Looking for tech help for Deere 850j

Hello, I'm hoping to get a little help from some Deere folks. I've got a 2008 850j dozer with a 9.0L. I have a reoccurring ecu code, 656.7, Cylinder 6 injector low fuel flow. It's always the same code so I don't think the computer is lying to me. The DTC is very specific and indicates that either the injector or the fuel restrictor is malfunctioning. I pulled #6 injector and had it tested. It failed in spectacular fashion. I then installed a new injector (reman) as well as a new feed tube and new fuel restrictor valve. Installed and torqued everything to spec. I still get the same DTC. I ohmed out all the injectors and all the injector leads--they all have the same values. Anyways, I think the ecu would recognize a circuit/signal issue and would supply a different DTC if I had circuit issues. I can run the machine at full throttle, no load without triggering the code ( I travelled for 30 minutes with no working load without issue), but as soon as I put it under heavy loading the code pops up. I've gone back an put a little more torque on the injector clamp and feed tube nut. Still have the code show up. I never did have the reman'd injector calibrated, but I find it hard to believe that programming injector fuel trim is causing my issue, but I could be wrong as I'm certainly not a trained pro at this.

I don't believe fuel pumps, or supply is the issue otherwise I think I would expect to seem more random and varied codes, i.e. cylinder 2, cylinder X, low rail pressure, etc... It's alway cylinder 6 low fuel flow!

My thinking is either the new (reman) injector is faulty or could I have an ecu issue?

Thanks for reading.

Funny or not so funny thing about those is, if u already changed #6 & the code keeps coming back, it’s probably the 1 next to it... SERIOUSLY..
Don’t u have to recal. the ecu to the new injector.??

thepumpguysc said:

Funny or not so funny thing about those is, if u already changed #6 & the code keeps coming back, it’s probably the 1 next to it... SERIOUSLY..
Don’t u have to recal. the ecu to the new injector.??

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Yes, you are supposed to recalibrate the new injector and I never did, but like I said I'm having trouble convincing myself that I'm throwing a code due to fuel trim calibration. I've replaced electronic injectors in other equipment before and never recalibrated without any issues. I've always understood injector fuel trim to be largely a matter of meeting emission spec's. I guess the reason I haven't done so with the dozer is that it has to be done with John Deere Service Advisor and it's about $1600 to get the dealership tech out here with his laptop even though I'm only 77 miles from their shop. Funny thing, I can get a heavy haul to their shop for $600.

You never stated how many hours your machine has and whether the injectors are original equipment. I personally am not a fan of replacing 1 injector on a high hour engine. Trims files are like the final tune , 1% or so. Its unlikely that is causing your problem.

I’m not a fan of the remaned injectors myself. The failure rate on the remains is shockingly high.

Just for kicks, swap 5 w 6 & see what happens.

Vetech63 said:

You never stated how many hours your machine has and whether the injectors are original equipment. I personally am not a fan of replacing 1 injector on a high hour engine. Trims files are like the final tune , 1% or so. Its unlikely that is causing your problem.

I’m not a fan of the remaned injectors myself. The failure rate on the remains is shockingly high.

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Yeah, I've had some episodes with remans before. I hesitated to go that route, but the dealership only had reman in stock so that's what I did. Machine has 5400 hours and all injectors are original. I've suspected for some time I bought a bum injector, but I think I'm at the point I need to pull it and have it tested just to rule out the possibility.

Update of sorts in case anyone is interested: Pulled #6 injector that was replaced and sent it in for testing. Results were the last thing I was expecting--the injector is actually OVERFUELING per the specs. Now I'm thinking that I've probably got some other leaking injectors that are contributing to a pressure and/or volume issue in the common rail. My thinking is that at 5400+ hours #6 was not the only leaky injector, but I probably have a few more with excessive overflow and return. I'm told that 5-6000 hours is the expected life of these Denso injectors, some guys get more, some guys get less. Anyway, I might have a case where there are other leaking injectors that are not bad enough to throw an individual DTC, but are contributing to a pressure/volume issue in the common rail. At full horsepower and torque demand there is enough leak off and fuel return that tricks the ecu into thinking that #6 has low fuel flow because there is a pressure/volume issue in the common rail. Not enough of an issue to trigger a low rail pressure DTC, but low enough to cause a supply problem at full demand. I'm going to pursue a return flow test and see if I'm in spec or if I'm way out. This won't identify any specific leaking injectors, but should give me a broad insight into the current state of things. I'm also leaning towards just replacing the other five injectors and taking it forward from there. Please comment and let me know if I'm just nuts. I'm pretty much out of ideas here.

