truck running lean
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Cross-Country
Joined: May 2021
Posts: 54
Likes: 1
From: northern Michigan
truck running lean
I pulled my truck out of a field months ago and got it running. While working on getting it running I adjusted the timing, by ear and adjusted the carter yf carb. The timing was pretty retarded so I advanced it a fair bit. The motor is a 240. I just looked at my spark plugs and they look like the truck is running a little lean. Do I back the timing off or adjust the carb? I have forgot the available adjustments on the carb so if someone has a tip please share.
Tuned
Joined: May 2009
Posts: 301
Likes: 40
From: East Tennessee
Automatic or manual choke? If automatic may want to just verify your choke is opening at it should. The old heat riser tube might be clogged. I've had trouble with mine on my 70's 240/yfa. Haven't really fixed it yet, just loosened the adjustment for the choke and it helped.
Mountain Pass
Joined: Aug 2014
Posts: 181
Likes: 58
You may wish to consider any gasket issues also... since you "pulled it out of a field" it may be in need of new intake manifold gaskets and carb gaskets. A vacuum leak will cause a lean condition that no amount of carb adjusting will fix, whether through a bad gasket or cracked vacuum hose. Air pulled into the mixture after the carb will lean an engine out easily. These can be tricky to diagnose as they can be small, a smoke pot can held locate them easily. I just went through the intake system on my '68 and found several issues.
Hotshot
Joined: Mar 2013
Posts: 14,255
Likes: 199
From: Phoenix, Az.
I don't like fixing gremlin after gremlin after gremlin. I prefer to "mouder" 'em right at the start. As Moe Howard used to say. 
Plus then "I" have a starting point of all the below. I know how old they all are. When I buy an old vehicle like mine and ours, I always go through it completely right away. Starting with anything rubber and fluids. Belts and vacuum, fuel, and brake hoses. Even the brake booster hose if so equipped. Then a COMPLETE tune up. Points, condenser (or a pertonix unit) , cap, rotor, all filters, oil change, PCV, spark plugs, and plug wires. Set timing and dwell of the points to spec. Then drive it for a couple of tank fulls and check the plugs again. This hits the wallet rather hard, but it takes care of some current and future gremlins.
Plus then "I" have a starting point of all the below. I know how old they all are. When I buy an old vehicle like mine and ours, I always go through it completely right away. Starting with anything rubber and fluids. Belts and vacuum, fuel, and brake hoses. Even the brake booster hose if so equipped. Then a COMPLETE tune up. Points, condenser (or a pertonix unit) , cap, rotor, all filters, oil change, PCV, spark plugs, and plug wires. Set timing and dwell of the points to spec. Then drive it for a couple of tank fulls and check the plugs again. This hits the wallet rather hard, but it takes care of some current and future gremlins.
Freshman User
Joined: Sep 2021
Posts: 35
Likes: 4
I don't mean to cause controversy, but in my opinion incorrect ignition timing can under some circumstances cause a high spark plug insulator heat condition that can mimic a lean appearance to the spark plugs. Changing the timing is easy, just to be sure that this is not an issue. It might not hurt to see if the mechnical advance mechanism in the distributor is frozen in place by corrosion. I do agree completely that an old vehicle that has not run in a long time could easily have vacuum leaks. They can definitely cause a lean condition. One other thing comes to mind, if the timing is O.K. and there are no vacuum leaks; crud, condensed water, and varnish may have partially blocked the jets and/or fuel passages in the carburetor.
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Trashyvixxen
1980 - 1986 Bullnose F100, F150 & Larger F-Series Trucks
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Sep 13, 2012 11:25 PM
