520H Dies after 10 minutes, then runs for hours

[Andy 0]

I picked up another 520H over the weekend complete with snowblower, wheel weights & chains & 48" deck. The deal was too good to pass up with the blower being quite a bit newer than my own and the deck being larger than the 41" that I am currently running.

 

The current owner got the tractor with the home last year. I was told that the tractor will run for 10 minutes and than stall. If you go get a drink, the tractor will start right up when you return and run for hours. The tractor came with detailed service records for the last 5 years at two different reputable dealers from the original owner. As near as I can tell the tractor was sent in for service after stalling 4x when the pto was engaged. The mechanic found weak spark on the second cylinder. At that time the coil was replaced along with plugs, filters etc. Shortly thereafter the tractor was sent in a few times since 2017 for the 10 minutes stall issue. I'm suspecting the new coil might be defective as the 10 stall seems to have started after the coil was replaced?

 

I will probably repacked the tractor along with one of the decks and my original snowblower, but would love to sort this issue out for the next owner.

Any thoughts?

[Lee1977 7,224]

Doesn't sound like a coil to me. Never seen one come back after a short time and run for hours. What model is this 520-H?  I have had some strange trouble with relays but not on a Wheel Horse as my 520 don't have them.

[Andy 0]

I can get the specific model number this evening. It was purchased new in '90 so it has the motion lever on the steering column. 

 

[lynnmor 7,858]

You need to get a baseline on how it actually performs instead of taking the word of others.  Check and clean connections, check the gas cap for venting and run the thing till it quits.

[Andy 0]

I plan on it. However, I've known the original, and 2nd owner long enough to know that the tractor will do exactly as they have stated. I figured I might be able to save myself some time if someone else has had a similar issue.

[Tuneup 1,452]

Maybe silly idea here but something to consider. Each time it happened, was he doing the same thing on the tractor? After the restart, he had passed the problem area and it was fine. My 516H decided it wanted to stall on a particular incline. I had to pull the hood and was ready with a shot of Gumout when it happened to prove it was not fuel. Easily repeated. Old mechanics school - always electrical first on the old school machines. Wiring. I bet if you bypassed the cutouts and put 12V directly to the coil, it would run forever. Good luck!

[Andy 0]

I finally got a chance to mow yesterday. As promised the tractor stalled in the first 10 minutes of mowing. Twice actually. Once with a pop from the exhaust and the other no pop.

The first time it stalled I realized I had dropped my ratchet. I spent a few minutes retracing my steps to find the tool before I gave up and restarted the tractor. The tractor started easily with no choke and the throttle set at idle.

 

The second time I didn't bother trying to find the missing tool. I disengaged the PTO and immediately restarted the tractor. The tractor started as easily as it did the second time with no choke and idle at throttle. After this stall the tractor ran 90-120 minutes while I finished mowing.

Both times it stalled there was plenty fuel in the fuel filter, and I kept an eye on the clear fuel line feeding the filter and could see plenty of fuel being pulled from the tank.

The tractor runs smooth and has gobs of power. The grass wasn't long, but there are several steep inclines. The tractor climbed them with no hesitation, all the while keep the blades spinning. The tractor does not surge at all, diesel when shut off, and starts easily when warm or cold.

In the past two years the tractor has had; new coil, new plugs and wires, new filters, hyrdro unit services, intake manifold gasket replaced, and new filters.

[lynnmor 7,858]

So the only thing that changed was the cycling of the PTO and seat switches? I would start there.

[chip61 666]

just for kicks can you rig some sort of test light to the bat side of the coil to see if for some reason you briefly lose power to the coil when it shuts off??

[tom2p 2,394]

11 hours ago, Andy said:

I finally got a chance to mow yesterday. As promised the tractor stalled in the first 10 minutes of mowing. Twice actually. Once with a pop from the exhaust and the other no pop.

The first time it stalled I realized I had dropped my ratchet. I spent a few minutes retracing my steps to find the tool before I gave up and restarted the tractor. The tractor started easily with no choke and the throttle set at idle.

 

The second time I didn't bother trying to find the missing tool. I disengaged the PTO and immediately restarted the tractor. The tractor started as easily as it did the second time with no choke and idle at throttle. After this stall the tractor ran 90-120 minutes while I finished mowing.

Both times it stalled there was plenty fuel in the fuel filter, and I kept an eye on the clear fuel line feeding the filter and could see plenty of fuel being pulled from the tank.

The tractor runs smooth and has gobs of power. The grass wasn't long, but there are several steep inclines. The tractor climbed them with no hesitation, all the while keep the blades spinning. The tractor does not surge at all, diesel when shut off, and starts easily when warm or cold.

In the past two years the tractor has had; new coil, new plugs and wires, new filters, hyrdro unit services, intake manifold gasket replaced, and new filters.

 

 

 

 

 did you find the ratchet ?

 

lol

 

I have a 416 that just recently began to exhibit similar issue - almost as if someone turned the key to off  

 

then starts immediately - runs great 

 

Edited October 15, 2020 by tom2p

[Andy 0]

I meant to close my last post with the news that I eventually found the missing ratchet.

 

Pro tip--- Tools are easier to find in short grass. Consider lowering the mower deck.
 

