Need a little help with a 1976

Mon Apr 07, 2014 2:39 pm

I've been looking for over an hour to find the proper wiring diagram for this cub and can't locate any info new enough. It's my neighbors 1976(all factory, untouched). It has an alternator, resistor block mounted to the back of the alternator, 12 volt negative ground, key start, safety switch attached to the clutch pedal. The problem is it cranks over just fine, but won't start holding it in the crank mode, but soon as you let off the key, it fires right up. I attached a dvm to the coil and it has full voltage with the key in the "on" position, but drops off to near nothing while cranking. There's only one wire attached to the "+" side of the coil which comes directly from the resistor block. The battery has just been charged overnight, so that shouldn't be an issue. I know there's a starter solenoid someplace under the foot platform, but I just wanted to look at a diagram before I really dug into things. Any help locating the newer wiring diagram would be appreciated.

Thanks, Rick

Re: Need a little help with a 1976

Mon Apr 07, 2014 3:25 pm

I've never found a clear diagram for that specific version. The latest parts catalog (TC-37F 8/79) has illustrations of a lot of the connections. They are on page 8-38.

I suspect you will find a defective ignition switch that is not connecting cleanly to the "I" contact when the switch is in the "S" position.

Re: Need a little help with a 1976

Mon Apr 07, 2014 3:45 pm

PM Bob Melusky. He developed one a couple years back.

Re: Need a little help with a 1976

Mon Apr 07, 2014 3:54 pm

Rick, you might want to give that resistor block another look. I had one go out a few year ago and it resembled the way you describe, appears to start when you release the starter. Let us know what you discover., Thanks, Tom.

Re: Need a little help with a 1976

Mon Apr 07, 2014 5:03 pm

I have a 76 international cub that does the same thing. It had the same alternator as yous with the resistor . However when i bought the tractor many years ago at auction the alternator was burnt up. I installed a one wire delco and eliminated the extra wiring. It still starts when you release the key after cranking. I found that the plug connections on the back of the ignition switch were corroded real bad to the point it wouldnt crank. I cleaned the connections a few years ago and that solved the problem till last summer. It is back to starting when I release the key to run position. I see a new ignition switch being installed soon

Re: Need a little help with a 1976

Mon Apr 07, 2014 5:32 pm

90% chance it is the ign switch, 10% connections on back of switch :lol: 100% it is one or the other, I have had to replace quit a few on the 140s, same switch.

Re: Need a little help with a 1976

Tue Apr 08, 2014 7:51 am

Thanks for all the tips. I'll look at things today and focus on finding the exact culprit area and report back.


Re: Need a little help with a 1976

Tue Apr 08, 2014 12:16 pm

Don't mean to be teaching gramma to suck egs, but check the battery connections. I had the same symptoms on my lo-boy, and it turned out to be corrosion on the positive battery cable connector at the battery. The clamp was tight, and looked clean, but when I pulled it off, I could see the inside needed cleaning.

