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Discussion Starter #1
Had my FIL's A cutting down some over growth in our lower field on Monday with the A and a pull behind sickle bar mower. I shut the A down to take a break and put some gas in it. When I tried to start it up it would just turn over with not a hint of firing up. After a number of attempts, I gave up and my BIL towed the A to the barn. Tuesday morning I went back to the farm and tried to start it again since it would be a cold start. Just cranked over and would not start. I pulled a spark plug wire and put a spare plug on it and grounded it to the block. No spark. I then tried an in-line spark tester just to make sure there wasn't any spark. Nothing on the tester. I know it has an IH H4 magneto on it. I've never done any work on the magneto other than putting a cap and rotor on it a few years ago. I don't know where to start or what to check out first. My FIL passed away in March of '18 and I don't know if he ever had anything done to the magneto. I'm sure nothing was done to it in the last 10 years that I know of. Any help/tips/tricks/guidance would be greatly appreciated.
 

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Kish JD 318/420/430
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I would take the cap off the distributor, see if it is rotating and check the cap/rotor out too. Then move to the magneto. I have a manual for the A, so I will look for a test on the magneto late today.
 

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If by chance, the cap and rotor happen to check out OK, if by chance, it still has the original shut off switch, remove the wire from the magneto, that runs back to the switch, and see if it will start. I've had the switch on my BN ground out the mag, even though it was pulled up in the run position. Even though it is always kept inside, some slight corrosion happened inside the switch, more than likely from going through several Spring sweats, going from cold temps to pretty warm humid days,and the cold metal will form moisture. I've had this happen several times, over the 40 some years I've owned it.

It just takes turning the button on the switch, while pulling up and down on it, and it seems to clean itself up. I usually give it a shot of WD-40 also, and it seems to help things out.

With all of the rain we've had the last couple years, I've also had a buildup on the lugs under the cap, and rotor button on my tractors with distributors. More like an advanced case of ionization, that normally happens over a period of time. But with the high humidity from all of the rain, it seems to be worse. They start and run fine, until you get to working them some, and when the distributor advances, that corrosion really fouls up the works. Usually cleaning them up by scraping off that buildup will get you by, and caps with brass lugs seem to be worse at getting the funky green buildup. But still my choice over the aluminum lugs.

Personally, I prefer to use either IH OEM cap & rotor, or Echlin from Napa. But, to each his own.
 

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Discussion Starter #5
Thanks, guys, for the info. I went to the farm this afternoon and did some work on the A. Note that a few years ago I replaced the stop switch because the original one that was on the tractor failed. My FIL was still alive then because I told him the new switch probably won’t last as long as the old one!! LOL. Here is a list of what I did and the results.
1. Hooked up the spark tester between the spark plug and the spark plug wire. Pulled up on the stop switch, made sure the tractor was in neutral and then hit the starter. Engine cranked over, but no spark.
2. Next, I pushed and pulled the stop while spinning it a little. Engine cranked over, but no spark.
3. After doing that I disconnected the wire to the stop switch. Engine cranked over, but no spark. I then reconnected the wire to the switch.
4. Next, I pulled the distributor cap off being careful not the loose the spring loaded center plunger. Inside of cap looked clean, no burn marks or build up of any residue. The rotor looked good also. I replaced both of these items I’m thinking about 5-6 years ago??
5. Next, I cranked the engine to make sure the rotor was spinning around. It was so on to the next step.
6. I pulled all the plugs, cap with wires on them off the engine. I had my BIL hand crank the engine over slowly. I was watching through the #1 spark plug hole to see the top of the piston. When the piston got to the top the rotor was very close to where the #1 post in the distributor cap is and the magneto snapped. I left it in that position.
7. Next, I pulled the cover off the top of the magneto to see what the coil looked like. It didn’t look bad, as I was expecting to see it burnt up a little.
8. Next, I took 3 screws out and removed the plate that covers the points. Again, I was expecting to see a mess in there also, but the points looked good. Maybe pitted a little, but clean. Also, checked the gap and they were at 0.013”. Which is where they should be.
So, that is where I stopped today, I hope I didn’t miss anything. I have a couple more questions. Does the magneto only snap when the rotor is at the #1 cylinder or does it snap on all four cylinders when they fire. Also, is there any way to test the coil and the condenser? Last, if the timing was off a lot on this engine I should still see a spark shouldn’t I or not?
 

