bad ignition coil problem I had but with a standard points ignition system. Is the coil hot to the touch when the engine won’t start? If your fuel level is fine, and have weak or no spark I would buy another ignition module and a coil and see if the problem persists. The modules burn out if allowed to sit too long with the ignition switch on but the engine not running.
Sounds like the fuel tank is full of crap. Takes 15 minutes to clog the filter, then a while to let the crap settle, repeat.
I had similar issue. Check your rotor arm, mine was shorting between the brass rivet and the metal clip that is in contact with the distributor shaft. This happens with cheap rotor arms when they get hot and expand. They then cool down , the shorting ceases and engine starts. Repeat.
Beware of “Genuine Lucas ones in a green box”. Decent ones are available from the Distributor Doctor in UK. He has had rotor arms made without this rivet
still more possibilities…heat in carbs…do the carbs have the insulation bloc tween carbs and intake? also…try some insulation wrap around the coil…see if problem persists…does seem heat related…hot fuel, or hot coil.
My first checks would be dirt in the fuel lines, as said above. It clogs and stops, then the wait allows fuel to get through the blockage, then running again uses that up and it has to wait until more has seeped through the blockage. If you are using higher ethanol fuel, the inside surface of your fuel lines may be degrading and causing the blockage. A switch to Teflon fuel lines may be needed.
I had exactly that problem on an Iso Grifo. Changed fuel filter and all was well.
Had same problem on a old Range Rover , the main lead from coil too dis was carbon , changed it too copper all was well again !
The distributor cap may have an intermittent connection to the coil lead. On some distributor caps there is a hidden screw, behind the carbon center brush, that makes electrical contact by screwing into the center lead of the coil wire. This screw and connection may not be robustly made and also may have some corrosion present if the cap is old. The warming up of the cap materials can make the electrical path fail, upon cooling back down it works fine again until heated.
There also are temperature-dependent tracking possibilities inside the distributor cap, those may be accentuated by a higher voltage coil setup.
also,…there should not be a suppressor on the coil wire at the coil…this cause hi heat build up in the coil, and by .these cars should not have modern spark plug wires…which are made with very hi resistance…for all the shielding and resistance necessary for modern super hi energy ignition systems, that have sensitive computer electronics (and radio interference). Too much resistance will cause many hard to assess issues…you will hunt all over. USE only wire that is zero or very low resistance…easily tested…put the meter attachments at each end…it should read zero resistance. Do not use modern wires from the auto parts stores.