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Rawze · 05-31-2025, **(Subject: Intermittent code 559 )**

(05-30-2025 )HueyEHester Wrote: We have this issue but it happens only at startup. We have a Cummins X15 Engine. We’ve already replaced High Pressure Fuel Pump, Relief Value & Pressure Sensor.

does it pass an injector leak test when done exactly like this video shows??
info: https://rawze.com/forums/showthread.php?...3#pid75483

HueyEHester

Hope to do the test either today or tomorrow. Will post results once it’s done.

amermextrucker

On mine it was fuel pump head , that 559 code is a real PITA.

marek4792

If it fails the leak down test and the high pressure pump checks out good. Ensure it is not the pressure relief valve going bad first.. then after that, Start capping injectors off.. You may have a bad tube and/or leaking injector(s).

HueyEHester

We did the Leak Down Test. It’s failed spectacularly. Went down 19041 psi in 60 seconds. It was 29131 at engine shutdown to 10080 at 60 seconds. We’ve got the Fuel Supply Connectors ordered and will put them in once we’re home and they are delivered. Will keep posting once that’s done.

Rawze

(Yesterday )HueyEHester Wrote: We did the Leak Down Test. It’s failed spectacularly. Went down 19041 psi in 60 seconds. It was 29131 at engine shutdown to 10080 at 60 seconds. We’ve got the Fuel Supply Connectors ordered and will put them in once we’re home and they are delivered. Will keep posting once that’s done.

start by replacing the pressure relief valve at the end of the rail. Its the cheapest part in the system. From there it gets more expensive.

HueyEHester

We’ve already replaced that. The only things left are the Fuel Supply Connectors & Injectors everything else has been replaced. Though we’ve got a Main Wiring Harness to replace and will get a ECM if needed.

mikkhh

Was it replaced with original part?

Aftermarket engine parts = failure guaranteed.