Blowing Oil

chieffan

Tractorologist
Senior Member
Member
#1
Onan M43. Has been running good but fuel pump was week/bad. Would die once the tank got down to 1/3 tank or so. External impulse fuel pump with the line through the engine cover. Removed the pump and covered the hole with duct tape. Put an electric pump on. Mowed for about 10 min and it started smoking. Found the oil filter was loose - tightened it up with a filter wrench. Cleaned the engine up some and back to mowing. Run another 10 min or so &n same smoking situation. Filter was 1/4 turn loose again. Why does the filter keep coming loose after I covered the impulse hole ? It ran for 1/2 hr or so before with no issue. The vent tube with filter is clean and connected from the top of the engine to the carb air cleaner so it should not be building up pressure in the crank case. Going to check the filter closer in the morning.
 

chieffan

Tractorologist
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Member
#3
Good question about the oil filter. If you have an extra fuel filter put it in the impulse line instead of the plug and see if anything changes.
Problem is it is not really an impulse line. There is a hole in the shroud with a hose fitted inside. A stem on the back of the fuel pump slides in the hole to the line and 2 screws hold the pump in place. I have some fuel filters that have the stem end. Not sure they would stay by themselves - might be able to tape them in place temporarily like. Will see what the oil filter looks like tomorrow.
 

4getgto

Tractorologist
Senior Member
Member
#5
Even if you were building up crankcase pressure somehow I would find it to believe it's loosening your filter.
I never tighten any oil filter any more than by hand. I'd say somethings going on with the filter, gasket, threads , maybe the mounting base. I'd definitely try a different filter.
 

chieffan

Tractorologist
Senior Member
Member
#6
Even if you were building up crankcase pressure somehow I would find it to believe it's loosening your filter.
I never tighten any oil filter any more than by hand. I'd say somethings going on with the filter, gasket, threads , maybe the mounting base. I'd definitely try a different filter.
That is what I am thinking also. On the Onan there is only about 1/2" of the filter that sticks out of the shroud. Not enough to get hold of let alone when it is hot so put the filter wrench on it to snug it down. Will know later today as the garden is green like a lawn and it is going to have to be dry enough to work it this morning. More rain on the way from the West.
 

chieffan

Tractorologist
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Member
#7
It wasn't the filter. Put on a new NAPA Gold, turned till it touched, another half turn and quit. Started it and let it run for about 5 in at fast idle. Everything looked and sounded good. Took it out to a bit of grass I didn't get finished yesterday. Full throttle cutting grass for about 5 min, turned the deck off and headed for the shed to park it. Lifted the hood and the whole right side of the engine was covered with oil, filter and all. The filter did not move as I marked it with a paint marker on the filter and shroud. The head was dripping with oil. Another problem to get solved by a good cleaning and drying. Then fire it up and run a full throttle with the head shroud off so I can see what the hell is going on.
 

Toomanytoys84

Aaron
Senior Member
Member
#9
Is there another crank case breather on the engine?

I had a brand new Tecumseh HS30 that would SOAK the back of the block under the breather. I used a thick Mcdonalds straw to extend the breather below the engine plate. It was on a minibike.
 

chieffan

Tractorologist
Senior Member
Member
#10
There is a crank case breather on top of the engine. Has a stainless steel mesh type filter in it. Fits tight, is in place to runs to the bottom of the air filter can. Aaron, yes it started when I changed the fuel pump. There is a hose that runs from the crankcase to the flywheel shroud where the barb on the back of the fuel pump slides in when the pump is mounted. I covered the hole/tube at the shroud with black duct tape and mounted the electric fuel pump in the same place as screw holes and fuel lines fit good. Been running this through my head and I think the line may have come off/out at the crank case, which would allow direct splash to exit when running full throttle. Will take a look this morning.

Thanks for the input and suggestions on this.
 

KennyP

Alice's Creator
Staff member
Moderator
Senior Member
#11
There is a crank case breather on top of the engine. Has a stainless steel mesh type filter in it. Fits tight, is in place to runs to the bottom of the air filter can. Aaron, yes it started when I changed the fuel pump. There is a hose that runs from the crankcase to the flywheel shroud where the barb on the back of the fuel pump slides in when the pump is mounted. I covered the hole/tube at the shroud with black duct tape and mounted the electric fuel pump in the same place as screw holes and fuel lines fit good. Been running this through my head and I think the line may have come off/out at the crank case, which would allow direct splash to exit when running full throttle. Will take a look this morning.

Thanks for the input and suggestions on this.
Yes that line is for crankcase pulses to work the pump. Plugging it should have no effect on the oil filter, though. I've done that on a couple of my Onan's with electric pumps.
 

olcowhand

Daniel In KY
Staff member
Administrator
#12
Did you check the oil level? Being you said the pulse pump went bad, most times when they go bad they allow fuel to be sucked into the crankcase, way over the normal level. This will most always cause smoking like mad, and thinned oil goes everywhere. But I figure you did check the level with all the oil filter leakage.
 

chieffan

Tractorologist
Senior Member
Member
#13
The oil level stayed good through all this. Don't take much oil to make a big mess. I cleaned it up again, got the end of the pulses tube out where I could see it. Run it a full throttle and oil started flying out the end of the tube. Put a 5/16" bolt in the tube, went and mowed for about 20 min and no oil leak. Don't explain the filter issue but this one is not moving so think it is good to go.
 
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