Dual Fuel 1.9 DG runs great on LPG but not petrol

[stephenwalls]

Hi,
I have a 1985 1.9DG engined WBX. When I first purchased her, she ran absolutely fine on petrol, but on more than one occasion when taking the van to get some work done, the van seems to lose all power, stalls at junctions and roundabouts, sometimes refusing to re-start. Depressing the throttle and then starting from cold seems fine and the engine starts with a high idle, but even when still on the choke, any attempt to drive the van ends up with it stalling and struggling to restart. Starting on LPG is a much better experience. The idle is super smooth and the van pulls just great. I've tried running on LPG until the engine is warm and, if I change back to petrol doing 40-50MPH, it seems to run fine until I let the revs drop and stall the engine again. On some occasions It's run just fine, but the problem that used to be intermittent, is now with me all the time.
New Fuel pump - tested and working fine
Cant find any vaccum leaks on any of the carb hoses
Carb was supposedly rebuilt by the previous owner
Runs lovely on LPG - so not a timing or ignition problem
Idle shut off valve makes a nice loud tick when energised and removing the power lead instantly kills the engine
The fuel tank, fuel lines and fuel filters are all new (problem preceded this change)

Before I pull the carb to bits can anyone offer any help on what the problem may be?

Many thanks

Steve

[maxstu]

Im clutching a straws here...but how about the fuel accelerator pump or float height?
I rarely use the petrol side of combination. Just now and then for a few miles and back on LPG. Purely to keep the carb clean
The LPG system usually has two solenoids. One for petrol and other for LPG. Perhap the switch over to petrol is not cutting out the LPG supply?
Check both solenoids are working/clicking as you move from one supply to another and back again using the buttons near steering wheel.
Whereabouts are you, still in Leicester?

[crazyhorse]

Interested in this also as my van runs well on lpg but similar symptoms on petrol