Starter juice ?

[Murf]

I'm getting back under the dash after a long absence and have a ?.. Is there always hot "juice" to the starter that could rotate the motor BUT unless the ignition switch is flipped on the motor shouldn't fire because the switch controls the juice to the regulator? correct ? or not?

[Lifer]

Since the big cable goes directly to the battery and the switch is manually engaged via the foot pedal, then yes, you should be able to crank the engine over with the switch in the off position. That's how it works with the "old time" civvy cars & trucks, anyway. The wiring diagram I downloaded several years ago is too cramped (small) for my eyes to see clearly now, but I suspect that it will reveal the same setup.

[Murf]

Since the big cable goes directly to the battery and the switch is manually engaged via the foot pedal, then yes, you should be able to crank the engine over with the switch in the off position. That's how it works with the "old time" civvy cars & trucks, anyway. The wiring diagram I downloaded several years ago is too cramped (small) for my eyes to see clearly now, but I suspect that it will reveal the same setup.

That's what I thought. I think I may have a coil issue...I pulled it out and the molded side is split around it. Perhaps moisture got in there and zapped it. I did a continuity test on it and I have continuity between the pos and neg terminals , is that normal ?

[Lifer]

If the molded casing is split, you have "coil issues" for sure! It needs to be replaced, no doubt about it.

On the continuity issue, yes...there should be continuity BUT it's possible that the primary winding (that's the one you checked for continuity) could be shorted out somewhere. You would still get a continuity reading, but current may not be going all the way around the circuit.

It's possible that there are other "issues" going on inside the coil, too, but the coil is no good anyway, so there's no point in trying to figure out what they are. Just replace it and be done.

[Nickathome]

Best thing to do if you have your distributor out and apart is to replace everything at once. This way if there was a problem with one of the components, it will be eliminated, and any future problems won't surface. That's what I did. I replaced the coil, points, condensor cap and rotor all in one fail swoop.

[Lifer]

Good advice! I always replace "hard to get at" parts whenever I have torn something down to where they're accessible. Saves time and knuckles that way. You only take it apart once.

[Murf]

Yea,,,as for the all the other components they are brand new...Since I popped the cap I went ahead and grabbed my distributor repair kit I had from one of the shows and replaced all the components. The contact on the points was slam wore out. The coil was the last item. I have a complete spare distributor I will pull the coil and try it..

[MSeriesRebuild]

I'm getting suspicious, you mentioned the coil was split. I've seen that several times, though never with a NOS or current replacement type coil. Good replacement coils will have a metal case. A few years back, some coils someone dug up from somewhere made it into so called new distributors that were marketed by S&S truck parts. Many wholesalers sold these units which promptly failed within an hour or 2. We had some of them also, customers came back on us, we stood behind the repairs necessary and quickly learned of the bad coils and after a once over discovered the shaft bushings were reamed to large also. This caused erratic performance and sticking points was also an issue in some. We pulled all our units from the shelf, installed and reamed correctly new bushings and replaced all the bad coils. No more issues after that.

The coils that were used had some type of plastic or possibly bakelite case, cracked easily and were absolutely no good at all. If this is what yours was, your experience is typical of many others.

What likely happened is this. S&S is constantly searching for military parts. They like finding large quantities of components that claim new or rebuilt status. One would think a huge outfit like them would check out surplus purchased items before they market them, evidently they don't. I'll give you an obvious example. Scott Rifken is the go to guy at S&S as far as military parts are concerned. He is in the know up to a point, but when it comes to technical do's, don'ts, why's, and wherefore's, well you know the story that is most times all to common. A few years back, I asked why they offered no new radiators for M37. Answer, they had no sample to send to the manufacturer to get duplicated. Well I fixed that by immediately shipping to him a good core sample for duplication. Sure enough in a few weeks, they were advertising new M37 radiators. I ordered up 1 unit to inspect it myself. Great looking, good quality unit. Only problem, they didn't go by the sample unit to build it. The top tank was designed so the cover plate would no longer fit over the end radius of the top tank and the bottom tank did not incorporate the up angled ends that allow the radiator to fit down in the frame all the way. Bottom line, without pretty extensive modification, it ain't happening when it's time to install. Cost us an extra $200 to get the one I bought to the point that it could be used. Got back with Scott, no clue, end of discussion, nothing done. Long story short, we now have a custom builder to build our replacements as needed.

