Engine surging at different times

[Charrie 18]

Hi, like the title says. I just finished replacing ignition pick up and ring and changed the oil on my 1990 520H with the P220 engine. I can't really say how well it ran last year because it was having the issue of just randomly cutting off for no particular reason. After reading the forum i decided to change the pickup. Now it starts much better and has not cut off at all while mowing. It is however surging at times. 

I usually mow at or around 1/2 throttle. When it started surging, I tried slowly choking the engine and that seemed to straighten the surging out.  After a short time with the engine slightly choked, it started surging again. This time I opened the choke all the way and it seemed to straighten out. I repeated this 2 other times within 30 minutes of use. The lower the throttle, the worse the surging. I could also see it on the gauge. I guess that's an HP gauge?  Later I raised the throttle to about 3/4 and then all the way up and there was no surging.  

 

So that' s all I know right now.  WE bought the tractor about 3 years ago and have probably used it around 10 hours total. I believe it has always had a slight surge to it at idle but not near as noticeable as today. 

 

What do you guys recommend I do first?

I changed the fuel filter last year and just finished changing the oil and filter yesterday. That brings up another subject. I put in just under 2.5 qts of 30WT ND oil and the dipstick read full. This morning when I checked the oil it showed to be way overfull. I noticed that the dip stick showed way over full before I changed the oil after sitting a couple of months without running. When I drained the oil. about 2 quarts came out so I know it is not overfilled.

 

The guy I bought it from bought it brand new and took good care of it. There has been a good bit of electrical work done to it and I am guessing that perhaps the fuse block was changed. There is a small vacuum hose perhaps that runs from the dash and down under the engine but it is cut on both ends. up in the dash and just before going under the engine. Have no idea what it is. 

It has always been hard to start after it sits a few days. The fuel filter empties and has to fill after sitting a few days. 

 

Thanks 

[lynnmor 7,307]

First, you run the engine full throttle while mowing.

 

The carburetor needs cleaned to stop the surging.

 

When changing oil and filter, use exactly 2 quarts of oil.

 

To check the oil do it twice as it may read overfull when you pull the dipstick the first time.

 

There is a vacuum hose from the intake manifold that runs to the HP gauge.

 

There is a small hose that runs from the bottom of the air filter housing to a switch behind the dash.

 

If any of the hoses are disconnected, at least plug them.

[Ed Kennell 38,196]

23 minutes ago, Charrie said:

It has always been hard to start after it sits a few days. The fuel filter empties and has to fill after sitting a few days. 

Probably because the fuel pump check valves are not drop tight.     Over time, the fuel flows back to the tank and the fuel pump loses its prime.

Common fixes are;

Install a shut off valve

install a marine primer bulb

install an electric fuel pump

 

I personally use primer bulbs if the fuel pump is working OK when primed.

I the fuel pump isn't pumping, I install an electric pump.

[SylvanLakeWH 25,594]

 

Heres my primer bulb. Works like a charm... couple squeezes and starts / runs perfectly...

 

 

Edited April 13, 2023 by SylvanLakeWH

[Achto 27,594]

10 hours ago, Charrie said:

I usually mow at or around 1/2 throttle

 

Like @lynnmor stated. Always mow at full throttle. It is better for the engine and much better for the hydro drive.

[953 nut 55,280]

10 hours ago, Charrie said:

When it started surging, I tried slowly choking the engine and that seemed to straighten the surging out.

That is a classic symptom of fuel starvation. Pick up a can of Seafoam or Berryman's fuel additive and use double the amount that the label calls for in your next couple of tanks of gas. This should do the trick.

If you have been using gas with ethanol you should switch over to ethanol-free gas, the ethanol leaves deposits in the fuel system and will destroy rubber components.

https://www.pure-gas.org/

[TJ5208 1,824]

1 hour ago, Achto said:

 

Like @lynnmor stated. Always mow at full throttle. It is better for the engine and much better for the hydro drive.

True it'll also help to keep everything cool. And mowing at full throttle will help how it cuts due to blade speed.

Edited April 13, 2023 by TJ Salyers

[Charrie 18]

Thanks for the replies!

I knew that higher throttle would produce a better cut but never thought about cooling the engine. I was thinking that less throttle = less wear. 

 

I use non-ethanol gas in all my non automotive machines. That Ethanol is some bad stuff when it comes to older equipment and cars.  I just ran across a can of seafoam when looking for the filter and oil the other day. I will defiantly try that first.

 

The vacuum like hose is just laying in there and not connected to anything. Perhaps someone ran a new line to the gauge, since it works, and left the old one.

