Toro Wheel Horse 520H - Oil in Air Filter

[mclaugh417 0]

Hey everyone.

 

I have a Toro Wheel Horse 520H that previously ran fine. It sat for a year because of a busy schedule and electrical issues I didnt want to deal with. I recently fixed the electrical issue and wanted to bring it back into service. I cranked it over, which took a long time because i am sure the fuel pump is quite weak, but regardless once it got gas it purred. Everything was great, but then it started to bog down, and I ended up having to push it back into the garage. Opened up the air filter and boommm...a bunch of oil. Nothing I have ever seen before. It was soaking the filter and pre filter. It sat for a few weeks and then I tried to fire it up. Knowing that the filter was certainly clogged at this point I tried to start it without the filter on. It ran great for about 5 mins at 2500rpm just sitting there. Then all the sudden oil started to come out of the breather tube, and it wasnt a small amount. Splattered all over the place. 

 

I know its a long description of the problem, but I want to be as accurate as I can in describing the issue. I know a bad air filter can cause oil, but i thought by running it without it would eliminate that. Could it be the breather itself? Valves, head gasket, or worse piston rings? It isnt to much oil, I mean its full, but not over by any means according to the dipstick. 

 

Just not sure where to go next, hope the knowledge and experience in this community can help me get it going smoothly again. 

[Ed Kennell 40,613]

Check the oil level.    Is it overfull and smelling like gasoline?

[squonk 42,698]

Also possible the rings may be stuck.

[JCM 10,026]

  to Red Square  @mclaugh417

[lynnmor 7,593]

 

Always start with a compression check when you have problems like that.  You may have sticking valves or rings from sitting unused for an extended time.  Was the oil clean when stored, moisture in it could have caused a problem?  If the engine wasn't maintained properly the breather or oil return holes can be blocked.

[953 nut 58,111]

All of the above are good suggestions. Since it ran well for about five minutes the other question to be answered is,  was there any whit smoke coming from the exhaust pipe indicating oil being burnt? If piston rings were stuck this would allow oil to become ignited in the cylinder along with some blow-by pressurizing the engine's crank case. The breather tube allows crankcase gasses to be burned while the engine runs rather than being vented to the atmosphere.

If you have not changed the oil I would suggest replacing the old oil and including a pint of Marvel Mystery Oil.

The service manual below should be helpful, it is a free download.

 

[Gasaholic 257]

They also have an oil pressure relief valve that , if stuck, can cause excess oil pressure and it has to go somewhere... I'd check oil pressure too.. had one Onan that did that, took a while to realize oil pressure was the culprit. 

[peter lena 9,097]

@mclaugh417  lubrication varnish is a commonality  with  engines , agree with @953 nut  on the additive , my personal choice has been RISLONE  ZDDP SUPPLEMENT ,  add 4 ounces to my oil changes , read bottle specs , operational running ease  is very smooth  / easy , no smoke  at all  and evident  cleaning oil changing flushes , also realise  there are many against anything  to help out this  issue . my suggestions are based on my experience /  results to a  change . I also add  STA -BIL  to all my fuel , fuel filters are always clean / clear  , instant starts  , zero engine smoke , just a suggestion , pete   

[lynnmor 7,593]

2 hours ago, Gasaholic said:

They also have an oil pressure relief valve that , if stuck, can cause excess oil pressure and it has to go somewhere... I'd check oil pressure too.. had one Onan that did that, took a while to realize oil pressure was the culprit. 

Good call on that.  It would be a pain to get to the oil pressure sending unit to connect a meter but it might be worth it.

[RED-Z06 2,481]

You have 2 problems here, possibly related.  The fuel pump runs off crankcase pressure by way of a hose.  If the diaphragm has failed, it can cause inefficient fuel pumping and, dump fuel right into the case.  The thinned out fuel eventually fills the breather housing ans geysers out the tube.

 

Oil pressure wont cause this, oil pressure is the resistance of the oil to be pushed through the bearing surfaces, you could have 80psi and not cause this.

 

I like the pulse style pumps myself, you can usually rebuild them or replace them entirely.  Its fairly straightforward to pull the pump, 2 screws and pull the flywheel screen..reach through the fan with hemostats if need be to push the line onto the pump if its not wanting to go back on from behind.

[Ed Kennell 40,613]

On 5/2/2025 at 8:03 PM, Ed Kennell said:

Check the oil level.    Is it overfull and smelling like gasoline?

