John Deere 855/856 hard starting

[MTGreen]

Got it, I will give both of those things a try. One more question: If the valves are out of adjustment, is the thinking that it would be creating too much compression, which is therefore slowing down the starting speed?

Adjusting valves tightens up slop in your valvetrain (a small amount is needed for normal functioning/thermal cycling -adjust to spec). That normal wear and tear slop accumulation effectively decreases the duration of your camshaft which means that your valves open later and close earlier which restricts the ability of your engine to breathe. Adjusting the valves brings it back up to near factory spec.
I don't think it has any measurable effect on compression unless maybe if it's grossly off spec, but it does have the effect of easier starting, theoretically improved efficiency, and less slop means less clatter

 

[Robin Veerman]

Get a professional to adjust the valves. Easy job to do….if you’re experienced. Probably less than an hour if you do some prep work for him like removing the valve cover…
If you understand how to find TDC for each piston maybe you could attempt it yourself.
ps. 900 some hours on a 35 year old tractor could also mean lotsa stale fuel and varnish residue. Work the dang thing with a bush hog or tiller for a few hours and clean the carbon out of it. Oh, and probably has summer diesel in it?

 

[MTGreen]

You don't have to find tdc. For each cylinder, rotate the engine by hand until one valve is fully open, then adjust the other (fully closed) valve on the same cylinder. Repeat until you get all your valves adjusted.

Once you have the valve cover off, going through the 6 valves is a 30minute max process even for someone who has never done it before, half that if experienced

Lots of YouTube videos on the process. Pretty much the same process for all pushrod solid lifter engines diesel or gas

 

[Hillwalker]

@hosspuller - got it, makes sense
@MTGreen - awesome, super helpful info
@Robin Veerman - thank you. I've ran it a ton all summer so bet the old fuel (if any) is long gone. Also, live in DFW...I'm not sure they even change diesel formulations here lol

Guess I know what my next project is; will have to figure these valves out. Wish there was an easier solution. Will report back.

 

[Fxfymn413]

My bet is low crank speed causing unburned fuel to collect in the cylinders due to an inability to generate enough compression to fire the fuel. Is the fuel fresh and of high quality? Did this start when you re-fueled? No wax in the fuel?

Use KISS and check for the obvious like a bad ground or an internally corroded battery cable. Have you tried connecting jumper cables to the starter and ground to eliminate the existing cables?

How about the starter? Us an ammeter and check to see what kind of draw it is making. If it requires a high amperage to spin it is most likely bad brushes or a bad connection in the solenoid.

What viscosity is the engine oil? Using single viscosity oil that is too thick for ambient temps will slow the start down.

 

[gstrom99]

Update?

 

[Hodado]

Get a professional to adjust the valves. Easy job to do….if you’re experienced. Probably less than an hour if you do some prep work for him like removing the valve cover…
If you understand how to find TDC for each piston maybe you could attempt it yourself.
ps. 900 some hours on a 35 year old tractor could also mean lotsa stale fuel and varnish residue. Work the dang thing with a bush hog or tiller for a few hours and clean the carbon out of it. Oh, and probably has summer diesel in it?

I’d definitely call a pro
You’ll have a hard time finding parts for that particular Yanmar believe me I know John Deere dealer is no help at all that model engine is obsolete according to them.Mine blew up a year ago and I was about ready to part it out when I finally found a replacement engine that costed me plenty

 

[Indiana haymaker]

I would not think its a fuel bleed problem or air in the lines because once its running and warm it restarts ok. and pretty sure you have looked around for leaks. I suspect the black smoke is from too much fuel at the start from the 4 tries, kind of like the kids rolling coal in their trucks. I know different parts of the country put fuel additives into both gas and diesel for winter usage, but it does not sound like its cold enough for that to be a problem. Is the engine cranking over fast enough for a normal start? you mentioned you changed the battery, so guessing it was cranking slowly then, did the new battery improve it? Have you tried any starting fluid? My old John Deere actually has a port to screw a can of starting fluid into

 

[boatmoter]

Hope all is well! I have a 1987 JD 855/856 compact utility tractor that has recently begun to be very hard to start first time in the day. It has 923 hours on it and a known history back to 2001-ish and has always been maintained well.

The tractor was used all summer for some general property upkeep and then I elected to do a full service on it in September of this year where the hydraulic, oil, coolant, and all filters (including fuel) were changed with all JD parts and JD fluids.

Current behavior is that first time in the day it will take nearly 4 attempts to start and it will blow a lot of black smoke while it is cranking. Once it has been started, it will stop and restart at will, unless around ~2 hours elapsed. Current weather is 58 degrees and it just exhibited this behavior again after resting for a few hours.

My suspicions as to root cause are either fuel-related or heat-related (32 degree nights versus 80 degree nights over the summer).

Here is what I've tried so far:
1. Using the tech manual, I have bled the fuel system at both the bowl and pump and did not see any bubbles. Have not yet progressed to the injectors.
2. Bought a test light and confirmed power at the preheater grid (this unit does NOT have glow plugs) when the light is on the dash, so I assume the heater is working.
3. Confirmed that the fuel stop solenoid activates upon start up and releases upon key turn off.

This tractor has had a history of effortless starts up until now and I'm hopeful I can restore that. Thank you in advance for any and all tips.

I have a 3 cylinder diesel in a international. it starts right up everytime in the summer. but it gets about 60 degrees here and I have to really lean on the Glow plugs to get it to start. I removed all glow plugs and tested them,you can remove the wires from all but 1 of your glow plugs and check them with a ohmmeter to see if you have a defective one or hook use a temperature gun and heat your plugs with key and shoot each plug at the base to see if their all heating up,much easier then removing the glow plugs and bench testing them. but if I warm the cylinder head with a blow torch a little it fires right up. same with a ford 2120 I used to have. maybe some diesels don't like cold weather. also,if it's smoking it has fuel to the cylinders, if compression is low it can cause a starting problem too.

 

[Dennisfly]

I had an 855 some years ago. It ran good but got hard to start in the cold weather (Virginia) with the air heater working properly. I installed a block heater and with some preheat it started OK in the cold. But, it became progressively worse and in a couple of years it wouldn't start, even with the preheat.

I did a compression check and all the cylinders were about half of what the specs called for. I pulled the engine and removed the pistons. The cylinders were in good shape with no ridge and little if any taper. When I checked the ring end gaps, they were all in excess of three times the maximum allowed. The main and rod bearings were good. I had the head surfaced, the valves ground, and honed the cylinders and installed new rings. It started easy and ran good until I sold it some years later.

Probably not what you wanted to hear but that's my story. I'd do a compression check next!