518H - carburetor Welch plug missing

[TC10284 109]

I've got a 518H with P218g. I don't have the tractor model number on me right now but can get it tomorrow.

 

I have to keep the choke closed about 75% for it to run stable. I'm sure the carb needs soaking (as well as valves adjusted while I do this), but before I go to the trouble of taking it off, I noticed the Welch plug is missing on the hole right over the adjustment screw with the plastic cap. 

 

With this plug missing, can it cause extra air into the carb requiring it to be choked so much? 

 

If so, where can I get a replacement? Can it be installed without taking off the carb/intake? 

Edited February 16, 2019 by TC10284

[lynnmor 6,770]

That happens often enough, and yes the engine will run poorly as you described.  Try a good auto parts store for a plug, I think it is a 3/8".  Some of the cheap carb kits included the welch plug but that seems to no longer be the case.  You might be able to replace without pulling the carb, but this might be a good opportunity to pull and check the intake split for leaks, properly clean the carb, set the float level, adjust the valves and paint the muffler.  When you install the plug, it doesn't take much on a tap with a punch and hammer to make it seat, too much force will buckle it in too far.  I like to use just a very small amount of fuel proof sealant on the edges before installing it.

[TC10284 109]

Something like this? 

https://shop.advanceautoparts.com/p/dorman-autograde-steel-cup-expansion-plug-3-8-in-height-0150-sold-by-each-555-115/22140482-P

 

EDIT:

Actually, I called about those and they can't get them even though they're on their site. 

 

EDIT 2:

https://smile.amazon.com/gp/product/B001C0F7QE/ref=ox_sc_act_title_2?smid=A10FHQ3X5ZKJY8&psc=1

 

 

Edited February 16, 2019 by TC10284

[lynnmor 6,770]

Those plugs appear to be a cup shape rather than like a dinner plate.  The hole to be plugged is probably too shallow for this type.  Check with NAPA at the counter for local purchase.  I didn't take a measurement for you just yet, so 3/8" is only my best guess, I can measure tomorrow, or you might be able to verify hole size.  I think this is what you want: https://www.carburetor-parts.com/Aluminum-Expansion-Plug-38_p_2319.html

[lynnmor 6,770]

I checked the welch plug size and it is indeed 3/8".

[bc.gold 3,399]

You can purchase the welsh plug from Brian Miller at http://gardentractorpullingtips.com/carbfuel.htm

 

[TC10284 109]

Here's what came. Will it not work?

 

https://imgtc.com/a/amrx4PG

[cleat 4,952]

I bought a cheap carb rebuild kit off of ebay.

It came with a new welch plug.

 

Can't tell you if it is right or not as I have not used the kit yet.

 

Cleat

[TC10284 109]

Update:

I ordered one of the carb rebuild kits off eBay a few weeks ago. Let the carb soak in cleaner overnight. Put back together. Put the missing welch plug back in and sealed with some high temp glue. Starts up and idles now.

 

Issue I'm having now is that I can open the throttle (slowly) to around 80-85%. Any higher and it acts like it's not getting enough fuel, or maybe too much air. I haven't tried keeping the choke closed a little to see if that helps. It gets sputtery and poppy...acts like it does when an Onan P2xxG backfires (which so far is a rare occurrence in my experience). Have the idle mixture screw set to 1 and 1/4 turns as the manual specified, but have tried everywhere from 1 turn to 2 turns. Guessing this won't help anyway since it's the "idle mixture screw". 

 

Additional info: It did smell like it had some bad gas in it. It was more yellowish in the filter at the carb, and air coming from valve exhaust smelled like old stale gas. I topped off the tank with fresh gas (over a gallon) and a new filter and let it idle for maybe 20min. But still can't open it all the way up. I know someone will probably tell me to drain the tank and put in fresh, but I really don't think that's the problem at this point. When I left it, the filter looked like it had fresher, clearer gas in the bulb. 

 

Any ideas on this? 

 

It's also not charging, but I will be testing that with some guides from here after I can get the thing to throttle all the way up...  

[TC10284 109]

One more thought on this. If the welch plug is installed a little "cock-eyed", meaning, one side a bit higher than the other, would that cause the full throttle problem? 

It was tough getting that welch plug into the hole and after it was in, I left it at that, as further hits seemed to only bend the plug out of shape. 

[lynnmor 6,770]

I guess it is possible to distort the welch plug enough that it interferes with gas flow inside, but I think that is unlikely.   If you used an excessive amount of cement on the plug, maybe that plugged things as well.  I think that you either missed some debris inside the carb or more junk was pushed in soon after the engine was started.  I flush all passages with a spray can of carb cleaner by using the straw on the can.  Old gas and old fuel hoses need to be replaced.

 

A weak battery and no charging will cause a weak spark.  Higher speeds and heavy loads require more spark energy.  Try running it with the battery charger in place.

