NM195 runs bad when hot

[Tom Reed]

I'm trying to diagnose what's going on with this engine. From a cold start it runs great and does not miss a beat for about the first 1/2 hour. Then it starts to surge, sometimes almost shutting down. Then it runs good for a while. This engine had sat for a long time and when I got it the rack was stuck in the pump. Yesterday I got tired of listening to it (and waiting) so I cleaned the injector with no change. Then I changed the nozzle with no change. Then I put a new barrel and plunger in the IP with no change. I do see "air" in the fuel line and when bled it seems to stop surging for a while. Could the fuel delivery valve be the issue?

The first thing is a lack of fuel, but the surging happens when under light/no load. Smooths out under a heavy load. Next step is to check the valve lash. Anyone have any other ideas. Could a valve be sticking?

Also where is the best place to get parts for one if these engines these days?

[veggie]

If it smooths out under load it's probably not a valve clearance issue.
I would suspect the governor. Or maybe the governor spring.
Is it the stock spring ?

Although it is strange that it happens only when it's hot.
Overheating
How clean is the cooling system? (Radiator or hopper?)

Parts are getting more difficult to find.
I got some from AliExpress. There are several sellers there.
Just do a search for "R195 parts".

[mobile_bob]

if you allow the engine to cool down, will it then restart and run fine until it is warmed up again?  without any other modification other than cooling down?

the air bubbles in the fuel line, can you elaborate on that a bit?

also when you removed the injector and replaced the plunger and barrel, was there carbon up past the very tip of the plunger?  i would expect carbon only at the very tip, if up more than about a 1/16" or so, you might be experiencing some compression blowback up the injector tip, which would introduce some air bubbles in the fuel line, that it the injector high pressure line.  if that is the case the injection pressure is set too low.

do you have pop tester to check the injector for cleanly injecting?  if not can you take it to a local shop that has one?

i am thinking this is related to the air bubbles you mention in the fuel line, just need to know if that line is the flexible supply line from the filter to the pump, or the rigid steel injector line.

on another path

how long have you had this engine in service?   

what fuel have you been using?  if pump diesel move on, if veggie oil you might have a valve gummed up a bit? maybe?

if you have a valve gummed up and not closing properly, you might be able to determine that by running until it starts acting up, shut it down  and immediately roll the crankshaft/flywheel up on compression and see or listen to determine if you can hear unusual hissing out own of the ports?  a sticking or gummed up valve should be evident if there is one sticking if you hear some compression leaking past.

i don't believe there is anything about the governor that could cause your issue, and as the old saying goes, it only takes three things to run,  that being air, fuel and compression.

1. air, it is unlikely that the oem airfilter is an issue

2. fuel, that being a good delivery of fuel, at the right pressure (or nearly so), at the right time (or nearly so) and doing so dependably (which is probably the issue)

3. compression, not likely the problem or it would not start, every diesel i have every been around, if it started it would continue to run so long as there was enough of #1 and #2 above.  i don't recall a single episode of a diesel starting to miss because of a loss of compression once running, however...

i recall one time with a cummins ntc-290 when they made the change from torque/turn method of overhead adjustment to the "top/stop"method.  the intake valve setting was .016" if you used the torque/turn" method and .011" if you used the "top stop" method. 

at the change over more than one mechanic would read the plate on the engine and set the valves using the wrong setting with the old method,  .011" would cause an engine to miss once warmed up as it was too tight when the valve stem elongated from being hot.

so it might be possible that the intake valve is set a bit too tight?  can't hurt to check the valve settings.

whatever the case, let us know what you find

bob g

[Tom Reed]

egie, The governor is wide open when it does this. Sounds like it's digesting air.

Bob, Running Red diesel. Just adjusted valves and found the intake a bit tight. I think it's still doing it, but haven't run it long enough. Once cooled down the engine usually restarts fine. Not always.

Air bubbles, while it's running bad, I'll crack the fitting coming out of the fuel filter and it runs better for a while. Looks like I might be getting some air.

Engine had sat for a long time the plunger was stuck in the barrel. Now has a brand new barrel and plunger. Before cleaning the injector the needle was all gummed up and It took a bit to remove from the nozzle. Once apart it cleaned up nice and sprayed well (not great) from the pop tester. No dribble and proper "rattle" just not the best pattern, so I used it.