 

 

                     Any results on this check?

[mclaugh417 0]

12 minutes ago, Ed Kennell said:

 

 

                     Any results on this check?

Just went into the garage. I wouldnt say it was really over full but it certainly smelt like gasoline.

[mclaugh417 0]

7 hours ago, RED-Z06 said:

You have 2 problems here, possibly related.  The fuel pump runs off crankcase pressure by way of a hose.  If the diaphragm has failed, it can cause inefficient fuel pumping and, dump fuel right into the case.  The thinned out fuel eventually fills the breather housing ans geysers out the tube.

 

Oil pressure wont cause this, oil pressure is the resistance of the oil to be pushed through the bearing surfaces, you could have 80psi and not cause this.

 

I like the pulse style pumps myself, you can usually rebuild them or replace them entirely.  Its fairly straightforward to pull the pump, 2 screws and pull the flywheel screen..reach through the fan with hemostats if need be to push the line onto the pump if its not wanting to go back on from behind.

I think you are right on this one. Not saying it doesnt have other issues as well considering its about as old as I am lol. But the fuel pump certainly seems to be weak at best. It takes a while to start, and the level in the clear fuel filter is really low even when running for a few mins. However I remember that never was a problem, it used to always be completely full of gas.

[mclaugh417 0]

21 hours ago, lynnmor said:

Good call on that.  It would be a pain to get to the oil pressure sending unit to connect a meter but it might be worth it.

Im hoping its not that. Going to try the easier solutions first lol. But im not surprised its hard to get at, seems like most things are difficult to get to on this machine. 

[Ed Kennell 40,613]

2 minutes ago, mclaugh417 said:

Just went into the garage. I wouldnt say it was really over full but it certainly smelt like gasoline.

Do not start it.  The fuel pump is leaking fuel into the crankcase.   Replace the pump, or remove it and add an electric pump and change the oil before starting.  If you do install an electric pump, plug the vacuum line to the old pump.

[mclaugh417 0]

On 5/3/2025 at 7:15 AM, 953 nut said:

All of the above are good suggestions. Since it ran well for about five minutes the other question to be answered is,  was there any whit smoke coming from the exhaust pipe indicating oil being burnt? If piston rings were stuck this would allow oil to become ignited in the cylinder along with some blow-by pressurizing the engine's crank case. The breather tube allows crankcase gasses to be burned while the engine runs rather than being vented to the atmosphere.

If you have not changed the oil I would suggest replacing the old oil and including a pint of Marvel Mystery Oil.

The service manual below should be helpful, it is a free download.

 

Thanks for the link! Im sure fresh oil and marvel will help. Believe Im going to replace fuel pump, change oil/filter and give it some marvel mystery oil (or something like it) and give it a go!

[mclaugh417 0]

2 minutes ago, Ed Kennell said:

Do not start it.  The fuel pump is leaking fuel into the crankcase.   Replace the pump, or remove it and add an electric pump and change the oil before starting.  If you do install an electric pump, plug the vacuum line to the old pump.

10-4. Plug it, like put a cap on the line? Also do you have a preference on either replacing the pump, or just getting rid of it and going electric? I know I can find aftermarket vacuum pumps pretty easy, but who knows how good they are. Granted, I guess anything is better than what I got going on right now.

[Ed Kennell 40,613]

Yes. plug the line.  I replace all my failing pumps with electric for two reasons.    

1. It eliminates the chance of fuel leaking into the crankcase.

2. It eliminates the slow starting problem caused by the pumps losing prime on the tractors with the low mounted tanks under the seat.

[John2189 507]

30 minutes ago, Ed Kennell said:

Yes. plug the line.  I replace all my failing pumps with electric for two reasons.    

1. It eliminates the chance of fuel leaking into the crankcase.

2. It eliminates the slow starting problem caused by the pumps losing prime on the tractors with the low mounted tanks under the seat.

What electric pumps do you use?

[pfrederi 18,364]

Facet Posi Flo  made in Elmira NY not China  get the 1-4 psi version

[Ed Kennell 40,613]

1 hour ago, pfrederi said:

Facet Posi Flo  made in Elmira NY not China  get the 1-4 psi version

for a long lasting pump.    The $10 CCP pumps are a 50/50 gamble.

 

   One caution on the e-pumps.....mount them below the tank so they are always full of fuel.    Do not let them run dry...they will die.

Edited 11 hours ago by Ed Kennell