 

 

[Handy Don 14,129]

One last note. An intermittent “close” on the seat safety switch would momentarily stall the engine. My very compact daughter in law regularly gets the same effect when she is wrestling the wheel for a tight turn and takes some weight off the seat. Took me some minutes to catch on and be relieved it wasn’t an engine problem, but a too strong seat spring. 

[Andy 0]

For those following along with my mystery.

 

I rigged up a test light to the coil, and triggered the safety switches to make sure it turned off as expected.

 

I ran the tractor around the yard for 10 minutes with no issues. Engaged the PTO and drove around and at almost exactly 10 minutes the tractor died. Engine cut out with one backfire as the engine spun down. The coil had power at all times, and the fuel filter was full of fuel. Tractor did not immediately start up, turned over but did not fire for a few seconds. Waited approximately 5 seconds and it fired right up.

The issue could be related to the PTO, or engine load. 

 

Weird.

[lynnmor 7,858]

I didn’t want to jump to the ignition module right away, but it’s starting to look that way.   It appears that the engine needs to be hot enough for the module to fail from heat sensitivity, the part that still is puzzling is why it will run after the first failure, perhaps it isn’t coming up to a temperature high enough in later runs.  If you test again, work it hard after the restart.

[Andy 0]

I'm with you Lynnmor. I'm leaning towards something in the ignitions system past the coil power supply. The fact that the coil never loses power (according to the test light) seems to rule out the safety switches.

I just can't get my head around the reason that it runs flawlessly for hours after the 10 minutes mark. I was mowing up steep inclines... well past what the owners manually deems safe to mow and it never protested. I keep thinking that it must be heat related, but the problems only presents itself at a specific temp. Any cooler, or warmer than that temp and it's fine.

If I can get it figured out I'll take it to Greg at Stanley's Lawn and Garden. He's awful sharp when it comes to these red tractors.

 

[Andy 0]

I spoke with Greg Stanley this morning, and he too thinks the ignition module is the likely culprit. He mentioned that see weird issues caused my the modules on many of the Onan engines they deal with.

He suggested I hook my trouble light up to the negative side of the coil. When cranking the engine right after it dies the light should flash on and off as the engine cranks. It is stay on, or off than the module is to blame.

I'll report back when I've had a chance to test further.

 

[lynnmor 7,858]

1 hour ago, Andy said:

He suggested I hook my trouble light up to the negative side of the coil. When cranking the engine right after it dies the light should flash on and off as the engine cranks. It is stay on, or off than the module is to blame.
 

Good test idea, just remember it is like catching a thief in the act because the condition can change quickly.

[Andy 0]

It's cool here today and the tractor ran about 15 minutes. I have the trouble light taped to the hood and the light had switched from flashing to solid on as soon as the tractor died. Tried starting the tractor and the light stayed on. Turned the tractor off and let it rest for a minute and the trouble light was back to flashing and the tractor was back to running. I've got an ignition module on order.

Thank you for all of your suggestions. It may be a week or so before II get a chance to swap out the part. I'll update when I do.

[lynnmor 7,858]

Here is a thread that may help you in pulling the flywheel.  If you need any help, just ask.

[tom2p 2,394]

On 10/15/2020 at 9:56 AM, Handy Don said:

One last note. An intermittent “close” on the seat safety switch would momentarily stall the engine. My very compact daughter in law regularly gets the same effect when she is wrestling the wheel for a tight turn and takes some weight off the seat. Took me some minutes to catch on and be relieved it wasn’t an engine problem, but a too strong seat spring. 

when my oldest kid was finally heavy enough to satisfy the seat safety switch he was able to cut grass with the tractor 

 

but one time he was moving fairly well - and the seat switch activated momentarily when he hit a bumpy part of the yard 

 

the tractor quit for a second - and then quickly resumed after a huge backfire 

 

the backfire scared him and he jumped off the tractor and ran into the house  lol

 

 

Edited October 17, 2020 by tom2p

[Andy 0]

Finally got around to installing the new ignition module today. Pulling the flywheel was pretty straight forward. Actually, getting the engine shroud lined back up was, by far, the biggest PIA.

 

I ran the tractor for 20 minutes with no issue (other than running out of gas). After refueling, I ran another 10 minutes or so without issue. I believe that the ignition module did indeed fix the issue.

 

If you are replacing an Onan ignition module, make sure the holes in the new bracket are the same as the old unit. Apparently the new units that Cummins are shipping don't quite line up and require a little filing of the holes. Dealer told me it would run, but the timing was off if I didn't file the holes and line it up exactly as the old one. Should have taken pictures.

[tom2p 2,394]

2 hours ago, Andy said:

Finally got around to installing the new ignition module today. Pulling the flywheel was pretty straight forward. Actually, getting the engine shroud lined back up was, by far, the biggest PIA.

 

I ran the tractor for 20 minutes with no issue (other than running out of gas). After refueling, I ran another 10 minutes or so without issue. I believe that the ignition module did indeed fix the issue.

 

If you are replacing an Onan ignition module, make sure the holes in the new bracket are the same as the old unit. Apparently the new units that Cummins are shipping don't quite line up and require a little filing of the holes. Dealer told me it would run, but the timing was off if I didn't file the holes and line it up exactly as the old one. Should have taken pictures.

sounds good 

 

what type of puller did you use to remove the flywheel ?

 

 

[Andy 0]

I used the wheel puller from Harbor Freight. You can only use two bolts whit this puller, but I took it slow, made sure nothing was binding up and the fly wheel popped right off.