Onan P220 surging/hunting at operate

[WheelHorse520H 708]

1 minute ago, Handy Don said:

On my tractor, the filter does not completely fill, more like ⅓ or ½ way. But I do see fuel sloshing around in there and steady squirts from the pump.

Sorry, I used to see a bubble on the top, probably closer to 2/3 full of gas. I should have been more specific.

[Horse Newbie 7,075]

28 minutes ago, Handy Don said:

On my tractor, the filter does not completely fill, more like ⅓ or ½ way. But I do see fuel sloshing around in there and steady squirts from the pump.

This is what I've noticed on my 1994 520H also...

When I first replaced fuel pet cock/ shut off valve at tank, new fuel line, new pump, new filter, the filter would only fill like 1/8 to 1/4, but the tractor runs fine. 

After a few runs, I noticed the filter had filled to about 3/4 ways full...

I think it varies now, but since it's running good I aint messing with it.

[WheelHorse520H 708]

5 minutes ago, Horse Newbie said:

This is what I've noticed on my 1994 520H also...

When I first replaced fuel pet cock/ shut off valve at tank, new fuel line, new pump, new filter, the filter would only fill like 1/8 to 1/4, but the tractor runs fine. 

After a few runs, I noticed the filter had filled to about 3/4 ways full...

I think it varies now, but since it's running good I aint messing with it.

I recently put a new line and pump in but the filter still had more gas before I did this surging cleaning than it does now. It’s strange.

[lynnmor 7,308]

2 hours ago, Handy Don said:

On my tractor, the filter does not completely fill, more like ⅓ or ½ way. But I do see fuel sloshing around in there and steady squirts from the pump.

It is strange how that happens but all of mine has air in the filter all of the time.

[Horse Newbie 7,075]

24 minutes ago, lynnmor said:

It is strange how that happens but all of mine has air in the filter all of the time.

Yes...mine ALWAYS has air in it too.

Edited August 23, 2021 by Horse Newbie

[WheelHorse520H 708]

I think the fuel line is clogged, so tomorrow morning I am going to disconnect both ends of the line and (drain it of course) blow it out with compressed air.

19 minutes ago, lynnmor said:

It is strange how that happens but all of mine has air in the filter all of the time.

It is, I filled the filter and line between the pump and filter just to make sure I had gas and it drained back down to a teensy weensy bit of fuel on the bottom. I also tried a spare fuel pump I had yesterday and it worked no better than the one that was there before it. So I put the other back on because it actually bolted to the engine.

[WheelHorse520H 708]

So I am really confused now. I get the engine to run good and now I have the correct amount of fuel in the filter but the engine just doesn’t run smooth. I keep adjusting the carb, I have good fuel flow and fresh gas, I took the top of the carb and cleaned it. I took the spark plugs out and cleaned them because they got dirty from my less than perfect tuning skills. It starts right up and stumbles and coughs and then comes back and runs at a very low rpm. I don’t know exactly what the range is because the tachometer is broken. I just can’t get it to run properly. Sorry for the short video, it’s all I could upload.

Edited August 25, 2021 by WheelHorse520H

[lynnmor 7,308]

How did you set up the carburetor without a tachometer?

 

Is the gray wire connected to one of the outside terminals of the voltage regulator?

 

What is the voltage on the voltmeter before you run the starter?

 

With the voltmeter jumping so much, I wonder if there are bad connections.

 

Have you checked the compression?

 

 

[WheelHorse520H 708]

1 minute ago, lynnmor said:

 

How did you set up the carburetor without a tachometer?

 

That’s what I think the problem is, I listened and hoped it was close, but I know in the video the idle speed seems wicked low to me.

 

2 minutes ago, lynnmor said:

Is the gray wire connected to one of the outside terminals of the voltage regulator?

Yes, it either reads 2000 rpm or none, it occasionally freezes somewhere between.

 

3 minutes ago, lynnmor said:

What is the voltage on the voltmeter before you run the starter?

About 12 volts.

 

4 minutes ago, lynnmor said:

With the voltmeter jumping so much, I wonder if there are bad connections.

 

If you look, the vacuum gauge does the same. With the air filter off I was able to get the voltmeter steady. And I had it that way a couple times today.

 

5 minutes ago, lynnmor said:

Have you checked the compression?

No, I do not have a compression tester. What do you recommend?

[lynnmor 7,308]

 

Any cheap compression tester from AutoZone, Advance Autoparts or Harbor Freight will be good enough.