I tell every customer that it's the same amount of labor to replace one injector as it is to do all six. If you haven't had any issues with the injectors and now one is failing. The others aren't far behind. It's a matter of when and not if the others will start falling.

Paul Council said:

I tell every customer that it's the same amount of labor to replace one injector as it is to do all six. If you haven't had any issues with the injectors and now one is failing. The others aren't far behind. It's a matter of when and not if the others will start falling.

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I hear you, but replacing injectors is not a labor issue for me as I can do this kind of work myself except for calibration which requires JDSA. It's more of a parts costs thing: 1@$400 vs 6@$400. I know everything mechanical and electrical has a service life and is destined to fail at some point, but I'm also a big believer in 'if it aint broke don't mess with it'; This excludes sensible maintenance and wear parts, of course. I've had and have known ag tractors that exceeded 10,000 hours with both mechanical and electronic injectors and some are still running fine to this day. I agree that it would be nice to just replace the whole set, but I can't necessarily afford this approach. I would also hate to think I pitched injector(s) that may have many more hours of life in them. My preference is to pinpoint the problem if I can, but like I said my diagnostic skills are just about run out here.

Another update for those of you who are sticking with this: I never had a chance to check the return fuel flow as I could never find a spec for this. I bit the bullet and had a JD tech come out. Great guy, but still painful for me $$$. He didn't like what the injector test said about over fueling (it was almost 15% over spec) so he installed another new reman, calibrated, did an ecu compression check, circuit test, and some other ecu ninja stuff. I put the dozer under extreme heavy loading (pulling an 11' root plow) and it almost immediately popped the same code--ecu 656.7 low fuel flow cylinder #6. Tech jumped back into the machine with the laptop.This time couldn't get it to code in 30 minutes of root plowing. I plowed for another 4 hours today and all seems great for now. The only thing I noticed was that the machine puffed white smoke for about 5 seconds when I first started it. I've never seen that happen, but otherwise it ran smooth and trouble free. Hopefully all is well. I have no idea what fixed this machine and neither does the tech. Any guesses?

Did you replace the fuel damper (the piece on the rail that #6 injector line is attached to) or the injector line? That code only shows when the ecu does not see a pressure drop in the rail when the injector fires.

mg2361 said:

Did you replace the fuel damper (the piece on the rail that #6 injector line is attached to) or the injector line? That code only shows when the ecu does not see a pressure drop in the rail when the injector fires.

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On the first go around I had replaced the flow restrictor. This piece attaches to the rail and is between the rail and the injector fuel line. It's basically a simple valve with a spring and a piston and every injector has one coming off the rail. Is this the damper? I also changed out the 'feed tube'. This is the piece that goes between fuel line coming off the rail, goes through the block and T's into the the stem of the injector. Deere says these 'feed tubes' are one time use.

sfowler said:

Deere says these 'feed tubes' are one time use.

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Yes, the feed tubes are one time use only.

sfowler said:

This piece attaches to the rail and is between the rail and the injector fuel line. It's basically a simple valve with a spring and a piston and every injector has one coming off the rail. Is this the damper?

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Yes, proper term I guess is Flow Limiter. The flow limiters reduce pressure pulsations. This ensures a steady pressure in the fuel lines to the electronic injectors. The flow limiters are also used to limit the maximum fuel flow to the injectors to prevent engine damage due to a failed injector or a high pressure leak by shutting off fuel to that particular injector.

I would have also replaced the line that connects the flow limiter to the feed tube.

Well even though I have solved my problem for cylinder 6 coding on me it seems I've picked up another problem. The motor stalls on the first start attempt after sitting overnite. It's as if it is hydro'd. Pop the key again and it will start up and blow white smoke for about a minute. Runs great after that. It's smoke and not steam. Coolant level is not going down and no coolant odor. If you shut down and come back in a few hours then there is no issue, but if you let it rest overnite then I'm guessing I'm leaking off fuel to other cylinders--more bad injectors. Looks like Mr. Paul Council had some real good advice and I should've just replaced all the injectors. It's frustrating solving this one piece at a time.