0559 FUEL RAIL PREASURE FAULT CODE LOOSES POWER

[CASPER1968]

I HAVE A 2009 FREIGHT LINER ISB 6.7 FAULT CODE 0559 IVE REPLACED THE SENSOR ON THE FUEL PUMP IVE REPLACE INJECTORS. PREASURE SENSOR ON RAIL. BUT I STILL HAVE THE SAME FAULT CODE THE FAULT CODE COUNT IS AT 1776 CHECK ENGINE LIGHT GOES ON OFF ON OFF ALL THE TIME MOREW SO AT HIGHER RPM" IVE SPENT OVER 6,000 DOLLARS AND COUNTLESS HOURS TRYING TO REPAIR THIS PROBLEM IF ANYONE HAS ANY IDEAS I WOULD BE SO GRATEFUL. THANK YOU IN ADVANCE.

[gearhead]

Watch the commanded pressure versus the actual pressure see if the match sitting at 1000rpm then drive it and see if actual drops. It may be fuel pump.

[hhow55]

Gearhead ,
You are one of the very best. I alway's appreciate it when you weigh in with a solution.

[snailexpress]

(05-19-2016 )gearhead Wrote:  Watch the commanded pressure versus the actual pressure see if the match sitting at 1000rpm then drive it and see if actual drops. It may be fuel pump.

So if actual is slightly lower then commanded fuel pump is bad?

[gearhead]

Not unless it's thousand or more and it could be the fpr valve also. I have seen fuel filters cause this. Most of the time if the pump is bad the commanded will match at 700 rpm no load. soon as you put 50% or more load the actual falls off, this does not mean for sure it's the pump. The proper troubleshooting must be compleated before the pump is proven to be at fault.