Edited August 25, 2021 by lynnmor

[Tuneup 1,433]

Watch out with that HF compression gauge. It's likely not true of them all but with Chinese QA you never know. Mine read 40% low. Almost cost me a rebuild of a very nice Honda 550. "Crap, how can that compression be 100 psi?!" Fortunately, I had my doubts. It's a nice kit otherwise.

[WheelHorse520H 708]

Went to Autozone this morning and got a compression tester. On the rear cylinder the battery was just starting to go weak. With all the starting and dying over the last year, the battery is in need of replacement but funds for that are not available right now. Anyway, the front was about 118 psi and the rear about 103 psi. I am also going to test it again after the battery charges again. I also noticed when I took the spark plugs out the front was wet but the rear was dry.

Edited August 25, 2021 by WheelHorse520H

[WheelHorse520H 708]

After the battery charged the rear was 105 psi and the front 115 psi. Not much of a difference between the two cylinders.

[lynnmor 7,308]

3 hours ago, WheelHorse520H said:

After the battery charged the rear was 105 psi and the front 115 psi. Not much of a difference between the two cylinders.

The engine may be sound then.  A compression test can miss a loose valve seat so you can't be 100% sure, but we now know that it is worth the time to proceed with other troubleshooting.  I would start by finding a reason for the voltmeter dancing around, perhaps you have intermittent power to the ignition.

[WheelHorse520H 708]

5 minutes ago, lynnmor said:

intermittent power to the ignition.

Shooting in the dark here but could I put a test light on the + side of the ignition coil and (grounding the other side of course) see if there is intermittent power. Also today before I did the compression test the directions said to warm it up but it would not run long enough. Then it just wouldn’t start. Now that I think about it this could be the intermittent ignition power you mentioned.

[lynnmor 7,308]

I'm talking about the voltmeter dancing like crazy in your short video.  Using a bulb like you suggested may be helpful, but an incandescent lamp may not react fast enough to flicker.  Running a jumper from the battery + to the coil + would give a solid source of voltage, just don't leave it on for an extended period of time.  Get ready, connect, then start.

 

No worries on the engine warmup for compression testing, we weren't looking for the last couple of pounds.

[WheelHorse520H 708]

11 minutes ago, lynnmor said:

Running a jumper from the battery + to the coil + would give a solid source of voltage, just don't leave it on for an extended period of time.

I’ll try it tomorrow. I thought about doing that but I forgot exactly how to do it.

 

12 minutes ago, lynnmor said:

No worries on the engine warmup for compression testing, we weren't looking for the last couple of pounds.

I figured it was close enough.

[WheelHorse520H 708]

I put the jumper on and it ran the same so I put on the original coil that I took off a while back thinking it was bad (spoiler alert: it wasn’t) that was before I got my RS account. It ran good with the original coil nice and steady, just to be clear this was still with the jumper from battery + to coil +, so good I turned the key to off and it still ran because of the jumper, so I choked it out. I took the jumper off and it started great. There was no hesitation, and then it ran poorly again. I have a hunch on the PTO switch not being totally secure because I couldn’t get it tight when I put a new switch in. Isn’t other ideas are greatly appreciated.

Andrew

[Handy Don 12,235]

53 minutes ago, WheelHorse520H said:

PTO switch not being totally secure

The PTO switch is possible, but so is the ignition switch itself or a bad connection, etc.

Right now you've changed from completely bypassing the ignition circuit to including all of the circuit. Personally, I'd start by examining the wiring diagram and then shifting the jumper to different places so it gradually includes more and more of the ignition circuit. At some point, it would start to do the "running poorly" thing again and I would know where the problem lies--the part of the circuit that I just added!

[WheelHorse520H 708]

56 minutes ago, Handy Don said:

The PTO switch is possible, but so is the ignition switch itself or a bad connection, etc.

Right now you've changed from completely bypassing the ignition circuit to including all of the circuit. Personally, I'd start by examining the wiring diagram and then shifting the jumper to different places so it gradually includes more and more of the ignition circuit. At some point, it would start to do the "running poorly" thing again and I would know where the problem lies--the part of the circuit that I just added!

That’s a good idea, glad I checked here first. Thanks.

[WheelHorse520H 708]

Sorry forgot to mention this, I think the issues are unrelated to the rebuild so I created a different Thread for that. Thank you all for the help with this.