Starting issues

[buddster33]

Hi there, had my car converted to lpg recently and everyting is fine apart from when starting the engine. I have made the following observations:

-If engine is run only on petrol engine will start fine.
-If engine is run on lpg then switched back to petrol for 1 second before switching off engine will start fine.
-If engine is run on lpg and the throttle is blipped (1500rpm) just before switching off engine will start fine.
-If engine is run on lpg and left idling on lpg when switched off it will take several cranks to start if left for between a couple of minutes or overnight.

I have took back to the installer a couple of times who plugged in a laptop but no difference.

System is a sequential AFC G3 with KME reducer and magic injectors.

A search of the forum suggests maybe a leaking injector flooding the intake manifold when switched off?

Any other theories welcomed!

[rossko]

A search of the forum suggests maybe a leaking injector flooding the intake manifold when switched off?

Unlikely with new equipment, but not impossible.

Other candidate is poor LPG setting up, leaving fuel trims a way out.

Least likely is poor injection point positioning, leaving a dollop of gas/air mix in the manifold.

[andy evans autogas]

who fitted the system and when ?. I fit the same system on a daily basis and have never had such problems with them ,the symptoms you are describe are similar to a regulator problem ie leaking gas through the vacuum when the engine is switched off , the only other thing it could be is it's the tuning is so far out and confusing the petrol trims. what car is it fitted to ?..............

[buddster33]

Car is a '04 Toyota Aristo (Lexus GS with Supra 3.0 vvti twin turbo engine). I understand what you mean about the fuel trims being out but how would blipping the throttle on gas before switching off prevent the issue?

[rossko]

A throttle blip generally resets short-term trims. Whether those would otherwise be "remembered" by the petrol ECU through a stop/start cycle I couldn't say, usually not -but all petrol ECUs behave differently.

Other possibilities were offered. Are you not taking it back to the installer?