Hello, My 89 XJS (Marelli ignition) is running full rich, smokes badly especially cold start, plugs turn black immediately and then start to fuel foul. Any thoughts on fuel control?

 

Ava?

 

Excessive fuel pressure.

Coolant temp sensor skewed full cold

Injector harness shorted to ground making injectors stay open

Others will add to the 'could be' list

Cheers
DD

 

TPS gone AWOL.

EFI Resistor pack multi plug needs a good clean.

Doug has spotted the rest in my head at this hour of the day, coffee 2 just started.

 

Major vacuum leak? Has the vacuum line to the ECU been damaged or come off? Vac line to the transmission modulator come off?

The XJS is a MAP (Manifold Air Pressure) management system, so it used vacuum as the load signal to the ECU. No vacuum = full throttle and maximum fuel demand.

 

On both banks? Not that you simply lack sparks on one side...

 

Hi acauto

As mentioned by Grant

Resistor Pack plug and socket needs a good clean, or it can play havoc with the Injectors



Resistor Pack Plug and Socket near front Headlight Nacelle needs to be really clean or it can cause problems with the Injectors



Resistor Pack Plug also needs to be Clean

 

Does it still run rich once the car is warm?

My 89 Marelli also runs very rich only on cold start, once warm it is ok.