Need some P220G experts... Got a tap/knock

[1990Onan520-H 15]

Hey all, need a little help. I pulled my 88 520 apart to adjust valves and decarbon because I heard a tapping when running and at 950 hours I figured it was due. It also started having to be choked to run and quickly got to the point where it would just totally die and almost not run. I cleaned the carb and that helped for a few days and then it all went down hill,  so I figured it needed intake gaskets. I only owned it a week or two before this happened so have no history on it.

 

When doing the work I noticed a knock or tap when moving the crank back and forth. Valves are removed and seats appear tight. So I dug further and pulled the pan because I figured maybe the rods were loose. The rods feel fine but I did notice the below "pin" is moving and when it hits what I would assume is some kind of thrust washer it taps. I see the same thing on the timing side and it doesn't move. The pto side is moving around. Does anyone know what this is and did I find my issue or is this normal?

 

 

[lynnmor 6,783]

The thrust bearing would have some play, I would be surprised that the noise you hear while running is coming from there. If you want to go deeper, the replacement main bearing may be one piece and eliminate the noise.

[1990Onan520-H 15]

I honestly don't care about the noise, but something sounds very loose and I'm worried it will let go and take out an otherwise very nicely maintained engine. Is the tapping I'm hearing normal? I can hear the tap tap more at tdc and bdc than when the piston is partway up the bore which made me think rod bearing. I also hear the tap tap on the rod ends connected to the crank, but also hear it on that thrust washer assuming that's what that is. How hard is it to check the main and would I really hear a tap tap like this with the engine off if the main had an issue? I wouldn't think I would. I pulled up on the crank and dont feel and major loosness nor does the thrust feel way off.

[lynnmor 6,783]

I can't tell if the noise is excessive, there will always be just a bit of play at TDC & BDC.  Try loading the piston and various parts by holding a wooden dowel against them, one at a time,  and rocking the crank as you did in the video.  If you believe that there is too much noise, it would be best to pop the pistons one at a time, perhaps you could could leave them in place at TDC and do the rocking.  Any chance that the noise is coming from the timing gears or governor?  Did you download the service manual?

[bc.gold 3,399]

Remove one plug wire while the engine is running, bad connecting rod keeps thumping bad wrist pin quietens down. Repeat for second cylinder.

[1990Onan520-H 15]

4 hours ago, lynnmor said:

I can't tell if the noise is excessive, there will always be just a bit of play at TDC & BDC.  Try loading the piston and various parts by holding a wooden dowel against them, one at a time,  and rocking the crank as you did in the video.  If you believe that there is too much noise, it would be best to pop the pistons one at a time, perhaps you could could leave them in place at TDC and do the rocking.  Any chance that the noise is coming from the timing gears or governor?  Did you download the service manual?

It very well could be from the timing set. Very hard to pin point. But I would think the noise being louder at tdc and bdc points to rods. It sounds like something is very loose. Could the timing set or governor resonate into the rods? It's very odd that the rods feel tight. It's almost as if the noise is coming from inside the crank and resonating into the crank rod ends and the thrust. Could mains cause this?

[lynnmor 6,783]

bcgold suggests that the wrist pins may be causing the noise and I agree that may be an issue.  Again, pushing against parts with a wooden dowel might reveal the bad part, for example; pushing against the piston while rocking the crank should dampen wrist pin noise.

[1990Onan520-H 15]

13 minutes ago, lynnmor said:

bcgold suggests that the wrist pins may be causing the noise and I agree that may be an issue.  Again, pushing against parts with a wooden dowel might reveal the bad part, for example; pushing against the piston while rocking the crank should dampen wrist pin noise.

I'll give that a shot but I don't hear the noise on the pistons, I hear it on the rod end on the crank and seems like thrust also. But I would think I would feel this by hand because it sounds loose and almost like it knocks around when I whip the flywheel back and forth. I hear a double tap sounds like.

[bc.gold 3,399]

On 1/11/2020 at 8:16 PM, 1990Onan520-H said:

I'll give that a shot but I don't hear the noise on the pistons, I hear it on the rod end on the crank and seems like thrust also. But I would think I would feel this by hand because it sounds loose and almost like it knocks around when I whip the flywheel back and forth. I hear a double tap sounds like.

 

 

Double tap.

