'71 C10 250 rough idle
July 20th, 2019, 2:45 PM
#1
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'71 C10 250 rough idle
Done about everything I can think of with this engine. Idles rough enough to die until it is completely warm, but still makes you think it will die when stopped at a stop sign. Give it the smallest throttle and it runs like a new truck. Up the idle enough to prevent stalling and it will diesel on shut down from throttle opening being too wide. I've done everything possible, complete new ignition components, new carburetor (not rebuilt), new fuel pump and filter, eliminated all vacuum lines, checked compression ok, adjusted valves, sprayed everywhere possible with WD 40 to locate possible vacuum leaks, used laser temp gauge to locate possible cylinder laying out, timing is by the book, dwell is by the book. I am at a loss as I love this old farm truck, but it's driveability sucks. Anyone have any idea what I missed. Another note had this issue before the new carb, new carb runs just the same as the replaced carb.
July 20th, 2019, 5:22 PM
#2
CF Monarch
Remove the gas tank, and replace fuel lines. You could have a hole worn into the fuel line. Since this is a mechanical fuel pump, it is pulling from the tank, thus if you have a pinhole in the fuel line, you are drawing air. Regardless, IMO it is fuel system.
July 20th, 2019, 7:49 PM
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Thanks for your input, but pretty sure it is not a fuel delivery issue. I have had the sending unit out a couple of times. Tank is squeaky clean and surprisingly even still shiny inside. I inspected the fuel line carefully more than once looking for wet spots that would be leaks. I also pressure tested the fuel line a couple of times to confirm that it didn't have a pinhole in it. I was also checking the screen on the fuel pickup in the tank. Those screens will intermittently clog if there is water in the tank since they are fine enough to prevent water passage. Like I said above the tank is squeaky clean. It doesn't act like fuel delivery just very rough idle. Any throttle above idle it runs like a champ with good power and no hesitation under acceleration.