MEP803a looses all compression. Lifter Problem?

[mepgen]

Update with pics! The lifters were taken apart tonight and all look good. The oil was not as thick as I remembered it, so I don't think that is the problem. All valves were removed and came out easily, no binding. The valve with the bent push rod was only out by .001", put blue sharpie on the valve and spun it around in the seat. Nice strip of sharpie removed uniformly around the valve, so it looks good. Will clean the head tomorrow and lap the remaining valves to make sure they are seating correctly. Once the head is assembled will fill ports up some with gas to see if there is any leakage around the valves. I even made sure all the push rods were clear of obstructions to oil flow and they all looked good.

So far I have found absolutely nothing that would cause every valve to contact the pistons. At this point the only other theroy I have to go with is out of control high oil pressure pumping up the lifters. After the top end is done I am going to check out the oil pump for a stuck oil pressure relief valve. Before I start this thing I after all the checks I am going to crank it with the dead crank switch with all the injectors out of it to see what the oil pressure it is making (with an external gauge and the on on the panel) before I try to start it. Any other ideas?

Also, where can I find a push rod? I looked around but could not find anyone selling them.

 

[Daybreak]

Howdy,

MEP-802A = Onan DN2M-1, Lister-Petter LPW2
MEP-803A = Onan DN4M-1, Lister-Petter LPW4

All the same insides but 2 cylinder or 4 cylinder

 

[DieselAddict]

They are being sold on eBay.

 

[lindsey97]

What about some dummy manually fooling with the governor/rack and causing the engine to overrev and float the valves causing damage?

 

[csheath]

Doesn't look like actual metal to metal contact. I wouldn't think the valves would contact the pistons even if the lifters pumped up all the way. In fact I would expect the lifters to pump up all the way normally but with proper oil and pressure they would have some give. I have been looking through some of the TMs but haven't found the operation for checking cam timing yet. I assume it has a fiber cam gear and when those begin to fail they can jump a tooth before complete failure. Just a thought.

 

[snowtrac nome]

I have seen this before with the 7.3 ford diesel. It has to do with the oil pressure relief valve, on the ford its in the return side of the oil cooler, when it builds pressure it effective turns hydraulic injectors into solid lifters and holds the valves open.

 

[Daybreak]

Howdy,
Order your head gasket now. It will take a while for it to arrive. Check which head gasket to get. There are some variations.

 

[mepgen]

Found the problem! First I took the front cover off the motor and checked the cam timing. Marks on the crank gear and camshaft gear were dead on, so not the problem. Checked the valve spring pressure at the installed height, it was 45 lbs (does anyone know what this value should be?). Did not seem unreasonable for a motor that turns at 1800 rpm. Then moved to the pressure regulator on the oil pump. Snowtrac was correct! The pressure valve was rusted in the shut position. I had to use a brass punch and the handle of a screwdriver to knock it out. It looks like condensation from the motor got into the valve and rusted it up, in the closed full pressure position. This is the only rust I have found in the whole motor. I even looked inside the oil pump through the threaded hole where the pressure regulator screws on and everything looks good, no rust or debris inside the pump. Pressure valve components are now soaking in evaporust.

So it looks like the oil pressure regulator gut rusted and stuck in the full pressure position, which in turn feed the lifters so much pressure they overcame the valve spring pressure and pumped up, which made the valves bounce off the pistons. Once it sat for a few minutes the lifters would bleed down enough that the valves closed and compression would return.

As for the head gasket, I found a decarb set branded poWer gaskets, made from a company in Turkey. Do you all think this set will be okay, or do folks only use Lister Petter head gaskets? I will not use any China made gaskets because I know they are probably junk.

 

[Daybreak]

As for the head gasket, I found a decarb set branded poWer gaskets, made from a company in Turkey. Do you all think this set will be okay, or do folks only use Lister Petter head gaskets? I will not use any China made gaskets because I know they are probably junk.

Howdy,
It should be fine. The Lister-Petter LPW4 has been around a long time. Just double check that the kit has the head gasket. Or as they call it, the head joint. A lot of de-carb kits has all the stuff, but the head gasket.
Do a little research as to which head gasket. I remember reading that the one with the blue is the preferred gasket to get.

Pete's thread has all kinds of good info.
Picked up 3 MEP-802A gensets and will be documenting making them all runners here

 

[Guyfang]

Good job mepgen!!

 

[mepgen]

Just got everything put back together today and fired up the genset. Motor ran great with between 50-55 psi oil pressure, generator produced power and everything works fine. Hopefully this thread will help someone if they experience the same problem that I did. Thanks for all the help!

 

[Guyfang]

Smokin!!!

 

[DieselAddict]

Excellent job!

 

[jamawieb]

Good Job! Did you access the oil pressure relief valve from the front cover or did you take the side cover off?

 

[mepgen]

I took the side cover off to access the oil pressure relief valve. I don't think it is possible on this motor to take the front cover off to access the valve. The valve is screwed into the oil pump next to the oil pickup tube.

 

[TheAlfredo]

I wonder if this could be the issue with my 803a. It starts and runs perfectly from a cold start. Once the engine runs for a whiie, it's RPm fluctuate slightly...you can see the Hertz go up and down. If I shut the gen down it won't re-start until it sits for a while....it just spins when cranking (like if I was dead cranking). And when it does restart it doesnt run perfectly as a cold start. I basically have to wait a day for it to run perfectly again. I thought it could be fuel pump...but this just threw me a curve ball.

My my engine does have signs of water intrusion. Looking through the oil filler, you can make out rust color inside (I can touch it with my finger and it doesn't rub or stain my skin....hoping it's just superficial.

My gen is missing the exhaust flap.

 

[csheath]

I wonder if this could be the issue with my 803a. It starts and runs perfectly from a cold start. Once the engine runs for a whiie, it's RPm fluctuate slightly...you can see the Hertz go up and down. If I shut the gen down it won't re-start until it sits for a while....it just spins when cranking (like if I was dead cranking). And when it does restart it doesnt run perfectly as a cold start. I basically have to wait a day for it to run perfectly again. I thought it could be fuel pump...but this just threw me a curve ball.

My my engine does have signs of water intrusion. Looking through the oil filler, you can make out rust color inside (I can touch it with my finger and it doesn't rub or stain my skin....hoping it's just superficial.

My gen is missing the exhaust flap.

What is your oil pressure reading? The tip off on this machine was high oil pressure.

 

[csheath]

Glad you got er goin mepgen!

 

[TrailLifeBill]

Excellent thread!! Thanks for documenting it so well.

 

[mepgen]

On my engine I saw no signs of water intrusion on the top end. Cylinders were clean, no rust on the top end whatsoever. The only place I saw rust was at the oil filter, on the threaded tube where you spin the filter on. I think water entered through that hole and settled in the pressure relief valve. Since the valve is shut when the engine is off it just set in there and rusted it up. If I had to guess only about an ounce or even less of water would be needed to fill up the valve and rust it shut. If you see evidence of rust/water at the oil filter tube I would remove the side cover and oil pressure valve. The side cover is easy to get off and so is the oil pressure valve. You will need to either buy another side cover gasket or make one. I used the old one as a template and made my own.