GQ TB42e - mystery"check engine" prob - Not at my wits end - yet.

[Luddite]

By process of elimination and getting a fresh set of eyes on things, it looks like the fuel pressure regulator has crapped itself and the injector "baskets" were clagged with E10 petrol "varnish". The regulator was changed 3 years ago before a trip into the desert "just to be sure" and now appears to be letting neat petrol straight into the inlet manifold. I have dug out the old one and will switch that back in to see how we get on. Three Dogs was on the money with the "dual fuelling" guess - all the black sooty crap was to do with petrol AND gas getting into the manifold at the same time, and not getting properly burned up. The clue was the motor ran fine on gas with no petrol supplied to the injector rail. Once petrol was put back to the rail, the crappy running happened again. Initially, blocked injectors leaking down was suspected. I learned that the injectors on dual fuel TB42e motor are "switched off" when on gas but this doesn't stop the fuel pump running, pushing fuel to the fuel pressure regulator and the fuel rail. When on petrol, the injectors "flutter" making the petrol mist in the inlet manifold. A pressure check of the injectors showed they were clagged up - but not leaking. The internal filter baskets were coated with "varnish" from ethanol mixed petrol preventing them from working properly anyway. It seems that E10 fuel is bad news for dual fuel EFI motors that only use petrol now and again, as the ethanol part sticks to the inside of the injectors and stops them working properly. They have been cleaned professionally now. It's fingers crossed that the regulator switch over will fix this issue.