Hello
 
Does anyone know where to start looking to stop pre ignition or run on problem on a standard MK2 Pinto setup.
 
Basically when the car is turned off the engine shutters and tries to keep running.  This happens about 50 percent of the time but much more once at full temp.  When cold it does not seem to do it.
 
Cheers
Andrew

Ignition timing

Could be low octane rated fuel too. You're not using ULP are you?  If you are try switching to a 98ron fuel and see if that helps.

not sure if theres an anti-dieseling solenoid on the pinto but there is one on the kent, mine was malfunctioning and opening when i was driving... i just disconnected it and engaged the clutch in first to stop the engine from running on

hot spots in combustion chamber, poor state of tune( idle speed too high, poorly setup or faulty carby, timing), overheating etc etc  can cause/contribute to engine run on.
 
Cheers
 

Too little ignition timing at idle creates running on because the throttle plate is open quite a bit at idle. At switch off the engine easily siphons fuel causing the run on. To combat this anti-die selling solemoids were created. The whole concept was stupid and ford was the biggest advocate for it in the seventies.

Best way to fix it is to rework the timing so you have about 10-12 deg at idle with about 34-35 total all in by 3500rpm. Adjust the carby to suit. Make sure you don't have more than 10 deg on vac advance.

If that doesn't fix it spray a good dose of water down the carby at fast idle. That should help clean up the deposits which can cause it