Hi everyone, first time poster here, I’ve been reading other helpful conversations on this site but I’m beginning to struggle so thought I’d join and see what you think. I have a 1986 John Deere 855 (Early model), with the 3TN75RJ Yanmar engine, run for 1,300 hours. I bought it January 2023 with just over 1,000 hours.
I apologize in advance for the lengthy post but there’s a lot to share and the little details might make the difference in figuring it all out.
I don’t recall much of anything being wrong with the tractor during the first summer of mowing/farming and I worked it fairly hard at times with the front end loader. Before the second summer of use I changed the oil, air filters, and fuel filter for the first time (notably the wrong air filter had been installed by the previous owner - it only had one air filter installed rather than the primary & secondary - I seem to remember it was in there snug enough, but I can’t be sure). That second season I noticed increased smoke coming from the Crankcase Breather/PCV tube, kind of a white or gray color. I noticed some oil consumption too, dropping from “Full” to “Low” on the dipstick range over the course of the summer (150 hours). The tractor also began to require longer cranking to get it to start, which got progressively worse over time, and would puff lots of black smoke for a few seconds after it finally started. Once started though, it always ran and performed great, until one day in the Fall of 2024 it wouldn’t start, and hasn’t since.
My aim has been to knock out all the easy tests & repairs in hopes that it won’t be necessary to pull the head off or send the injection pump in for testing.
So far I’ve done the following:
-The battery passed three tests at AutoZone. It seems to loose juice quicker than I’d like though, so when trying to crank the engine for testing etc. I use a jump battery pack to keep the crank speed fast and to take it easy on the tractor battery.
-Confirmed the manifold air heater/cold start aid dash light works properly (does not have glow plugs), and the air intake hose above the manifold heater becomes warm to the touch so that seems to check out but I’d like to test voltage still.
-Fuel quality is good.
-Changed ALL rubber fuel lines. I thought this would be the big fix because one of the return lines above the injectors broke apart in my hands after removal. It still didn’t start.
-This 855 model has the electric fuel transfer pump; I tested flow and saw 750ml over 30 seconds, far exceeding the minimum 200ml. I saw 0 psi on the pressure test, below the 3 psi minimum, but given the high flow I’m not sure I trust the reading and should probably test pressure again.
-Bled the fuel lines, but bleeding methods differ between the operator’s manual and technical manual, so I combined their methods to be thorough: started with the two screws above the filter housing, then the screw before the fuel injection pump, then all three injection lines just after the injection pump (simultaneously), and finally the cylinder 3, then 2, then 1 injection lines at the injection nozzles. Notably I saw a small amount of rust-colored fuel/liquid leak out when bleeding the 3 injection lines (just after the injection pump); the black factory paint was still intact before I bled those 3 indicating they had never been bled before. Also it was tough to tell if air bubbles were present on the bleed screw just before the injection pump because fuel squirted out in a higher-pressure “beem” (right in my face) rather than dribbling out like from the 2 filter bleed screws. I suppose it’s higher pressure due to the smaller ¼” line leading to that last bleed screw from the filter housing compared to the 5/16 hose upstream going from the tank to the filter.
-The fuel shut off solenoid tested out fine.
-Confirmed there’s no coolant in the oil, and doesn’t appear to have oil in the coolant, which bodes well for the head gasket.
-I discovered that the secondary air filter (inside the primary filter) is dirtier than expected on the inside of that filter, toward the end where air would exit the filter en route to the engine. The “dirt” looks similar to the dry-ish black grime on the outside of my engine that I assume is from diesel that leaked from a rubber fuel hose. There isn’t a ton of the grime in the filter, but enough to mention it. The outside of the secondary filter isn’t too dirty, and the primary filter is dirtier, but not enough to be alarmed. Perhaps the secondary filter gasket wasn’t pressed tight enough against the metal filter housing; it didn’t have the necessary wing nut (my fault) on the secondary filter (underneath/inside the primary filter), so it was relying on the primary filter’s wing nut to press/sandwich the secondary filter between the primary filter and the metal filter housing. I’m sure I spun it on there tight, but maybe it was never going to be tight enough without the secondary filter wing nut added. And if it is diesel grime on the filter, I think it entered the air intake from a leak near the fuel tank because that grime was all over the oil cooler fins behind the grill where the fuel tank is located and the air intake plumbing begins. It seems plausible the grime bypassed both air filters, unfortunately.
