Cold starts

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Scott72scout

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Just bought a 72 Scout decided to swap out my six cylinder for a 345 now it will not start. Truck will run if I roll it off but will not start with starter. The 345 is out of 78 Scout has a prestolite dist.

Thanks scott
 
Scoutboy74
thanks for replying I have traced my wiring down and have not found a problem. Everthing seems to be correct when I check for spark at my spark plug it will jump over 1/4" but it's a red spark not blue. Appears to be a weak spark I installed a jumper from + on battery to + on coil engine still not starting.
Thanks scott
 
Scott, your initial description May have confused me. Is the starter capable of cranking the engine over? From what I gathered, you can only get the engine started by compression (rolling it in gear), so I assumed that the starter motor isn't functioning. Please clarify exactly what is and what isn't happening when you turn the key.
 
The starter is working and cranking over the engine. Have installed new plugs,wires and correct cap and rotary button for prestolite dist. Truck will run when rolled off but it is not running smooth it idles fine. Did get it to crank one time when it was hot.
 
Okay, thanks for the clarification. What's the history on this engine? Was it starting and running well in the donor vehicle recently? Is the coil an oem or aftermarket model?

I know you bypassed your ignition wiring with a jumper from the battery with the same bad result, which would seem to rule out low voltage through your run circuit to the coil as the problem. Just so we can assign some tangible numbers, can you measure the surface charge of your battery making sure it is fully charged? The reading should be between 12 and 13 volts. Then do the same at your coil + with the key switched on just long enough to get the reading. Have someone help you take the same reading at the coil + during starter crank. In both cases, voltage should be nearly identical to battery reading.
 
The surface charge of the battery is 13.20. The voltage reading at coil with key switch on reads 12.9. Voltage during cranking at battery is 10.5 and at the coil is 6.6
 
Battery surface charge looks good, as does coil + with key on. Not sure about your battery reading during starter crank. The starter motor does draw a fair amount of current, so some drop in voltage is to be expected, but more than two volts? I dunno about that. The reading that most concerns me is at the coil + during starter crank. That's exactly half of your battery surface charge, which is a huge voltage drop. That doesn't seem right.
 
The 6.6v while cranking is the problem. You have a ballast resistor or resistance wire that is not being bypassed under cranking conditions. Please review schematic for your IH in our electrical form.

While cranking you should see full available battery voltage.

Look at the starter solenoid. The two small ones are the focus here. One has the switched power fed from the start contacts in the ignition switch identified by an "s" in the solenoid. The other is supposed to supply battery voltage to the + side of the coil while under start conditions identified by an "r" on the solenoid.
Verify the "r". Connections. For a test run a fresh wire from the r terminal to the + coil stud and attempt a restart.
 
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Hey Robert, if he had some type of resistance in the coil feed circuit, wouldn't that be indicated in his measurement taken at the coil with the key on? His reading of 12.9 indicates full voltage in the run circuit. How can he have full voltage in run and be severely reduced in start?
 
scoutboy74 said:
hey Robert, if he had some type of resistance in the coil feed circuit, wouldn't that be indicated in his measurement taken at the coil with the key on? His reading of 12.9 indicates full voltage in the run circuit. How can he have full voltage in run and be severely reduced in start?
Click to expand...

Ko and points open there will be no current through the resistor thus no voltage drop. While cranking and the points making contact (intermittently) the resistor will drop the 4v. Making the coil voltage 6.6.
 
Just call us hi-fidelity and quadrophonic:ciappa:
well here's what I'm gunna ask for next...an under hood pic or two from the passenger side of the bay that clearly shows the circuitry connected to the coil. That will likely put this story to bed once and for good. Know what I mean, vern?
 
Oh, one more thing rk. Sailor jerry and I have ass-oomed that since the distributor is a prestolite, that there aren't any breaker points in play here. '78 Scout with presto...I guess it could be the points variety, but I'd be stooperfied if'n it was. Guess we better get clarreefyd up on that too.
 
That won't matter. The electronic dealio's will or should encounter the same voltage drops across the ballast/resistance wire while generating spark.
 
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Back the the problem at hand.

You have combined two different vintages of Scout II's that have created a voltage issue.

One it the host sii which is a 72 258 points type ignition system. It feeds the coil + terminal through a resistance wire designed to give the coil only 2/3 of the available battery voltage when driving and running. This is not the case in start when the resistance wire id bypassed by a wire from the r starter solenoid as I stated earlier.

Two is the transplanted engine, a 78' 345 which we believe came with the prestolite ignition. These from memory like the Holley gold box equipped IH's did not have the resistance wire and r terminal starter solenoid bypass wire.

Please follow the bypass wire test below.
I recommend connecting a temporary wire from the + battery terminal directly to the + coil terminal and trying to start. It is safe for the test but disconnect the wire after shutdown.
 
He already tried the jumper method and still failed to start. With the cross-mojination involved, we really need to see some good pics of his ignition setup.
 
We have to start fixing the issues as we find them. The starting ignition voltage is the first verified defect. Fix it and then we can move on.
 
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