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 7.4L GM backfires
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eshover
Senior Member

146 Posts

Posted - 09/18/2014 :  10:05:27 AM  Show Profile  Visit eshover's Homepage  Reply with Quote
I have a 2000 GMC bus with 7.4 propane IMPCO system in it. Lately it has been backfiring occasionally. Sometimes it may quit and others it may not. It might backfire once or it may backfire several times. No constant actions. Could it be a cam position sensor doing this?
Replaced plugs and wire in February.
Thanks,
ED

Fastback
Top Member

1500 Posts

Posted - 09/19/2014 :  04:22:27 AM  Show Profile  Reply with Quote
Is a dedicated propane conversion engine with a distributor and the only factory tune up specs being for gasoline engine? If so what are your spark plugs gapped at? We always ran our plug gaps no more than .035 on propane, seemed to help eliminate crossfire from the wires and inside the distributer cap.

Why yes, the ORIGinal CHARGER is a Fastback
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eshover
Senior Member

146 Posts

Posted - 09/19/2014 :  07:25:21 AM  Show Profile  Visit eshover's Homepage  Reply with Quote
This has individual coils on each cylinder. I put new NGK Iridium plugs in it now. Also new plug wires. Set the gap at .032. Will see what happens now. It has thrown no service lights on the dash so I don't think it's a cam sensor.
ED
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