Backfiring through carb..only sometimes
Thread Starter
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Tuned
Joined: Oct 2001
Posts: 328
Likes: 4
Backfiring through carb..only sometimes
Hi all.
My F150 4x4 with 360 motor is having some serious isses.
The problem is that (only sometimes) it begins backfiring up through
the carb when I try to accelerate. I didn't have this problem until
I replaced the carb (twice) due to the other one failing.
Again, this is rather intermitent, but when it does happen, I can barely get the truck to move. I've verified the timing with a timing light both at idle and under load. The distributor seems to advance fine when the engine is reved.
I'm running out of hair to pull and could really use some advice.
Thanks!
My F150 4x4 with 360 motor is having some serious isses.
The problem is that (only sometimes) it begins backfiring up through
the carb when I try to accelerate. I didn't have this problem until
I replaced the carb (twice) due to the other one failing.
Again, this is rather intermitent, but when it does happen, I can barely get the truck to move. I've verified the timing with a timing light both at idle and under load. The distributor seems to advance fine when the engine is reved.
I'm running out of hair to pull and could really use some advice.
Thanks!
Senior User
Joined: Dec 2000
Posts: 435
Likes: 0
From: Nebraska Farm
Backfiring through carb..only sometimes
I chased the same problem last year and discovered it was because of a spark plug wire was burned off inside the dist. cap. It apparently was fine under normal conditions, but when it needed more juice for a load, it would fire late or not at all. It could have been a weak spark and was leaving fuel in the cylinder, until the vacuum advance sparked it early and would ignite the whole thing at the wrong time. ANYway, it might be worth checking.
Senior User
Joined: May 2001
Posts: 133
Likes: 0
Backfiring through carb..only sometimes
You said you verified the distributor was advancing (mechanically) when the engine was reved; try putting a light on the timing when the vacuum advance in connected while reving and see what the timing is. You could have faulty or out of adjustment vacuum advance that is retarding the motor too much under load causing a backfire.
Thread Starter
|
Tuned
Joined: Oct 2001
Posts: 328
Likes: 4
Backfiring through carb..only sometimes
Opened up the Distributor cap and found quite a bit of metal
shavings. excessive play was evident. Replaced the complete assembly
and now it's running like new.
Thanks for everyone's input.
shavings. excessive play was evident. Replaced the complete assembly
and now it's running like new.
Thanks for everyone's input.
Posting Guru
Joined: Oct 2001
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From: Culpeper, Virginia
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Senior User
Joined: Dec 2000
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From: Nebraska Farm
Backfiring through carb..only sometimes
Glad to hear we helped. Its good to know we're good for something.
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New User
Joined: Nov 2001
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From: Houston USA
Backfiring through carb..only sometimes
I too am havin problems with a carb backfire on acceleration. I recently installed a new holley to replace a really crapped out auto lite. Chenged the fuel filter. (I think it could just be contaminants)but then again it might be something else. Vacuum is good, runnin about 6 deg. btc on normal idle and 36 at high. I've got a 71 ford F-100 with a 302 and 351 cleveland heads.