Need help w/M715

nc4x4dude

nc4x4dude

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Joined
Mar 31, 2007
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Wilmington
I have a 67 M715 with a Mopar 440. It is push button start. When I push the button to start it cranks up but when I let go of the button it dies. If I push the button and hold it, it stays running but the starter keeps turning with the bendix not engaged though. The push button has 2 wires, one to its own 20 amp fuse and the other goes to the solenoid. All fuses are fine and all wiring appears to be intact. Could it be the solenoid? Everything is wired on a panel and has its own fuse. There is a toggle for the ignition which comes on when flipped, it runs to a seperate solenoid. Any help or suggestions would be great. Thanks, James
 

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Bad ground maybe? On the second (ignition) solenoid? Meter it and see if/when you lose output thru the relay. Starter solenoid pulled in maybe completing either ground or power thru the coil of the igition solenoid??
 
I sounds like you have the Starter solenoid hooked up wrong.

Are you using the ford type on the fender?
if so there are 2 small connector terminals one is for start and one is for Ignition and should go to coil.
To start it you need to have a Ignition switch that will apply power through a resistor to the coil. once you have this you can hit the start button and it will stay running. to shut if just flip the Ignition switch off. you can use a toggle switch for that.
 
Sounds like no run voltage to the coil. For starting, the coil gets full voltage, then gets reduced voltage for running to reduce the heat build up on the coil. Just a guess, but the coil probably gets its start voltage through the solenoid the push button is connected to (likely) or through the aux terminals on the the starter solenoid (not likely), then gets its run voltage through the second solenoid to the resistor and on to the coil. If that resistor is bad or any of the connections through it to it the coil aren't good, you'll get that symptom. The ignition switch takes care of the resistor by-pass switching on the OEM setup, so whoever built your setup accomplished the same task with the solenoids and switches you described. The resistor looks like a ~3 x 5/8 x5/8 or so rectangular ceramic block on a bracket and it's probably mounted on the firewall or the inner fender. When current is flowing through it, it gets HOT! So be aware it'll burn the fawk out of you.
 
Deezul, you hit the nail on the head! Just ran outside and took both resistors (I had a spare) off the firewall and they were both blown (see picture). The first one blew on the trail 2 years ago but when it did it would turn over but not fire. This problem was the opposite so I didn't think to check it. I honestly didn't know it was a resistor and that you could visibly see that they were bad just by looking at the backside. I now understand ignition systems alot better. Thanks for all your responses.:driver:
 

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Ahhh, missed the Mopar connection... Way back when, I had a '77 or so Cordoba (only 2 good things about that car...good seats and fun to drive). Lost a couple of these while I had it.
 
The old Mopar axiom is that if the switch is on and that resistor ain't hot enough to thaw Hilary's heart, that's the problem. I never left the driveway without a spare in the glove box wrapped in foam to protect it. I guess because of that, I never had one fail. That's not to say I didn't replace a few for "preventive maintenance" reasons since there's a definite lifetime surrounding the heat/cool cycles it'll tolerate. I always pulled 'em off during tune-ups to check for the center core cracks that develop and replaced 'em if necessary. The '76 W350 4X4 with a 318 and 4 speed box is still running around the farm with 380K+ on it, BTW.

Yeah, it does smoke a bit, but it still starts and runs great every time you turn the key, and the AC will still frost your testicles.

PS: The originals had a high temp mounting bushing between the body and the bracket to damp vibration so as to extend the life of the things. No damping bushing shortens the life big time, but AFAIK, replacements don't come with a new bushing, and the originals get hard as a rock and flatten out from the heat and the elements, and will break away when you take the mounting hardware off. Probably why so few still have a bushing on the bracket.
 
Fired right up (and stayed running with new reistor) Went to Napa, auto zone, and Jeep dealership and no one had the exact resistor. The coil is tighter/smaller on the new one. Would this affect the ohms traveling through it and affect anything else? See picture, bottom one is the original.
 

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The resistor's appearance may or may not indicate a different value. The resistor's wire diameter, the coil diameter, the number of turns, and the core material together determine the actual operating impedance values, and there were several versions and values between models. So, if they've changed those to reach specs and increase structural reliability, the appearance may vary from manufacturer to manufacturer. If the books list the replacement number as being correct, but the appearance is different, things should be OK. If you know or can find the spec on the original unit's proper resistance and you can check the new one with an volt/ohmmeter, that'll tell you if you're in the ballpark. The one way to be sure is to make sure the resistor is the one that's listed as matching the coil you have. Find out what the coil application is from its part number and make sure the resistor is the one for the same application, otherwise, the new one may have a short life span, too. A mismatch could also shorten the lifespan of the coil and distributor components.
 
X2,^... just get out the ohmeter and measure the resistance of new and old ones.
 
I don't know what year my motor is I got the part by looking at late 60's early 70's mopars because it is a "raised block" 440, I will have to identify my motor or go off the coil which is a new MSD.

I can't measure resistance of the old one as it is blown.

Thanks.
 
I know that came out sounding dumb..LOL. I would be inclined to measure the resistance of the two halves and add them. IIRC its kirchoff's law of electricity that says resistance is additive. At least he could determine if they were close which I think was the original question.
 
Go by the distributor components and ignition coil combo you're using in order to select the right resistor. The part numbers on each should indicate the original applications, and looking those up will tell you if they're a match. Guess it goes without saying that the distributor pieces should match the ignition coil, and the resistor should follow. Maybe somebody here will know which dizzy and coil combo is appropriate, whether it was OEM on a 440 or not. As for me, I can't tell ya.
 
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