MEP803a looses all compression. Lifter Problem?

[mepgen]

Hi all,

First post here. Just brought home my first 803a today and am having an engine problem. When I go to start the generator the motor will begin to start (you can hear the cylinders begin to light off) and then the motor seems loose all compression and start to freewheel. If you start cranking the motor immediately (or even a minute or two) after the failed start attempt the motor just spins (with no compression) until you let it set for a few minutes and then when you crank it with the dead crank switch (or main control panel switch) the motor has compression again. When you try to start it again the same thing happens. In the freewheeling condition you get hardly any suction from the intake or pressure from the exhaust. After setting you get much more intake suction and exhaust pressure.

Looking in the manual for the engine it appears as if there is no adjustment on the rocker arms? Am I correct on that? It seems like when the lifters begin to pump up once the motor begins to make oil pressure the valves are hanging open just enough to loose compression. Also, when the engine is freewheeling the oil pressure gauge pegs itself at 80 PSI. I don't know if that is normal or not. I took that valve covers off and the valves are moving like they should but it seems like not all the rocker arms are getting oil from the push rods. I am not new to engines, but this one has me a bit stumped. Is it the lifters (stuck or debris?) or something to do with the oil pressure being too high?

The inside of the motor ls clean and the unit is not wet stacked (the exhaust manifold and muffler are not gummed up, just normal carbon residue). The unit is clean, Tier 2 reset in 2011 (was manufactured in 1998 and has just over 900 hours on the clock.

Thanks!

 

[jamawieb]

Take the oil refill cap off or the dipstick out to see if it has back pressure. It could be the piston rings. If you don't have a large amount of back pressure I would say the valves. You are correct, the valves have no adjustment.

 

[mepgen]

Thanks jamawieb. I did take the refill cap off and put my hand over the hole while someone else cranked the motor. There was no noticeable back pressure. At first I thought the valves were sticking, which is why the valve covers came off. As far as I can tell the valves move freely and the rocker arms do not have excessive play in them. If the lifters are pumping up I hope the valves did not hit the pistons.

 

[Suprman]

Maybe water got in and some rust causing valves not to seat. Could the starter be slipping and even though it makes noise only turning the motor slowly when it sounds like its freewheeling.

 

[1800 Diesel]

Agree with Suprman about a possible cause in the valves not seating. Also it could be the valves are somewhat binding in the guides and not seating all the way. Put some marvel oil around each valve stem and let it sit a few minutes and then take a piece of wood (like a 12" section of shovel handle) and tap the top of each valve (with the wood actually hitting the rocker) with a decent sized ball peen hammer to confirm good spring tension & snap-back of the valve. Roll the engine over as needed to set up each valve spring to have no compressing. If you get any valves that don't drop and instantly snap closed, then you found the culprit.

If that doesn't identify anything you may have to pull the injectors to spray oil in each cylinder to see if compression improves. Possibly this engine had water in a few moons ago and someone tried to start it up with rust ridges and broke a compression ring or two.

The only other things that come to mind is cam timing or injection timing being off--unlikely but possible.

Can't address the lifter question since I haven't torn into one of those engines, but assuming the lifters are hydraulic (and not solid) the high oil pressure shouldn't be an issue. Again I'm not familiar with the lifter and rocker arm setup but during rebuilds if someone set up the valve train too tightly (and I'm guessing here) it would seem possible for excessive valve opening to prevent valve seating when it was supposed to seat.

Interesting problem here. I'm confident someone familiar with those engines will figure out the issue... good luck with it!

Edit with new info:

Found this in (ARMY) TM 9-2815-253-24: PDF page 71: "Removal of any part of the valve gear will allow the hydraulic tappet to extend and hydraulically lock."

Possibly the rocker assembly was loosened enough and the lifters extended enough to not allow the valves to seat 100%. Sounds crazy but it's possible. That would mean the lifters would not bleed down though. The TM says it only takes about 15 minutes for them to bleed down.

One other consideration--I noticed these engines use one of three different thickness head gaskets-- 0.053", 0.058" or 0.063". If someone installed the incorrect/thicker gasket in your engine, this would reduce compression during starting for all cylinders.

 

[Bmxenbrett]

I believe the injectors go directly into the cylinder on these engines. Ribble some oil around them and watch when you crank it.

 

[Scar59]

Not familiar w/ the 803A. Are these engines equipped with automatic de-compression for starting?

 

[1800 Diesel]

Not familiar w/ the 803A. Are these engines equipped with automatic de-compression for starting?

Nothing in the TM about a decompression lever like the Yanmar air-cooled engines.

