I was working on a 2007 F-350 6.0L today with an extended crank when hot and low ICP pressure under full load. I performed the regular ICP tests including air pressure test, dead heading the pump, checking engine oil pressure and examining the IPR valve. During my diagnosis I came across another option for testing the ICP system.

I know many shops are now using nitrogen at high pressures (up to 2000psi I've heard) to find leaks in the HP oil system. I do not have this option at this time but I notice if I command the IPR to 85% and then crank the engine with the FICM relay out to prevent it from starting the computer will only allow 44% duty cycle max. This equates to around 1,600psi but when you stop cranking the duty cycle with return to 85% which will not hold the pressure but will maintain over 500 psi for a few minutes.

This test can be performed immediately on a hot engine without any disassemble and may be useful for determining if the system has a leak with high pressure than shop air.

Ryan from British Columbia