The ole 559 code

[Gill Oruga]

(12-28-2022 )Smooth Wrote:  Just putting feeler out see if anyone has run into this before I start the never ending 2350 Fuel rail Test.

Code 559 - Triggered 9 times over a week period.

Fuel Pressure Leakage Test of course first go to, 30 Sec - 22000 psi at 60 Sec still holding 18K. I have seen much worse

But the oddity is When I start the Leakage Test , The trucks starts building pressure as normal around 15K Psi it bottoms out back 5-6K and basically starts over. It did the same thing 3 consecutive times. But each time after it does that truck builds to near 30K psi and stabilizes as it should.

Before starting the Test I did change the High Pressure Relief Valve

Thought would check for anyone that has had a similar issue in the past before i start in with the never ending Tests.

I noticed the vast majority of X101 engines do this. I went crazy trying to figure out why but never found the cause.

What kind of values do you see on the snapshot?
Check what your ECT was during the fault and check what the fuel pressure values were. I've noticed large spikes (10,000psi+) in fuel pressure are usually caused by a relief valve. While low spikes (around 4,000-5,500psi difference) ends up being an injector or pump head.

Based on your test I would say get it hot and test the pump head.