Backfiring through the carb

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Oct 7, 2004 | 08:50 AM

51dueller

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From: Saskatoon SK Canada

Backfiring through the carb

My Motorcraft 2150 is backfiring through the carb. What can I do to stop this. I does it when I crank the engine. Any help is much appreciated.

Oct 7, 2004 | 12:21 PM

fmc400

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From: Austin, TX

Is your choke shut before you start the motor?

Oct 7, 2004 | 12:55 PM

51dueller

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From: Saskatoon SK Canada

The choke plate is shut when it starts but we had it held open to see if it was flooding and it still backfires through the carb. I hope it isn't a stuck valve.

Oct 8, 2004 | 03:00 AM

Ford_Six

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From: The Big, Oregon

Any other info, year, engine size, miles?

Oct 8, 2004 | 08:23 AM

Redbob

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From: North Texas

Quote:

Originally Posted by Ford_Six

Any other info, year, engine size, miles?

See, we're supposed to know that "51" has a, well, '51.
<grin>

Coupla things will cause backfires:
Much too rich a mixture (like from a stuck carb float) results in very slow-burning combustion that is still going on when the intake valve opens again, producing a backfire.
Or if the timing is much too much advanced, it might do it.
This can happen if the centrifugal advance mechanism gets stuck.

Regards,
- R

Oct 8, 2004 | 12:56 PM

51dueller

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From: Saskatoon SK Canada

It's an '84 Mustang 302 that original had CFI but has been converted to a Motorcraft 2150. Don't know miles since I got it from a wrecker

Oct 9, 2004 | 02:38 AM

Ford_Six

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From: The Big, Oregon

Well, since it isn't a 51, I may be able to help you out a bit.
It sounds like the timing chain jumped a tooth. Engines from this era had a plastic rim on the cam gear that wore away after about 70k, and once that happened, there was major slop in the chain. Check your timing, even if you can only do it while cranking. If it isn't right close to 5*, then the chain may have skipped. Also, if the engine sat for a long time, it may have a stuck valve, but that wouldn't be the end of the world.