Denso "Common Rail" Fuel pump

jlittle2212 · Nov 5, 2015

John Deere 850J.. Will start and run fine until warming up. After warming up, it will pull the engine down and the only way to keep it running is to have RPMS under 1200. If you continue to give it fuel, it will die. Have to use hand primer pump to restart it.

When you crack an injector line on the rail, should fuel squirt up when cranking? I am not real good on the common rail with electric injector setup.

Thanks again..

GaryHoff · Nov 5, 2015

First quick check on these is the fuel cap, make sure the breather is not plugged, you should not have a vacuum in your fuel tank.

Common rail is not suppose to give lots of fuel at the injectors. It will not squirt. Common rail is designed for high fuel pressures, and lower fuel flow. It is not generally good practice to "crack" the injector lines on common rail. Most manufactures only allow you to tighten/loosen the injection lines 3 times. After that they recommend replacing them

I know the 850j is hard to get the air out, especially if its gotten in the fuel rail. I usually crack loose the line feeding the rail to bleed the air.

jlittle2212 · Nov 5, 2015

GaryHoff said:
First quick check on these is the fuel cap, make sure the breather is not plugged, you should not have a vacuum in your fuel tank.

Common rail is not suppose to give lots of fuel at the injectors. It will not squirt. Common rail is designed for high fuel pressures, and lower fuel flow.

Have checked cap, changed out from another machine same problem. Checked all lines, check valves, regulators no leaks on system. Will run okay when cold, the problem is just when it warms up and problem has gotten worse over the last few days.

GaryHoff · Nov 5, 2015

Do you have lots of pressure in your fuel tank?
How much fuel is coming from your return line?
Did you check your rail relief? It should have no fuel coming from it. If its bad, usually it is very hot.

jlittle2212 · Nov 5, 2015

Doesn't seem to have lots of pressure in the tank.
Getting good flow from return line.

Where is the rail relief located? I changed the rail regulator with a known good regulator as well.

GaryHoff · Nov 6, 2015

The return line shouldn't have too much flow. Hard to describe, but excessive flow means too much leakage from something. I don't have it, but sometimes there is a return flow spec.
The rail relief will be at the end of the common rail.

jlittle2212 · Nov 6, 2015

GaryHoff said:
The return line shouldn't have too much flow. Hard to describe, but excessive flow means too much leakage from something. I don't have it, but sometimes there is a return flow spec.
The rail relief will be at the end of the common rail.

I'm thinking the injector pump is shot. Could be wrong. I am guessing the relief would be closest to the sensor on the rail?

GaryHoff · Nov 6, 2015

Possible the injection pump is bad. Bad pump should be getting hot too.

Relief should be on the other end, away from the sensor. (relief is 17)

Typically a bad rail relief will do this : After first starting it will run ok at an idle. If you throttle up the engine or put on a load, a fault comes up, and the engine will die or run poorly.

Also, if you had a bad rail pressure sender, or if you unpugged the rail pressure sender, it will usually make the rail relief fail.

jlittle2212 · Nov 6, 2015

It will run fine under loads until it gets hot. Then, it starts to fail... If it dies during failure, the only way to get it started back is to use the hand primer to prime it back up and it will start back up, just still be sluggish as it was.. But, if you let it cool off, it will fire right back up without priming and run until it gets hot again.

jlittle2212 · Nov 6, 2015

Here is my setup.

GaryHoff · Nov 7, 2015

29 is the rail relief.

What your describing seems to me like you are loosing rail pressure when the machine gets hot. I don't think it would be from a bad rail relief, because a bad relief should do it all the time, but check it anyways. I think its more likely a bad injector causing your faults. You need to check your leakage from your injectors into drain line 23. The injector that has the most leakage will be the faulty one. The fault one should also be hotter than the other ones too. Check the injector temps before the machine gets too warm

ih100 · Nov 7, 2015

Have you gone through the basics before getting expensive? Filters, water in fuel, blocked or kinked feed lines? Might sound obvious, but you wouldn't be the first person to think the worst when it's something fundamental?

jlittle2212 · Nov 7, 2015

ih100 said:
Have you gone through the basics before getting expensive? Filters, water in fuel, blocked or kinked feed lines? Might sound obvious, but you wouldn't be the first person to think the worst when it's something fundamental?

Been through all the basics.. I always find myself looking over the small stuff myself.. lol I made sure this time.. I decided to change the injector/transfer pump on Friday so I will see on Monday.

jlittle2212 · Nov 7, 2015

GaryHoff said:
29 is the rail relief.

What your describing seems to me like you are loosing rail pressure when the machine gets hot. I don't think it would be from a bad rail relief, because a bad relief should do it all the time, but check it anyways. I think its more likely a bad injector causing your faults. You need to check your leakage from your injectors into drain line 23. The injector that has the most leakage will be the faulty one. The fault one should also be hotter than the other ones too. Check the injector temps before the machine gets too warm

You think one bad injector would cause this? The engine does not miss, its just like its starving for fuel. These injectors are inside the head.. Have to remove all the crap above the rocker box cover just to check or r & i.. :Banghead Love John Deere

cutting edge · Nov 8, 2015

jlittle2212 said:
You think one bad injector would cause this? The engine does not miss, its just like its starving for fuel. These injectors are inside the head.. Have to remove all the crap above the rocker box cover just to check or r & i.. :Banghead Love John Deere

You haven't mentioned service codes. Which ones are coming active when the problem happens?

jlittle2212 · Nov 8, 2015

cutting edge said:
You haven't mentioned service codes. Which ones are coming active when the problem happens?

No codes...

nowing75 · Nov 8, 2015

What is the fuel psi? I have had issues with high leak off in the cat dozers we have. From what I hear is the pumps are not normally the problem. And you should never crack the lines on a cr motor.

jlittle2212 · Nov 8, 2015

nowing75 said:
What is the fuel psi? I have had issues with high leak off in the cat dozers we have. From what I hear is the pumps are not normally the problem. And you should never crack the lines on a cr motor.

14-20 psi. Deere calls for a minimum of 29.. It fluctuates.. Tell me more about this high leak off.. What gets me thinking pump is where you got to prime it back to start after running.

jlittle2212 · Nov 9, 2015

LOoks like nowing was correct... Pump did not fix it.. I'm going back to the machine this week. Operator said some codes came up this time!!!

nowing75 · Nov 9, 2015

On the cats I have done you take the return line off of the injection pump and crank the engine and measure the fuel. If it's over than your injectors are leaking. The problems I have had is the pressure when hot would be low and the machine would be hard to start. What is the cr psi?

Denso "Common Rail" Fuel pump

Well-Known Member

Senior Member

Well-Known Member

Senior Member

Well-Known Member

Senior Member

Well-Known Member

Senior Member

Well-Known Member

Well-Known Member

Senior Member

Senior Member

Well-Known Member

Well-Known Member

Senior Member

Well-Known Member

Senior Member

Well-Known Member

Well-Known Member

Senior Member