[mickey21]

I believe I should give an update on the situation.

I have been given the price quote for an overhaul of the complete gas distributor with the stepper motor by a workshop in Netherlands owned by a former Koltec mechanic who is specialized in refurbishing their products. The offer included overhaul of the distributor and relocation of the stepper motor electronics away from the engine block which was a good idea. The offer was fair but to my surprise when I started working on the engine to take the part out I discovered that gas regulator which was repaired 2 years ago leaks gas. Taking into consideration that repairing both of these parts would cost almost what local shop would charge me for a dedicated system, I considered it unreasonable and opted for installation of: AC Stag Q max Bacic ecu for a 6 cylinder engine, new injectors and Tomasetto AT12 pressure reducer. I had a manometer installed on the reducer as well so I have a CNG led level fuel indicator in the cabin. What is also a good thing that Volvo's gas level sensor from the cylinder is connected as well, so the old fuel gauge on the instrument cluster also works.


For now, system is working great: less fuel consumption, more gas used from the cylinder before it is depleted (more range), seamless switching between petrol and gas. I do notice a slower response to the throttle when running on CNG but not a lack of power once it goes up to the revs and I have error codes for low fuel pressure and lean mixture at cylinder 1. However, the system was just installed last week and I have been told to run the car for a while until ecu maps are rebuilt and data collected so they can connect diagnostics later on and see what needs to be adjusted. Probably gas nozzles would need to be rebored a bit, that is what they told me.

So my factory CNG system gave up finally after 400000 km, hopefully this new one will serve for as long with less maintenance needed which will be more available and cheaper.

@dikidera and ele288, thank you very much for initially sending me on the right track with your suggestions and helping me resolve the problem with my car at the end.