Weak air intake on an MEP-803A

[diogenescreosote]

I have an MEP-803A that I bought with 500 hours. It now has 950 hours. I've changed the oil once and run it at about half load for the 450 hours I've owned it. Visually it is in good shape.

It was working swimmingly until one day it would not turn on. On cranking the engine, the sound was smoother than normal, and it did not bark at all. The fuel pump is pumping, and I opened up the injector pumps to make sure fuel was getting into each one, and they look fine.

So I disconnected where the air hose goes into the engine and, on cranking, I do not feel nearly as much suction as I would expect to.

Any ideas, folks?

 

[Scoobyshep]

Disclaimer: I have never touched this model, nor do I claim expertise on it.

That being said, my best guess stuck/improperly seated valve/improper lash. I cant imagine checking valves being that difficult.

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[DieselAddict]

+1, you likely have a valve leak. If you can pull the injectors you can do a pseudo leak-down test by blowing air into the injector hole and see where the air comes out. Obvioulsy with the cylinder to TDC of the compression stroke.

 

[Ray70]

I 2nd or 3rd.?? the leaking valve theory. Probably hanging up on carbon deposits if you have been running under light loads.
Typically the motor will seem to crank more steadily and smoother instead of the pulsating you hear with good compression.
I have purchased several 803's that would not start for this same reason and I have a quick trick to get them started.
Bring one of the cylinders up to TDC and remove the valve covers rocker arms , keepers and valve spring from 1 valve.
Put a cordless drill onto the valve stem tip and spin the valve while pulling up on it slightly.
Give it a dozen or so revolutions, then reassemble and move on to the next valve.
Do all 8 valves then let the machine sit for 1/2 hour to ensure the lifters have all bled down.
Start it up!
An even better method that I use is adding a little compressed air to the cylinder. This will actually let you hear as soon as the valve is seated, usually only a couple revolutions. It also helps blow carbon out of the way of the valve seat.
Only issue is you need to make an adapter to get compressed air in through the injector hole, otherwise just use a helper and a rubber tipped blow gun a non-OSHA safety ( bleed hole ) blow gun.
Once you get it running, progressively load it up till you are at 100% and burn off as much crap as possible out of the head.