-The air restriction indicator had been removed by the previous owner and its port capped off so I couldn’t test the primary & secondary filter restriction, so I bypassed the entire intake by unplugging the hose near the air heater (after the filter housing) to put unrestricted air directly into the engine, but it still didn’t start.
-I even went as far as putting a gasoline-soaked rag over that opened/unrestricted intake hose mentioned above (and unplugged the air heater for safety) and the engine still wouldn’t start. Supposedly if it had started in that scenario, the engine health would have been proven to be okay (according to a Deere mechanic, see link below) but I’m still holding out hope. Link: J D 855 won't start
I’m Planning to do:
-Test engine compression.
-Valve clearance - measure/adjust.
-Test injector nozzle spray patterns and inspect for any irregularities or injector leaks.
-Blow out metal fuel lines with compressed air just in case it’s restricted, then re-do bleeding.
-Inspect exhaust for restrictions, but I’m not sure how to do that without disconnecting pipes/manifold.
-Test crank speed.
-See if there’s a broken starter spring in the governor assembly.
-Test voltage/resistance at both the fuel transfer pump and the manifold air heater.
-Check injection pump timing and see if the plunger is stuck.
-Check oil pressure if that’s possible on a tractor that won’t run.
Questions I’m stuck on:
-Can I get an accurate compression reading without warming the engine (since I can’t get it to start)?
-What is the purpose of the wire seal on the engine’s right hand side near the throttle linkage, and if the wire were compromised would it affect the tractors ability to start? One end of the wire is lightly wrapped around a threaded bolt nearby and I can easily remove the wire from the bolt.
-Can I assume if there was an issue with the seat safety switch that the engine would not crank? Since mine cranks I’m hoping to rule that one out.
-What oil grade might prevent a diesel from starting? I live in Maine, the snow has melted now, and I’m using 15w-40 synthetic.
-The manuals say to bleed fuel lines until there are “no bubles”, but what would bubbles look like? A cluster of little bubbles? Larger infrequent bubbles? Sometimes I’m not sure if what I’m looking at are bubbles or if it’s normal so I’m not confident that I’ve bled it properly. Also it’s easy to shut (and know when to shut) the 3 bleeder screws before the injection pump - they are downstream of the electric pump, which is constantly on when in ignition switch position 1, so when the bubbles are gone you’d in theory shut the valve and then switch the key off. Easy peasy. But the 6 fuel injection line fittings downstream of the injection pump are a different story... They release fuel intermittently (when the cylinder would need fuel), and only while cranking. Am I supposed to close those fittings while cranking after bubbles are gone, or let the cranking stop after bubbles are gone and then close the fitting? It seems like if you let the engine stop cranking and then close the fittings it would be a chance for air to be let back inside the line since the fittings are loosened. But I think it would be crazy to try to close a fitting while cranking since access for a wrench is tight, all the while trying to difficultly time the closing as fuel is injected during the cycle. Seems like a good way to burn out a starter too.
-Would you recommend using a magnetic block heater at this point?
-The red water temp light is illuminated during engine cranking - is this a problem and could this result in an engine not starting? Coolant level is about 1 inch below the bottom of the bowl under the cap.. maybe that’s too low and triggers the light?
-Where is the governor on this JD 855 and would a broken spring in the governor be accessible for replacement?
-Is it possible for an amateur to check the injection pump timing (not necessarily fixing, just testing)?