Line from pump is solid with banjo fittings.

Not real long, enough to run a couple of tanks of fuel through it. 9 Gal tanks.

Here's some pics.

[Tom Reed]

The business side

[Tom Reed]

Silo

[Tom Reed]

Closeup of engine

[Henry W]

Is the fuel return line from the injector going directly to the fuel tank? If not, the engine could develop air pockets and in turn feed air to the injector pump, injector line or injector. From your pictures it looks like the fuel return is possibly looping back to the stock fuel filter. And if that's the case that could very well be the problem. The preferred method would be to have the return line go to a separate fuel tank return.

I see the injector pump is pulling from the stock filter. The banjo fitting washers, washer on the top bolt on the filter and rubber sealing washer on the canister have been known to leak.

If your able, remove the air cleaner assembly and take a few pictures on how the fuel system is plumbed and post them so we can see what you have.

I see the cap vent is open. But double check the vent hole on the cap.

About the Governor. I would recommend pulling the timing cover off and check all fasteners. And possibly replace them with high quality grade 10.9 fasteners.

Especially check the the Governor ball spacer. Some were plastic and some steel. If it's plastic get rid of the lock washers and bolts and replace them with grade 10.9 flange bolts. And use the upgraded LOCTITE 243 it works better than 242 on oily fasteners. It has more holding strength also.

Here is something I posted years ago.

http://www.microcogen.info/index.php?topic=285.0

About Parts, there is a person in Florida that should be able to get any parts you might need.

http://www.mastersfarmsupply.com/home.html

The persons name is Marshall Masters

He bought all the Chinese diesel parts from Hardy Diesel years ago.

If he does not have the part, he mentioned that he can order it.

I see the injector pump is pulling from the stock filter. The banjo fitting washers, washer on the top bolt on the filter and rubber sealing washer on the canister have been known to leak.

[Tom Reed]

This engine came from a Hardy Diesel generator. Yes the return line from the injector goes to the stock fuel filter, I will cut the line and run it to the tank. that seems to me the only way for air to get in the system. Governor is all steel.

[Henry W]

Do you know if the return line is stock? If it was altered that is most likely your problem. Do you remember if the original fuel tank had a return fitting?
If not, than the fuel line was pitched up towards the tank to allow air to escape into the tank.

I noticed that the rubber fuel line is plumbed so air cannot escape. Which in turn will starve the fuel pump.

Try pitching the fuel line up towards the fuel tank.

I modified my previous post with additional info.

[Tom Reed]

Never seen an original tank, return line to filter does look original. Fuel hose is sloped up just hard to tell in photo.

[Henry W]

I looked at the picture again and I see how the air is supposed to get purged.

Look at the inlet fitting on the stock filter. It is the highest part. If you look at the rubber fuel lines lowest point you will see it's lower than the injector pump upper fuel line fitting. What is happening the stock fuel filter canister is loading up with air to the point that the fuel level drops below the upper injector pump fuel line. And in turn the injector pump is getting starved.

Pitch the rubber fuel line up towards the tank and it should solve the problem.

The fitting where the rubber fuel line is hooked up has to be the lowest point after the tank.

[Tom Reed]

Oh, for those that have read this far. I am making bbq pellets from used wine making oak. The ChangnChi is running a hammer mill with a 1/4" screen to turn chunks and strips of oak into sawdust. It blows into a cyclone on top of the silo. That system can fill the 16' silo in about 5 hours.

[Tom Reed]

I looked at the picture again and I see how the air is supposed to get purged.

Look at the inlet fitting on the stock filter. It is the highest part. If you look at the rubber fuel lines lowest point you will see it's lower than the injector pump upper fuel line fitting. What is happening the stock fuel filter canister is loading up with air to the point that the fuel level drops below the upper injector pump fuel line. And in turn the injector is getting starved.

Pitch the rubber fuel line up towards the tank and it should solve the problem.

The fitting where the rubber fuel line is hooked up has to be the lowest point after the tank.

I will give that a try. Thanks Henry.

[Henry W]

Never seen an original tank, return line to filter does look original. Fuel hose is sloped up just hard to tell in photo.

It looks like the center of the fuel line is lower than the fuel filter fitting. It looks like it's pitching down. If that's the case work the rubber fuel line so the entire line is pitched up towards the tank.