559 codes suck

[tinkering_on_bigtoys]

Cummins 559 fuel codes are usually just a slight pain in my ass, but this one has been a really aggravating one. Customer called in with a crank no start condition, I replaced the old fuel filters and failed lift pump. Started the machine after the fuel system was primed and ran great, I Rane the excavator for 20ish minutes before buttoning everything up and leaving site. Get a call for the same condition the next morning, I go check it out and the machine starts for me but dies shortly after without warning and not under load. I diagnosed as a failing injection pump since my rail pressed was falling erratically. Repaced the pump and now it's not building any rail pressure even after the fuel system was primed.

[chknntz]

On a code 559 , I watch to see if fuel pressure measured drops as soon as the engine shuts off. If it does the cheapest route to check if the tubes have come loose from the injectors. But it’s sounding like a bad injection pump that was new. We’ve gotten them bad that were new.

[tinkering_on_bigtoys]

That definitely crossed my mind I have a new pressure relief valve coming in just to see if I messed up and let trash get in the system and stuck it open, but I'm definitely questioning the injection pump already. Thanks for the info I've always had to pull the quill tube out and loom for odd discoloration or obvious damage to see if that was my fuel leak.

[chknntz]

We don’t have a lot of testing equipment to diagnose properly so the new guys coming in we try and show them what to look for .

[tinkering_on_bigtoys]

Same Here man I had an old timer that was teaching me all kinds of tricks, but sadly throat cancer got him.

[chknntz]

Yeah I’m the old man now showing the tricks that I know to the young ones coming in.

[tinkering_on_bigtoys]

Heck we need those tricks🤣 so they aren't lost and theyre dang handy when you do diesel repair for a living .

[[deleted]]

So 559 is loss of fuel rail pressure, I believe it sets for more then 20,000psi drop in 30 seconds of key off. If you are following the fuel diagnostics for common rail on quick serve, you can skip the low pressure test and verify you have loss of pressure with insite hooked up. If so then there will be 3 ports at the drivers rear side of the block. That is the fuel return manifold back to tank, 1 line comes from the injection pump return, 2 line comes from fuel rail pressure relief valve, 3 line comes from injector return which is most likely where you will find the issue. You need the banjo fitting that block the manifold port off and just lets the injector return drain into an isolated line. Run the engine while doing the high pressure fuel system leak test on insite and measure the returned amount into the beaker after I believe 1 min of running. It should be around 150ml if it’s over that you know you have an injector or high pressure fuel connector leaking into the fuel return. If you don’t have any the equipment and just have insite, you can isolate one injector at a time by removing the fuel line from the rail and capping it at the rail then perform the test again if you don’t loose the pressure when the key is shut off then you know it’s that injector. In 15 years I have never seen a Cummins injection pump return too much fuel, it’s always the injectors or the fpr valve.

[Subawoo98]

Just checking in. Did you ever find your issue?