New coil installed on my 520-HC

[cafoose 3,135]

I got a new coil for my 1988 520-HC. I was having problems starting it when hot. I tested the old coil primary and got 3.3 ohms, the new coil was 3.4 ohms. The secondaries were open on the old coil and 21.66 k-ohms on the new coil. I got some metal bar stock with holes in it at Lowes to make brackets. I used a hose clamp to attach the brackets to the coil. I clamped the brackets to a large socket and cut a little at the bend so it would bend completely around the socket. Then I beat it around with a hammer to form the curve to go around the coil. The tractor started right up and ran great. I was about to mow with it and I noticed I had a flat in one of the front tires It would not pump up and it has a tube in it.I took the wheel off and the tire off the rim and found a big hole in the tube then I found a lot of wire coming out through the bead where it contacts the wheel I have four lawns to mow tomorrow and I desperately need a tire or tire and wheel. @ericj do you have anything I can use? I tried to pm you and it won't let me. It says " ericj cannot receive messages. " when I try to send it.

[6bg6ga 271]

Good Job!!   Just as good if not better than the original.

[953 nut 51,511]

      Very good job on the coil mount. Hope you can get a tire before the lawn gets completely out of hand.

[N3PUY 1,031]

Wal-Mart or a farm supply store should have a tire.

[ericj 1,576]

my in box is full and not sure how to clear it, need to renew my supporter membership, if you have a forward swept axle, no I don't have any any, I have some for the 3/4 front rims, but they all need at least  a tube. tractor supply or west side Walmart should have tube and maybe a tire. although they might only have 16x6.50x8 instead of the 16x7.50x8 tire that should be on a 520 with the foreword swept axle. I did send you my phone # in one pm if you still have it, good luck

 

 

 

 

eric j  

[cafoose 3,135]

2 hours ago, 953 nut said:

      Very good job on the coil mount. Hope you can get a tire before the lawn gets completely out of hand.

I have a couple other tractors but they still have blades on them. My 876 with a 36 inch deck, and my C-120 with a 42 inch deck if I need to I can put the decks on and use those.

1 hour ago, N3PUY said:

Wal-Mart or a farm supply store should have a tire.

I checked tractor supply website and they don't have any in stock listed online. Mine is a 16x7.50-8. I doubt Walmart would have it if they don't. My tire is shot so a tube won't work.

[cafoose 3,135]

1 hour ago, ericj said:

my in box is full and not sure how to clear it, need to renew my supporter membership, if you have a forward swept axle, no I don't have any any, I have some for the 3/4 front rims, but they all need at least  a tube. tractor supply or west side Walmart should have tube and maybe a tire. although they might only have 16x6.50x8 instead of the 16x7.50x8 tire that should be on a 520 with the foreword swept axle. I did send you my phone # in one pm if you still have it, good luck

 

 

 

 

eric j  

It looks like I do have the forward swept axle if I'm looking at it correctly. My tire is 16x7.50x8 can I use 16x6.50x8 if I can't find 16x7.50x8?

[ericj 1,576]

yea it's 1" narrower then what came on it. Dale's mower service would have the 7.50, but he is above Cabella'a up on 78, over an hour drive, might try Penn tire in the morning. they have a store on Roosevelt Ave and in Dallastown.  Not sure who else may carry the 7.50's. I've seen the 6.50's on other 520's so not that big of a deal unless you want originality.

 

 

 

 

eric j 

[953 nut 51,511]

        If you have a boat trailer or other trailer with 8" wheels on it they have one inch hubs;    could work in a pinch.

[cafoose 3,135]

2 hours ago, 953 nut said:

        If you have a boat trailer or other trailer with 8" wheels on it they have one inch hubs;    could work in a pinch.

Nope don't have one I did get it fixed I cleaned up the rim with a wire brush on my angle grinder and cut the wires sticking out of the tire then I got a slime tube at tractor supply and got it fixed then I got my mowing done.

