Mep-802a compression question

[jstew0903]

I just bought two 802a generators. One is a tier 2 and runs well with 25 hrs on it. One is missing parts and been picked over. It has 425 hrs on it. Both are from 1995 from what I can tell.

For the running tier two one I have a lot of blowby from the dip stick hole when I pull it. I've read where there shouldn't be any blow by on these engines. My question is with the two cylinders going up and down at the same time how can there not by an in and out type of blowby? Just seems like the physics would say there should be. When I put a socket with a rachet on and turn the engine over I do have compression but I think I can hear it bleeding by the piston/rings. It is a rebuilt engine(by the tag on it). It's there an amount of time that the rebuilt engines need to seat the rings and such? I will say this generator starts great and runs great at a load so far. No smoke outside if what I've seen in others under load. Any advice on where to go would be great. I did the first oil change at the 25hr mark.

The second one I have I tried to turn over with the socket and rachet and it hits a point where I cannot turn it over. Is that what the normal good compression should feel like? Pretty much feels like it's hitting something but I don't think it is.

Appreciate everyone's time. Thanks for accepting me in this platform.

Jason

 

[Ray70]

You should be able to turn the engine over fully with a ratchet and you will hear compression leaking into the crankcase while doing so.

Compression leaks past the rings while cranking slowly, mainly due to the speed it is turning and the lack of high cylinder pressure which helps seal the rings against the piston grooves and the cylinder walls, so a lot of compression leaks into the crankcase.

The one what seems to hit a spot where you can no longer rotate with a ratchet probably has a mechanical issue.
You can confirm this by either removing the injectors or holding a valve open and trying to rotate it again, but I bet you will find the same issue.

As for the "pressure" in the crankcase, the cyclical motion of 2 pistons in line does create a huge air pulse within he crankcase and will feel like severe blow by if you remove the oil cap or dipstick, HOWEVER, if you attach a manometer to the crankcase you should find that you have a slight vacuum on a good engine.

This is because your hand over the oil cap will feel the outward air pulse but it will overlook the opposing inward suction because your brain will tell you something is wrong!
In reality the inward vacuum is slightly stronger than the outward pulse but it can only be measured with a manometer.

 

[jstew0903]

You should be able to turn the engine over fully with a ratchet and you will hear compression leaking into the crankcase while doing so.
Compression leaks past the rings while cranking slowly, mainly due to the speed it is turning and the lack of high cylinder pressure which helps seal the rings against the piston grooves and the cylinder walls, so a lot of compression leaks into the crankcase.
The one what seems to hit a spot where you can no longer rotate with a ratchet probably has a mechanical issue.
You can confirm this by either removing the injectors or holding a valve open and trying to rotate it again, but I bet you will find the same issue.
As for the "pressure" in the crankcase, the cyclical motion of 2 pistons in line does create a huge air pulse within he crankcase and will feel like severe blow by if you remove the oil cap or dipstick, HOWEVER, if you attach a manometer to the crankcase you should find that you have a slight vacuum on a good engine.
This is because your hand over the oil cap will feel the outward air pulse but it will overlook the opposing inward suction because your brain will tell you something is wrong! In reality the inward vacuum is slightly stronger than the outward pulse but it can only be measured with a manometer.

Thank you very much for your detailed reply.

I will check the one with a manometer. I'll order one today. I'm assuming a dial type would be best? I'm seeing a lot of them that are digital.

The second one I spoke with another member here on this forum and he said to pull the glow plugs and rotate it and see what happens. Sucks it has only 425hrs and it's likely shot.

If the engine has some sort of mechanical issue are they worth rebuilding? Is it a common one to find replacement parts for a machine shop? I'm in North Florida if anyone knows of a good machine shop I could use in the future.

 

[Denvercaitland]

Highly unlikely scenario but may be worth a look.

When I acquired my 803a I ran into a similar problem with turning the engine by hand. It turned out that on cylinder was hydro locked

The various steps I followed and advice I received are detailed on thread :

"Mep 803a hydro locked"

Cheets

 

[Denvercaitland]

Highly unlikely scenario but may be worth a look.

When I acquired my 803a I ran into a similar problem with turning the engine by hand. It turned out that on cylinder was hydro locked

The various steps I followed and advice I received are detailed on thread :

"Mep 803a hydro locked"

Cheets

Cheers

Mep 803a hydro locked

In process of getting 803 running ( never fired up this far). A bit of history; got this set on Canadian version of gov surplus. No history, no indication of conditions at time of purchase. Set has 1810hrs and from different marking on various parts looks like it was serviced then parked...

www.steelsoldiers.com

 

[Guyfang]

Read the TM on vacuum checking. It also shows you how to build a cheap manometer. If you find that the second gen set has a bad engine, here is what would do. Take the oil filler cap off, drill a hole through it, and stick a copper tube through it, and seal it with a good adhesive. Hook up your home made Manometer to it. Put it in the runner, and test your vacuum that way. This is what the pros do in rebuild. And if you want to spend money on a store bought manometer, do so.

