Thread: Won't run on petrol!

1996 4.6 V8, dual fuel.
Runs fine on gas, so assuming no problems with ignition.

Wont run on petrol. When you change over from gas it will JUST run on petrol but can not be reved or driven.

35psi fuel pressure at fuel rail, error codes say open circuit on injectors, brand new fuel filter.

My assumptions so far are, fuel pump and fuel pressor regulator are OK (35psi at rail), ignition is OK (runs fine on gas), crank position sensor OK (or wouldn't have ignition for running on gas).

The problem must have something to do with the electrical interface between gas and petrol.

The gas system is a vapour style only 18mths old.

Any comments or suggestions.

Originally Posted by ytt105

Thanks Bee Utey

I just went out to try and find the earth wires for the injectors, could n't figure out their location from RAVE.
I was going to check them and then work on the relays as you advised. However, the car now runs fine on petrol and lpg. The only thing I've done is turn off the fridge.

The fridge has been in the car for the last few days as the car was used for a wedding car on the weekend and had some drinks in it. The battery that the fridge runs off is a very old (65a/h) one that is well past its time. It will only keep the fridge going for a day, not much longer.

The other problem I know off is the alternator is only giving off 13.9 volts, so my assumption is: not enough volts to run the fuel injection and the fridge at the same time?

Good to hear its going again!

You won't find "earth wires for the injectors" as there aren't any. The injectors have 1 feed wire (brown/orange stripe) that powers then from 12 volts. All the negative wires from the injectors go straight to the ECU. The LPG fitter will have cut the 12 volt supply somewhere, you need to look at the harness and see where it has been taped up. Its only a precaution to check everything someone else has done, but its good to know where the injector-cut relay/s live.

As far as the alternator voltage is concerned, the regulator on most alternators varies with temperature. What counts is the battery voltage while you are driving with all accessories on, under bonnet temp is up. Anything over 12.7 volts at the battery indicates its not being discharged at that moment. Try going for a longer drive, pull over, leave the engine running, hop out, test the battery voltage with at least 1500 rpm. 13.9 would be just fine in that condition. Best is fit a remote battery gauge.