[cafoose 3,135]

4 hours ago, ericj said:

yea it's 1" narrower then what came on it. Dale's mower service would have the 7.50, but he is above Cabella'a up on 78, over an hour drive, might try Penn tire in the morning. they have a store on Roosevelt Ave and in Dallastown.  Not sure who else may carry the 7.50's. I've seen the 6.50's on other 520's so not that big of a deal unless you want originality.

 

 

 

 

eric j 

I do have the swept axle correct? I found the exact tire on amazon but I have to wait for it so I did a quick fix explained in my last post. Later I may get two new tires off amazon.

https://www.amazon.com/Carlisle-Turf-Saver-Lawn-Garden/dp/B005O5X99U/ref=pd_lpo_vtph_293_tr_t_3?_encoding=UTF8&psc=1&refRID=GE5W1TGMGTJJE5913FFX

[cafoose 3,135]

When I got my mowing done I shut the 520 off and tried to restart it and it would not start again After sitting for about a half hour it started and ran great. I'm guessing module? What else could it be?

[6bg6ga 271]

Your coil is new. If my understanding of the module is correct it is either going to work or it isn't. I haven't heard of any that were intermittent. What I would do is this. Won't the lack of oil pressure keep one from starting? If so I would check the level. I would also bypass the safety controls and run a B+ from the battery to the coil positive and see if it starts. You'll probably have to run it for it to warm up and then shut it down and see if it starts and if not bypass the safety controls and see if it starts then. If not then do the module test which is to connect 12VDC to the positive of the coil remove the negative from the coil and put your meter on VDC and connect one probe to ground and the other to the negative module terminal. Rotate the engine by hand noting the meter reading and the meter should show 12 volts when it hits between the two alignment marks on the housing. Rotate it further and I believe about 1/2 a rotation or so and it will drop down off 12v to about 1 volt or so. If it does this the module is ok.

16 hours ago, cafoose said:

I got a new coil for my 1988 520-HC. I was having problems starting it when hot. I tested the old coil primary and got 3.3 ohms, the new coil was 3.4 ohms. The secondaries were open on the old coil and 21.66 k-ohms on the new coil. I got some metal bar stock with holes in it at Lowes to make brackets. I used a hose clamp to attach the brackets to the coil. I clamped the brackets to a large socket and cut a little at the bend so it would bend completely around the socket. Then I beat it around with a hammer to form the curve to go around the coil. The tractor started right up and ran great. I was about to mow with it and I noticed I had a flat in one of the front tires It would not pump up and it has a tube in it.I took the wheel off and the tire off the rim and found a big hole in the tube then I found a lot of wire coming out through the bead where it contacts the wheel I have four lawns to mow tomorrow and I desperately need a tire or tire and wheel. @ericj do you have anything I can use? I tried to pm you and it won't let me. It says " ericj cannot receive messages. " when I try to send it.

 

Is that 30meg i'm seeing on the meter for the secondary resistance of the old coil?  

[cafoose 3,135]

1 hour ago, 6bg6ga said:

 

Is that 30meg i'm seeing on the meter for the secondary resistance of the old coil?

That's what my meter reads on an open circuit notice the bar on my meter under the numbers is maxed out if I remove the probes it reads the same. I will try your suggestion when I get a chance

[ericj 1,576]

yes you have the forward swept axle, when I teat the module, I hook my meter up to the - side of the battery and the negative side of the coil, then spin the motor over by hand. you should read 12 volts and then drop down to 1 1/2 volts then back to 12, if it does this then it is ok . if it don't drop then it is bad. it may test ok cold but then act up after running and warming up. usually about 15 minutes is all it takes to act up. could it have flooded out and caused it not to start. or a fuel problem. good luck

 

 

 

 

eric j 

[6bg6ga 271]

Either way will work to check the module. I suggested taking off the coil terminals for safety sake. This way you can be sure it won't start.

