2012 Isx 2350 475 with codes 4726 and 0559

[ahrenbenjudah]

Ok, I'm back.

Took forever to get the gauges in hand. And then its been below freezing for near on a week here.

So following the Cummins diag tree, I checked the fuel pressure of the lift pump at the filter manifold. Install a compucheck and cycle the key, psi should be above 10psi. Mine reaches about 16.

Then checked the fuel pressure of the high pressure pump at the filter manifold. Crank for at least 10 seconds at 150rpms or better with the lift pump not plugged in. Pressure should be above 10psi, mine reached about 30.

Double checked the pressure relief valve (I installed a new one at the very beginning of this debacle). Cummins test is replace the banjo bolt with a banjo test fitting and install a hose to the end of the test fitting. Put it in a bucket, do 4 cycles of 15 second cranking. No more than 10 drops in total is the allowance. Mine didn't drip at all.

I'm about to go back out and do the High-Pressure Fuel Pump Return Flow Test. Which will tell me if the pump head is bad or the fuel pump adapter/inlet metering valve is bad.