Hi, This is my first time posting. I am working on a Cat 321d serial- MPG00894 This machine had a small fire around the fuel filters and burnt off some of the fuel lines. I replaced all the lines and installed a new fuel pump, new filters, lower wiring harness was repaired, new ecm etc. The machine runs great. All speeds on the throttle work fine. After 30 sec of running, the display blinks red and says high fuel rail pressure. Could it be a sensor, bad high pressure relief valve? Any thoughts and help on this would be appricated. thanks Joel
Can you post a photo of the screen when the high fuel rail pressure alarm comes up please.
I have seen stuck open or failed mprop (proportional valve ontop of high pressure fuel pump) that cause high rail pressure codes. It is most likely a mechanical failure as you dont have any codes to indicate an electrical fault?
I am not beside the machine now. I will post a pic when I get back this morning. I had thought of a failed mprop valve. The fuel pump is new from cat. The valve came installed. It still could be the valve. I have a fuel pressure reading in the service menu of around 90psi. Obviously that reading is not the rail pressure. I do not have cat software to hook up to the machine. I would have to get cat to come out and do it.
Simple test, is with engine running disconnect the plug on the mprop. If it develops a diesel knock the mprop is functioning and it may be a failed rail pressure sensor.
I will try that and let you know. The pressure sensor is new. It could still be bad though. Thanks
When I unhook the mprop with the engine running it shuts off instantly. It will not start with the mprop unhooked. Hook up the mprop and the machine fires right away.