[6bg6ga 271]

12 hours ago, cafoose said:

That's what my meter reads on an open circuit notice the bar on my meter under the numbers is maxed out if I remove the probes it reads the same. I will try your suggestion when I get a chance

 

With respect to your meter..... The bar moving across the bottom is supposed to be an indicator that the meter is seeing a resistance. The more resistance it sees the more the bar goes toward the right. To me your meter looks to have a problem on that scale as it is showing 30.00 M. You think its an open and I think its a problem with the meter. ANY meter when put on a resistance scale shows nothing until the probes either measure something or they are shorted together. I haven't had that particular model of Radio Shack meter but the ones I have owned (all of them) always show an open or absence of reading until they are measuring something. An indication like what yours shows is usually an indication that the meter was on the resistance scale and saw voltage. I believe that scale is no longer accurate. You could however perform a test like the one below in my post to be sure.

 

Since I use a number of different meters both at home and at work I do keep a few resistors on hand to check my meters for accuracy. I would really borrow a 1 meg resistor from someone or buy one and test out the 30M scale on your meter to see if its true or not.

Edited May 1, 2017 by 6bg6ga

[6bg6ga 271]

Picture of meter is rest state on the Meg scale. Note  the triplett shows 1 on the very left side and there is a dot lit up showing 200 on the bottom. The Rat Shack always shows OF when not measuring anything.

Another picture of the Triplett measuring a 3.3 meg resistor and its showing 3.38  Another picture shows the Rat Shack measuring the same resistor and its showing 3.404 Meg. 

 

Some might wonder why I have two meters. Actually I have close to a dozen different types to satisfy different needs. The triplett is less than $100 and provides me the capability to measure transistor  HFe so I can match them. The Rat Shack gives me true RMS voltage so I can measure amplifier outputs  plus a frequency scale so I can check the output of my signal generator. Both are over kill for lawn tractor work. The point I'm trying to make here is one needs to be able to check their meter to know if its working properly.

The resistor used is a 3.3 Meg 5 % which means it can vary + or minus 5% from its stated value and both meters measure it within that range. Which one is closest? Well that would require another more accurate meter that has been recently calibrated.

[cafoose 3,135]

I just went out and hooked VOM + to coil + and VOM - to battery - turned key to on position rotated engine by hand VOM reading went from 12.87 to 9.87 volts.Seems like the module is bad correct? I did not start the engine yet today. Wife called me for lunch so I did not get to warm it up yet to retest.

[6bg6ga 271]

Yes, its bad or going down hill fast

[cafoose 3,135]

So there is no need to test it hot? Where is it located and how difficult is it to replace?

[6bg6ga 271]

Some people would try to tell you that you need to take it to an engine shop and have them do it and pay them. I will tell you to go to Harbor Freight and buy a puller set and do it yourself. Remove the housing around the flywheel, remove the cage or cover plate or what ever your engine has over the flywheel, remove the center flywheel bolt and pull it out and then screw it in 3 or 4 threads and stop. Get the puller out of the box put two bolts thru it into two of the 4 bolt holes surrounding the center flywheel hole. Tighten up the center bolt onto the one on the center tighten it up and the flywheel will pop and come loose. You will now see the stator and under the stator you will see the blk pick up with two wires on it. Remove stator to remove the ignition coil. Its held on by two 10-32 bolts. Note you will probably have to remove the coil, coil wires, and HT wires along with the coil. Also the linkage to the governer.

 

There is a youtube video on it you can watch and learn.

[boomers_influence 106]

cafoose

you ARE NOT doing the module test correctly.

please e/mail me and i will send you pages 8-1 and 8-2 from the P service manual.

 

boomers_influence@yahoo.com

 

thank you. boomer ( the used onan engine parts guy, also NOS and new )

[6bg6ga 271]

Good Catch!!

 

Got to post #15 for an explanation. Be sure to pull the plug wires.

[onanparts.com 178]