Robins EH65 Spewing Oil/Fuel from Crank Case Vent

[3rd Coast]

Morning Everyone,

My PT422 with the Robins motor has about 800 hours on it. It has been running great since the summer time. Over the weekend it became very hard to start and once it was running, was stumbling pretty bad. I pulled off the intake filter and there was oil everywhere, spewing out of the crank case vent(i think that's what it is anyway). I shut the motor down and pulled the dipstick. A geyser of oil shot of it. I got it in to the garage, shut off the fuel. Drained the oil/fuel mixture and changed the filter. Loaded the motor back up with fresh oil. It was clear to me that somehow fuel had made its way in to the oil and way overfilled the crankcase.

With the fresh oil change and a quick degreaser bath, the PT fired right up. I pulled it out in to the driveway and let it warm up and increased engine speed for awhile and just let it run with the filter removed so I could keep an eye on it. Eventually the breather started misting very light coating of fuel or oil(not sure which as it was pretty clear). I have searched through the threads and have seen similar problems, its just not clear to me if there was any resolution. I plan to do a compression test, which I did a few months ago and was all good at the time. Any tips on diagnosing?

 

[m5040]

If it were mine, I would just install a manual fuel shut off (and use it), check the oil frequently and run it as is. The mist you see is IMHO normal, that is why it has a breather. If you cause damage (some, minor, severe or otherwise) what are your choices? Put a new engine in? Rebuild? I think you should run it, but you didn't mention if it ran smooth after the oil change, so I am assuming that it did.

 

[FordnMassey]

Hi,
I don't know the motor specifically, but the options for fuel reaching the crankcase are fairly limited in most motors. The fuel pump, if present and cam driven, is the most likely candidate. Second would be the needle valve in the carb, if present, stuck open, causing fuel to overflow the bowl into the intake manifold from where it would have to trickle past the rings to reach the sump.
Both of these would be happening slowly when sat, and a fuel isolation valve would stop the majority of the fuel in both cases. In the case of a fuel pump leaking thru into the crankcase, one pump full of fuel could still trickle in after each use, until the pump was empty.
Anybody else have any other ideas?

 

[3rd Coast]

If it were mine, I would just install a manual fuel shut off (and use it), check the oil frequently and run it as is. The mist you see is IMHO normal, that is why it has a breather. If you cause damage (some, minor, severe or otherwise) what are your choices? Put a new engine in? Rebuild? I think you should run it, but you didn't mention if it ran smooth after the oil change, so I am assuming that it did.

I have a shut off after the pump, and I have it switched off for now. It ran fine with the oil change. My assumption was the float was leaking or something and thats how all the fuel got in.

But you say the mist is normal, and that may be, I hadn't considered it. Thought it was strange that it didnt mist like that at start up and took awhile before it began. I noticed it also was seemingly saturating the air filter enough that I noticed a difference in motor sound when I pulled it off.

Could it also be the long cranking to get this thing started in the cold? Below 20* and it's near impossible to get it started. It always fires eventually but takes a lot of cranking.

 

[ponytug]

I have a shut off after the pump, and I have it switched off for now. It ran fine with the oil change. My assumption was the float was leaking or something and thats how all the fuel got in.

But you say the mist is normal, and that may be, I hadn't considered it. Thought it was strange that it didnt mist like that at start up and took awhile before it began. I noticed it also was seemingly saturating the air filter enough that I noticed a difference in motor sound when I pulled it off.

Could it also be the long cranking to get this thing started in the cold? Below 20* and it's near impossible to get it started. It always fires eventually but takes a lot of cranking.

Sorry that you are having issues. It isn't uncommon, and I doubt that it is long cranking.

The usual culprits are a leaking carburetor or a leak in the fuel pump (isn't your fuel pump vacuum driven?). I believe that you can get a leak through the diaphragm on the fuel pump to the vacuum to the crank case.

If you have been using your fuel cutoff, I guess I am curious if it is before or after the fuel pump.

All the best,

Peter

 

[3rd Coast]

Sorry that you are having issues. It isn't uncommon, and I doubt that it is long cranking.

The usual culprits are a leaking carburetor or a leak in the fuel pump (isn't your fuel pump vacuum driven?). I believe that you can get a leak through the diaphragm on the fuel pump to the vacuum to the crank case.

If you have been using your fuel cutoff, I guess I am curious if it is before or after the fuel pump.

All the best,

Peter

I have a fuel cut off valve before and after the fuel pump. I was not using either prior to this mess, I only started this weekend when I changed the oil.

 

[ernemats]

I would call Terry at Power Trac and get his input on it.

 

[5030]

It's a Robin engine btw and I have one on my trailered sprayer. I'd say it's time for a cylinder hone and new rings.