 

[Guyfang]

3-5. CRANKCASE VACUUM.3-5.1. General. The value depends to some extent on the type and size of air cleaner installed on the engine.Regardless of type air cleaner used, vacuum with a clean air cleaner must not be less than a minimum of 0.79 in. (20mm) water gage (WG). The vacuum is measured with a manometer at the lubricating oil dipstick hole with the engine running. In engines in good condition vacuum increases slightly with engine speed but not proportionally. 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.3-5.2. Measure Vacuum.NOTE Average vacuum should be 1.37 in. (34.8 mm) WG. Minimum allowed is 0.79 in. (20 mm) WG.a. Remove lubricating oil dipstick.b. If water manometer is available, connect one end of a 0.374 in. (9.5 mm) OD plastic tube to a water manometer.Insert other end of tube into dipstick hole. Refer to FIGURE 3-1.WARNING The noise level when operating could cause hearing damage. Ear protection must be worn.c. Start engine and record reading on manometer.d. Stop engine, disconnect manometer and install oil dipstick.e. If water manometer is not available, place a piece of thick paper over the oil fill opening. If crankcase vacuum retains paper, vacuum is good.


Go to TM 9-2815-253-24, page (PDF reader page number) 3-12 and there is a picture of a home made water manometer. Make one. Hook it up. You watch it during your startup sequence. See if you have vacuum during the early part of the start, and if you loose it when the engine freewheels. i would also put a compression gauge on the cylinders. Test them, to see if there is compression, during start, and if you lose it later. If you can get ahold of a borescope, take a look see in the cylinders.

Scar, There is no automatic Decompression as far as I know of on this engine.

A bit of info about oil gage and oil pressure. I would check it with a independent gage anyway.

View attachment TQGoil Press Gage.pdf

 

[csheath]

3-5. CRANKCASE VACUUM.3-5.1. General. The value depends to some extent on the type and size of air cleaner installed on the engine.Regardless of type air cleaner used, vacuum with a clean air cleaner must not be less than a minimum of 0.79 in. (20mm) water gage (WG). The vacuum is measured with a manometer at the lubricating oil dipstick hole with the engine running. In engines in good condition vacuum increases slightly with engine speed but not proportionally. 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.3-5.2. Measure Vacuum.NOTE Average vacuum should be 1.37 in. (34.8 mm) WG. Minimum allowed is 0.79 in. (20 mm) WG.a. Remove lubricating oil dipstick.b. If water manometer is available, connect one end of a 0.374 in. (9.5 mm) OD plastic tube to a water manometer.Insert other end of tube into dipstick hole. Refer to FIGURE 3-1.WARNING The noise level when operating could cause hearing damage. Ear protection must be worn.c. Start engine and record reading on manometer.d. Stop engine, disconnect manometer and install oil dipstick.e. If water manometer is not available, place a piece of thick paper over the oil fill opening. If crankcase vacuum retains paper, vacuum is good.


Go to TM 9-2815-253-24, page (PDF reader page number) 3-12 and there is a picture of a home made water manometer. Make one. Hook it up. You watch it during your startup sequence. See if you have vacuum during the early part of the start, and if you loose it when the engine freewheels. i would also put a compression gauge on the cylinders. Test them, to see if there is compression, during start, and if you lose it later. If you can get ahold of a borescope, take a look see in the cylinders.

Scar, There is no automatic Decompression as far as I know of on this engine.

A bit of info about oil gage and oil pressure. I would check it with a independent gage anyway.

View attachment 704511

That is interesting.

In the automotive world a pegged oil pressure gauge could indicate a stuck oil pressure relief valve. Haven't looked to see if the 803 has one but most positive displacement pumps require some method of regulation.

 

[mepgen]

Thanks for all of the replies. Fairly certain the starter is working correctly. The flywheel seems to be turning quickly and the oil pressure gauge goes up to over 80psi but I will double check that when I get home. I am going to borrow a borascope and check out the cylinders. Since I have to pull the injectors out for that I will also attempt to run a compression check on the motor if I have the correct adapter for my compression gauge. I might get ambitious and pull the intake manifold and exhaust manifold off and attempt to check out the valves. Before I do all that I will try to make the homemade manometer to see if I have vacuum when I try to start it. It will only fire about 4-6 times before it starts to freewheel. There is a video on GovPlanet with them trying to start it. Since the auction is over (and it is setting in my driveway) can I post the item number? I read the rules and I understood them to say that after the auction is over you can post info about the item but not direct links if the link will be removed after a short period of time. Am I correct on this (I don't want to be a rule breaker on my third post!)