 

 

[1990Onan520-H 15]

2 hours ago, bcgold said:

 

 

Double tap.

 

 

Are you saying that "double tap" I hear is possibly the main bearing?

[tom2p 2,393]

On 1/10/2020 at 9:19 PM, 1990Onan520-H said:

Hey all, need a little help. I pulled my 88 520 apart to adjust valves and decarbon because I heard a tapping when running and at 950 hours I figured it was due. It also started having to be choked to run and quickly got to the point where it would just totally die and almost not run. I cleaned the carb and that helped for a few days and then it all went down hill,  so I figured it needed intake gaskets. I only owned it a week or two before this happened so have no history on it.

 

When doing the work I noticed a knock or tap when moving the crank back and forth. Valves are removed and seats appear tight. So I dug further and pulled the pan because I figured maybe the rods were loose. The rods feel fine but I did notice the below "pin" is moving and when it hits what I would assume is some kind of thrust washer it taps. I see the same thing on the timing side and it doesn't move. The pto side is moving around. Does anyone know what this is and did I find my issue or is this normal?

 

 

 

hope I'm wrong - but appears there is an issue 

 

many engines make all sorts of noises and clatter - including P216 and P220 Onan - when they are running 

 

but this is a fairly significant noise at rest 

 

I don't believe that noise is typical - but I'm not familiar with Onan engines (other than using them)

 

Keep searching / inquiring until you can locate someone that has experience with these engines 

 

need an answer / explanation before the engine is run again 

 

[1990Onan520-H 15]

7 minutes ago, tom2p said:

 

hope I'm wrong - but appears there is an issue 

 

many engines make all sorts of noises and clatter - including P216 and P220 Onan - when they are running 

 

but this is a fairly significant noise at rest 

 

I don't believe that noise is typical - but I'm not familiar with Onan engines (other than using them)

 

Keep searching / inquiring until you can locate someone that has experience with these engines 

 

need an answer / explanation before the engine is run again 

 

 

I tend to agree. Something sounds way too loose for my liking. But could this actually be a main? I wouldn't think a main could knock like that at rest with a simple back and forth movement. I'm wondering if it's something in the timing set. I'm honestly about to throw it back together and just run it. I hate to just let it blow up, but I don't have enough knowledge about these engines and can't continue to spend the time on it.

[tom2p 2,393]

words of a previous boss :

 

 'hope is not a good strategy'

 

lol

 

 

unfortunately this was a strategy followed by NASA with the space shuttle program 

 

they hoped the solid booster o-rings would seal properly in low temps 

 

they hoped the broken pieces of foam observed during takeoff did not damage tiles / carbon carbon significantly 

recent boeing 737 max another example ... hoped the air speed sensor did not fail 

 

 

Edited January 18, 2020 by tom2p

[1990Onan520-H 15]

7 minutes ago, tom2p said:

words of a previous boss :

 

 'hope is not a good strategy'

 

lol

 

 

unfortunately this was a strategy followed by NASA with the space shuttle program 

 

they hoped the solid booster o-rings would seal properly in low temps 

 

they hoped the broken pieces of foam observed during takeoff did not damage tiles / carbon carbon significantly 

recent boeing 737 max another example ... hoped the air speed sensor did not fail 

 

 

Not much hope here. I know I'm throwing together a ticking time bomb that might send a rod past the NASA space shuttle after 5 minutes of running again. Lol. Maybe my OCD will get the best of me but only time will tell. Too cold to work on the engine at the moment anyway. Although sure would be nice to have my plow tractor back. Shoveling sucks!

[bc.gold 3,399]

2 hours ago, 1990Onan520-H said:

Are you saying that "double tap" I hear is possibly the main bearing?

 

Worn mains don't tap, just loss of oil pressure, mains are first to receive oil from the oil pump any loss at the mains starves the rest of the engine of lubrication.

 

The crankshaft has oil passages drilled to pass oil received from the main journals to the connecting rods.

 

Cut the oil filter open to see what metals have been captured in the paper.

 

Locate a copy of the shop manual for your engine, use manufacture specs

 

 

Edited January 18, 2020 by bcgold

[Greentored 3,201]

If you havent put it back together yet (or if you have) what does this sound like if youre not at TDC/BDC? Rods changing direction CAN make a little noise, albeit not as much as yours is making. 

