One of the most common problem areas with the 6.0L engine is the high pressure oil system. Leaks are common - especially with the late 04 and up oil rails, and the 05 and up (original) STC fitting. Even with no leaks, the IPR valve could have failed or be stuck open from debris ..... OR the HPOP could have failed.
With HPOP failures (very similar to leaks in the High-Pressure oil system), you will see a lack of power with high IPR numbers and ICP less than desired. From what I understand, the only sure
way to identify a bad HPOP is to remove the pump and remove the cover and rotating assembly to inspect it. That said, according to forddieseldoctor, if you open the pump you make junk out of it.
NOTE - the axial pumps were only used on the 7.3 and '03 - '04 engines. The '05 and up pumps were a "4V" style cam shaft operated piston pump that is more robust than the axial pump (thanks to @Hydro
for this note)
The 03 and 04 HPOPs have a much higher failure rate than the 05 and up pumps. EVEN SO, the 05 and up HPOPs CAN AND DO fail occasionally!
Note that even though the late 04 engines had the change to the wavy oil rails (AND the HPOP capacity was increased slightly), the HPOP in that model year still had
the swash plate design. The HPOP design was not changed until the 05 model year and as such, the "failure prone" STC fitting was introduced in that model year also. Even though the early model year (03-04) HPOP discharge piping did have a type of snap-to-connect fitting, it was not the same as the failure prone 05 and up fitting). When people talk about a failed STC fitting on the HPOP discharge, they are referring to the 05 and up pump.
Pretty much everyone is aware of the air testing used to identify a leak in the High-Pressure oil system.
Identifying a bad HPOP is more difficult. In fact, it is usually identified after everything else in the High-Pressure oil system has been determined to be working as it should.
As far as I know, there are only a few ways to identify a bad HPOP.
The most common method to identify a bad HPOP is by conducting the air test (IMO this is best done from the IPR valve port w/ the test fitting that is installed in place of the IPR valve). Note (again IMO) - if you have a leak in the high pressure oil rails, STC fitting, or even from an injector, it is best to repair these first and then repeat the air test.
First remove the oil filter housing cap and then remove the oil filter.
Then, apply shop air to the high-pressure oil system (150 psig air is recommended).
If air leakage OR a gurgling sounds are heard from the oil filter housing, then that means the air is flowing backwards through the HPOP.
When listening at the oil filter housing, it is best to depress (close) the oil filter drain valve at the bottom of the housing. Sometimes "air sounds" from the crankcase can interfere with this test.
In addition, air flowing in reverse through the HPOP will also be able to be identified if air flows out of the turbo oil supply line (aerated oil will be expelled).
The difficulty with this test is that air may not flow backwards through a failed HPOP in every HPOP (internal) position. It may leak in one orientation, but not in others. In this case, it is best to bench
test the HPOP (ie remove the HPOP and do the air test with it in a vise on the bench). When testing on a bench, the HPOP gear can be rotated to test for air leakage in all of the pump "internal positions". Sometimes when you try to spin it by hand, you might hit a "dead spot" with it (won't turn anymore). It is bad if this happens.
The video below shows air testing an HPOP on the bench (as well as showing the testing of an IPR valve with air). The HPOP discussion starts around 1:00.
The second method to identify a bad HPOP is not as much of a "sure-thing" as the first ....... but it is easier. NOTE - I read this on the forddoctorsdts.com web site.
A bad HPOP will often times cause a repetitive fluctuation in the pressure of the High-Pressure oil (ICP pressure reading).
To detect this, you need to be confident that your ICP sensor is reading/working properly and does not have any wiring issues.
For this test, you need to have a scan tool that will graphically display engine parameters. ForScan on a laptop will do this (and of course the Ford IDS system will also).
Connect up the scan tool. Set the tool to the graphical display mode.
Watch the ICP pressure (and voltage) when cranking.
If you see a saw-tooth pattern for the ICP reading, chances are you have an HPOP issue.
My impression is that this type of erratic ICP reading would be seen more on the early style HPOP when it had failed (not so much the 05 and up).
I am chasing an intermittent no start/ start stall on a 4/03. It may only happen once a week, but once the truck is started it will be fine for several days. Fuel pressure never seems to be an issue @ 54-55psi. Low oil PSi climbs as it should. I have several recordings, some times it looks as if ...
One difficulty with this test is that a bad ICP sensor or connector can sometimes cause this type of saw-tooth behavior as well. That is why you have to be confident in their condition to begin with.
Lastly, an HPOP can have a leak at the bottom yellow (suction port) o-ring. This issue will cause behavior that will be similar to when the early HPOPs would blow out the suction side ball bearing (BB).
Most of the time, a leaking suction o-ring is due to improper installation (including installing the wrong o-ring in that position). If there has been no recent work on the HPOP, then I would not suspect an issue there.
If the engine won't start "Nose High" (on an incline or "up slope"), but will start on a decline (down slope), then this suction side leak might be the cause.
SOMETIMES, a suction side leak on an HPOP can be bad enough to cause an issue with low base oil pressure (the IC gauge drops to zero). This will mainly happen with a big suction side leak (like the BB falling out of the HPOP). A high side leak would RARELY act this way.
Bulletin 19417 2003-2007 f-super duty/2003-2005 excursion 6.0l - watch for oil flow from the base engine oil pump.
Some 2003-2007 f-super duty and 2003-2005 excursion vehicles equipped with a 6.0l diesel may exhibit low base engine oil pressure caused by a leak in the high pressure oil system. If a high pressure system leak is severe, the high pressure pump may use a larger volume of oil than the base engine (gerotor) pump can produce while cranking. If base engine oil pressure is low, remove oil filter, hold down the oil drain valve (left side of housing) with a screwdriver and crank the engine while watching for oil flow from the base engine oil pump. If flow is present, use the updated diagnostics for the high pressure oil system
(electronic version of PC/ED manual, section 4, step 10e). If there is no flow at the oil filter housing diagnose the base engine oil system first (workshop manual section 303-01c).
Effective date: 10/06/2006
An interesting video on swash plate pumps: