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GMC V6 and V12 Engines Engine repair and rebuilding

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  #1  
Old June 23rd, 2013, 08:14 AM
Snags Snags is offline
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Default Ignition help

I'm trying to get my 63 with a 305E up and running but it doesn't seem to be putting spark out of the coil. The truck has sat for about 8-10 years without running and I have put in a new battery, starter, coil, wires and plugs. The resistance wire looked a little chaffed near the coil so I cut off the last 3 or so inches and butt-connected a few inches of "regular" wire and hooked up the coil (this may have negated the actual resistance properties of the wire). The resistance wire seems to (not sure but I know it doesn't go to the starter) go from the positive side of coil to the connector on the fire wall, and this connector was a little corroded so i sprayed some electrical connector cleaner in it and blew it out with the air hose. There is also a green wire running from the positive on the coil to the R terminal on the starter solenoid. When I turn the starter over and remove the coil wire to the distributor and place it near the fire wall I don't see any spark. Any helpful suggestions?
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  #2  
Old June 23rd, 2013, 09:43 PM
raycow raycow is offline
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Default Re: Ignition help

Standard troubleshooting procedure:

Take off the distributor cap so you can see the points. Turn on the ignition switch and rotate the engine by hand until the points are open. Now use a multimeter or test lamp to check for power at both the (+) and (-) terminals of the coil. If no power on either one, you have a break somewhere between the coil and the switch. Work backward toward the switch, checking at each point where there is a terminal or connection until you find the break.

If you have power at (+) but not at (-), disconnect the lead going to the distributor. If you have power at (-) now, you have a short to ground somewhere in the distributor or the connecting wire. If you still have no power at (-) with the lead disconnected, you have an open coil primary, but this is VERY rare.

If power at both (+) and (-), turn the engine by hand until the points are closed. Now you want to see power at (+), but not at (-). If you still see power at both terminals, you have a break between the coil and the distributor, or else the points aren't making contact.

Ray
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Old June 30th, 2013, 07:56 PM
drembo drembo is offline
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Default Re: Ignition help

My truck had sat for about 10 years and I had the same problems. It turned out that a rat had eaten through the wire to the coil from the ignition switch inside the cab at the firewall. I had to remove the heater duct to find it. The color of that wire is sort of magenta color if I recall.
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Old July 7th, 2013, 05:39 AM
Snags Snags is offline
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Default Re: Ignition help

Thanks gents for all the helpful info! I replaced the points/condenser and all is well Thanks Ray for your very thorough instructions...those were great.
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  #5  
Old July 8th, 2013, 07:28 AM
raycow raycow is offline
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Default Re: Ignition help

Snags, you are very welcome. I'm glad to hear that you were able to locate and fix the problem.

Ray
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