Forum for air cooled diesel engines and clones

[jakemaxwell806]

Ah, OK - I think if you look at the last video I posted, you can see the "throttle / governor" bouncing, and hear the engine smooth out a bit if I hold it ~1/2 throttle. This would be the same motion I believe, right?

I watched the video try turning that screw in some until it smooths out like you was holding it that screw is your rpm limiter it could possibly be turning a few more rpms then it should be getting valve float the valve springs are weak in these engines 4000 is all I can turn my engine with out it starting to do that flutter with pulling I let it get under load then open on up some more to deliver note fuel

 

[xp190]

Looks and sounds like the issue I am having, flames shooting out of the exhaust causing everything to cook, as well as the rough running.
From what I found on mine, and what 90 said, it sounds like an electrical issue brought on by something else.
Either the oil filter is plugging up causing the low oil shutoff to kick on and off, or as I suspect in my case, the wiring to the fuel pump solenoid came loose resulting in a bad bouncy connection when the engine vibrates having the same effect. At least I hope that's all it is, once I put mine back together I will know for sure now that I know internally everything is fine.

90 question for you, you said to soak the piston in purple power to get the carbon off, I have an Canadian equivalent of purple power here called Zep Purple, it says it's bad for aluminum, I'm using Zep 550 formula instead which is supposed to be safe for aluminum, I will see how well it works in a few days.

xp

 

[OldRedTractors]

OldRedTractors


I read your previous posts and you mentioned you hadn't pulled the filter yet, that should be next step to determine if anything is going on inside.
My first silent generator looked exactly like yours but with a different name.
I was letting a friend use it during a huge ice storm several years ago when it failed at 40 hours or so. It kept shutting down due to low oil pressure and was skipping & popping like yours.
The problem was a failed cam bearing which plugged the filter causing the shut down.
I also repaired a Yanmar L70 mil surplus that had the same symptoms and that issue was corrosion on the injector lobe that caused the hardened cam surface to flake off which changed the injection event at full speed. The cause of this was wet stacking then prolonged sitting allowing moisture to corrode the cam.
Your symptoms are similar but you say the injector lobe is perfect. Did you rotate the engine to look at the entire cam?
If the cam is good and the filter is good I would look at the injection pump, possibly a restriction in the inlet of the pump.
The pump can be disassembled quite easily for inspection.
Prepare a clean area and remove the spring retainer and carefully remove plunger.
The fit is extremely precise so care in removing and reinstalling it must be exercised as it can get stuck, do not force!! Use Finesse!
There should be no surface defects.
Care in handling is essential as moisture on your hands can cause corrosion so handle carefully and use diesel to clean & lube during reassembly.
One other thing to look at are the valves, check valve clearance if ok turn engine over to TDC so valve won't fall into engine and and remove the valve springs to so you can check for a worn guide, very unlikely!
That's all I can think of for now.
90cummins

Thanks 90cummins! Here is what I've done today:

- pulled the oil filter, and it's fine. A few very tiny flakes visible after cleaning it, perhaps 5 to 10, but nothing I wouldn't expect from an engine with only 60 hours on it and one oil change after initial break-in, perhaps 50+ hours ago. Certainly not plugged nor anything alarming

- Yes, I looked at the fuel pump cam, turned the engine over, and it looked fine all the way around best I could see.

- I pulled the pump and disassembled - easy once I came up with a way to compress the spring Nothing to see there as far as I could tell. Everything looked brand-new, smooth, no wear marks or scoring, everything clean, and no obstructions in the feed to the plunger. The pump plunger can be reinstalled 180 off, which would make it not function, so thankfully I paid attention to that in reassembling it. Clever and simple mechanism actually... but nothing obviously wrong.

Next step is to pull the valve cover and see what's going on with the valves. Hard to believe anything seriously wrong, given how easy it starts, but I'll look to see if the clearances are too tight or something.

I can't see the fuel cut-off being the cause of this, but I could try running 12v directly to the solenoid valve to be sure.

I'm tempted to just junk the whole thing and bite the bullet and buy a Kubota, but now it's personal!

 

[OldRedTractors]

I watched the video try turning that screw in some until it smooths out like you was holding it that screw is your rpm limiter it could possibly be turning a few more rpms then it should be getting valve float the valve springs are weak in these engines 4000 is all I can turn my engine with out it starting to do that flutter with pulling I let it get under load then open on up some more to deliver note fuel

Well, perhaps, but I didn't change that, and it previously was running the right speed for the generator output (3600), so I'm hesitant to mess with it. Also, it's not running up against the governor stop, but oscillating back and forth at less than full throttle.

