Diesel Dave
Senior Member
@materthegreater , I think Deere included that AT318139 pump in the 75G catalog by mistake . I believe the 24 volt version is part # MIU802991 .
See screenshot below.
See screenshot below.
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2019 Deere 75G
- Thread starter materthegreater
- Start date
Columbo
Senior Member
Based on your tests, I would replace the lift pump as the next logical step. Certainly before going further into the high pressure system in my opinion.
materthegreater
Senior Member
So I ordered a new pump from the dealer earlier this week, specifically asking the salesman if it was a 24 volt pump. He said it didn't say, but was listed for my machine so it must be. They called to say it was in yesterday, so I picked it up this morning and it was the AT318139 pump. But nowhere on the box did it say anything about voltage, and the connector fits the machine, so I installed it. It didn't go up in smoke immediately, but it also didn't give any better pressure results than the original pump. Now I'm stumped as to how it can provide the proper flow, and it can build the proper pressure, but somehow can't do it when the engine is running.
John Shipp
Senior Member
What about the MIU802991 Diesel Dave posted in #61?
John Shipp
Senior Member
So is it still these results?:
Key on engine off: 4 psi
Key on engine idle: 1.5 psi
High idle no load: 1 psi
High idle under load: 0
If the lift pump and flow is good, it's letting a lot of fuel flow when at high idle? Where's it going...
Key on engine off: 4 psi
Key on engine idle: 1.5 psi
High idle no load: 1 psi
High idle under load: 0
If the lift pump and flow is good, it's letting a lot of fuel flow when at high idle? Where's it going...
mg2361
Senior Member
Did you ask for the MIU802991 pump? There are 10 available in the Deere parts depot in Grimsby, which serves your local dealers.
If the pressure drops off at full throttle, and the suction side from the tank to the HP pump is good, the issue may be in the high pressure fuel system.
Please provide the machine serial number.
If the pressure drops off at full throttle, and the suction side from the tank to the HP pump is good, the issue may be in the high pressure fuel system.
Please provide the machine serial number.
materthegreater
Senior Member
I ordered over the phone and they didn't tell me the part number. I did ask if they needed the serial number and he said no, it's the same for all 75G machines.
Yes, approximately. Where it's going is exactly what I'm wondering. My first thought was that the original pump was just getting tired and the pressure was dropping off at the higher flow demand.
I didn't ask for a specific part number, I told him I needed a pump for a 75G, and asked if it was a 24v pump.
The machine serial number is
1FF075GXJJJ016799
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materthegreater
Senior Member
Just for kicks, I tried pinching off the return line and the pressures remained higher, and it gave error message 157-15, which appears to be high fuel rail pressure. So I'm wondering if there's a problem with whatever regulates the pressure. What does regulate the pressure anyway?
mg2361
Senior Member
Better keep an eye on your engine oil level. Pinching the fuel return on HPCR fuel systems can blow out the shaft seal on the HP pump.
materthegreater
Senior Member
Hopefully that didn't happen. I didn't see the gauge go higher than 4.5 psi. How is the pressure supposed to be regulated in this system?
Columbo
Senior Member
Did you check the fuel volume test with the new pump? Seems like you might need to dive into the high pressure/electrical sensor/wiring side after all, unfortunately. I re-read the trouble shooting procedure @mg2361 supplied and it looks like there are some simple tests that can be done. However, some of the other tests seem to require service advisors to complete, mainly to monitor pressures? Can a regular fuel pressure gauge of the appropriate specs be installed temporarily somewhere on the common rail if service advisor is not available?
materthegreater
Senior Member
I have not checked the volume with the new pump. I may not be fully understanding the entire troubleshooting procedure, but the way I read it is that the high pressure tests only come into play once the low pressure side is within the specified ranges. This quote below from the guide seems to be pointing to the "rail limiter". I'm not sure what or where that is.
I think the next thing I'm going to try is replacing all the rubber fuel lines. Am I missing something from the troubleshooting procedure?
Columbo
Senior Member
Sorry, I guess I overlooked the fact you still had 0 psi at high idle with the new pump. No bueno. That said, the section you quoted from the troubleshooting instructions seems like the next step.
Columbo
Senior Member
In looking at the fuel diagram, I believe that the fuel limiter is another name for the main rail relief. See below from the troubleshooting-
materthegreater
Senior Member
Good catch. I was thinking that there was a separate pressure regulator for the low side and high side, but it doesn't sound like it.
mg2361
Senior Member
Unfortunately, no. Only the low pressure side can be pressure tested with gauges.
mg2361
Senior Member
The electric fuel pump is self regulating.
materthegreater
Senior Member
Ok, that makes sense. So if the pressure drops below the specified values and all the lines are clear, then it must be loosing too much volume somewhere which prevents it from maintaining proper pressure?
materthegreater
Senior Member
Does this common rail pressure from the monitoring screen read the same value that Service Advisor would read? This is in MPa but it converts to 117 psi. Is this close enough to the desired zero value? If not, I guess it means the sensor is bad?
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materthegreater
Senior Member
Presuming that the monitoring screen is reading the correct value, I tried wiggling the wire at the connector and didn't see any difference. So then I tested the voltages as explained below. Both were approximately 5v. I also checked the wiring harnesses near the ECU, because there was evidence of mouse activity in the area. All the wiring looked good.
