How to fix Blowby

[fa35jsf]

Fired up my generator and I’m using it to run my house right now, bad weather in the area.

I decided to pull the oil dipstick while it was running to check for blowby. I’ve always had some mild blowby but today it was very strong/ hot. I would definitely consider it severe blowby.

The generator is NOT smoking or getting bogged down. It started just fine and is running fine.

So is there an easy fix or does this require a full engine tear down? I’ve heard pull the injectors and put an ounce of something called magic oil in each cylinder and then let it sit for a few days.


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[jamawieb]

As long as its performing well dont worry with it. Just try to load it down more and see what happens.

 

[NDT]

Could be excessive moisture in crankcase steaming out. Change oil before condemning engine.

 

[fa35jsf]

As long as its performing well dont worry with it. Just try to load it down more and see what happens.

Are you sure? I’m talking like blowing strong!


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[fa35jsf]

Could be excessive moisture in crankcase steaming out. Change oil before condemning engine.

I didn’t think about that. I only run this generator a handful of times a year and usually only for 30-45 minutes. Never really load it down.


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[fa35jsf]

I should probably mention that the unit seems to vibrate a little more and maybe sounds a little louder than when I first got it. I know that’s not exact quantifiable unit of measure but it’s the best I got.


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[Chainbreaker]

Which model MEP generator?

Also are you talking about Marvel Mystery oil when you are referring to "magic oil? Oil in cylinders left to sit is usually used in an attempt to free a stuck ring(s). If you have reason to believe it has a stuck ring(s) that might help.

I would do as suggested and run it for an hour or two at ~75-100% rated load and see if it improves. Regarding vibration and louder sound... if you sense any unusual vibration or knocking noise while load testing I would shut it down to further troubleshoot the source.

 

[fa35jsf]

Which model MEP generator?

Also are you talking about Marvel Mystery oil when you are referring to "magic oil? Oil in cylinders left to sit is usually used in an attempt to free a stuck ring(s). If you have reason to believe it has a stuck ring(s) that might help.

I would do as suggested and run it for an hour or two at ~75-100% rated load and see if it improves. Regarding vibration and louder sound... if you sense any unusual vibration or knocking noise while load testing I would shut it down to further troubleshoot the source.

802a

And yes to marvel mystery oil. I guess it could help. Certainly couldn’t hurt.


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[Valley Rock]

How does the engine relieve itself of crankcase pressure normally, does it have a draft tube or a PCV system ?

Make sure that is working properly first .

Mud wasps build nests in draft tubes, pcv valves get stuck etc.

 

[fa35jsf]

How does the engine relieve itself of crankcase pressure normally, does it have a draft tube or a PCV system ?

Make sure that is working properly first .

Mud wasps build nests in draft tubes, pcv valves get stuck etc.

I’m not really sure. To be honest these engines are of such an old design they may not incorporate a pcv. It may just be a vent to the outside. Maybe someone who has more knowledge can help me with that one.


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[Zed254]

My 802 vibrates a good bit more than my 803. You can watch the oil cap chains jumping all around on the 802s GovPlanet runs.

 

[Bmxenbrett]

That is not blow by. Its just the crank splashing aroud in the oil. Its normal. Dont mess with a perfectly running set.

 

[Bmxenbrett]

My 802 vibrates a good bit more than my 803. You can watch the oil cap chains jumping all around on the 802s GovPlanet runs.

Thats normal also. Remove the chain.

 

[Triple Jim]

An 802 has two cylinders with pistons that go up and down together, correct? That causes a huge amount of crankcase pulsing. How about doing a compression test to see if you really have excessive ring leakage.

 

[Ray70]

Correct Jim, both pistons move in unison, so removing the oil filler cap will result in huge pulsations that could easily be confused as excess blow-by.
If you were loosing compression the motor would probably smoke for 30 seconds or more at start up. Load the machine up and if it performs correctly then you are fine.
As a side note, crankcase pressure is vented from the rocker arm covers into the intake runners through small tubes located in the corner of each rocker cover. ( where the small bump is ) the vent tubes may look like alignment pins for the rocker covers, but in fact they vent into the head's intake runners.

 

[Guyfang]

I’m not really sure. To be honest these engines are of such an old design they may not incorporate a pcv. It may just be a vent to the outside. Maybe someone who has more knowledge can help me with that one.


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Gentelmen, the MEP-802 and 803 are supposed to run with a crank case vacume. Not positive pressure.

 

[Guyfang]

An 802 has two cylinders with pistons that go up and down together, correct? That causes a huge amount of crankcase pulsing. How about doing a compression test to see if you really have excessive ring leakage.

I would suggest a crankcase vacume test also.

 

[devilphrog]

I would suggest a crankcase vacume test also.

Agreed with Guyfang's statement. A quick test is to pull the dipstick with the engine running and get a piece of paper (or plastic bag) and let it 'hover' over the dipstick tube. If it sucks down over the hole, all is well. If not, you have a ring sealing issue. I had a unit I bought from GP that ended up having stuck rings and my assumption is when they did the run test at the yard it cracked 2 of the pistons causing a blowby condition. But if it isn't smoking and is running fine, I wouldn't mess with it.

Maybe put some MMO in the cylinders to loosen things up when you aren't running it, but you'll know if it's bad enough insomuch that the unit will be incredibly hard to start (no compression) and will smoke at all times. Also, get an infrared thermometer (I think they are around $15-20 at Harbor Freight), and check your exhaust temperatures for a cold cylinder. It'll be pretty apparent if it's bad enough.

The unit that had the cracked pistons on still made electrical power, and smoked really badly and had enough blowby that that the dipstick would shoot out while running.

What are you doing to load the unit electrically? A load bank, old kitchen range, etc., and how many amps are you able to put on the unit during a load test?

 

[Triple Jim]

Agreed with Guyfang's statement. A quick test is to pull the dipstick with the engine running and get a piece of paper (or plastic bag) and let it 'hover' over the dipstick tube. If it sucks down over the hole, all is well. If not, you have a ring sealing issue.

I'm afraid that with a 2-cylinder engine that paper is going to flap wildly no matter what the condition of the engine is.

 

[fa35jsf]

Well no need for the crankcase check. If I pull the dipstick while running and hold my hand 6 inches away it will still be sprayed with a fine mist of oil.

It didn’t use to be this bad.

I don’t have a good way to load test right now. All I can do is plug it into the house and use an electric range but the wife hates resetting clocks when I swap power, plus I have to walk 200 feet from unit to range to make adjustments.

I will probably build a breakout box with a bunch of plugs that I can plug into the unit and connect some space heaters to. That would at least get me a way to load test at the unit.


Big question, if I were to pull the injectors in order to put MMO or compression test each cylinder, would I have to replace o-rings on the injectors?


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