Back to distributors, none of the batch was good unless the repairs I mentioned were made. Understand the military surpluses items for many reasons. They found that these units were defective quickly, that is obvious, in turn they gather up the lot and all of a sudden a huge lot of NEW M37 distributors are up for bid as surplus. Some guy with $ signs in his eyes buys the lot knowing the demand will be good, he soon finds out about the defective units also. Then comes S&S with feelers out for M37 stuff, a sale is made of the defective units, S&S markets them without checking them out, others buy from them without checking them out, they are sold to individuals who will check them out when they fail. It certainly sounds like you may be one of those individuals when you speak of a cracked coil case.

It cost us with parts and labor, about $150 each to fix the ones we had on the shelf. Then we had over $300 each invested in them, with a small profit% added in order to come out, now we have someting we can't sell. Why, I'm told by prospective customers, we can buy a new one from S&S for under $200. I got these to use on our rebuilds anyway, so I went back and installed electronic ignition in them to make them a top notch unit, we are using on our rebuilt engines.

And so it goes when buying surplus parts and components, even when dealing with large, reputable outfits like S&S. I still buy a lot from them, however, if the items I'm buying turn out not to be as advertised, we have an up front understanding that a full refund is in order if we find issues.

[Cal_Gary]

I blew the civvy coil open on my M because I forgot to include the ballast when I rewired the truck
Gary

[Murf]

Charles, yes, it's what they refer to as "molded"....It's no suprise it is cracked. I think it was rebuilt (distributor) in the 70s.

The tag on it says:

COIL, IGNITION, MOLDED 24 VOLTS
CODE/P/N: 19207-8712400
MFR: 90997 F.S.N. 2920-089-3607
CONTRACT: DAAE 07-68-C-0959

"CAUTION-USE EXTERNAL
RESISTOR UNDER COIL" US

[MSeriesRebuild]

Charles, yes, it's what they refer to as "molded"....It's no suprise it is cracked. I think it was rebuilt (distributor) in the 70s.

The tag on it says:

COIL, IGNITION, MOLDED 24 VOLTS
CODE/P/N: 19207-8712400
MFR: 90997 F.S.N. 2920-089-3607
CONTRACT: DAAE 07-68-C-0959

"CAUTION-USE EXTERNAL
RESISTOR UNDER COIL" US

This sounds like the stuff that was typical to the M715 distributors as new, they had a chip type (wafer) ballast resistor mounted beneath the coil in the water-proof housing. That didn't work well either, the resistors were tossed out and the coils replaced with the original type used in other vehicles quickly to eliminate the issues. This was another of the many M715 engine related issues, all of which I know too well as I was actually there when the M37 phase out was in play and were replaced with the very problematic M715. Not to run down the M715, however issues were MANY at the onset, many bugs were worked out along the way, but for anyone to even suggest they ever got close to being the reliable trucks the M37's were, totally rediculous.

[Murf]

ok, the next question,,,,Will I still need the resistor with an aftermarket (metal cased) coil? I'm thinking yes..it looks like it also serves as a spacer to put the coil contact point up near the distributor cap spring.

[MSeriesRebuild]

ok, the next question,,,,Will I still need the resistor with an aftermarket (metal cased) coil? I'm thinking yes..it looks like it also serves as a spacer to put the coil contact point up near the distributor cap spring.

Just do whatever you need to do to get things in the correct position. Preferably I would use a spacer of sorts other than the resistor itself, but I guess you could simply cut the wires off and reuse the wafer as a spacer. You may find the original type coil used in other distributors will be slightly taller and fit correctly. My memory isn't serving me on all the details at the moment, but you can check that out easy enough when you get the replacement coil.