3.9 on LPG inconsistent idle

[HangOver]

The LPG cuts out and usually straight back on again but ........
It does not do it ALL the time, sometimes it idles fine, (around 500-600rpm) it is very inconsistent but consistent enough to happen several times a day,maybe 5-10 times in the space of one hour of city driving.

Never while under acceleration
Never with revs over 11/1200 rpm

I can hear what I presume to be a solenoid? in or around the LPG tank clicking on/off sometimes repeatedly until I accelerate away or switch to petrol.

It sounds to me like the idle is too low but having never adjusted an LPG system I’m not sure. Its only started to do it in the past 2 weeks or so and seems to be getting worse, but maybe that’s my imagination.
What I don’t want to do is turn up the idle and mask some unrelated problem, if you know what I mean.

I have replaced the following after this issue arose and it has made no difference:
Spark plugs, (iridium, gapped -1, heat range -1)
Distributor cap & rotor arm
ignition leads
coil
condenser
vavuum advance, about 2 weeks prior to issue

[MMEJ]

Make and photos of system would help:D

[bee utey]

The safety cut-out reads an ignition pulse to determine if the gas should stay on. If the ignition pulse input is incorrect sometimes the signal loss will cause the safety cut-out to drop out. Find the wire that feeds ignition pulses to the safety cut-out, make sure it is connected to the negative side of the coil, or alternately wrapped tightly around the coil lead about 6 turns.

[HangOver]

heres some pics of the system, no idea which wire is the safety cut-out?

I was hoping it was just the idle, not sure which is screw is the idle though but didnt really wany to turn it up yet till I ruled out that it could be no other issue that a high idle would hide.

[HangOver]

im guessing the two wires in the forground are for the LPG system as they look aftermarket

[bee utey]

im guessing the two wires in the forground are for the LPG system as they look aftermarket

Guessing is a mug's game. Get your fingers dirty and trace the wire to see where they go. You may possibly have to snip a couple of cable ties to trace the wires through the maze. Really!

Check where the black wire goes. If it goes to the safety cut-out signal input and is connected wrong at the coil (ie positive instead of negative) that's your problem. The safety cut-out is a "black box" connected to 3 or 4 wires, input from the gas switch, input from the negative side of the coil, output to all the gas valves, and earth. Trace the wires back from the coil and gas valves to a common point, and that will be the safety cut-out.

If that is a GT40 coil then your ignition may be failing to fire. I know there are many people that do this but it is still wrong. You should have an electronic coil.

[HangOver]

thanks for the info so far, as soon as i get a second I will trace the wires and see where they go and check them for continuity.

I was wondering about the coil, although it was changed after the issue started. You mention an electronic coil, do you mean a coil pack?

[bee utey]

I was wondering about the coil, although it was changed after the issue started. You mention an electronic coil, do you mean a coil pack?

A coil pack is more than one coil. Like, I mean, qty (1) one coil recommended by electrical boffins to be used with this kind of electronic ignition, e.g. Bosch part number BIC290 is one recommendation I have read about.

https://www.aulro.com/afvb/images/imported/2011/05/95.jpg
Example of a BIC290 "electronic" coil