Gents, In need of some help and guidance. Long story but here's the short version. Had Lambdas fitted to aid tuning of LPG and it was discovered that petrol running very lean. Attempted to reset petrol via AFM as per the book, but despite altering the volts up to 3.5V couldn't get much change on Lambda. Then toook RR to MOT test center and put it on CO2 analyer and despite altering Volts up and down from .9V to 3.5V couldn,t really change the CO2 reading still very lean. Swapped AFM for known good one same result. Have replaced every pipe on induction side and checked plenum chamber for leaks. Factory value is 1.5 volt but have reset to 1.8 volt just to see if when I check again at end of week it makes a difference although it shouldn't Have to say truck runs well on petrol except takes a bit of cranking to start when hot.
Anyone got any advise??

what happens when you disconnect the lambdas

The lambdas are only wired into LPG ecu and are only used fot setting the LPG fuel map. If I disconect the Lambdas ther is no change. Im obviously missing something as despite using a gas analyser and the Lambda reading via the LPG software I cannot change the air/petrol mixture which is by all accounts far too lean. Luckily I only use petrol to start but worried that having petrol mixture too lean will damage the engine.

have a read of this

Fuel injection

POAH, Thanks for the link. Cheers Nick

Setting the ecu fuel mixture would be done on a co machine and 1% at idle non cat
With lambdas the Afm should be set at 3.5 ohms on the two outer pins of the Afm disconnected and then the ecu and lambdas will adpt and control once set do not adjust.

Now if you are referring to the gas running lean then depending on the system you have it could either be the mixer not capable of delivering or you are using a mono point system

Vougese39, Thans for the info. The LPG is multipoint and is lpg fuel map has been and is spot on. I attempted to set the air/petrol on a CO macine and despite turning the hex screw on the afm right in and right out I couldn't alter the CO reading, have tried another know good afm, same result!!! At present Lambdas only wired to LPG ecu and non cat tune resister in place What am I doing wrong? Cheers Nick

you need the cat tune resister fitted so the ecu sees the cats