620 IGN switch causing misfires?

[metalmonkey47]

It's a strange thing, so i'm gonna give you guys a little insight on what I'm dealing with... You'll have to read through it to really understand what i believe may be the cause...

 

 

 

 

It started a few weeks back, when I was going for a little drive to get monkeygirl. Out of nowhere, the truck develops a strange misfire. It's pretty bad. I pull over and grab my tools. I keep a timing light and a ton of tools locked in my bed box. Everything was right, no vac leaks or nothing. I drive straight to her house with nothing more then a inconsistent misfire. I pulled apart the weber expecting to see some garbage in the float bowl, which was non-existant.

 

I've literally replaced nearly every component on this truck that could be at fault. Plugs, wires, cap, rotor, points, condenser, fuel filter, etc. All have less then 2K miles on them.

 

The trucks been okay for about a month. It hesitates sometimes, but its very rare that it does it.

 

 

 

 

I got in the truck a week ago and turned the key to 'start' and nothing happened. All my lights went out until i turned the key back to "ign on," with a brand new Yellow top Optima, Cables, and starter. I reached under the dash and jiggled the wires around on the IGN switch and found the plate on the back that the contacts were mounted to was loose. The switch was replaced the day I drove the truck home.

 

I had the same odd misfire when I drove the truck the other day, but it was worse then ever. I had no power and the truck wouldn't idle. I managed the make it to work and had an idea.

 

 

 

 

Is it possible that the two problems are related to the switch? If the contact plate on the back of the IGN switch pulls away from the switch, then it IS possible for that to cause a misfire/no run situation if they have poor contact with each other?

[Z-train]

The key switch controls power to the harness & starting/ignition circuit.Highly doubtfull that the switch is causing a running issue.

[chester]

it sounds like what happened to me. My problem was a bare wire that was shorting and causing the miss. So I would look at your wiring. I am probably wrong as I have electric ignition.

[ggzilla]

If the contact plate on the back of the IGN switch pulls away from the switch, then it IS possible for that to cause a misfire/no run situation if they have poor contact with each other?

 

Yes.

 

 

Is it possible that the two problems are related to the switch?

 

1. "the truck develops a strange misfire"

Highly unlikely that the ignition switch caused that, since it happened before and after you replaced the switch.

 

2. "I had no power and the truck wouldn't idle"

The ignition switch won't cause this. The idle-cut solenoid circut can cause it, also worn ignition points can cause it.

[banzai510(hainz)]

I alwasys do a lash pad ck also if you havent done one in awhile valve could be getting tite. or if if all of a sudden runs like its on 3 cylinders ck to see if lash pad fell off.

 

if point ignition ck that also.Gap

old spark plug wire(get NGK NE64s)