MX5200 Common Rail Pressure sensor testing.

[RHR]

Does anyone know where I might find the parameters for the fuel rail sensor. volts/psi
With key on it reads .3 volts, with engine running idle it reads .73. This is the test per the WSM. While cranking it has .7 volts. New injector pump and has fuel to low side 73 lbs. Will not start. Starts with gas rag and has same power it always had. Will not start without gas rag.

 

[JerryMT]

Does anyone know where I might find the parameters for the fuel rail sensor. volts/psi
With key on it reads .3 volts, with engine running idle it reads .73. This is the test per the WSM. While cranking it has .7 volts. New injector pump and has fuel to low side 73 lbs. Will not start. Starts with gas rag and has same power it always had. Will not start without gas rag.

After it starts with gas rag, what does it read? I would assume the operating pressure in the rail is pretty much constant with the engine running and the ecu controls the duration of the opening of the fuel nozzle to supply the fuel to the cylinder. When you get it started, check the sensor at several different rpms with and without load and see what type of readings you get.
Do you have a supply pump that feeds the IP "(New injector pump and has fuel to low side 73 lbs." I assume you mean psig.). What does it read at no load and with load and several different rpms?

There are probably several sensors that feed info to the ecu like ambient temp, coolant temp, etc some can cause timing change which can cause starting difficulties if the sensor output is wrong.

Do you have a system description that tells you how the system is supposed to work?

 

[lugbolt]

Yeah I went to school on this stuff but darned if I can remember what the pressure/voltages were! It may not have even been addressed. What was addressed (burnt into my brain) was how diagmaster "sees" the voltages and pressures and what they can mean.

Typically (but not always) having to "help" start it, and if it will self-sustain after it starts, means injectors. The injectors will sometimes bypass too much fuel, causing no start condition, or more often hard start condition. Remove them and send them out for testing before you go much further. Mark the serial numbers of the injectors and which cylinder they go to! If you have to replace one, you'll have to have the serial number programmed into the ecu by the dealer.

if they are bypassing too much fuel you'll usually (but not always) get a code for low fuel pressure. If you get a code for high pressure, you'll have to replace the fuel rail assembly. Not that common but it happens.

If less than 5 years old, let Kubota eat it. 5 yr emissions warranty.

 

[Fordtech86]

New injector pump

The high pressure pump I am guessing? Why was that replaced? What was the original concern, was it different then now?

 

[lugbolt]

by the way the use of a dvom for testing is inconclusive. Really needs to be on a computer to watch everything in relation with each other. It's a system not just a few components.

also if it were me, I'd like to see the freeze frame data. SCV current, rail voltage rail pressure, among other things. You can't get freeze frame data unless you have the stuff. Additionally, I'd like to see a list of what codes are populated in the ecu, past and present. Past codes often give a clue to what's going on currently.

kind of like modern cars. You can't do much without knowing the data and you can't get all the data without the proper software/hardware. I don't agree with it but ain't nothing I can do about it.

 

[RHR]

Took it to dealer again yesterday. They ran digimaster. I watched and talked with mechanics. No codes.
The fuel rail pump had been replaced a few weeks ago by a local tractor mechanic. As it was rusted from water in fuel. His laptop program gave lots of codes. My bad
Trying to save a little.
The dealer mechanic said I probably have a dirty rail with pressure leaking off. I'm putting a new one on tomorrow.
Thanks guys.
I'll report back

 

[lugbolt]

Took it to dealer again yesterday. They ran digimaster. I watched and talked with mechanics. No codes.
The fuel rail pump had been replaced a few weeks ago by a local tractor mechanic. As it was rusted from water in fuel. His laptop program gave lots of codes. My bad
Trying to save a little.
The dealer mechanic said I probably have a dirty rail with pressure leaking off. I'm putting a new one on tomorrow.
Thanks guys.
I'll report back

it almost sounds like the previous mechanic cleared all the codes. I don't recommend doing that unless it's a function of it being the only way to get rid of a check engine light. Now, the dealer has no idea what codes were stored previously, and those codes would have given a clue as to what may have been going on, and without those clues, he's likely simply throwing parts at it. If it had water in the fuel and was rusted, figure on replacing the injectors too. All 4 of them.

 

[RHR]

it almost sounds like the previous mechanic cleared all the codes. I don't recommend doing that unless it's a function of it being the only way to get rid of a check engine light. Now, the dealer has no idea what codes were stored previously, and those codes would have given a clue as to what may have been going on, and without those clues, he's likely simply throwing parts at it. If it had water in the fuel and was rusted, figure on replacing the injectors too. All 4 of them.

The dealer cleared allthe codes the first time I took it as they had to get the new supply pump learned in the system
This was when they told me I needed a new rail pressure sensor. I put a new sensor on and took it back to the dealer as it still would not start.
This time they tell me it's a injector leaking back to the fuel tank
then they change it to a bad fuel rail. I did not question them about this, but how can my tractor idle, spin all four wheels when loading dirt with it if there is something wrong with the fuel rail. It is a simple part. The supply pump does not pressure up the common fuel rail with the starter. I took the rubber lines off of the injectors and 2 bubbled fuel and two dripped fuel. I disconnected the bango bolt from the relief valve on the end of the rail and no leak there while starting. There is fuel coming out of the c port on the supply pump going back to the fuel tank. Is this normal?Could this be where I'm losing pressure?