if you have 20 thou side ways freeplay on the distrib shaft, your couple of days good starting may well be incidental. if the 20 thou is up and down, it is no problem.
your motor is an f227 flat head continental, I believe, the loose wires may have been related to you problem.
Do you fill your LPG tank from a bulk tank with only gravity and pressure, or do you have a pump to feed the fuel to the tank? or do you get a service to come with filled tanks? Sometimes a tank that is filled from a cold bulk tank (with no powered pump) will have some pressure problems after being brought inside and warmed up and will act as if it is empty when it feels partially full. About a 15 Celsius degree temp change is all it takes to create the problem, especially if it is slightly below freezing when you fill the tank.
tell Rob we promise to be gentle
;-)

Hi again,
Well good news, Rob did something to it (well a few things) and its been starting everytime for the last two days! It had been playing up for months so he's pretty excited about it.
NOw, what did he do I hear you ask,
(and even if you didn't I'm going to tell you anyway)
He wriggled the ignitions wires (very technical)
He tightened up the elbow thingy where the gas goes into the carburettor (it was loose apparently)
Cleaned connections and tightened wires in some little black box thingy
Cleaned the wires and solenoid with some sandpaper

Which was the magic cure???? stuffed if I know, coz he didn't test it between each thing

Thankyou to those whose replied

when you first have the issue does the lpg regulator have frost on it or is it very cold? (with the engine warm)
if so you may be low on antifreeze

make sure the contact tips arent damaged or tarnished
try cleaning them with a small file (disconnect the battery negative and short the tips with an insulated screwdriver first)

the points should be set at.020 of an inch (.508mm) use a feeler gauge

Hi prentice,
Rob says "but it always has spark, even when it won't start"
(not a very good spark though)

It is propane powered, and yep, it has points

we'll check the coil voltage tomorrow (in the daylight)

Hello Robert t, Check the simple things first.
When the unit won't start does it have battery voltage at the coil???

I think your coil might be heating up or the condenser in the distributer and breaking down
(I assume it has points for ignition)
Could be lots of fun stuff. Is the unit GAS or Propane powered?
I have seen crazy little gremlins that can cause you lots of trouble.
One step at a time, let us know