D8K with D342 Spacer Plate Engine: Tons of Black Smoke and No Power

[BHathaway52]

Hello All,

I have a D8K I did an in-frame overhaul on for a client a couple years ago. He has used it intermittently since then, but it sits a lot. Maybe 100 Hrs on it since the rebuild.

It has started black smoking badly at all throttle positions and low on power. The owner says it is using fuel like crazy even while sitting idling. Not that these things ever got great fuel economy! Haha It is hard to start up, usually needs a little ether, but always has been a bit hard to start. Probably from the starter dragging some and he has overheated it several times since the rebuild and I have had to do the headgaskets again; cylinders probably got washed out some.

- It has a new turbo and I pulled the exhaust and intake side and both look good on the turbo.

- I pulled the Air/Fuel Ratio on the end of the injection pump and the diaphragm and springs looked good in it. Haven't been brave enough to venture into pulling the governor assembly.

- I am trying to think back and I believe I put new injector tips on it, but it has been a few years so blanking on that!

- The outer air filter was sooted up bad so I am definitely replacing that and that should help some, but I do not believe it is my main issue.

- I noticed a few exhaust leaks at points on the manifold so I will be repairing those in case that is losing some pressure to spool up the turbo.

- I did notice the hand pump to prime up the system does not pump up hard like it used too. It pumps up some then goes soft. Could that be a symptom of a fuel injector dumping fuel?

 

[Mobiltech]

On the point of the air filter being black with soot I would be checking the precleaner to see if it’s melted and also the dust ejector system attached to the exhaust to see if it’s sucking the way it should.
Having exhaust leaks under the hood could also cause this. If they are bad they will also cause low boost making more black smoke.

 

[Vetech63]

Black smoke is unburned fuel. Lack of air or over fueling injector/s. Loss of compression can cause this also. Have you tried cracking the injector lines while its running to see if it clears up or smokes less?

 

[BHathaway52]

Haven't tried cracking injectors, will give it a shot, and will also check out the pre-cleaner and dust ejector.

Thanks guys!

 

[Old Magnet]

Are you sure about the air/fuel ratio controller diaphragm? A failed diaphragm would mach those symptoms.

 

[BHathaway52]

The diaphragm looked in great shape, but I have never seen one before so I may be wrong. I'll take some picture of it.

I'm assuming engine oil is supposed to be coming out from where the air/fuel ratio controller installs?

 

[tctractors]

If the AFRC has a damaged Diaphragm or pipe it usually just lacks power and fails to reach the power point, the idea of it is to limit the rack travel until the air boost in the inlet track can handle more fuel, you can adjust the AFRC to make black smoke or run fairly clean, a possible cause of smoke is fuel pump timing incorrectly set, Torque flooded or other heavy load placed on engine, the ether comment I find worrying as I have never needed to use this even with worn out engines that have 25'000 hrs into them, check crank end float might be something worth doing, other than that I would pull it to bits and start again, don't forget rod numbers to the windows as new motors hate overheat so think of piston damage.

 

[chidog]

Diesel engines throttle by way of the amount of fuel introduced into the combustion space.
If the pump is putting excess fuel at idle it shouldn't idle well unless the air is restricted enough to cause that. I'm curious what the valve lash is, and what else could restrict air? And or the proper spray pattern?

 

[Oxbow]

Are you sure about the air/fuel ratio controller diaphragm? A failed diaphragm would mach those symptoms.

Wouldn't it be the opposite? A failed diaphragm wouldn't release the rack once boost started and prevent fueling?

Should have read to the end, tctractors addressed this.

 

[Oxbow]

I am reminded of a 980C that suddenly had a similar issue. The operator unknowingly had moved the bucket lever to the locked in raise position at idle and it almost killed the engine.

I was wondering if there could be a parasitic load on the engine from a hydraulic or torque converter issue causing the symptoms? Just a thought.

 

[Dave Neubert]

Could be a head gasket blown between the cylinders

 

[56wrench]

You said the inlet and exhaust sides of the new turbo ‘looked’ good but how did it spin?

 

[nicky 68a]

It worries me that only 100 hours or so has been racked up on this engine since rebuild.
I note you’ve had to pull the heads back off it in those 100 hours.
It all seems abit of a disaster for a rebuilt engine.
However,the time that’s passed since the rebuild may well of attracted all sorts of breakdown in air filters,air intakes etc and oil seals could have been weeping in that time.
Something seems off here.

 

[Darwin09]

The quote" he has overheated it several times" is a flag for me.

 

[tctractors]

I would check the oil level in the flywheel case to make sure the scavenge pump is coping, if this pans out o.k. I would pull your engine down chap as something is a knacker job, to check the pump timing you will need the timing plate service tool to bolt on the Alpha Drive.

 

[BHathaway52]

Hey guys, finally back to this disaster of a dozer! Haha

I did find the air mixer was melted and replaced that as well as the air filter and that seemed to help for a little bit, but it has since then gotten weaker and weaker and will barely pull itself now.

I took apart the governor assembly on the end of the injection pump and worked the rod back and forth along with the governor wings while sprayed down with penetrating fluid. They seemed quite stiff at first, but felt pretty good once I was done. I assumed this was moving the fuel rail inside the pump as well and hopefully freeing it up? Picture attached showing the assembly I was working on.

Also have attached a few videos of it running. This is at WOT on the injection pump. I have little to no range on the throttle lever. Didn't realize you couldn't hear me in the videos so enjoy my pantomiming!

Dumb question, but gotta ask it because I don't know. When you say check the oil level in the flywheel housing case do you mean the dipstick under the seat or is there another location to check?

It struggles to build up oil pressure to initially release the little piston in the injection pump and fire off, but once it does my pressure gauge spikes up fast and shows great oil pressure. I'm suspicious my started is on it's last leg and not turning over the engine near fast enough.

 

[.RC.]

It sounds like one of those single cylinder Lanz Bulldog tractors.

 

[BHathaway52]

Lordy it totally does!! XD

 

[Mark250]

Just a stupid question, but did you check that expansion plugs in the head have not popped out. if i recall this engine in the trucks had the lifting bracket over the expansion plugs and not easily seen

 

[BHathaway52]

I have not! I'll try to look those and see what we have.