1986F150Six Posted September 20, 2021 Author Share Posted September 20, 2021 That is probably the W/BK wire and goes from the "S" terminal on the alternator to the choke cap. It provides the 7.5V to heat or assist in heating the choke. It may have originally been sheathed and in some clips on the valve cover bolts to keep it off the exhaust manifold. While you are doing a "wiggle test" grab the top portion of the carburetor and see if it is loose on the throttle body as this is a common problem on the carbureted 4.9L engines. The wire in question does indeed have a black stripe; I just didn't see it at first. The jiggle test must have been a fluke as when repeated this morning, wiggling that wire as well as other parts of the wiring harness did not change the running of the engine. I removed the air cleaner housing and started the engine. It ran poorly. That is the intermittent part as sometimes it starts and runs well, but at other times, it starts poorly and runs poorly, missing badly. It was very humid this morning, so I wonder if moisture plays a part? The upper half of the carburetor is not loose. I have just returned from placing an order for ignition wires, distributor cap and rotor. All will be here by Wednesday AM. I will check the vacuum and if necessary, purchase a cigar [for those of you who have been around the forum for awhile! Link to comment Share on other sites More sharing options...
Gary Lewis Posted September 20, 2021 Share Posted September 20, 2021 The wire in question does indeed have a black stripe; I just didn't see it at first. The jiggle test must have been a fluke as when repeated this morning, wiggling that wire as well as other parts of the wiring harness did not change the running of the engine. I removed the air cleaner housing and started the engine. It ran poorly. That is the intermittent part as sometimes it starts and runs well, but at other times, it starts poorly and runs poorly, missing badly. It was very humid this morning, so I wonder if moisture plays a part? The upper half of the carburetor is not loose. I have just returned from placing an order for ignition wires, distributor cap and rotor. All will be here by Wednesday AM. I will check the vacuum and if necessary, purchase a cigar [for those of you who have been around the forum for awhile! I’ve been around this forum probably as long as anyone () and I think it time for a cigar! I’m guessing when you moved the wires you moved some hoses as well. Link to comment Share on other sites More sharing options...
1986F150Six Posted September 20, 2021 Author Share Posted September 20, 2021 I’ve been around this forum probably as long as anyone () and I think it time for a cigar! I’m guessing when you moved the wires you moved some hoses as well. I did move hoses, but nothing changed this time. This truck is so very original that all of the colored plastic vacuum lines are still in place. Link to comment Share on other sites More sharing options...
1986F150Six Posted September 22, 2021 Author Share Posted September 22, 2021 I did move hoses, but nothing changed this time. This truck is so very original that all of the colored plastic vacuum lines are still in place. I just replaced the ignition wires, distributor cap and rotor. Near the ignition coil and distributor, I found several non-ignition wires with cracked insulation. Apparently, 37 years is taking a toll on under hood wiring. The old distributor cap had minimal corrosion on the terminals. There was moderate corrosion on the coil post. I cleaned it with steel wool and applied dielectric grease. All connections were treated to dielectric grease. The engine fired to life and seems to run very much better. There was no missing or shuddering. I will reserve judgement until driving it a few more times under different weather conditions. Next on the list is to check the carburetor and timing as the idle is a little high, possibly due to a vacuum leak. Oh yes, Gary, I will purchase another one of these: imageService.imageservice Link to comment Share on other sites More sharing options...
Gary Lewis Posted September 22, 2021 Share Posted September 22, 2021 I just replaced the ignition wires, distributor cap and rotor. Near the ignition coil and distributor, I found several non-ignition wires with cracked insulation. Apparently, 37 years is taking a toll on under hood wiring. The old distributor cap had minimal corrosion on the terminals. There was moderate corrosion on the coil post. I cleaned it with steel wool and applied dielectric grease. All connections were treated to dielectric grease. The engine fired to life and seems to run very much better. There was no missing or shuddering. I will reserve judgement until driving it a few more times under different weather conditions. Next on the list is to check the carburetor and timing as the idle is a little high, possibly due to a vacuum leak. Oh yes, Gary, I will purchase another one of these: Sweet!!!! Link to comment Share on other sites More sharing options...
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