 

The primer bulb is pretty nifty. Where do you get one at? What kind of electric pump is used and i guess its wired to the switch? So the factory fuel pump has a back flow valve in it? All this makes since since the filter is usually dry after a couple of days. Still amazing how much faster it starts now.

 

The meter shows 758 hours on it. What maintenance should be done around now? how many hours do these engines usually run before needing major work? 

The PO had a shop that done much of his work but i have no idea if they ever adjusted the valves or anything like that. I do know that when i took the flywheel cover and flywheel off, it was amazingly clean under there. Mostly just dusty and much of that is probably from my use. 

 

Thanks 

Charrie 

 

 

 

[RED-Z06 2,221]

I see this surge alot on Onans, pretty easy fix, remove the filter and base plate to expose the carb.  Remove the choke, then the 4 screws that hold the carb top on.  Lift the carb top off, the gasket usually stays intact, then lift the float out..the needle is on the float so dont let it fall out.  You'll see various jets in the base section, blow them out with air and cleaner...blow out the bowl area.  Then reassemble.  One of the jets is the pilot jet..it gets plugged and you get a surging idle.

[Charrie 18]

Do not use a carb cleaner spray?

 

 

 

[RED-Z06 2,221]

24 minutes ago, Charrie said:

Do not use a carb cleaner spray?

 

 

 

You can..but compressed air is whats going to move it.  The pilot jet is so tiny that 1 piece of sand will block it and this inhibits air fliw to the idle circuit.

[Charrie 18]

Okay, Thanks!

[DukeRooster 2]

Mine surged aggressively. I changed the fuel line from the tank to the pump and put new fuel filters on one before the pump and standard after the pump. I put new plugs in NGK TR5. And high octane clean burning gas. No more surge. Can't say which step fixed it but she purrs like a lion now. 

[Tuneup 1,433]

Mine surged as well, though it's a P216. She would even stall at times and always on inclines. These engines are very sensitive to carb float level. Do it right and she'll climb hills forever.

 

Where in the Georgia mountains? I'm in Jasper so can't be that far from you.

[Charrie 18]

Thanks for the replies! 

Before we bought it my son pulled the plugs and checked the compression. I remember the plugs were like new. I forgot the compression numbers but they was good. 

Two urgent projects now. fix the surging, RT axle seal is leaking, and need tubes in the rear tires. 

I plan to remove the RT rear wheel and check for play in the axle tomorrow and go from there. There is a supplier in Dalton Ga who said they could have the SKF 11124 seals within a couple of days. They also sell bearings but I need to double check the part numbers. i also made a mistake in the first post. This is a 1994 520H

I believe the outer bearing number may be B-1816

 

Though I am sure that the proper way is to split the rear end but I also read a post that says that you do not have to split the rear end to replace the outer bearing.

" Also if you feel that spliting the case is too much you can install the bearing without spliting the case, by just driving the old bearing into the case, the O.D. mating suface for the bearing is approx. 1 3/4" and the bearing is 1 1/4". So the old bearing will still be captured by the case. I ve heard of this being done with no adverse effects."

What do you guys think about that method of replacing the bearing if needed? Many jobs I depend on my son to help with but he seems to be fixated on his new girlfriend and doesn't seem to have much spare time these days!  With mowing season starting, I hate to have it out of service for weeks.  I can do the seal but don't know about separating the rear end with all the gears in there. 

 

Tuneup, I am up here in the North Weast side near Cisco GA, close to TN

[lynnmor 7,307]

Are you sure that the axle bearings need replaced?  They usually last the life of the tractor unless they were severely abused.  There is considerable play in and out and that is normal.  There should be almost no play up and down.

 

Driving a bad bearing inside is asking for trouble, the needles can scatter and do serious damage.  If a bearing failed, know that the axle acts as the inner race and it can be damaged without you knowing it.  A bad axle can take out the new bearing.

 

Removing the left side case isn’t too bad and you might be able to service the transmission with just that removed.  The right is less than fun.

[Charrie 18]

Thanks for the reply Lnnmor,

I finally got the rear wheels off the ground and was able to check for play in the axle bearings. i didn't take the wheels off though. Instead I just jacked it up from the hitch placed a board under each wheel and pried up and down as I held my thumb and forefinger on the housing and hub at the same time. I could feel no up and down play at all. YAA!

I did hear some slight noise in the middle where the gearing is. I guess that was the opposite end of the shaft inside the housing and would be normal It was not enough to show any play on the wheels themselves.  

 

So I ordered 2 SKF 11124 seals that should be here in a couple of days.

I guess that the woodruf keys are fairly easy to find.

 

Well thanks all and now its time for me to get to work!