2012 Isx 2350 475 with codes 4726 and 0559

[ahrenbenjudah]

Update. Okay. So I did the high pressure fuel pump return flow test. Crank until you get a steady stream of fuel, once you have that steady stream, put your hose in to a graduated cylinder for 15 seconds. Do that twice. If the fuel you collected is over 350ml then the head is bad. If its under 150ml, the fuel pump actuator is bad. I never really got a steady stream, but collected about 90-100ml over 30 seconds. So, down to KW to get an actuator. $550 later, slap it on, and still the same issue.

No fuel pressure in the rail at key on, truck will crank and crank.

So I got a wild hair and while I was cranking it, juiced it with some starting fluid. She started up after a second and kept running. Insite hooked up to it while running and the pressure stayed at what was commanded. I let it run for a bit, then I shut it down while having the data logger open. As soon as the key was off, I lost ALL pressure in the rail. Immediately.

Cranked her back up and she started again no issues. I figured I would run an injector performance test to see if any of them were underperforming. I was able to start the test, but before it could finish the first injector, the test stopped because the fuel rail decay was too severe to continue the test.

Truck wanted to run a regen so I let it, it completed that with no issues. After that was finished, I checked for any codes and I have a 4726-Engine Fuel Leakage-Data Valid But Above Normal Operating Range-Moderately Severe Level.

So, Insite says to do an injector test, which I can't do, but I can do an isolation test which is the alternative. Then it says to test the pressure relief valve. So hopefully I can get to that first thing in the morning. It has since starting dumping buckets here and I'm tired of being wet.