Another area to look is the timing gears, they can knock as a valve 'noses over' a cam lobe and tries to rock the cam in the opposite direction. However, that would be void if you have the valves and springs out.

For you guys that have rolled a single cylinder engine over by hand, they make a lot of racket very similar to this, usually in the cam overlap phase. Not sure if a twin would be the same.

My P220G will make some noise when rolling over by hand and rocking back n forth, and REALLY bangs if I push the crank back n forth against the thrust washer.

OCD can be a real b***h sometimes haha.

[lynnmor 6,783]

Considering your concern and the time that has gone by dealing with this noise, it seems to me that the simple job of disassembly should have already taken place. 

[1990Onan520-H 15]

3 hours ago, lynnmor said:

Considering your concern and the time that has gone by dealing with this noise, it seems to me that the simple job of disassembly should have already taken place. 

The more I take apart the more this costs not only time but gaskets. I'll probably end up pulling the flywheel and timing cover too now because my OCD will get the best of me. Maybe there's a broken crank key or something. It's odd because those noise is quieter when the engine is sitting on the flywheel vs on the oil pan.

[1990Onan520-H 15]

Well I've narrowed down my knock. The whole timing set feels a little loose when engaging, but if I hold the cam gear one direction the noise is gone. This is pretty weird that steel gears would wear this much. Is this normal? They don't look all that worn out, but timing is going to be a few degrees off and I'm wondering if this is why it was stalling on me. Or is there something else that would be causing this?

[lynnmor 6,783]

Place the weight of the engine on the crankshaft end and repeat the test.  We are looking for main bearing wear.

[1990Onan520-H 15]

9 hours ago, lynnmor said:

Place the weight of the engine on the crankshaft end and repeat the test.  We are looking for main bearing wear.

You mean flip it down on the flywheel and rotate the block? The noise didn't seem to change when I did that. Could still hear it.

[lynnmor 6,783]

25 minutes ago, 1990Onan520-H said:

You mean flip it down on the flywheel and rotate the block? The noise didn't seem to change when I did that. Could still hear it.

Just put a block of wood under the crank end shown in your photo above.  With some of the weight of the engine on that wood, the crank will be pushed towards the cam and all main bearing clearance will be removed.  Now if there is still too much clearance in the gears, perhaps the cam bearings are the problem.  This is work best done by someone that can use a dial indicator and proper measuring tools, apparently you don't have the tools or knowledge to do this basic measuring.   Since we can't actually see the extent of the problem, it might be that everything is within a normal range, or maybe wear is too much.  The cam gears, and every mating part will need a bit of clearance and you might be expecting it to be near zero.

[1990Onan520-H 15]

9 minutes ago, lynnmor said:

Just put a block of wood under the crank end shown in your photo above.  With some of the weight of the engine on that wood, the crank will be pushed towards the cam and all main bearing clearance will be removed.  Now if there is still too much clearance in the gears, perhaps the cam bearings are the problem.  This is work best done by someone that can use a dial indicator and proper measuring tools, apparently you don't have the tools or knowledge to do this basic measuring.   Since we can't actually see the extent of the problem, it might be that everything is within a normal range, or maybe wear is too much.  The cam gears, and every mating part will need a bit of clearance and you might be expecting it to be near zero.

What basic measuring should I be doing?

[1990Onan520-H 15]

I put a block of wood under the crank and still have the tap. Maybe I am just not used to steel gear timing sets. I'm not used to an engine having this kind of a tap or knock but also never worked with a timing set like this before. I have a dial indicator so can check clerances.

Edited February 1, 2020 by 1990Onan520-H

[bc.gold 3,399]

37 minutes ago, 1990Onan520-H said:

I put a block of wood under the crank and still have the tap. Maybe I am just not used to steel gear timing sets. I'm not used to an engine having this kind of a tap or knock but also never worked with a timing set like this before. I have a dial indicator so can check clerances.

 

Worn timing gears would give a distinctive whining sound with the engine running,

 

What were the metal particle found in either the disassembled filter element or from the oil you drained from the engine, those metal particles have  story to tell.

 

When a wrist pin goes astray often the cir-clip falls out thus allowing the pin to float from side to side inside the cylinder, the image below is not of your engine type its facsimile showing damage.