 

[xp190]

Hey OldRed, if you have a chance, try the 12V straight to the fuel cut-off and let me know if it makes any difference, because if it doesn't, I gotta keep looking, I got a replacement genset already, but with this one it is personal for me as well. There has to be a real cause for the flamethrower effect.

xp

 

[90cummins]

ORT said; I can't see the fuel cut-off being the cause of this, but I could try running 12v directly to the solenoid valve to be sure.

That statement jogged my memory!!
On the silent diesel generator I repaired it had several problems.
One of the problems was skipping like yours (after) I installed new rings and cut new valve seats in it.
I found that the power to the injection pump was erratic. I traced to problem to the remote start black box which was sensitive to vibration and position.
That part was not available so I had to make one.
Took me quite some time to build a circuit using relays that allowed me to retain the low oil pressure shutdown system.
As I recall I had to install a momentary push switch that would allow it to start & run until oil pressure activated the run solenoid.
Running power directly to the solenoid would be my next move!!
90cummins

 

[xp190]

I have that black box for remote starting, I guess I will be trying this as well.

xp

 

[OldRedTractors]

ORT said; I can't see the fuel cut-off being the cause of this, but I could try running 12v directly to the solenoid valve to be sure.

That statement jogged my memory!!
On the silent diesel generator I repaired it had several problems.
One of the problems was skipping like yours (after) I installed new rings and cut new valve seats in it.
I found that the power to the injection pump was erratic. I traced to problem to the remote start black box which was sensitive to vibration and position.
That part was not available so I had to make one.
Took me quite some time to build a circuit using relays that allowed me to retain the low oil pressure shutdown system.
As I recall I had to install a momentary push switch that would allow it to start & run until oil pressure activated the run solenoid.
Running power directly to the solenoid would be my next move!!
90cummins

Thanks - I'll give that a try. Didn't have time today, and unfortunately it's now going to be a week or so before I can get to re-installing the pump and giving it a go with the jumper wire.

 

[xp190]

I think I fond the issue with my 186f.

I finished taking everything apart, I got the cylinder done, new rings, everything checked for specs, no real issues found, until I started putting everything back together and took out the oil pump.
The outer ring was all broken up into pieces, which, when I thought about it explained what was going on.
I have not tested this, but here is my theory, please let me know if it makes any sense.
The outer oil ring pump broke up into pieces, but not in every spot, it broke up into three pieces leaving one of the pump chambers intact and all the others leaking the oil out, this resulted in an uneven pressure build up. For every chamber that was hit which was cracked, the oil would escape, but for the one that stayed intact, the oil moved as expected. So what we have is a very inefficient oil pump.
What this resulted in, is the oil sending unit fluctuation on and off as the oil pressure fell and raised back up once per every revolution of the oil pump. The oil sending unit caused the fuel solenoid to kick out just as often, which then resulted in the engine initiating a shutdown, and then restarting at a fairly high frequency, this is why the engine was missing.
In order to bring up the rpm after one such initiated shutdown, the fuel pump would dump more fuel into the cylinder, so a very rich mixture, but since on the next revolution it was probably shutting down again, a lot of the unburnt fuel would make it into the exhaust where it would burn up later causing the flame thrower effect.

Pretty simple reason for the failure, I've never seen one of these oil pumps fail, but that is the only thing I found wrong with the whole thing.
I'm curious to see what you guys think.
I will post a picture of the broken up oil pump soon so you all get a better idea of what I'm talking about.
New oil pump is on order.

xp

 

[OldRedTractors]

xp,

Interesting find! I'd suspect that would impact the oil pressure overall for sure, but I don't know if it would cause it to pulse. Given the speed the pump turns, it's hard to imagine the pressure fluctuating or dropping low enough quickly enough to cause the switch to detect it - I just wouldn't think a mechanical switch would be that sensitive. I would think it would be lower overall, but relatively constant on average. And I'm not sure what would cause oil pressure to to drop with increased RPMs with a failed pump like that.

I suppose that if the pump was cavitating or sucking air at higher speed, that could cause a pressure drop for sure. When I get back I'll bypass the fuel cut-off on mine and see if it changes anything. Your explanation of the behavior does make sense, but perhaps it's more electrical than oil pressure related.

Feels like a Sherlock and Holmes case!