Truck back fires

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Dec 18, 2007 | 05:49 AM

JimG1098

Thread Starter

Fleet Mechanic

Joined: Jan 2007

Posts: 1,847

Likes: 37

From: Eastern shore,Salisbur,MD

Truck back fires

Good moorning all and a happy holliday season. Have been thinking about my truck and what I may do. The truck backfires when you step on the gas.
Truck idles well and timing is correct at 10 BTDC. Truck starts well and points and cap are clean.

I have not physically traced the plug wires for reversals yet. VaCUME ADVANCE APPEARS TO BE WORKING. My thoughts are this. I am thinking of having the holly 2bbl rebuilt by a pro, ( if I can find one). Might there be any other things I should be looking at while I tale the carb out. ( 1954 f-750, 279 ci )

As a side topic, I now can put my the 54 in my garage with my 99 f-150 for the winter ( heated). A little tight, but I can still walk arround. On days I work on the truck, I pull out the 99 and move the 54 over. Loving this garage.

My wife has the garrage that is attatched to the house. All for herself. Keeps everything good!

Thanks for any info and enjoy the hollidays

Jim G

Last edited by JimG1098; Dec 18, 2007 at 05:51 AM.

Dec 18, 2007 | 07:03 AM

needhelp49

Elder User

Joined: Sep 2007

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From: webster wi

back fireing throw carb or exshaust a ton of things can cause it bent valve worn lobe on cam timeing

Dec 18, 2007 | 07:04 AM

needhelp49

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From: webster wi

oh and happy holidays to you to

Dec 18, 2007 | 08:34 AM

ALBUQ F-1

Fleet Owner

Joined: Jul 2004

Posts: 27,290

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From: NM

Does it backfire contiinuously and is it out the carb or out the exhaust? If it's continuously, it's almost certainly a firing order issue (if you've recently removed/replaced the wires). It could also be a bad ignition condenser, or points that have insufficient gap. Start with the basics, the carb is not likely a problem.

If it just chuffs a couple times when you step on it, check the accelerator pump.

Dec 19, 2007 | 12:28 AM

lewislynn

Senior User

Joined: Mar 2006

Posts: 167

Likes: 2

Quote:

Originally Posted by JimG1098

Do a compression test first to see if it's a valve.
Are you having carburetor problems? Your carburetor could be too lean.

Take your carburetor to a shop that builds engines, like a speed shop.
You're usually better off rebuilding what you have rather than buying rebuilt.

Dec 19, 2007 | 05:55 PM

robertr

Senior User

Joined: Oct 2001

Posts: 276

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From: Spokane USA

JimG

If you only find the backfiring under load, one other common cause is a coil going bad. If you have another coil around that you could use, a quick try of that would be an easy means to eliminate the coil as the cause. Tune up shops can easily find such a problem by running a scope check, but the cost to do that would likely be more than the price of a coil. A bad coil will show up very clearly on a scope ignition pattern. Easier and cheaper to just try another one, and see what happens.

Food for thought anyway........

Bob in Spokane

Dec 29, 2007 | 07:34 PM

JimG1098

Thread Starter

Fleet Mechanic

Joined: Jan 2007

Posts: 1,847

Likes: 37

From: Eastern shore,Salisbur,MD

Hi gang,

working on the truck backfireing. Taking all of your advise, Went to check plug wires, Can not physically trace them, they are in insulators. How can I check them, Tried to use ohm meter, cant get reading. Also tried to use trouble light, can not get it to light, I did however, get a reading on the Dist to coil secondary wire,

What is the best way to trace and check out plug wires.

Thanks,

Jim G