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So as I understand, the top center wire goes Hot when switch is in the on position and this power feed goes to the coil. Then the bottom center get's hot when in the start position to feed the coil. I did a voltage test and I'm concerned. Both the top and bottom center hot leads are both hot when the ignition switch is in the on and start position. Is this supposed to be that way or is something screwed up?

There should be 2 that are hot one for interior/fuel pump and one for the coil.

My 77 has a black wire hot in on, and a black/yellow hot in start.

when I'm in start, I only get 7.5 vdc to the coil.

If you only get 7.5V when in start your resistor bypass relay is not working. This circuit applys 12V to the coil + terminal during starting.

Rechecking!

There is a heavy black wire from the battery to the switch. At on, a black/yellow wire and a blue wire to the fuse box are hot. The black yellow continues to the resistor and the blue to the accessories. At start, only the black/white wire should be hot. At acc, only the blue wire should be hot. Sorry about the misinformation.

The black/white and black/yellow shouldn't both be hot in either position.

I have 2 blacl/yellow wires coming from the switch. should they both be hot in on and start?

My schematic shows 5 contacts with a black/yellow wire connected to #1 and #5. It also shows them spliced together away from the switch. One is hot in on, and the other in start. Since they are connected somewhere, both will be hot in both positions.

The black yellow wire that is hot when the starter is engaged goes to the resistor bypass relay and then straight to the positive side of coil with full battery voltage. On mine its a black wire with a blue stripe. The black yellow wire that is hot when the key is in the on/run position goes to the ballast resistor then to the positive side of coil with reduced voltage. The negative side of the coil has a black wire with a red stripe which goes to the distributor/points/condensor I think it should have the same voltage as the positive side of the coil when the points are closed. The purpose of the resistor bypass relay is to give the coil more base voltage to work with to make a hotter spark to start the truck when the starter is sucking the voltage down. The reason for the resistor is that full battery/system voltage burns points fast and is hard on coils.

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1980 4x4

o.k. mine is wired the same, bit I get 11.5 pre resistor when in on. then it gives 7.5 when in start. blacl w/blue wire gives 7.5 only in start. Bad relay? I don't understand if the voltage to the ballast resistor should not be present when ign. is in start, thus feeding only the 12vdc full current line.

Bypass relay is bad. If it is working you will have 11.5V on both ends of the resistor just like you have the 7.5V there now.

You should be able to push start it.

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1980 4x4

couldn't push start. been sitting now since august. I noticed the stock resistor had the same voltage before & after the resistor so I guess that the resistor is bad. I have a back up one to use. I jumped 12vdc to the (+) of the coil & still no hot enough spark. maybe I should just replace relay somehow.The relay is the 4 prong right? not the 5 prong?

5 pin is the fuel pump relay. 4 pin is the resistor bypass relay.

http://www.luvtruck.com/PDF/Series9&10.pdf

So I'm at this point. The voltage from the resistor circuit goes from 11.5 in on, to 8.5 in start. The black w/blue line gives me 8.5 in start. Seems hardly enough to start. Don't I need 12vdc? Also, I unplugged the relay and the voltage reads 8.5 from the ignition switch. It only reads 11.5 when the black/white connector that goes to the starter is unplugged. Is it normal for the starter to draw so much that the voltage drops 3-4volts? If so, then how do I obtain 12 vdc to shoot my coil when starting? The clutch switch was bypassed and get same readings. Also, anybody know what the other switch is at the clutch pedal with the 2 green wires?

Have you done a load test on your battery?

If your battery is good, then there is a poor connection somewhere between the battery and where your testing. Start at the common causes like the fuse block or the ignition switch itself and check with your meter.

The other switch with the green wires operates the coasting richer solenoid on the carburator when you are coasting in 3rd or 4th gear.

Battery @ 12.36. When cranking, it drops to 10.8 v. The black w/white wire that's on the starter circuit from ign. to the starter & coil reads 8.8 at every splice & connection. Then reads 11.5 when the starter is disconnected from the circuit. Is there a fuse line that could be faulty @ the fuse box, which is related to the switch losing voltage? SWitch get's 12.36 to it. Gives 12 to acc. then 11.5 in on(think the blower motor starts the draw) Then 11.5 to the starter wire(with clutch not pressed) & 8.8 when clutch engaged. Could the starter draw this much, or as I get it from the thread, that a possible weak fusebox connection could do it too? Box was lemon juice cleaned 2 months ago. But didn't solder the rivet joints. Still wondering where I'm able to get 12 to coil+ while in start... without getting bleed back voltage so I can fire this off. also, I find it strange that outta 3 local parts stores, they can't get me a coil wire.

Disconnect the resistor from the coil. Run a wire directly from the battery to the + terminal. It that doesn't give you a good spark, your problem is from the + terminal on.

So as trying this method before(using a temp. spark tester) I had the wire to + coil hooked up still. Got all the warning lights lit up in the dash, was told this is normal but not good to do. Will trying this with both + wires disconnected, still work? or does one of the wires stay on?when starting, my battery goes from 12.36 to 10.5v. is this normal ? Starter is pulling right? so how would I get 12 to the coil? But even at 8 votls to the coil, shouldn't I get enough spark to ignite?

ALso, so either bad metal connections in the fusebox, or bad wire connector(dirty,ect) can prevent or lower voltage?