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2008 Hino 338 P0087

Fltidefan

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I have a 2008 Hino 338 that we recently purchased and converted to a dump truck. It showed up to us with a P2002 and we have with thru the DPF system and replaced all the sensors and installed a new filter. It also in setting a P0087 code. I have went thru and blew out the fuel lines and replaced the SCV when it ohmed out of specs. I am at a loss for what next. When connected to the DX2 software, the common rail pressure stays on target until it gets to about 90 MPa then starts to tail off, eventually dropping to around 20 MPa at full throttle. Any help would be appreciated.
 

Hino123

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Does it have any other codes? Do you have access to DX2? What is the max fuel temp? At idle what is the "pump current target final value" when up to temp? Did it also set a P0088? Sometimes if the pressure limiter valve opens when it sees high pressure it will nor re-seat and bleed off pressure in the rail. Intermittent connections at the common rail pressure sensor are fairly common. Wiggle test the plug end while looking at the live data. I have seen issues with the SCV wires fretting, perform a wiggle test there as well and report back.
 

Fltidefan

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All other codes are clear. It originally had a P2002, but we have replaced the filter and sensors. We have DX2, I used it to reset the DPF settings after filter replacement. I tried to do a pump relearn after replacing the SCV but I can't get it to work. It hasn't set a P0088. The max fuel temp is 230 degrees. The pump current target final value fluctuates between 1420 and 1433 mA. I have performed the wiggle tests and no changes occurred.
 

Hino123

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With that high of fuel temps and that low Ma on the pump current. I would suggest replacement of the pump. While I cant guarantee that this is the root cause of your problem, I can guarantee that pump is on its way out. When you take the pump coupler out be sure to inspect it closely for cracks. Spec on the pump current target is 1550-1950ma. Let me know if you need further assistance. good luck
 

Fltidefan

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How critical is doing the pump relearn process? I tried doing it after replacing the SCV, but I couldn’t get it to work. I’m not sure if the problem was me, Hino program, or the truck.
 

greasytshirt

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Sometimes it just doesn't work. I don't have an explanation. It eventually figures it out by itself.
 

Hino123

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How critical is doing the pump relearn process? I tried doing it after replacing the SCV, but I couldn’t get it to work. I’m not sure if the problem was me, Hino program, or the truck.
Like Greasytshirt said, it will learn itself. It is not critical. I know some guys that never do it. The problem with it is that the instructions are incorrect in DX2 and the old DX. I have it in my notes, but cant remember off the top of my head. I believe it has something to do with the key cycle. I think it says to key the truck off, but by "off" they mean on acc. Something to that effect. I spent like 2 hours messing with it one day. I use a DST-I made by Denso as an interface unit for Hino's. They don't make them anymore and I doubt unless you work at a dealer you would have one. When I replace pumps I program them with the DST-I. There is a setting for forcing regens, resetting DPR status, checking DPR back pressure and learning pumps. They are very handy if you ever see one pop up for sale. Its like the Nexiq but has the ability to be used as a stand alone tool without DX. Anyway not being able to learn the pump would not cause the issue you are having. If you cut one of the o-rings on installation of the SCV that could cause low rail pressure. I really think a weak pump is the issue here though. Good luck.
 
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