520h "surging?"

[ericj 1,578]

for about $ 20.00 you can buy the new parts above and replace them. I replace them most of the time when I get a new to me tractor. especially if it was a non runner.

 

 

 

 

eric j

[Walhonding520 25]

So the rubber seal on the tank shutoff valve was torn and around the bottom of the screen in the tank. Also, the screen was folded and pinched at the bottom. Am I correct in assuming that this would cause my symptoms? Also, where is best place to buy a new valve and rubber seal?

[WVHillbilly520H 10,374]

1 hour ago, Walhonding520 said:

So the rubber seal on the tank shutoff valve was torn and around the bottom of the screen in the tank. Also, the screen was folded and pinched at the bottom. Am I correct in assuming that this would cause my symptoms? Also, where is best place to buy a new valve and rubber seal?

I'm sure it didn't help with the surging and replacing it after 20+ years should just be part of preventive maintenance, the one I pictured above is on eBay under WH fuel shut off valve, Jeff.

[Walhonding520 25]

That helped nothing. Surging is actually worse now and I'm running out of options. I might just have to take it to someone with more ability then me.thanks to all who responded at gave suggestions 

[daveoman1966 3,762]

Is the INTAKE MANIFOLD leaking at gaskets ? ? ? ?

[WVHillbilly520H 10,374]

One more little diagnostics tip with it running (warmed up preferred) spray some carb cleaner around the base of the carb and intake manifold, if the rpms speed up then you have carb to manifold gasket ,manifold gasket head leak or worse the 2 piece manifold seal has let go, if the rpms don't speed then not any of the above apply and it only cost you a little more time and a little more carb cleaner, Jeff.

[WVHillbilly520H 10,374]

BTW my Anniversary 520H did this even removing the carb top multiple times for cleaning and changing filter and fuel line to carb, until I removed it completely tore it down and soaked the main body and related metal parts in a can of "Gunk" carb cleaner (Walmart/Advance Auto ect) for a day or two then used compressed air and a can spray carb cleaner through the every orfice I could find/see and installing a new carb and accelerator pump kit before putting it all back together, solved mine but...Jeff.

[Walhonding520 25]

I guess I'll try taking it apart and cleaning it one more time. I haven't seen any leaking around the intake. For a while it was running much better so I guess it just plugged up again and needs another cleaning.

I did take the fuel pump apart and it seems clean. Back together and there is plenty of fuel running through the fuel filter.

[SadieCoonhound 8]

On 7/23/2017 at 8:50 AM, lynnmor said:

Look at the last photo above.  Down near the bottom of the carb you will see a welch plug, make sure it is still there.  I have had one fall out and it gave the same symptoms you described.

 

As always, check the compression first thing.

 

It may be a good idea to just pull the exhaust, intake, carb, and valve covers and do it right.  The exhaust can then be painted, the valves adjusted, the intake checked for sealing and the carb cleaned thoroughly.  Intake gaskets, especially cheap ones, can get sucked in causing similar problems, so use real Onan gaskets there.

The only thing that seemed to cure the surging on my 520h was doing what lynnmor is suggesting. Take the carb completely off the engine, take it apart and soak it overnight, etc. 

[WVHillbilly520H 10,374]

7 hours ago, Walhonding520 said:

I guess I'll try taking it apart and cleaning it one more time. I haven't seen any leaking around the intake. For a while it was running much better so I guess it just plugged up again and needs another cleaning.

I did take the fuel pump apart and it seems clean. Back together and there is plenty of fuel running through the fuel filter.

Those Onan fuel pumps aren't rebuildable and the OE aren't cheap, I get them off eBay 2/$20 cheap insurance when it finally won't pump anymore usually from a pin hole in the diaphragm, Jeff.

[Walhonding520 25]

Thanks. I think I'll get it soaking tonight. I have been doing some searching for a cheaper option of fuel pump. I found a Briggs option but will buy what you have there hillbilly. Will most pumps of that size work anyway?

[WVHillbilly520H 10,374]

35 minutes ago, Walhonding520 said:

Thanks. I think I'll get it soaking tonight. I have been doing some searching for a cheaper option of fuel pump. I found a Briggs option but will buy what you have there hillbilly. Will most pumps of that size work anyway?

Yes, I had one of those "round" Briggs style pumps on mine for quite sometime because I couldn't bring myself to pay $80+ for the OE Onan, then found those and have been pleased so far, Jeff.

[cleat 6,732]

I am using the same ones.

They actually seem to have better check valves than the original one.

 

Just watch and be careful when removing a fuel line from it as they are very brittle and break easily.

 

Cleat

[Walhonding520 25]

Ok. While running sprayed carb cleaner around one of the seals on what I think is the intake manifold. It stops surging for a second then starts again. Repeat and it stops for a second and starts again. There is seems to be air blowing out as well when I spray cleaner. Is this the bad seal referenced above. Form what you said above this doesn't seem like a simple or cheap thing? It's in the front cylinder.

[lynnmor 7,390]

See my post on 7/23/17, and quit swimming upstream.

[Walhonding520 25]

Thanks. You sound like my wife. Sometimes I get fixed on one thing lol. I see you recommend Onan gaskets. Best place to get them?

[ericj 1,578]

2 hours ago, Walhonding520 said:

Thanks. You sound like my wife. Sometimes I get fixed on one thing lol. I see you recommend Onan gaskets. Best place to get them?

onanparts.com

 

 

 

 

eric j

[Searcher60 209]

You could have disconnected the plug wires, removed the fuel hose from the carb and stick it in an empty water bottle. Crank engine and see if bottle fills with gas. Surging on a 520 is usually running lean. Something clogged in carb. Not always. 

Edited August 21, 2017 by Searcher60

[Walhonding520 25]

Just ordered intake gaskets. Hope to have repair complete next week when they arrive. Replacing fuel pump too just because.

[Walhonding520 25]

Intake and exhaust gaskets replaced. One was bad. Still surging. Carb has been soaked. Would the top gasket on the carb be bad right above the choke? Could this be a cause?

[WVHillbilly520H 10,374]

See my post #32 above carb kit from Onan parts.com ,if you're soaking the carb it needs a kit and maybe the accelerator pump replaced as well, but also with what I said earlier use the carb spray to help narrow down diagnose vacuum/gasket leaks, I believe the accelerator pump was only on 94/95 and newer models.

[Walhonding520 25]

I have noticed it doesn't surge if I have been mowing for an hour. I'm assuming that heat has caused something to expand and seal wherever the leak is. Does this sound right?

[cleat 6,732]

1 hour ago, WVHillbilly520H said:

See my post #32 above carb kit from Onan parts.com ,if you're soaking the carb it needs a kit and maybe the accelerator pump replaced as well, but also with what I said earlier use the carb spray to help narrow down diagnose vacuum/gasket leaks, I believe the accelerator pump was only on 94/95 and newer models.

Never seen one on any of mine.

 

[Searcher60 209]

If you pull the choke out slightly does the surging stop? Can you find a sweet spot with the choke where the surging stops? Maybe you got a governor issue?

[WVHillbilly520H 10,374]

8 hours ago, cleat said:

Never seen one on any of mine.

 

96 and newer then my Anniversary is actually by serial number a 97 but it definitely has the accelerator pump