Nanni, Kubota, Three-Cylinder Diesel Won't Rev in Gear

[surfmachine]

Ahoy, my nanni 3.75HE diesel, with a TMC 40M twin disc technodrive revs to 4000 rpm in neutral, but when forward or reverse is engaged I can only get 1500 rpm out of it, even when manually advancing the throttle on the motor?
Motor just at 1000 hrs and serviced all filters and oil 25 hrs ago.
It has been getting progressively harder to start and I had to bleed the line to get it to start last night.
Checked
*the prop shaft rotates freely,
*The propellor and shaft are not fouled,
*plenty of fuel,

The motor sounds sweet in neutral and revs quickly to 4000 rpm, even with the throttle connection disengaged and the motor in gear it will not rev beyond 1500 revs when manually advancing the throttle to full power position.
Could it be the fuel pump or injectors?
Does anyone have a diagram of the Kubota fuel injector?
I am in a remote island, Nias, 100 nmiles off the NW coast of Sumatra.
Please help with advice if you can?
Fair winds from Keith.

[DeepFrz]

You didn't say if it ever revved higher than 1500 rpm in gear or if this is a new thing.

[daddle]

Keith -

In these diesels, typically, the fuel control lever does not directly move the injector pump fuel control rack. But rather pulls on a remarkably tiny spring inside that pulls against the governor spring. Any tiny rust or grime in the area can stop the injector pump fuel rack from moving.

Unloaded, the fuel rack does not need to move very far. Engine in gear it needs to move all the way. Your situation as described.

Mine had a tiny spot of rust once. From a leaky water pump">raw water pump seal, which is nearby...

You might try removing the fuel control cable from the engine. With the engine off exercise the fuel control lever a few hundred times (have your crew do it while you surf). Maybe it will break free.

Daddle in Surf-free Borneo

[surfmachine]

Here is he engine specs, it has bosch injectors.

ENGINE SPECIFICATION
Number of cylinders : 3
Displacement : 719 cc
Bore - Stroke : 67 X 68.4 mm
Compression ratio : 23/1
Max. pressure difference between cyl. : mini 3 b
Compression pressure : 29 to 33 b
Maximum speed without load : 3800
Maximum RPM in load : 3600
Idle RPM: 1050
Max. torque :
Firing order : 1 - 2 - 3
Rotation : Anti clockwise
INJECTION
Type of injector : BOSCH JET
Fuel injection pressure : BOSCH MD MINI
Injection pump manufacturer : 140 b
Injection timing : 20 to 22°
TIGHTENING TORQUE
Arm head cover cap nuts : 0.4 to 0.6
kgF/sq.cm.
Cylinder head bolts : 4 to 4.5
Flywheel bolts : 5.5 to 6
Connecting rod bolts : 2.7 to 3.1
Rocker arm bracket nuts : 1 to 1.15
Main bearing caps bolts : 1.3 to 1.6
Main bearing caps bolts : 2.7 to 3.1
Nozzle holder assembly : 5 to 7
Glow plugs : 0.8 to 1.5
LUBRIFICATION
Oil pressure at idle RPM : 1 bar
Oil pressure at maximum load : 2b to 4.5b
Recommended oil : API CD 15W40
Oil pan capacity
- mini :
- maxi : 3.3 l
Gearbox model : HBW 50
Oil capacity : 0.3 l
Recommended oil : ATF
COOLING SYSTEM
Capacity : 4 liters
DIAGRAMS
Valve clearance (cold)
Inlet : 0.15 to 0.20
Exhaust : 0.15 to 0.20
Valve recessing : 0.30
PISTON RINGS
Piston ring gap :
Piston top compression : 0.15 to 0.30
Intermediate : 0.30 to 0.45
Oil control : 0.30 to 0.45
CYLINDER HEAD
Cylinder head surface flatness : <0.05 mm
SEA WATER PUMP
Water flow : 22 l/mn
GLOW PLUGS
Resistance : ? 0.90 ohm

[surfmachine]

Cheers mates, it always revved to 3800rpm in forward, it is a new development, seemed to get a lot worse after the crew threw the motor into full reverse when we making the passage from sibolga to nias when the depth went below 100m and the depth guage started reading down the zero, it only works to 100m! But I dont suspect any gearbox damage?
Maybe it is starving for fuel, the fuel pump faulty or injector nozzles partially blocked?
I will check the throttle linkage to the pump!
Thanks.

[Sailorman Ed]

Keith, sorry I cannot help with any good suggestion but can you tell me the manufacturer and PN of the white fuel filter on your engine? Nanni painted mine all blue so the real PN is obscured.
I suspect Daddle has it right but you could remove the fuel injector, reconnect the fuel line and check the spray pattern.

Ed
Nanni 4.150HE

[senormechanico]

Exhaust mixer getting plugged with carbon?
My Volvo let me know all of a sudden. Same symptom.
I knew right where to go because I'd been putting it off for a loooong time!