-Would I be able to gain access without too much trouble to see if the injection pump plunger is stuck?
Thanks for helping with any of these issues - I hope we can figure it out!
I apologize in advance for the lengthy post but there’s a lot to share and the little details might make the difference in figuring it all out.
I don’t recall much of anything being wrong with the tractor during the first summer of mowing/farming and I worked it fairly hard at times with the front end loader. Before the second summer of use I changed the oil, air filters, and fuel filter for the first time (notably the wrong air filter had been installed by the previous owner - it only had one air filter installed rather than the primary & secondary - I seem to remember it was in there snug enough, but I can’t be sure). That second season I noticed increased smoke coming from the Crankcase Breather/PCV tube, kind of a white or gray color. I noticed some oil consumption too, dropping from “Full” to “Low” on the dipstick range over the course of the summer (150 hours). The tractor also began to require longer cranking to get it to start, which got progressively worse over time, and would puff lots of black smoke for a few seconds after it finally started. Once started though, it always ran and performed great, until one day in the Fall of 2024 it wouldn’t start, and hasn’t since.
My aim has been to knock out all the easy tests & repairs in hopes that it won’t be necessary to pull the head off or send the injection pump in for testing.
So far I’ve done the following:
-The battery passed three tests at AutoZone. It seems to loose juice quicker than I’d like though, so when trying to crank the engine for testing etc. I use a jump battery pack to keep the crank speed fast and to take it easy on the tractor battery.
-Confirmed the manifold air heater/cold start aid dash light works properly (does not have glow plugs), and the air intake hose above the manifold heater becomes warm to the touch so that seems to check out but I’d like to test voltage still.
-Fuel quality is good.
-Changed ALL rubber fuel lines. I thought this would be the big fix because one of the return lines above the injectors broke apart in my hands after removal. It still didn’t start.
-This 855 model has the electric fuel transfer pump; I tested flow and saw 750ml over 30 seconds, far exceeding the minimum 200ml. I saw 0 psi on the pressure test, below the 3 psi minimum, but given the high flow I’m not sure I trust the reading and should probably test pressure again.
-Bled the fuel lines, but bleeding methods differ between the operator’s manual and technical manual, so I combined their methods to be thorough: started with the two screws above the filter housing, then the screw before the fuel injection pump, then all three injection lines just after the injection pump (simultaneously), and finally the cylinder 3, then 2, then 1 injection lines at the injection nozzles. Notably I saw a small amount of rust-colored fuel/liquid leak out when bleeding the 3 injection lines (just after the injection pump); the black factory paint was still intact before I bled those 3 indicating they had never been bled before. Also it was tough to tell if air bubbles were present on the bleed screw just before the injection pump because fuel squirted out in a higher-pressure “beem” (right in my face) rather than dribbling out like from the 2 filter bleed screws. I suppose it’s higher pressure due to the smaller ¼” line leading to that last bleed screw from the filter housing compared to the 5/16 hose upstream going from the tank to the filter.
-The fuel shut off solenoid tested out fine.
-Confirmed there’s no coolant in the oil, and doesn’t appear to have oil in the coolant, which bodes well for the head gasket.
-I discovered that the secondary air filter (inside the primary filter) is dirtier than expected on the inside of that filter, toward the end where air would exit the filter en route to the engine. The “dirt” looks similar to the dry-ish black grime on the outside of my engine that I assume is from diesel that leaked from a rubber fuel hose. There isn’t a ton of the grime in the filter, but enough to mention it. The outside of the secondary filter isn’t too dirty, and the primary filter is dirtier, but not enough to be alarmed. Perhaps the secondary filter gasket wasn’t pressed tight enough against the metal filter housing; it didn’t have the necessary wing nut (my fault) on the secondary filter (underneath/inside the primary filter), so it was relying on the primary filter’s wing nut to press/sandwich the secondary filter between the primary filter and the metal filter housing. I’m sure I spun it on there tight, but maybe it was never going to be tight enough without the secondary filter wing nut added. And if it is diesel grime on the filter, I think it entered the air intake from a leak near the fuel tank because that grime was all over the oil cooler fins behind the grill where the fuel tank is located and the air intake plumbing begins. It seems plausible the grime bypassed both air filters, unfortunately.
