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Author Topic: LPW2 / DN2M compression challenge  (Read 12606 times)

fastbackperry

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LPW2 / DN2M compression challenge
« on: March 14, 2016, 08:59:34 PM »
Hello.  New to this site and looking for some help on a Lister Petter engine LPW2.  Not finding anyone who knows about them IN DEPTH on the Steel Solders site.   Engine is in a MEP 802A generator set.  What I'm having a problem with is engine compression.  It doesn't have a lot of hours but I've narrowed it down to the valves are not fully closing due to the rocker arms not being loose enough.  This is a hydraulic lifter engine and this usually means that the push rods can be turned by hand when engine has set for awhile when the lifter is on low part of cam.  Technical Manuals say push rods should turn as well.  Anyway, I can loosen the rocker nut and literally feel the valve retainer lift upwards quite a bit.   Didn't measure but clearly it's allowing compressed air past the valves.  Engine turns pretty freely as well where other engines of this type don't turn over by hand at all due to a lot of compression.  This is the case with the 4 valves when on the lowest portion of the cam or no lift.  So the engine turns over with little to no compression because of this.  I could loosen the rocker nut and then have compression but that wouldn't be good with the engine starting without the rocker tight.  O boy could that result in something drastic.  Anyway. I see nothing in the manuals that will help.  Then only thing I can think of is to buy a bunch of thin washers in random thicknesses, like around .010 to put under the rocker pedestal until I get a combination of washers when tightened down by the nut to allow me to turn the push rod by hand.  This is not how it was designed but I don't know what else to do.  Any and all help is appreciated in advance.  Thank you.  Perry

Just a thought after proof reading this.  Could someone have put the wrong oil into this unit and that is not allowing the hydraulic lifter to not compress????.  I bought it from a company who uses way bigger generators than this 5K unit.  They had just had it serviced a several months ago when it was running good but had never ran it since then.  I see a NAPA filter on it, which is fine, but I'm wondering now.  Might need to do an engine flush with Dextron ATF or something, drain, and refill with correct oil. 

mike90045

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Re: LPW2 / DN2M compression challenge
« Reply #1 on: March 15, 2016, 03:42:02 AM »
oil viscocity was my first thought.  maybe pull the plugs and crank for a while to send lube all around after you flush it ?

carlb23

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Re: LPW2 / DN2M compression challenge
« Reply #2 on: March 15, 2016, 11:30:46 AM »
Check the pushrod length?

Thomas

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Re: LPW2 / DN2M compression challenge
« Reply #3 on: March 15, 2016, 01:46:49 PM »
Have you checked he lifters to see if they are stuck? Thomas

38ac

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Re: LPW2 / DN2M compression challenge
« Reply #4 on: March 15, 2016, 03:09:51 PM »
My inclination is your going to find other problems
Too thick oil is a stretch unless they put road tar in the crankcase. The oil is going to leak by quickly after sitting just a few minutes the lifters should be relaxed.  Something is either assembled wrong or timed wrong,,,   

I am no LPW expert, I do have a LPW2 and 4 in the shed that I can check the push rods though.

Butch
Collector and horder of about anything diesel

fastbackperry

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Re: LPW2 / DN2M compression challenge
« Reply #5 on: March 15, 2016, 03:20:26 PM »
Thanks for the input.  Butch. No need to pull a cover.  The TM's say the push rods should turn when no cam lift.  That's how all other hydraulic valve engines I've worked on have been as well.  But thank you for the offer.  After I got the unit home I did get it to start and run for a couple hours shutting down and starting numerous times then it wouldn't start.  Clearly a diesel engine needs compression and fuel.  Injectors spray great.  As noted there is very little if any compression due to all valves not being able to fully close.  The only link in the mechanical system that has a variable of change is the hydraulic lifter.  Everything else is fixed/constant.  I'm going to go ahead and drain it and try correct and thinner oil.  Will post results. 

dieselgman

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Re: LPW2 / DN2M compression challenge
« Reply #6 on: March 15, 2016, 03:42:39 PM »
The Alphas had a lot of problems with their valve trains and especially with the hydraulic lifters. That engine calls for normal 15-40 diesel lube oils except during break-in. There is a specific procedure for compressing the lifters with a special tool... basically to purge them of air. If they do not compress with either time lapse or the special compression tool, then replacement is called for. It is possible to experience bent pushrods, valves contacting the pistons, and broken rocker arms as related effects.

dieselgman
Ford Powerstroke, Caterpillar 3304, Cummins M11, Too many Listers to count...