[TC10284 109]

On 3/18/2019 at 3:16 AM, lynnmor said:

I guess it is possible to distort the welch plug enough that it interferes with gas flow inside, but I think that is unlikely.   If you used an excessive amount of cement on the plug, maybe that plugged things as well.  I think that you either missed some debris inside the carb or more junk was pushed in soon after the engine was started.  I flush all passages with a spray can of carb cleaner by using the straw on the can.  Old gas and old fuel hoses need to be replaced.

 

A weak battery and no charging will cause a weak spark.  Higher speeds and heavy loads require more spark energy.  Try running it with the battery charger in place.

 

Update on this. 

I went out to work on it again and a fuse was blown. Replaced fuse and still no start. Replaced the ignition switch with a new one and it finally turned over and started up. 

 

Connected up a battery booster, opened throttle and same deal. I've also noticed that it will governor hunt around 25 to 50% throttle. 

 

So, closed the choke about 40-50% and I was able to open the throttle just about all the way. No hunting either. I didn't try all the way. Didn't want it to backfire really bad, if it did. 

 

Havent tried draining the gas yet. Thinking i'll do that and have the carb cleaned again. 

What about the float? 

 

Also tested the regulator rectifier and saw that it wasn't working properly. I replaced it and now it is charging properly. 

[lynnmor 6,770]

20 minutes ago, TC10284 said:

 

Havent tried draining the gas yet. Thinking i'll do that and have the carb cleaned again. 

What about the float?

 

Since the choke test improved performance, the float is likely OK.

 

I really think that the carb has debris in it.

 

Did you remove the intake, inspect it carefully for leaks and re-install using OEM gaskets?  I have had cheap gaskets quickly turn to mush. 

[TC10284 109]

19 minutes ago, lynnmor said:

 

Since the choke test improved performance, the float is likely OK.

 

I really think that the carb has debris in it.

 

Did you remove the intake, inspect it carefully for leaks and re-install using OEM gaskets?  I have had cheap gaskets quickly turn to mush. 

 

When I removed the intake/exhaust to adjust the valves, the intake and exhaust both got a new set of Onan/Cummins gaskets, yes. 

 

I have not tried the WD40 spray test yet, but I will now. 

Edited March 20, 2019 by TC10284

[TC10284 109]

On 3/19/2019 at 9:11 PM, TC10284 said:

I have not tried the WD40 spray test yet, but I will now. 

 

The WD40 spray test did not yield any noticeable results. I sprayed everything that looked like an opening on the carb (aside from the top of course), the whole intake including gasket area, and the valve covers around gaskets. 

 

Drained all gas. Put in fresh 93 a day old from the pump. No change. 

Still, choke at 50% improves and allows me to open to full throttle. 

So I pulled off the carb again and will retry cleaning, and probably a little more hitting on the welch plug to get it less "cock-eyed". May order one of the cheap no-name ones from eBay as well. 

Edited March 23, 2019 by TC10284

[TC10284 109]

The cheapo replacement carb I ordered from eBay fixed the problem. I'm still going to take apart the original carb and let it soak for a few days, then reassemble. 

 

Now all that's left is:

Fixing the drifting throttle cable

Fixing the troublesome light switch (same problem on pretty much any other 520H I own has)

Fuel gauge drops from half to E when I turn on the switch, then goes back to half when I turn off. 

Edited April 4, 2019 by TC10284

[cleat 4,952]

Please let us know exactly how the engine runs with this carb.

 

I would like to know how smooth, powerful, quick starting, smooth idle etc the engine has with this carb.

 

Years ago I put a cheap carb on a 16HP Kohler and it started great, idled great, revved up great, but had less power.

 

I fixed up the original carb and my power came back.

 

If your works properly, that might fix a lot of problems for a lot of people.

 

Cleat 

[TC10284 109]

3 hours ago, cleat said:

Please let us know exactly how the engine runs with this carb.

 

I would like to know how smooth, powerful, quick starting, smooth idle etc the engine has with this carb.

 

Years ago I put a cheap carb on a 16HP Kohler and it started great, idled great, revved up great, but had less power.

 

I fixed up the original carb and my power came back.

 

If your works properly, that might fix a lot of problems for a lot of people.

 

Cleat 

 

I'll try to get a deck on it ASAP and let you know how performance is. I don't have a "before" to compare to though, since I am fixing it up after buying it running very poorly. 
I can say that, comparing to my 520's and 416's, at full throttle, it sounds just as mean as the rest. 

 

As far as how smooth and smooth idle:
It does not sputter at all at idle, or revving up or back down. It's pretty equivalent to my other Onan Wheel Horses. Keep in mind I have NOT changed the spark plugs yet. I'll be checking those soon. 

 

Starting up cold takes maybe four seconds or less? I haven't really paid attention to that. 

[TC10284 109]

It did backfire on me once mildly yesterday when I throttled down rather quickly after pulling a trailer for a truck through the yard to move it. 

Other than that, working OK so far. 

[cleat 4,952]

One of my 520's would do that sometimes.

Turned out to be a rust hole in the muffler allowing air in I guess.

 

Welded that up and all was good.

 

Cleat