another 6.0 down. 05 f550 was running around all day on and off yesterday. shut off at the end of the day and then wouldnt start again. tested the ficm ignition in 48v cranking 48v then it started 48v. tested hpop pressure with guage in icp sensor spot slowly went to 300 then started dropping down to 200 while cranking. so am i looking at a hpop or a hpo leak? i ran the pigtail wire to the ipr valve and pressureised the hpop system with air and i couldnt hear a leak but not 100% sure. i have no way of checking ipr actual desired ipr pressure. batteries were fine but have been on a charger all day. i would assume the stc fitting has not been replace before

 

STC fitting most likely, might as well get the new fitting and the standpipe and dummy plug kit and make it right all at once so you won't have the problem again. tousley Ford sells the Standpipe and dummy plug kit for $102 and the STC fitting for $38

 

Agreed with Bob, just go ahead and replace it. If the pump was bad you'd likely not even build the 200 or 300psi you had. Probably just a leak. 05's are super notorious for the STC fitting.