2019 Deere 75G

[mg2361]

Does this common rail pressure from the monitoring screen read the same value that Service Advisor would read?

Yes. Start with the rail pressure sensor per the instructions. It needs to be ruled out.

 

[materthegreater]

Yes. Start with the rail pressure sensor per the instructions. It needs to be ruled out.

Thanks, that eliminates the need to get someone to come connect to the machine with Service Advisor at this point anyway. I will order the sensor today.

 

[materthegreater]

So the sensor arrived and I plugged it into the harness before installing it. KOEO value was about 25 psi. So I removed the old one and installed the new one. KOEO with it installed (and lift pump running of course) was about 52 psi. I then started the engine and ran it at low idle for a minute. Now the supply pressure is showing 0 or close to 0 psi even at idle, but still about 4 psi KOEO. I shut off the engine and let it sit for a while and then checked rail pressure and it seems to be settling down to about 52 psi (immediately after shutting it off and checking the rail pressure again showed about 150 psi. It must be retaining some pressure for a little while after shutting down).

Earlier I checked for return leakage from the rail limiter and none showed up at idle. I have not yet checked that under high load.

 

[materthegreater]

Another question: how does the sensor seal to the rail? After restarting I'm getting some leakage between the sensor and the rail. The old one had some whitish goo on it which I assumed was just sludge buildup, but maybe it was some sort of sealant? I had assumed there would be an o-ring or some sort of seal but didn't see one. Maybe I just didn't torque it enough, does Deere list a torque spec for the sensor?

 

[mg2361]

Interesting! I can find the torque spec of every sensor but the rail sensor. On Deere engines they are approximately 104-118 FTLB (there is actually an initial torque, then a torque turn).

Most sensors do not use a gasket or sealant. Grease is sometimes spec'd for the threads.

 

[materthegreater]

Interesting! I can find the torque spec of every sensor but the rail sensor. On Deere engines they are approximately 104-118 FTLB (there is actually an initial torque, then a torque turn).

Most sensors do not use a gasket or sealant. Grease is sometimes spec'd for the threads.

Thanks, I tightened it to 110 ft lbs and it doesn't seem to be leaking now.

I checked return leakage next and there was a negligible amount of fuel in the test hose, probably just residual from the fitting:



While testing that, I watched the rail pressure and it didn't drop anywhere near 20 MPa as stated in the troubleshooting guide:

Problem or Situation:
157.18 (Yanmar code P0094) sets when actual rail pressure is 20MPa (2900 psi) or less for 5 seconds or
more.
After the code is set, it will limit injection amount (target) ~58MPa (8555 psi) rail pressure. This condition
remain and the code will continue to be active until the conditions are met (key cycled) to reset the ECU.
Possible root causes - Low side fuel restriction or degradation in supply fuel system, excessive leakage from
high side components, sticking SCV, or various electronic fuel control components (IE. rail sensor).

So now I'm confused. Are there other criteria that can set the 157-18 code?

 

[materthegreater]

Also, after replacing the sensor, it won't start right up, but cranks for while before firing. Is that just because there is some air in the rail that will be purged after a running for a bit?

 

[Columbo]

Thanks, I tightened it to 110 ft lbs and it doesn't seem to be leaking now.

I checked return leakage next and there was a negligible amount of fuel in the test hose, probably just residual from the fitting:

View attachment 361494

While testing that, I watched the rail pressure and it didn't drop anywhere near 20 MPa as stated in the troubleshooting guide:


So now I'm confused. Are there other criteria that can set the 157-18 code?

I read that as “if the minimum pressure is 20MPa or less for 5 seconds” it sets the code. So if I understood you right, you’re not seeing a pressure drop? Do you still have the code when running?

 

[materthegreater]

Correct, while watching the pressure on the screen, I tracked the machine around until the code came up and the pressure varied from about 40 MPa to over 100. It didn't drop below 40 even for a split second. Once it triggers, the check engine warning stays on until the machine is shut off.

 

[mg2361]

There was no fuel flow from the rail relief, correct?

the pressure varied from about 40 MPa to over 100. It didn't drop below 40 even for a split second

Actually, they did not explain that well. The DTC means that the actual rail pressure was lower than the desired rail pressure by 20 MPa for more than 3 seconds.