Question about 1978 Chevrolet C1500
My 1978 Chevy truck is acting up. Sometimes when I drive 15-20 miles it wants to choke down and sometimes die. Other times it runs perfectly like it came off the show room floor. The only thing that is not stock on it is the Holley 4-barrel carburator that I have had for 4 years. If anyone has any ideas I would greatly appreaciate them. By the way it has a 350 engine.
Not sure what "choke down" means. If you mean run really rich and smoke black, like the choke is stuck, look at the choke linkage. If you mean lay down and give no power, but not smoke black and not sound farty and blubbery, that is likely not a choke problem.
Look at the fuel filter. They can be mostly clogged but pass enough fuel to get by under most situations; also their internal gunk load can shift, causing a filter that was serving okay to be clogged at a moment's notice.
Check the gas cap and the tank vent / evaporative emissions system - if air can't get in to replace the fuel you removed from the tank, pretty soon your fuel pump is trying to **** fuel out of a tank that is already under a vacuum.
If those two are OK, throw an ignition coil in it. They are cheap and easy enough, and a failing one will intermittently lay down and give weak sparks. If you can catch the truck in its failure mode, try loosening one of the plug wires (either end) and holding it a half inch away from its previous mount. You should get fat bright blue sparks jumping the gap, snapping as they fly; if they won't jump that far, or sound or look wimpy, your coil is suspect.
If you change your coil and the problem goes away, give the truck a tune-up - cap, rotor, plugs, and wires, and also change the ignition module (an extra $20 for a cheapie.) Coils don't die of old age; they die of overwork, like trying to push very high voltage through high-resistance spark plug wires and across worn-out plugs. The ignition module has to handle all of the power that goes through the coil, and if the coil is stressed, so is the module. They can fail without warning, stranding you until the module cools down enough (30 minutes to six hours) that it will run again.
Posted on Nov 16, 2009
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Posted on Jan 02, 2017
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