Running poorly 6mpg
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Junior User
Joined: Dec 2010
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From: Thunder Bay
Running poorly 6mpg
My 85 f150 runs poorly, getting 6 mpg. Checked timing 10 btdc, had carb rebuilt. Was suggested to me to change timing to 12 to 14 degrees, cant get past 10 with distributor,,was suggested I just move the plug wires to get more degrees???? The truck has 1bbl with duraspark but all pollution stuff had been removed when I got truck..Could that be the problem? I also have a 79 F100 with a complete motor so I have tried using its plugs, wires, cap and rotor. Any suggestions greatly appreciated
Elder User
Joined: Apr 2010
Posts: 645
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From: Richlands, NC
Yes. that could be the problem...
Have you tried adjusting your fuel/air mixture on your carb? Maybe changing your fuel filter? What about air filter?
I know changing my air filter actually added a few MPG's to mine.
What engine does it have?
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Junior User
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From: Thunder Bay
I have changed fuel and air filters, compression test 150 per hole, fuel air mixture is fine but just not burning the fuel...Cutting out the muffler today,,it leaks and as someone suggested a plugged exhaust,,,just happen to have a good muffler in my boneyard
Post Fiend
Joined: Dec 2007
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From: Lost
Sounds like this truck has had the feedback system removed, and the duraspark ignition swap performed already. Is the vacuum advance hooked up? If either the vacuum advance or the mechanical advance in the dist are not working, that would cause a poorly running engine, and excessive fuel consumption. A carb needing rebuilt will also do the same.
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Junior User
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From: Thunder Bay
It has been suggested after all the tests including changing the fuel pump that possibly my timing chain has jumped? Too bad there was not a window to check! It's in the garage now,,,can only avoid the task for so long. Fortunately my 79 F100 is purring, however it only has 63,000 km.
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Post Fiend
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From: Lost
There is no chain in a 300, it's direct gear to gear. However, the cam gear was made out of a plastic-type material, and could be worn down.
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Post Fiend
Joined: Dec 2007
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From: Lost
Gears can be replaced. It's not the easiest job in the world, but can be done by someone with average mechanical skills, and a few special tools.
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From: Thunder Bay
Although I checked for tdc for timing the truck runs misses and stumbles and everything else is okay,,cap , rotor ,plugs and wires so this is my last option. Would this be what you would check? I do have average mechanical skills,,,just completed a frameoff on a 41 ihc.
Lead Driver
Joined: Jul 2009
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From: Sheffield, AL
jazz1,
Welcome to the forum!
You posted that the Duraspark distributor conversion has been done and that the carburetor has been rebuilt... is it the original feedback carburetor?
This engine is very sensitive to vacuum leaks. Check all vacuum lines [including brake booster and PCV]. Make sure you have the carburetor base tightened well and that no leaks can be found around the intake manifold.
Welcome to the forum!
You posted that the Duraspark distributor conversion has been done and that the carburetor has been rebuilt... is it the original feedback carburetor?
This engine is very sensitive to vacuum leaks. Check all vacuum lines [including brake booster and PCV]. Make sure you have the carburetor base tightened well and that no leaks can be found around the intake manifold.
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From: Thunder Bay
I checked the number on carb Autoline C6246 w/o ac, w/o Canada emissons)..I checked and it is for a 1982 F250 Supercab 4.9 so I guess that is not the original feedback carb. I have found there is gas flowing into carb about halfway down the carb on the passenger side when engine is idling. So its getting way too much fuel to operate properly. I sprayed ether all around the intake, engine, vacuum hoses and did not find any vacuum leaks.
pedant
Joined: Jan 2008
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From: EXTREME southwest CT
As Dave suggested in the other thread your float level may be too high.
My thought was that check ball/weight was either missing, assembled incorrectly or the transfer tube was disconnected at one end.
Did you set the float height to the specific carb that you actually have???
I know there are two styles of float and like three different float heights across the years.
My thought was that check ball/weight was either missing, assembled incorrectly or the transfer tube was disconnected at one end.
Did you set the float height to the specific carb that you actually have???
I know there are two styles of float and like three different float heights across the years.