Won't idle on gas after backfiring

[Doggy1964]

Hi guys.. I have a Series 1 Discovery with an after-market Impco gas system fitted, (which was installed ~10 years ago.)
A couple of days ago I was driving to work when it backfired 5-6 times over about 30 seconds but then stopped backfiring and continued to run ok. I drove along the highway for another 40 minutes before slowing to stop at a red light when it stalled. I attempted to restart it but it just cranked without firing. I checked that nothing obvious had come loose or been blown of with the backfiring but it all appeared ok, (visually.)
I pressed the primer on the gas converter then attempted to start it again and it fired briefly before stalling and continuing to crank. I primed it again and tried to start it again, this time jumping on the accellerator the second it fired.. It started this time but once I dropped the revs below ~1500rpm it stalled again.. I followed this procedure again this time keeping the revs over 2000rpm, waited for the lights to change then slammed it into drive and managed to make it work, (briefly knocking it into neutral any time I was approaching a red light and keeping the revs up then putting it back into drive as the lights changed.)
I'm assuming the backfiring has done some damage, possibly to the diaphragm? I haven't pulled it apart to have a look yet but was checking to see if anyone else had any advice or things to look for?

Cheers!
Doggy

[Keithy P38]

I'm no gas expert, especially the older systems! Have you checked that it hasn't blown a vacuum line from the intake system somewhere (brake booster, distributor advance, etc)?

Sounds like low manifold vacuum to me.

Cheers
Keithy

[frantic]

I've had 3 cars on gas, hopefully it's not the diaphragm , but a high chance is a hole or loose fitting between where the gas goes into the intake and the engine. My old statesman was serviced by a mechanic who had no experience with gas and he left the air filter loose which meant it sucked air not gas, but would run ok on petrol. My playdough , a 98 v6 was serviced by a bloke who knew his gas systems and he removed a 20c sized plug from between where the gas came into the intake and the engine and fitted a flameproof expanding sock/ stocking over the hole so that if it evey did backfire it wouldn't blow things loose and not run on gas. it only backfired once forcing us onto petrol before it was fixed. It backfired a few times after but no problem as the solution worked.
The third was direct gas injection so no backfire ever.