Misfire

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Usmc83
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Misfire

Post by Usmc83 » Thu Sep 17, 2020 3:28 pm

Decided to pressure wash engine bay today. Something told me not to , I recently did a semi tune up cleaned plugs , oil change including oil bath , Dialed in carb And Filled tank with the good stuff 92 oct . It was running tip top.
And then I pressure washed engine. No issues at first and just before I finished I hit the undercarriage concentrating mainly on the tranfercase . A little bit later it started missing . I checked plugs, wires and distributor for moisturizer . Only # 2 plug wire had moisture but nowhere else. Fired it up again and it still ran rough. Trace the issue to the # 4 wire , as when disconnected there was no change , all other wires when removed Made it run worse.
Disappointed with myself I took a break for an hour or so and began pricing wire sets. To be sure it was #4 I decided to try one more thing , I would try connecting another plug wire from my truck to Verify. Before doing so I fired her up One more time and Low and behold no more missing it sputtered a bit at first then finally leveled off I took her for a spin she ran fine no more issues.
Anyone have an idea what happened?


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W. Winget
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Re: Misfire

Post by W. Winget » Thu Sep 17, 2020 5:52 pm

You likely have a wire with cracking insulation, the water entered and shorted it out until it dried out.
You could have hit it with some spray silicone which would displace the water and temporarily seal the wire (temp being ??? how long)
When you get an opportunity, buy another wire, used or not, maybe not even from a MUTT will do as long as the length matches.
NOS is better, maybe from a genset? might be cheaper than a MUTT set.
V/R W. Winget
Looking for 1918 Standard B 'Liberty' truck parts

Usmc83
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Re: Misfire

Post by Usmc83 » Thu Sep 17, 2020 7:05 pm

Well I took it out for another spin a little further this time, it ran great when I got back home I decided to keep it running just to be sure, after a while it started sputtering slowly at first after a few minutes more frequently. Total time of drive and idle 10-15 minutes temp stayed steady at 180 ish

Rickf
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Re: Misfire

Post by Rickf » Fri Sep 18, 2020 5:01 am

Eventually the bad wire will burn through to the point that it will no longer fire the plug. As Will said, you need a new wire. I have a ton of wires I got in the pile of stuff I got with mine but they are buried deep in a storage box right now. Before selling them I need to test them.
1964 M151A1
1984 M1008
1967 M416
04/1952 M100
12/1952 M100- Departed
AN/TSQ-114A Trailblazer- Gone

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W. Winget
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Re: Misfire

Post by W. Winget » Fri Sep 18, 2020 6:00 am

Another trick you can try is start it at night, open the hood and look to see the errant sparks running around the wires, etc. (old technique reminded me from a recent post on finding a fault)
The silicone will displace the water, it cannot magically seal the gap in the insulation. understand if you were to remove the stainless wire braid it would ground out less, only way to do that would be slitting it lengthwise I think, and only in an emergency.

Wires are simple, I have seen a Model T displayed locally with barb wire for sparkplug wires.. :lol: . as long as it is not grounding anywhere other than the top of the plug and the distributor hole it will transmit electricity.

Splashing water on them will short to ground causing a misfire, the silicon will displace the water, but not as a permanent solution.
V/R W. Winget
Looking for 1918 Standard B 'Liberty' truck parts

Rickf
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Re: Misfire

Post by Rickf » Fri Sep 18, 2020 6:16 am

Problem with the "look for the spark in the dark" trick is the metal shielded military wires. The bad wire will arc to the metal shielding inside and the chances of seeing it are slim. Part of that trick was to spry water on the wires with a spritz bottle. That you could still do and if it immediately starts to misfire you have a bad wire. But probably the easiest thing to do is to swap the wire that is misfiring with one from a cylinder that is good. If the misfire follows the wire then you have your answer. If the misfire stays in the same cylinder then there are other problems but do not rule out a fouled plug from the bad wire.
1964 M151A1
1984 M1008
1967 M416
04/1952 M100
12/1952 M100- Departed
AN/TSQ-114A Trailblazer- Gone

Usmc83
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Re: Misfire

Post by Usmc83 » Fri Sep 18, 2020 9:55 am

Thanks guys. It ran a little rough at first start this morning then smoothed out after 5 minutes or so . Drove it a few blocks and it ran fine. Let it continue to run at home afterwards, total time running from first start about 40-45 minutes and it ran fine with the occasional m 151 sputter now and then but ran fine. However I’ve ordered a set of new plug wires so as not to have this problem in the future. Thank guys for all your input 👍🏽


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