-The air restriction indicator had been removed by the previous owner and its port capped off so I couldn’t test the primary & secondary filter restriction, so I bypassed the entire intake by unplugging the hose near the air heater (after the filter housing) to put unrestricted air directly into the engine, but it still didn’t start.
-I even went as far as putting a gasoline-soaked rag over that opened/unrestricted intake hose mentioned above (and unplugged the air heater for safety) and the engine still wouldn’t start. Supposedly if it had started in that scenario, the engine health would have been proven to be okay (according to a Deere mechanic, see link below) but I’m still holding out hope. Link: J D 855 won't start
I’m Planning to do:
-Test engine compression.
-Valve clearance - measure/adjust.
-Test injector nozzle spray patterns and inspect for any irregularities or injector leaks.
-Blow out metal fuel lines with compressed air just in case it’s restricted, then re-do bleeding.
-Inspect exhaust for restrictions, but I’m not sure how to do that without disconnecting pipes/manifold.
-Test crank speed.
-See if there’s a broken starter spring in the governor assembly.
-Test voltage/resistance at both the fuel transfer pump and the manifold air heater.
-Check injection pump timing and see if the plunger is stuck.
-Check oil pressure if that’s possible on a tractor that won’t run.
Questions I’m stuck on:
-Can I get an accurate compression reading without warming the engine (since I can’t get it to start)?
-What is the purpose of the wire seal on the engine’s right hand side near the throttle linkage, and if the wire were compromised would it affect the tractors ability to start? One end of the wire is lightly wrapped around a threaded bolt nearby and I can easily remove the wire from the bolt.
-Can I assume if there was an issue with the seat safety switch that the engine would not crank? Since mine cranks I’m hoping to rule that one out.
-What oil grade might prevent a diesel from starting? I live in Maine, the snow has melted now, and I’m using 15w-40 synthetic.
-The manuals say to bleed fuel lines until there are “no bubles”, but what would bubbles look like? A cluster of little bubbles? Larger infrequent bubbles? Sometimes I’m not sure if what I’m looking at are bubbles or if it’s normal so I’m not confident that I’ve bled it properly. Also it’s easy to shut (and know when to shut) the 3 bleeder screws before the injection pump - they are downstream of the electric pump, which is constantly on when in ignition switch position 1, so when the bubbles are gone you’d in theory shut the valve and then switch the key off. Easy peasy. But the 6 fuel injection line fittings downstream of the injection pump are a different story... They release fuel intermittently (when the cylinder would need fuel), and only while cranking. Am I supposed to close those fittings while cranking after bubbles are gone, or let the cranking stop after bubbles are gone and then close the fitting? It seems like if you let the engine stop cranking and then close the fittings it would be a chance for air to be let back inside the line since the fittings are loosened. But I think it would be crazy to try to close a fitting while cranking since access for a wrench is tight, all the while trying to difficultly time the closing as fuel is injected during the cycle. Seems like a good way to burn out a starter too.
-Would you recommend using a magnetic block heater at this point?
-The red water temp light is illuminated during engine cranking - is this a problem and could this result in an engine not starting? Coolant level is about 1 inch below the bottom of the bowl under the cap.. maybe that’s too low and triggers the light?
-Where is the governor on this JD 855 and would a broken spring in the governor be accessible for replacement?
-Is it possible for an amateur to check the injection pump timing (not necessarily fixing, just testing)?
-Would I be able to gain access without too much trouble to see if the injection pump plunger is stuck?
Thanks for helping with any of these issues - I hope we can figure it out!
