Komatsu PC138USLC-10 #KMTPC245LFUF40688 has SAA4D95LE-6 ESN 704399 engine. Having an issue with code CA559 ail Pressure Low. When observing rail pressure on the monitor: With throttle turn all they way high Traveling the machine in high speed to create a load Rail pressure was erratic, fluctuating momentarily as low as 6,000psi less then the desired rail pressure. Commanded value was 26,000psi and actual would dip down to 19,000psi at times. Until finally CA559 was set and engine de-rated and defaulted to 6-7,000psi Made both fuel filters new, no change. Checked fuel sump for debris, clean. Drained sample from tank through petcock, looks good. No fuel leaks visible. Put a inline sight glass and pressure gauge on the line from the low side pressure pump after the filter housing. So where the injection pump is receiving pressure after everything. 1600rpm: No air, 157psi (spec is minimum 128psi at high idle) Separated the injector return, rail return, and pump return. Engine running with no load at 1600rpm for 1 min Injection return was 100ml (190cc/min spec) Rail return was 0 (ignore the residue seen in the picture I didn't empty it fully) Pump return was 400ml, with a heavy pulsing flow I included some pics if anyone is curious how I set this test up. I'm inclined to think that the injection pump is causing the low rail pressure. I have a suspicion that one of the plungers is bypassing fuel. Komatsu does not list a return spec for this pump so I don't have a comparison. I believe it is a Denso HP4 pump. #6275-71-1120 #29400-1790 I did already change the SCV, the spec was listed at 3-5ohm and my original at 8ohm, but the new in box from dealer was also 8ohm and did not fix the issue. Any input appreciated.
returns, again ignore residue in rail return
Update, Pump replaced problem corrected Also the service document was incorrect, SCV should be 5-15 ohm according to Denso
Hii Bullitt i have nearly the same Problem with a PC 138-10, sometimes i got the troublecode CA 559/112 Railpressure very low. when i check the enginedata the pressure in the rail is ok (soll-ist) and withe no reason the mailfunktioncheck comes. Straing ist that the waterseperator is half empty when this trouble happens i alsow instal a electric supplypump but it doesnt help i alsow checkt the return fuell the pump was 300ml the rail was 50 ml and the injektors was 200ml do you have some datas for me for checking the engine ? srry for my bad english and thanks for help. greetings from austria
The fact that you have rail return volume at all is a bad sign. There should be 0, none, nothing. The rail is simply a safety purge in the event that the fuel had nowhere to go. I would service the rail, new sensor, new safety valve and see how she acts.