BRC Sequential System Problem

[Battler]

D2 4.6 Auto with the BRC gas system and it won't stay on gas.

Sometimes it will stay on gas for 10-20klms and other times it just switches straight back to petrol.

And it's getting worse.

On gas at idle getting multiple misfires only on left bank. Perfect on petrol.

I've tried to reprogram it with BRC software and I can get it running perfectly at 3000rpm and down to about 1500rpm but not at idle with load.

Also, it doesn't change over to gas now until the engine is at about 90c or above. It use to changeover nearly straight away.

The system is about 10 years old.

Could it be the vaporizer that's stuffed?

Thanks
Michael

[bee utey]

The vaporiser, AKA converter, normally needs an occasional tighten of the six bolts holding the assembly together. Hardly anyone does this so there's a good possibility your through bolts are loose enough for coolant to leak into their threads and jam them up. If they snap off you'll need a new converter.

The two most common faults after coolant leaks are:

1. Temperature sender dodgy. Once they get defective they go open circuit and the gas ECU suddenly sees an ice cold converter and shuts down. Wriggle the wires to the temp sensor with the engine idling on gas and see if this causes the engine to change back to petrol.

2. The pressure relief valve dies and lets a constant stream of gas into the vacuum hose and therefore the inlet manifold. Just pull the vacuum hose from the converter off with the engine idling on gas and see if LPG issues from the converter.

Parts are readily available for these converters but be aware there are various slight differences by year. The main difference I'm aware of is with the temp sensor, the earlier one is a vapour temp sensor with a cable attached and the later one is a water sensor with a direct plug on it. I repaired an early type last week, not particularly difficult.

[Battler]

Thanks Bee utey.

It's looks like it's the temperature sender. I can't get it to idle on gas now but I can get it to changeover from petrol to gas by pulling the wires. When I let go it switches back to petrol.

Also, and I should have mentioned this before, when it did run on gas it immediately went open loop and then closed loop when it switch back to petrol.

Thanks for your help.
Michael