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He has a point, Roger - but an uncertain one…
Basically, the diode pack is an interconnection to trigger the fuel relay while the engine is running. If one diode fails to block; power is applied to the starting circuit by the closed reed switch on the AFM. When the key is returned from ‘crank’ to ‘run’ power is still applied to the starting circuit - and the ECU will stay in ‘cranking’ fuelling mode…
However, this will not impede starting…
However, if the read switch fails to close with the flap open the fuel relay will disengage the key is released to ‘run’. Again, this will not interfere with starting - the fuel relay being engaged by the cranking circuit.
When the AFM is disconnected, the ECU only loses air flow data, and will drop to ‘minimum’ fuelling - either due to a built-in default, or an unintended fluke of its construction.
Disconnecting the AFM will not interfere with any other engine management functions, or the engine itself. But the mere fact that the engine runs with this disconnection also means that these functions should also work properly when AFM is connected - weird…
One possibility is that the ECU persistently overfuel due to signals transferred through, but not ‘manipulated’ by, the AFM. Though the xk can stand a lot of fuel, there is a limit - a look at the plugs for sign of ‘wet’ overfuelling may be tried…
Or there may be more than one fault interacting - which certainly complicates matters…
I dearly like to know the solution to this - so keep us informed? When solved we will slap our collective brows and say, as usual; “Of course, why didn’t we think of that”…
Frank
xj6 85 Sov Europe (UK/NZ)
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