[Healer52]

Valve adjustment?

[Ex-Calif]

- In gear at 1500 crack the fuel line to each injector one at a time. Verify change in rpm and that fuel is being delivered. Noted by a "pulsing" stream of fuel.

"It has been getting progressively harder to start and I had to bleed it last night"

This indicates to me that the system was not bled properly during service or that there is a leak in the low pressure side of the fuel system allowing air in.

- If air in the system troubleshoot and correct leak on the low pressure (suction) side of the fuel system.

Are you getting any smoke?

[daddle]

[QUOTE=Ex-Calif;521634"It has been getting progressively harder to start and I had to bleed it last night"

This indicates to me that the system was not bled properly..[/QUOTE]

Possibly. That clogged elbow idea is reasonable too and fits with the sudden application of power comment. But hard starting will also result from the stuck injector pump rack. The pumps are often set up to inject full rich as startup.

[Ex-Calif]

Originally Posted by daddle

Possibly. That clogged elbow idea is reasonable too and fits with the sudden application of power comment. But hard starting will also result from the stuck injector pump rack. The pumps are often set up to inject full rich as startup.

Daddle - Don't disagree. There are a couple of things my grandma told me when I started mechanicin' 30 years ago.

- If something doesn't work go back to the last thing you "flucked" with. In this case a fuel filter change

- Things gradually changing over time are wear-out modes - "getting harder to start" over time. "Increasing amounts of black smoke lately." "Temperature has been steadily getting higher over the last few months."
- "Hardware failures show up immediately. "The rack stuck." "The fuel pump failed." "Engine was fine yesterday and today it won't start."

I admit I am not the world's best diesel mechanic and 95% of the time my theories here are without the benefit of a manufacturers manual. Without specific maintenance info it is very hard to be accurate. It is also hard to be accurate by remote control on the internet.

However - boat diesels are pretty simple. The critical things like injector pumps are also super reliable in general.

In this case I am thinking a volumetric problem. To make more power you need more volume (air+fuel) - It is an air problem or a fuel problem.

Air is simple - Inlet blocked, outlet blocked, valves operating properly. That's it - nothing else. (OK - failed piston rings and head gaskets are another animal)

Fuel is also pretty simple -

- Reliable supply to lift pump = Fuel tank filled, outlet not blocked, supply to lift pump not leaking.
- Reliable supply to injector pump = Fuel filter bowl o-ring not leaking, all lines to injector pump secure and not leaking. Properly bled.
- Reliable supply to cylinder = Injector pump working, no leaks, injectors not clogged, return line not leaking.

[surfmachine]

Thanks for your prompt reply to my query.
I have done as has been suggested, but still no go past 1800 revs in forward or reverse!
1. the mixer manifold was really clean, new in 1/4/10, but some salt build up on the salt water inlet side inside the inlet hose.
2. Got some clean diesel and ran it straight into the injector pump, bypassing everyhing, worked exactly the same.
3. fuel pump is delivering 1.5litres of clean diesel per minute, so ok on the delivery side.
4. tightened all the hose clamps.
5. the clean fuel used had no additives in it.
6. this fuel has been used in the motor for 4 months now, only effect has it has been harder to start, but starting fine now.
7. did notice that the front left engine mounting bolt had sheared in the last 25 hours of use, it is sitting nearly on top of the existing bolt stump, I will get it welded up or replaced in Teluk Dalam, here on Nias.
8. one other issue is that the new crew threw the motor from forward to reverse, during the passage here, at 1500 revs when the depth guage started reading down to zero as we had gone over a 100m deep, but this did not seem to have caused any problems?
9. Gearbox is full of atf and a nice red colour.
10. Prop and shaft were pretty clean, now all shiny and clean, no fouling there, spins easily by hand and folding prop is working ok.
11. Can it be a gearbox problem or dirty injectors?
12. does the bosch injector pump have a built in limiter auto throttle loader?
thanks very much from Keith.

[surfmachine]

No visible smoke, just seems to labour when put into gear, maybe I should disconnect the prop shaft and see what effect this has?

The sheared engine mounting bolt doesn't appear to affecting it too much, it has a flexible coupling and the broken bolts are sitting almost on top of each other.

Yes excalif, I did not bleed it properly before starting it after last service 25 hrs ago, but is bled properly now and no leaks on the delivery side, all gaskets to filters tight.

Next step will be to disconnect prop shaft and see what happens?

Thanks from Keith.

[Ex-Calif]

Packing gland hot in gear?
Smoke?
Cracked the injectors one at a time under load and observed rpm?

Still thinking of the simple and "cheap" stuff.

[surfmachine]

Power loss problem found!!!!! How to fix it?

Problem is no fuel being delivered out of injector pump to number 1 cylinder, removed metal line to injector and nothing coming out of the top of the pump for number one. Number 2 and 3 pumping ok!

Do I remove the top of the fuel pump and go from there?

Please offer some advice if you can.

Cheers from Keith