38ac

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Re: LPW2 / DN2M compression challenge
« Reply #7 on: March 15, 2016, 03:42:56 PM »
Another thing I didnt mention but might apply here is a lot of the current crop of surplus saw service in the desert conflicts. I am pretty deep into the ex miltary Yanmars and most every one of them has been "dusted" to one extent or another and that's why they got pulled from the machines, they got hard to start.  Sometimes a few hours breathing good air they will seat back in and start OK, other times not. A good thing is there are many LPW2 engines for sale right nowmany of which are brand new. A good time to pick up a spare.

Good luck!
Butch
Collector and horder of about anything diesel

fastbackperry

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Re: LPW2 / DN2M compression challenge
« Reply #8 on: March 16, 2016, 12:29:14 AM »
OK.  Drained the oil and poured in diesel.  Turned it over a bit and noticed it actually laboring a bit. Moved over to start knob and it began to start.  Let it run low rpm several seconds to flush diesel around.  Stopped it and then just turned over a bit more, then started it again shortly.  Drained and put new filter on adding new Amsoil 5w-30.  I wanted thinner then 15w-40.  It wouldn't start and took some time before it finally did but it's not right.  Blows a little blue and there is more crankcase pressure then I like.  There is bubbling happening under injector pumps and when I pull the dip stick there's a bit of blowing going on.  Anyway.  It looks like I got hosed on this deal.  I read what Dieselman said and maybe the lifters are the issue.  The valves don't appear to be bent as the lift right up a bit after rocker nut is loosened.  Pulled a couple push rods and they are straight.  Even if the valve train was working properly I have the blow bye issue so I'm leaning towards just buying one of the truly new engines from someone.  Rebuilding these engines looks to be rather costly.  It's difficult to even find a gasket for these engines for a reasonable price.  Judging by how many of these used engines that are being Government Liquidated I'm thinking the U.S. tax payer got hosed as well.  The MEP 002 and 003 units had some issues but there wasn't nearly endless auctions of used engines for them on GL.  Anyway.  Maybe  the bores are within tolerance and just new rings are needed then go through the head and do something with the lifters is an option.  It's just the cost of parts compared to a new engine.  Thanks for all of your thoughts and comments.  Perry

dieselgman

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Re: LPW2 / DN2M compression challenge
« Reply #9 on: March 16, 2016, 02:37:19 AM »
We have the L/P factory rebuild stocks for these, everything is readily available... costs of parts vs purchasing good surplus engines is perhaps a valid equation to figure out though. A few hundred bucks plus shipping sounds pretty good alongside the costs of a full rebuild kit plus labor. There are still plenty of them in service out there, and they are a popular modern genset mover if you want very small footprint and a good reliable standby plant. I am pretty sure the government would have continued their use if the parent company (L/P Americas) had remained in business and were able to support the thousands of units they sold to our military agencies. As far as being hosed... I doubt that to be a valid assumption. I have reviewed many of the contract documents and these units were "hard bid" at very attractive discount levels to our government. I know that much of the military business is not run this way however... plenty of waste and corruption of one sort or another is likely to be involved.

dieselgman

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mike90045

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Re: LPW2 / DN2M compression challenge
« Reply #10 on: March 16, 2016, 02:40:19 AM »
I'd do a couple 5 minute runs with cheap 5-30 oil to flush all the diesel out of the crankcase.  I think you have spoiled the expensive amsoil with residual diesel.    These oil changes  and short runs may clean crud (rust) off the cylinders and get it flushed out.  maybe in a day it will clean the rings up too ??