MEP803a looses all compression. Lifter Problem?

[TheAlfredo]

Started the gen 30 min ago. Oil pressure was a steady 50. Now it's reading close to 40 (on the gens gage).

Ive also been reading that in taking off the oil filler cap there should be enough vaccume to hold a piece of paper to it? That is impossible on mine. It just blows the paper away.

Gens now been running for 40 min...about 60 degrees out and it is purring along. Just turned it off and it restarted. Going to leave it running for a bit. This is the longest I've had it running with no issues. ��

 

[mepgen]

Sounds like your pressure valve is working fine. Since you said the flap was missing it water could have gotten into some of the cylinders. The cylinder walls may be rusted up and the rings may be sticking. Here is what the manual says about crankcase pressure:

A fluctuating vacuum may indicate faulty oil seals, valves, or piston blow-by troubles. Crankcase pressure can cause serious oil leaks
and often occurs in engines which need overhauling.

The longer you run it the rings may begin to un-stick and seal better. You really will not know what is going on unless you pull the head. How many hours are on the unit?

 

[TheAlfredo]

Bought the generator with 6hr. I have just over 8hrs on it now. Today it ran 100% perfect. My only concern is the lack of vacuum in the oil filler cap. Had a mechanic that was working on a skid steer look at it....and he wasn't concerned at all. But he has never worked on one of these engines either. Yesterday he was guessing that it was the fuel pump.

I was going to run the gen today and disconnect and test the fuel pump when the gen acted up. But as I said, it ran perfectly.

I have the gen at a friends warehouse...was waiting to make sure it ran fine before bringing home. But I think I'm going to bring it and run it a few more times and then put a load on it.

 

[csheath]

I've never heard of any engine having a vacuum under normal circumstances. They will produce some pressure from combustion gases getting by the rings into the crankcase. How much depends on the condition of the rings. Zero to slight pressure should cause no concern.

Some race engines will have an exhaust scavenging system or even a vacuum pump that can evacuate the pressure and in some cases even create a vacuum.

If it were huffing smoke out of the oil fill hole I would worry.

It seems like most of these will get down around 20 _ 25 lbs of oil pressure at full temp and load.

 

[Chainbreaker]

Sounds like there could have been a fuel restriction (old gunky fuel or other contaminant) somewhere in the fuel delivery...pump, lines, valve, etc. that caused it to starve for fuel during your earlier runs. Apparently with your running fresh fuel through it, with several restarts, it eventually cleared itself out. Your plan to run it some more and then put loads on it seems to be right approach now. I would not be alarmed about the crankcase pressure given your description. As long as it is not blowing oil or mist out the oil filler cap opening nor blowing smoke out exhaust after warmed up it should be fine.

 

[Guyfang]

I've never heard of any engine having a vacuum under normal circumstances. They will produce some pressure from combustion gases getting by the rings into the crankcase. How much depends on the condition of the rings. Zero to slight pressure should cause no concern.

Some race engines will have an exhaust scavenging system or even a vacuum pump that can evacuate the pressure and in some cases even create a vacuum.

If it were huffing smoke out of the oil fill hole I would worry.

It seems like most of these will get down around 20 _ 25 lbs of oil pressure at full temp and load.

Read the book. Look In the -24 manual. The Listter- Peter engine has negative crankcase pressure. There are instructions on how to build a simple water manometer.