John deere 6820 common rail tractor

[Ngasi]

Hi all,
I am new to this forum. I am in Africa-Tanzania
I have a problem with a john deere 6820 common rail tractor
1. The tractor starts and idles very rough with knocking
2. When revving up the knock disapears but it only goes up to 1450rpm.
3. I managed to get a small scanner which accesesed several engine parameters but to my suprise the rail pressure is always 1016kpa and the reading does not change.
4. As a test I disconnected the rail pressure sensor, to my suprise the reading remained the same but the engine idle became very smooth.

I do suspect a faulty prssure sensor.
Please help me with any advise on the way foward.
JD services in this region is crap.

 

[daveydiesel1]

Can you not get the sensor checked anywhere? Order part online if no local dealers?

 

[Ngasi]

Helo,
The only option I have is to order the pressure sensor online.
Even JD themselves can not do it here.
I requested them to show me pressure readings and they could not. Its unbeliavable.
I have checked the number RE520930 or denso 6141.
They once sold me a used sensor only to see its denso 6131. I belive its two different things.

 

[Ngasi]

I have decided to work on this tractor my self and possibly help others here ib Tanzania as JD services are unbearable.

 

[Phil P]

It’s quite common to get a bad contact on the pins in the plug for the rail pressure sensor, it’s rare for the sensor to fail but not unheard of.
A bad contact or failed sensor would give the symptoms you describe, you should get a fault code when the sensor is unplugged and the ecu light (top left on dash) should start to flash.
If your not getting a fault code and no change unplugging the sensor I’d be have a look at the wiring.

 

[Ngasi]

Hi Phil,
Thank you very much for your response
Yes when I unplug the sensor i get the code when the rail presure sensor is disconnected.
I also checked the wiring from ECM to the sensor and all was OK.
Voltage readings when I disconnect rail pressure sensor and switch On
Reference voltage = 5volts
Ground = 0volts
Signal = 4.9 volts.
When I connect i get
Refference = 5volts
Ground =0volts
Signal 1.3volts

 

[daveydiesel1]

Bit odd that jd are shakin up dealer network in europe and gettin rid of good dealers and they dont care about the dealer problems in your area

 

[Phil P]

Hi Phil,
Thank you very much for your response
Yes when I unplug the sensor i get the code when the rail presure sensor is disconnected.
I also checked the wiring from ECM to the sensor and all was OK.
Voltage readings when I disconnect rail pressure sensor and switch On
Reference voltage = 5volts
Ground = 0volts
Signal = 4.9 volts.
When I connect i get
Refference = 5volts
Ground =0volts
Signal 1.3volts

I have a feeling you shouldn’t be seeing any voltage on your signal wire when it’s unplugged! Sounds like it’s shorting across to you 5v supply line.
I’ll have to double check the pin voltages but unfortunately my service advisor computer is in the sick bay at the moment?.
I’ll try and test on a tractor tomorrow if I get chance.

 

[Ngasi]

Hi Phil,
I really appreciate. Will be waiting to hear from you.
If you confirm zero volts, then I will have to run separate cables out side of the harness from ecm to the rail pressure sensor and see what happens. I tried to measure resistance across the 3 wires and results were no short ( I used a fluke ohm meter).
Waiting to hear from you.
Thank you very much guys.

 

[tweedale terrier]

I have decided to work on this tractor my self and possibly help others here ib Tanzania as JD services are unbearable.

unbearable or unpayable ?

 

[Tractortech]

Now Then..
Have you checked for error codes?? Another thing to check is the 'cruise control' knob on the right hand console, is it turned fully right??
Ideally you could do with a computer with Service Advisor.
Pin 1 - 427 - P3
Pin 2 - 475 - R1
Pin 3 - 946 - R3
I'd disconnect the ECU and check continuity, short to both + & -.
Does your signal voltage disappear if you disconnect the ECU??

 

[Ngasi]

Helo?
Yes I have two current codes
The first is SPN 97 FMI3 water in fuel
The second SPN 636 FMI 10 cam shaft position sensor
There is no water in fuel its clean diesel
I cant find a cam shaft sensor. I checked in the manual and it said the engine uses two sensors to monitor speed. The crank shaft sensor and the pump speed sensor, so I stoped looking for it. Possibly I miss understood.
Can these codes cause the engine to derate and limit rpm?.
Regarding the voltages when the ECU is connected, I will have to do that later as I had to go back to town after a week in the bush working on it.
Unfortunately I do not have a service advisor computer I am using a crude Launch code reader I bought for trucks. Its one reason I hade to come back and start searching for a computer and servi e advisor software. If you have reliable contacts I will order from there.
Again thank you very much for your response.

 

[Tractortech]

The 'camshaft' sensor is located under the HPCR fuel pump. It's identical to the one you can easily see at the front of the engine on the crankshaft.
Make sure all the connectors are clean and dry. The WIF sensor can loose the connector seal and allow water in causing the same code. The wires in that area can rub / get damaged and create error codes..

 

[Ngasi]

Hi
Ok will have a look at that too.
Please if you know a reliable contact where I can purchase the computer with service advisor.
Best regards

 

[Ngasi]

Hi Phil,
I really appreciate. Will be waiting to hear from you.
If you confirm zero volts, then I will have to run separate cables out side of the harness from ecm to the rail pressure sensor and see what happens. I tried to measure resistance across the 3 wires and results were no short ( I used a fluke ohm meter).
Waiting to hear from you.
Thank you very much guys.

Hi Phill
Do you know what should be the rail pressure at Idle? For this 6820 common rail tractor.

 

[Phil P]

Hi Phill
Do you know what should be the rail pressure at Idle? For this 6820 common rail tractor.

This any help?

 

[Ngasi]

Thank you very much.
I have ordered a scan tool and new rail pressure sensor. Hope to receive them end of next week then will go back to the bush to work on the tractor.
Will let you know the progress.
Again thank you very much

 

[Ngasi]

Hi Phil.
It is my hope you are doing fine.
Am doing OK. Corona is actually afraid of us.
I am about to go back to the farm to work on this tractor JD 6820 common rail 6.8 liter engine.
I have hired a bosch preasure reader to see how the presure behaves.
I also wabt to carry out a leak back test.
Do you have the specifications for leak back volume?.
I am planning to use simple pipes and calibrated flasts to get the volumes.
Best regards,
Ngasi

 

[Timbo]

Replace the Rail pressure sensor, and check carefully the connector pins make good contact with the new sensor. New plugs are available from JD and they are often a problem not making a good connection.

After that check the Suction Control Valve on the HP pump., which are also prone to sticking and causing very high rail pressure (and engine knock) at idle.

 

[Ngasi]

Ok.
Thisnia what I have done so far
1. New pump
2. New pressure sensor
3. Reman injectors
4. New pressure reliefe valve
5. New suction control valve - but I have a problem here, as JD came up with that partnumber and it is a long suction control valve. I have been reading in a manual which says it should be the short one 27mm.
Any one with 6820 common rail with that short suction control valve please share with me the part number.
Best regards,
Ngasi