mg2361
Senior Member
So long as the donor machine has the same engine and injection pump it should work.
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850C series 2 fuel control problems
- Thread starter Farmerditcher
- Start date
Farmerditcher
Member
Well we are still not going with this dozer. Put a different ECU on it today and it did not change a thing. We are confident that fuel flow and pressure to the inj pump are not a problem.
Like I said earlier, it VERY consistently starts and runs fine for 2-3 hours every morning before it gets in a mood. First thing it will do is begin missing for 30 seconds or less before it begins wildly accelerating and deaccelerating until it dies, missing all the while. During this time the ECU takes control of the throttle and we can't control it. Also still seeing the F434 and F431 codes that pop up as the issue arises. Once it throws a fit after a couple hours of warming up it will remain in it's mood for several hrs. The first thing that occurs is always the miss, followed by the wild throttle. It will restart normally and run for a minute or less all day long after the mood begins.
I am curious why we are getting a miss as this is a typical Bosch inline pump with mechanical injectors. If the miss is being caused by a pump or injector problem, would that trigger the ECU to start acting wild with the throttle? And WHY would it take 2-3 hours of working to show up?
Sorry for all the questions as we are getting a little worn down here. We are very thankful for any and all advice we can get at this point! Thank you.
Like I said earlier, it VERY consistently starts and runs fine for 2-3 hours every morning before it gets in a mood. First thing it will do is begin missing for 30 seconds or less before it begins wildly accelerating and deaccelerating until it dies, missing all the while. During this time the ECU takes control of the throttle and we can't control it. Also still seeing the F434 and F431 codes that pop up as the issue arises. Once it throws a fit after a couple hours of warming up it will remain in it's mood for several hrs. The first thing that occurs is always the miss, followed by the wild throttle. It will restart normally and run for a minute or less all day long after the mood begins.
I am curious why we are getting a miss as this is a typical Bosch inline pump with mechanical injectors. If the miss is being caused by a pump or injector problem, would that trigger the ECU to start acting wild with the throttle? And WHY would it take 2-3 hours of working to show up?
Sorry for all the questions as we are getting a little worn down here. We are very thankful for any and all advice we can get at this point! Thank you.
mg2361
Senior Member
I would rig up clear lines in the supply and return lines to see if you are getting air (or pulling a vacuum) when the issue acts up, possibly from something floating around in the tank. If the engine starts to starve fuel fuel it will act just like that (miss, wandering rpm). The rack position codes might be a reaction to what the controller thinks it should be seeing (rack position vs engine rpm).
thepumpguysc
Senior Member
- Joined
- Mar 18, 2010
- Messages
- 7,535
- Location
- Sunny South Carolina
- Occupation
- Master Inj.Pump rebuilder
mg is correct.. the ONLY WAY to rule it out is to put clear lines on the inlet..
Its not uncommon for the rack actuator in the inj. pump to be worn & act up when it gets warm.. actually its VERY common.. I couldnt count how many I've replaced.. literally in the thousands..
Its not uncommon for the rack actuator in the inj. pump to be worn & act up when it gets warm.. actually its VERY common.. I couldnt count how many I've replaced.. literally in the thousands..
greasynails
Member
Check the fuel cap/tank vent isnt plugged and drawing a vacuum in tank over time. Clear lines may not show anything if its not moving any fuel but a supply pressure test will.
Johann Barnowski
New Member
@Farmerditcher were you able to figure out your problem. Our 850c is doing the exact same thing. Same codes and same symptoms. It's like you've got our machine. We had the pump done just under a year ago
Last edited:
Farmerditcher
Member
So after rigging up a section of clear line in front of the lift pump we began to notice small bubbles going in when the machine would begin acting up. Bypassed the fuel filter/water separator and still were getting bubbles. Decided to check if we had a screen in the outlet of the fuel tank. Sure enough found one and it had a bunch of crap around it. Took it out and are running an inline screen up near the engine where we can change easily. I feel now that our problem all along was definitely rusty crap in the fuel tank that was building up on the screen after a couple hours of running. Then it would start getting air somewhere as it was under a vacuum. Seems amazingly simple now!
Our next step should be to take the tank off and cut it open and clean it but thats too big an undertaking at the moment. Looking down the fill hole you cannot even see much of the bottom of the tank as there is a baffle that runs down near the hole. Do any of you have experience or an idea for cleaning a tank like this?
Thank you all for your help along the way with this dozer!
Our next step should be to take the tank off and cut it open and clean it but thats too big an undertaking at the moment. Looking down the fill hole you cannot even see much of the bottom of the tank as there is a baffle that runs down near the hole. Do any of you have experience or an idea for cleaning a tank like this?
Thank you all for your help along the way with this dozer!
realjob
Active Member
Maybe rig a a circulation pump tied to suction line and return with filters. I would make sure your pump will at least move as much fph let it run over nights. Just my fat guy idea.
Jason
Jason