Any ideas as to why diesel engine wont rev past 2000RPMS`s?

[Karlsenkystfiske]

Si this is a John Deere 4045TFM50 that I use for propulsion and hydraulics on board my fishing vessel. When I try to push it towards max. rpm`s with load from the propeller, it shoots up there, and then winds rapidly down to about 2000 RPM.
The air filter is clean, and I just changed coarse and fine diesel filter. Which in all honesty looked clean already
This is a video link of me trying to push it

A friend of mine had a similar problem with a cummins diesel. He had to have the turbocharger overhauled. Mine only have 5700 hours on it, but 13 years is still 13 years in a pretty demanding environment.

 

[Roberto]

A more or less clogged fuel tank air vent might cause that, in particular if the tank is full.

 

[Karlsenkystfiske]

That is not the case here. Lots of space to vent.
I should add that the engine is able to attain high speed if I reduce propeller pitch.

 

[Knig]

The fix here is hearsay, a sealine I test drove had a similar problem in Gosport and it turned out to be a return fuel line blockage.

 

[Karlsenkystfiske]

The fix here is hearsay, a sealine I test drove had a similar problem in Gosport and it turned out to be a return fuel line blockage.

Do you know how it got cleaned out?
I dont think it is the case for me, as there is two return lines, One going to each fuel tank. The clogging vein would have to be between the T-piece and the fuel injectors then. But I do see how it is possible

 

[lustyd]

If you just changed the filters I’d change them again as a first port of call in case you got a duff one or you did something wrong or left something open or loose. Assuming it was working before the change, or did you change them as a possible fix?

 

[JOHNPEET]

You sure that you haven’t got something going on with the propeller pitch control! The rpm seems to jump very quickly from 2000 to 2500! Almost too quickly for that to happen with load on the propeller, but it could happen if the load or pitch suddenly dropped off! The gentle decline in rpm from 2500 back to 2000, could then be due to the load or pitch slowing being reapplied!

Just a thought!

 

[Knig]

Do you know how it got cleaned out?
I dont think it is the case for me, as there is two return lines, One going to each fuel tank. The clogging vein would have to be between the T-piece and the fuel injectors then. But I do see how it is possible

No, sorry, I just enquired as I was interested in buying but it got sold before I had decided to go ahead.

 

[Tranona]

That is not the case here. Lots of space to vent.
I should add that the engine is able to attain high speed if I reduce propeller pitch.

Is it a variable pitch propeller? If so then the suggestion in post#7 is worth investigation. The revs are being limited by the propeller load by the sound of it not by a shortage of fuel.

 

[oldharry]

If the filters have recently been changed then its more than likely one is leaking very slightly, creating microbubbles. Too small to actiually stop the engine, but enough to reduce the charge at each squirt of the injectors.

 

[Tamino]

The Turbocharger of my Yanmar-motor failed at about 1200h. Max rpm 2000/' without load. I had to change it.

 

[WFA]

Is the exhaust restricted?
My (naturally aspirated) engine would reach max revs off load but plateaued at 2,000 rpm under load, accompanied by an alarming loud (prove to be) drive plate chatter. After much head scratching I removed the exhaust bend and hi presto! The exhaust bend was almost completely closed with a build up of hardened exhaust debris.
The engine couldn't burn all the fuel being delivered at higher revs because it couldn't fully purge and recharge the cylinders with clean air between power strokes. The struggling engine trying to push a 10 ton boat along caused surging which put the drive plate dampers to work! Otherwise there was no indication such as excessive exhaust smoke probably because it's a wet system discharging close to the water line and well out of normal sight.
I note that the 4045TFM50 has a heat exchanger bolted direct to the exhaust manifold, as has my Volvo Penta. I found the heat exchanger outlet port a bit sooty but otherwise clear, the adjoining exhaust bend inlet held the choking debris.

 

[Slowboat35]

The OP says it winds up but then reduces to 2000RPM - my immediate thought is air starvation if the engine is enclosed, but...
then says it revs OK with finer pitch selected, in which case it is load related and thus either a fuel flow restriction or probably more likely the VP prop is running beyond its normal coarse pitch limit/stop undemanded. If the engine isn't enclosed I'd start by investigating the prop's functionality.

 

[Karlsenkystfiske]

The OP says it winds up but then reduces to 2000RPM - my immediate thought is air starvation if the engine is enclosed, but...
then says it revs OK with finer pitch selected, in which case it is load related and thus either a fuel flow restriction or probably more likely the VP prop is running beyond its normal coarse pitch limit/stop undemanded. If the engine isn't enclosed I'd start by investigating the prop's functionality.

Not so enclosed that its not getting enough air. No difference if I leave the engine room door open
It has never had a problem turning the propeller with max pitch before. I have even contemplated getting a bigger prop, or coarser pitch because the engine has ran so easily with it.

If the filters have recently been changed then its more than likely one is leaking very slightly, creating microbubbles. Too small to actiually stop the engine, but enough to reduce the charge at each squirt of the injectors.

This started before I changed any filters. And the engine has run many hours since. No way there is any air bubbles in there now.

Is it a variable pitch propeller? If so then the suggestion in post#7 is worth investigation. The revs are being limited by the propeller load by the sound of it not by a shortage of fuel.

It sure is! Governed by a Nogva 1131. So hydraulic control of the pitch. But there is no way the pitch is suddenly too high for the engine. Just to be no problem at all running full speed and full pitch. No I am going in 6 knots with a engine not being able to do more than 2000 rpms

 

[lustyd]

This started before I changed any filters. And the engine has run many hours since. No way there is any air bubbles in there now.

Very useful to know. Was the old filter clean, and have you checked the new filter?

 

[Karlsenkystfiske]

The fine filter is no way of knowing really. It has the construction of an oil filter. The coarse filter consists of an inlay made of what looks like a piece of matress. "Porolon" I think they call it. Was not dirty. Just a few rust flakes. I change it regularly, so dirt doesnt get a chance to build up. Have not checked it after changing. Dont believe I will see anything.

 

[vas]

If I were a betting man, my money would be on the turbo...
easy to remove the air filter I hope, is the turbo spinning easily and nicely, is the lots of play side to side? do vanes look worn?
do you have a boost gauge, if not for 20-30quid you can get all the bits needed to temp fit one in the e/r and see if the boost is what it should be.

 

[Karlsenkystfiske]

So I removed the air filter and had a look at the vanes. Looked and sounded just fine. Removing the air filter did nothing to remedy the problems either. No surprise as I cleaned it properly about 150 running hours ago.

I then proceeded to remove the control cable from the fuel pump control arm. And woila! I could operate the engine as nothing had happened. It reved up and down like a racecar! No hestitations even with full pitch applied. So we have been barking up the wring trees here. Surely iy must have sufficient quantities of both air and fuel?!

But I dont understand it at all. The control cable is putting the control arm in the same positions as I do by hand :S
Once I connected the control cable it is not reving past 2000 RPM`s! Makes no sense to me.


Control arm going all the way to the high idle stop screw. But the control cable is connected and it wont rev past 2000 RPM`s.

 

[scottie]

Refit the cable to the remote control
take phone photos for comparison
check for missing split pins and or locking nuts
if you can get fitting instructions it will make setting up easier

 

[Bilgediver]

Si this is a John Deere 4045TFM50 that I use for propulsion and hydraulics on board my fishing vessel. When I try to push it towards max. rpm`s with load from the propeller, it shoots up there, and then winds rapidly down to about 2000 RPM.

Definitely check the turbo is clean and appears OK also the air-cooled however is there a possibility the hydraulic system pump has faulty controls and is loading up the engine.