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My A has the mag, it went bad so PO put a battery coil on it and ran wires to make it work. --In your case I would put new points in it.---Looking good and being good are 2 different things. If you saw any pitting at all, there is your problem. It only takes a slight film/burning to make them lose contact. You can take them out and file/grind them to clean them up a bit and try that. I hate mags on everything!! ---Changed most of mine to good dist. ignition.
 

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The snapping you're hearing is the impulse on the mag. It's designed to retard the timing, until it starts, the centrifugal weights over ride the impulse, then makes it fire at TDC. If you were hand cranking it without the impulse, or improperly timed, there is a good chance that it will kick back.

Like Sonny said, if you see some pitting on the points, change them out, along with the condenser. They are rather finicky on that sort of thing. You might also look over the wires inside the mag. Check and make sure there are no bare spots, shorting it out. Especially the lead wire going to the points.

Unlike Sonny though, I love my magnetos..!! No worries if the battery is down, and not starting. I always hand crank my A anyway. It sets in the barn with the front blade on,and chains on the back, mainly for plowing snow, although it has pushed it's share of fill material. It has sat as much as 2 years without being started. With some fresh gas, full choke for 2 cranks, it has always started on the 3rd crank. They can't be all bad, they still use them on airplanes..!!
 

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Kish JD 318/420/430
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Here are some videos from youtube:

Condensor replaced on magneto (external

Magneto rebuild

Magneto diagnosis

Magneto on the test bench
 

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Kish JD 318/420/430
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The service manual didn't anything except to remove/installing it or making sure it is timed up correctly to cylinder 1 and TDC.
 

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Discussion Starter #11
Thanks everyone for the info and vids. Through the information I've obtained in this thread, I have a couple more things I want to check before I pull the mag. If it rains I'll be working on the A. If it doesn't I have about 2 to 3 days of grass mowing to do! I'll post up what I find and what I'm going to do. Thanks again. :thThumbsU
 

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Discussion Starter #12
One more question. While I was sickle bar mowing with the A last week the cover with the ammeter and a knob below the ammeter fell off. I have the screws so I guess the nuts fell off, (must be a boy tractor), so I zipped tied the cover back on. Today I took the zip tie off and was checking the wiring, etc in the box. There is a fuse mounted on the lower left hand corner, on the inside of the face plate. Not sure what amps it is but I can see that it is blown. It's an older glass tube type fuse. What is this fuse for? I looked at the owners manual and my I&T manual and can't find anything on it. Does this fuse have anything to do with the ignition system? I'd like to know before I pull the mag. Thanks for your help.
 

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Kish JD 318/420/430
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Fuse is for the lighting circuit, the resistor on the switch, that is there is to dim the lights, it is 5 ohms, The fuse is a 20 Amp and is to protect the circuit if there is a short or over current condition. There is another resistor that loads the generator field circuit it is 2.5 ohms.

In the manual I have (red service manual IH_A,AV,B,BN_SV, 70 pages) look at page 45
 

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I'm hoping this link will work. https://www.messicks.com/wiki/caseih/farmall-a Select Farmall A in the list, and it will take you to a complete online parts book for your A. It is divided up by function groups. If you select electrical, when the next page opens, select magneto, and it will show an exploded view of it, part descriptions, and part numbers. Cse/IH used to have these too, but a few years back, they dropped the straight A's C's & such, and just have the Super models listed now.

Pretty handy, when looking for parts..!!
 

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Discussion Starter #15
Russ - Thank you for the info.
DJ54 - Thank you for the link. It works. I'm looking up part numbers now. I've bookmarked the site.
 

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Discussion Starter #16
OK, another question. I removed the mag from the A and brought it to my shop and removed the coil and condenser. I noticed in the Steiner Tractor Parts vid, when the young lady removed the coil from the mag she is rebuilding, there was an insulator on each end of the coil. I do not have those on my coil. The coil was a tight fit in the mag housing. Here is a link to the part I'm referring to: https://www.messicks.com/cas/54056 Its item 32 on the parts list, Coil End Insulator, p/n 49593D. Are these required?
 

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Kish JD 318/420/430
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I would think so, other wise it would most likely short out the coil without it, same thing on the condensor insulators.
 

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Discussion Starter #18
Thanks Russ, I kind a figured that. That tells me the coil must have been replaced at one time and they didn't put the insulators back on the coil. I'll have to call Messick's tomorrow to see if I can get them there. In their parts diagram they must be able to get the condenser insulators but you have to call about the coil insulators. If I can't get them there I'll have to start searching for them.
 
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