 

[jstew0903]

The hydro locked theory does sound like a possibility. I forgot to mention that the exhaust is unbolted and sitting on the manifold. I'm wondering if they poured something through there to loosen something up? I did look into the exhaust manifold and didn't see anything that seemed wet.

I will make a manometer and check the running one. Appreciate all the help. It's greatly appreciated.

 

[jstew0903]

Cheers

Mep 803a hydro locked

In process of getting 803 running ( never fired up this far). A bit of history; got this set on Canadian version of gov surplus. No history, no indication of conditions at time of purchase. Set has 1810hrs and from different marking on various parts looks like it was serviced then parked...

www.steelsoldiers.com

"I can turn crank clockwise and counter by hand then engine just lock solid"

That sounds exactly like what I'm experiencing with mine. I'll keep you posted. I appreciate you posting the link to your getting your unit back up and running. It was a great read.

Jason

 

[Ray70]

Back to the glow plug thing.... an 802 doesn't have glow plugs. It only has pre-heaters in the intake manifold.
Either remove the injector or take off the valve covers and hold a valve open ( this can be done you prying down on the valve tip ) while you turn the motor over by hand an see if any liquid comes out of the open valve.

 

[jstew0903]

Back to the glow plug thing.... an 802 doesn't have glow plugs. It only has pre-heaters in the intake manifold.
Either remove the injector or take off the valve covers and hold a valve open ( this can be done you prying down on the valve tip ) while you turn the motor over by hand an see if any liquid comes out of the open valve.

Thanks for pointing that out. I was warned by someone not to take any more than one injector out at a time? Is there something I should be careful of when removing the injectors? Something about the timing or something.

Jason

 

[Denvercaitland]

Jason,

The fuel injectors are what , as per ray 70 suggestion, you want to remove. They are located on top of the head to the left ( If you are facingthe radiator). The injection pump (fuel pump - timing issue .... one at the time) are mid engine to the right ( arguably requiring more TM reading and care in removal and reinstalling )

 

[Ray70]

That's exactly correct.
If you have trouble removing the injectors another way to open the valves is to remove the rocker arm nut on 1 valve per cyl. and put a few washers or a larger nut over the stud to act as a spacer then put the original nut back on and tighten it down until the valve is just off it's seat a little bit.

Some times just loosening the nut and retightening will cause the lifter to expand and it will hold the valve open for 10 - 15 minutes until it bleeds back down.
I would not recommend cranking it over with the starter at this point, turn it by hand and see what happens.

 

[jstew0903]

That's exactly correct.
If you have trouble removing the injectors another way to open the valves is to remove the rocker arm nut on 1 valve per cyl. and put a few washers or a larger nut over the stud to act as a spacer then put the original nut back on and tighten it down until the valve is just off it's seat a little bit.

Some times just loosening the nut and retightening will cause the lifter to expand and it will hold the valve open for 10 - 15 minutes until it bleeds back down.
I would not recommend cranking it over with the starter at this point, turn it by hand and see what happens.

Thanks again for all of the help. I'll remove only the injectors on top only and report back. With the exhaust being unbolted I wonder if someone poured something in the exhaust. Like marvel mystery oil or something.

Would there be any reason to do this outside of rings needing freed up? The engine only has 425 hrs on it. Looks clean on the outside.

 

[Denvercaitland]

Remove injectors and turn engine over to see what comes out of injector holes ( PS - - liquid in the cylinder , if any, will come out VERY forcefully. ) oil of any kind may not necessarily be bad - water would be a nightmare scenario.

 

[Guyfang]

I would not turn it over with the starter. First off, any fluid in the jug WILL hit the ceiling, and I don't care how high yours is. Secondly, if you have any kind of engine problem, it will only make it worse. Turn it over by hand.

 

[jstew0903]

Thank you. I will definitely turn it over by hand. It won't be for a week or two. I won't be where the generator is being stored. Praying it's not water in there.

Jason

 

[jstew0903]

Took some photos of what I'm working with. Figured I would take some photos and show you what I'm working with visually. This is the one I suspect is hydro locked. 425hrs

Is this one been pillaged too much to try and put back together outside of the compression issue? Curious what you all think. I like a challenge but I don't want to get lost in a waste of time.

 

[flyfishtrailer]

I am nowhere near the expert needed to really give you a yay or nay, but it doesn't seem too bad, and parts can be found here and on other sources (although generally cheaper here with better service!) Might be a fun garage project for the winter.

 

[jstew0903]

That's what I was looking for. My son is 18 and he really likes working on things with me. My idea was to rehab it and use it for our Cabin when the power goes out (which is quite often). I ended up buying the running one to have one we could use straight away.

If anyone has parts they want to sell from a donor I'll buy them. I will attach more photos.

Thanks again

Jason

 

[Light in the Dark]

Yeah those photos don't look bad at all... All the leads you see are disconnected from a single TB (genhead output) just behind the firewall near the air filter.

Look forward to more photos.