Re: Need a little help with a 1976

Wed Apr 09, 2014 9:24 am

Sorry for the winded reply. Day 2. One step forward(kinda) and 3 steps backwards :shock: Yesterday I went out to the barn determined to fix this thing. I grabbed my 12v tester and was able to reach behind the dash and touch each terminal on the switch. Batt terminal was live. Next was to test the start terminal, which worked fine----lit the test light while in the crank mode. Next was the ign term. Click the key to the "on" position and test lite lit. Turn the key to the right in the start mode and the lite went out :shock: Next I removed the switch from the dash and retested all the terminals. Again the lite would go out when testing the ign terminal and during cranking. You could move the key slightly left and the lite would come on. This same style switch was used back several years ago when I built my logsplitter. It was made by Indak. I experienced 2 of these switches failing within 6 months and ended up buying a better quality switch(double the money) and it's been working great for years. IH offers this switch which appears to be this same Indak brand. Before I purchased one and have it fail a few months down the road and the neighbor calling me again, I decided to investigate and see why the switch is prone to failure. The crimp around the outer potmetal housing was fairly easy to straighten. I carefully removed the back fiber plate which had contact buttons and discovered inside a copper contact plate with two small springs beneath. This plate has locating tabs and rests on top of the main plastic pivoting body of the switch which rotates as the key is turned. Indak designed this rotating body with a steel spring wrapped around plastic designed to have that spring action while starting. The plastic has worn and allows the switch to rotate farther to the right than designed which allows the copper contact plate to rotate just passed the contact button attached to the "ign" prong. I then noticed the back fiber plate had a locating notch and the main outer potmetal housing also had a locating nub. I decided to carefully file the fiber notch alittle wider so I could rotate the fiber plate just a little allowing the "ign" contact to make connection. I put the switch back together,temporarily cycled the switch, and things worked perfect. I carefully tapped the crimp back around the fiber and reinstalled the switch in the tractor. Connected the battery again and fire things up. The cub fired right up. I shut it off and tried it again, it started quickly but I still noticed that when I held the key in the start mode it wouldn't fire until I let up and the starter disengaged. I then rechecked the switch with my tester and the switch was still working perfect, even turning the key hard to the right. I decided to test drive the cub around town. The neighbor asked me to look at this cub because it was running for about half an hour and would quit while mowing the grass last season. He installed a new condensor and a new 12v coil thinking that could've been the problem. Eventually the cub wouldn't even start for him. I found the points out of adjustment and burnt bad. I installed the new points and the cub fired right up, but that's when I noticed the issue with the ignition switch.

I drove the cub all around and even mowed alittle in my back yard. Drove perfect and never missed a lick. Decided to ride down to the mechanic shop and show off my fine work :{_}: Arrived to his place and shut off the cub. Talked to him for a couple hours and when I tried to start the cub to come home------------nothing :evil:

We checked everything out and this cub is making me feel real stupid. Ignition switch is still working perfect, but now we can't get any spark out of the coil, even when jumping from battery to coil. I took the points back out, inspected them and reinstalled them---nothing. I also took no1 plug out and made sure number one piston was up on compression and lined up the notch on the pully, the rotor was pointed at number 1 on the cap. I also noticed the number one plug was completely dry, even after all that cranking. Removing the drain plug on the Zenith shows it's getting gas flow to the carb. Sounds like a couple different issues going on here to me.

I'll report back. Something weird is going on(famous curve ball saga) so I'll check all possibilities, such as battery connections and the resistor block circuit. I may have to remove the hood to get an accurate wiring routing.


Re: Need a little help with a 1976

Wed Apr 09, 2014 9:36 am

When all else fails, bring it to the Bash. We'd like to see you again. :D Good luck with it Rick!

Re: Need a little help with a 1976

Wed Apr 09, 2014 11:04 am

I know you've been meticulous about checking things out. It almost sounds like a broken or shorted wire on the primary circuit, perhaps where the lead from the coil to the points goes through the distributor. Just a thought.

Re: Need a little help with a 1976

Wed Apr 09, 2014 11:53 am

Don't worry about the fuel until you get the spark problem sorted.

It's got to be a problem with the coil itself, condenser, or points.

Re: Need a little help with a 1976

Wed Apr 09, 2014 7:05 pm

If you have fire coming to the Dist. I am betting on the points they can look good and be junk

Re: Need a little help with a 1976

Thu Apr 10, 2014 7:15 pm

Well, it seems to be fixed and runs and starts perfect every time. Jim was first to suggest looking at the switch, which did indeed not supply voltage at the ign terminal during cranking. I fixed that and it works perfect every time now. The second issue that continued, even though the switch was fixed, was pinpointed from "bythepond88" and his suggestion. I found the negative cable all corroded under the battery where it attaches to the battery box bolt. After a good cleaning it now has no voltage drop at the ign switch during cranking. Thanks Jim and Michael and all the other suggestions. While working on this I removed the hood and completely went through the entire harness checking things out and made a diagram that I posted in a separate post.

Thanks again everyone,

Re: Need a little help with a 1976

Fri Apr 11, 2014 12:20 pm

Glad to hear you got it straightened out.