 

[Guyfang]

That is interesting.

In the automotive world a pegged oil pressure gauge could indicate a stuck oil pressure relief valve. Haven't looked to see if the 803 has one but most positive displacement pumps require some method of regulation.

Indeed, it has a pressure relief valve.

 

[Guyfang]

The water manometer is easy. look at the picture. I made one in about 45 minutes. Drilled holes in a board. Used zip ties to secure the clear plastic hose. Drew some lines across the board and Wah La!! High speed, low drag water manometer. Easy, simple and precise!

 

[mepgen]

I may have found the problem with the motor. I had the valve covers off from last night and decided to check out the push rods. Cylinder 3 exhaust push rod is bent. The rest of the push rods look fine (I still have to really check them per the manual). The head is coming off since I now have to check the valves to make sure they are not bent. I took off the intake and the exhaust manifold and checked out the valves as best as I could with the camera. Intake valves look okay and the exhaust valves have slight layer of carbon buildup (no wetstacking). Cylinder number 2 intake looks to have diesel spray in it and exhaust ports on cylinder 3 and 4 also seem to have some wetness to it. If I had to guess it looks like the intake valve on cylinder 2 and the exhaust valves on cylinders 3 and 4 may be sticking. I will know the whole story when I pull the head.

 

[TrailLifeBill]

If you don't mind - while you are tearing into it - could you post pics of any issues you run across?? Fortunately, I haven't had to tear mine down - but am always interested in keeping up with other's experiences in case I ever have a similar problem.

 

[mepgen]

Update! I pulled the head off tonight. Every single valve kissed the top of the pistons. They did not crash into them (no mark on the piston or valve) but you can see the imprint in the carbon (I have pics I will post later). No sign of wet stacking or water intrusion in the motor and you can still see all the crosshatching in the cylinder walls. Took apart a lifter and on the valve with the bent push rod and it was fine. Camshaft lobes and lifter looked good. I removed one valve (was running out of time) and choose the one with the bent push rod. Valve slid right out, no binding at all and stem looked good.

After all of this, I still have no explanation as to why the valves hit the pistons. I would think if the cam were out of time it should not try to start then freewheel. It still seems like the lifters are pumping up and holding the valves open. Could really high oil pressure do this? Too thick of oil? I don't know what oil is in the motor except it is new (I think govplant put it in to start it). I am going to take the pressure regulator out of the oil pump to see what is going on there. One interesting thing to note, the lifter had dark oil inside of it and the crankcase oil is clean. It also seemed to me that the oil in the lifter was a higher viscosity than regular diesel oil, like it may have gelled some. I cranked this motor a lot with the dead crank switch and I only saw oil come up one push rod. Other than that, any ideas? I really think the problem is still there, since I have not found the smoking gun yet.

Traillifebill, I have been taking pics along the way and will try to post them tomorrow.

 

[DieselAddict]

Do you think that the lifters are collapsed instead of pumped up? Could the valves be not opening at all?

I would suggest taking the lifters apart and making sure they are all OK. Refill them with clean oil.

Timing could certainly cause the valves and the pistons to touch. Does the cylinder with the bent pushrod look any different than the others in respect to the mark on the piston from the valve?

 

[mepgen]

I don't think the lifters are collapsing. If they were the engine would not freewheel. It was freewheeling like a gas motor with no spark plugs in it. Compression would return when you let the engine set a few minutes. I am going to take apart every lifter and inspect/clean them. The cylinder with the bent push rod has a bit more imprint in the carbon than the others (I took pics and will post them tomorrow).

The more I think about it the oil in the lifter was thicker and somewhat lumpy. It is hard to describe, almost like it had snot mixed in with it. I have seen that before with synthetic oil that gelled up in an engine. Does the Army run synthetic oil in these gensets?

 

[Guyfang]

The army does not run synthetic oil. Or didn't when I worked contracting. HDO-15W30, or what ever was directed in the LO.

 

[Ray70]

Do the valves move freely ( try moving them by setting up a pry bar and a fulcrum to push on the valve tip ) or are they binding up in the valve guides? If you bought that one in PA last week ( or maybe it was the week before ) I saw the video and my first thought was that the valves are sticking in the guides. If they hung up momentarialy the pistons would have come up, touched them and pushed closed. I would take all valves out, check for bent ones and buy the head set on Ebay for $200, it comes with everything you need.
If no valves are bent, it might be as simple as cleaning the valve stems, guides and lubricate and reassemble. Its actually very easy to do.