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Discussion Starter · #1 ·
My F915 has almost no power under load and billows smoke. I see complete kits for rebuild which include liners. Should I just do rings, bearings, gaskets and seals, or everything? Unsure on hours as hour meter has been dead since I purchased it.
 

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With black smoke, that's typically unburned fuel, so I'd start with looking at the fuel system first. IDK anything about the specifics of your engine, but it could be an injector or high pressure pump issue, or even something before that. It's still possible an engine rebuild is in order, but that's relatively expensive and time consuming, and may not fix the problem (it may still be a good thing to do, if compression is low or there's some other reason to do it).

I would suggest getting the service manual for the engine (likely not cheap from JD), and then go through it's diagnosis procedure (I would expect it to have one) for black smoke. You'll want it anyway, to do the engine rebuild right, if you do go through with that.
 

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A bunch of random thoughts;
1. if it overheated - why? Does it usually run hot? My yanmar loses A LOT of power when it is too hot (radiator blinding or clogged radiator)
2. Does it run any different cold vs hot?
3. Air cleaner new?
4. Most diesel problems are fuel injection related. Injectors / injection pump / *air in fuel supply from tank to injection pump is the #1 most common problem with diesels
5. Before you jump to a rebuild, you really need to determine where your problem lies. I would start with a compression test.
Even if it shows low compression, I might try soaking the cylinders with decarbonizer. My yanmar had very low compression due to rings carbon sticking on all three cylinders (long story behind that).
 

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To your original question, liners are only needed if the cylinders are in really bad shape (need to measure). Since diesel fuel is a lubricant, the cylinder walls don't wear like a gasoline engine. If a rebulld is necessary, I would not be surprised if a simple hone and ring job is all that is needed - at which point I would also have the head checked, surfaced as needed, and a valve job.

To my original post - rebuilding the engine will do you NOTHING if it is a fuel problem (which would be my first guess)
 

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Discussion Starter · #7 ·
There was a build up of crud in the cooling system. Did a flush. Took many flushes to get clean water. This running issue only happened after the overheating. I recently did a fuel system rebuild except injectors. New lines, pump, filter, and so on. Completely bled the system. FWIW, until this it actually produced very little smoke. It's always been down on power since I bought it. Still starts without glowing. Only under load does it smoke. It's not consuming oil. And no oil coolant mixing.
 

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Do you have the manual/info for how to calibrate the fuel pump? They typically will have a specific way to do it, both so it's timed correctly and pump out the right amount of fuel and can require the use of special tools to do it.
 

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If the overheat event was the change to the black smoke, then I would think about head gaskets and stuck rings (carbon)....and now that I think about it, possibly injectors affected by the overheat.

Even having always been low on power, I would not necessarily jump to the conclusion that its a rebuild issue. It could still be the fuel system not being 100%.

Recommendations???? Bleeding is free - so worth a try. I think injectors can only be tested in a shop with the right equipment - I think similar for your injection pump. I would definitely do a compression check. I'm guessing it might be low, but if it not low, then you know to be chasing a fuel issue. If it is low, it could be head gasket, rings, or valves.

You say it is a new pump. Can I assume you mean the lift pump and not the injection pump?
 

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A good injection shop will charge $15 per injector nozzle to test. Well worth it in my experience with that engine. Not cheap to rebuild, little over $100 each...Compression check can't hurt. I have had the best luck using the glow plug holes for this. The Harbor Freight Diesel Compression Tester works fine.

Don't get into the injection pump until ALL other options have been exhausted.

Lift pump pressure min spec is 3psi I think.

Do you know if the previous owner adjusted the fueling ever? Things get hairy if that is adjusted incorrectly.
 
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I assume that your new lines are also in the tank too. With that and new lift pump, I think you are not sucking air - but there was one member that eventually found their filter housing to be the source of the air leak. All the same, I think an air leak would only account for the low power. Air in the line typically compresses at the injector and delays the injector from opening - resulting in less fuel. So long as the fuel still atomizes the same, I would expect that fuel to burn. There would just be insufficient fuel for good power.

Typically, the black smoke means unburnt fuel. The two things that would typically cause that are low compression (rings/valve/head gasket) or weak/stuck injectors letting too much fuel in.

To Knocknock's comment - stay out of the injection pump. It is rarely the issue and requires the skills and tools that most of us don't have.
 

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Discussion Starter · #14 ·
I'm pretty sure it's the compression. Wish this had happened a month or so from now as I still have, at least, a Month of cutting ahead of me. More likely 6 weeks. So time is of the essence. Been looking at f series diesels but most people selling can't be bothered to get back to you. Darn FB
 

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In case you have carboned rings causing low compression, it may be worth removing the glow plugs, soaking the cylinders with decarbonizer or marvel mystery oil. Let it sit for a day. Stoke the engine with glow plugs out. Repeat another time or two. After last soak, stroke the engine many many times to get the liquid out. Then glow plugs back in. I'd do an oil change too. And see if its any better.
 
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