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The GMT800 Silverado/Sierra 1500 and 2500 (non Heavy Duty) (light pickup trucks) were released in 1998 as 1999 models.

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GMC sierra 5.7 only starts when you arc # 3 plug wire

Ok never seen this before and have no idea 2000 GMC sierra 5.7 will not start. I was checking for spark on the #3 plug to see if I’m getting fire and the truck cranked and ran smooth as long as I’m jumping it to the exhaust manifold. I tried it on all other plug wires no start it only cranks when you arc the # 3 plug wire. Also hooked the wire back up while the truck was running and the truck died no start until I jump the wire???? Any ideas I need y’all’s brain power thank you

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@alcorn What happens when you replace the plug but leave your connector off? You'e tried new plugs....This is weird!!!! It somehow shortens things out. Bad Coil a possibility?

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I did try leaving the connector off it will not start unless the plug is in and a screwdriver in the wire is held at the exhaust manifold allowing it to arc the fire. It only works on the #3 all others do not have any fire unless the number 3 is arced on the manifold. Then it cranks and runs smooth as if it’s firing on all 8. To note I just did a head gasket job. I’m going to chase my grounds today and I’ll post any findings

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Vernon alcorn will be eternally grateful.
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