wont run on petrol but will on gas??

well the title says it all... have a 1993 4.2 lse that wont run on petrol but will on gas!! the injectors are not pulsing..fitted new ecu and changed main relay...still nothing! any ideas???

Is the pump running?

yes the pump's running and fuel is getting to the rail.

Does it start on petrol? If it does, once it's started, disconnect the MAF or if it starts on gas, disconnect it and then switch to petrol. Reason I say this is my 3.9 will start and run for 4 or 5 minutes and then stop and will not restart until stone cold again. If I disconnect the MAF once it's started from cold, it'll continue to run. It won't however start again with the MAF disconnected.

pkr03 said:

well the title says it all... have a 1993 4.2 lse that wont run on petrol but will on gas!! the injectors are not pulsing..fitted new ecu and changed main relay...still nothing! any ideas???

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Injectors are on a switched earth. Check, clean and re-check all earth points, especially on the injection loom. Maybe try a continuity test on the injector part of the loom.

Thre was a similar problem posted not that long ago, if I remember well that was a fault in the injector loom. Do a search for details.