I have a 1995 psd that is stalling at idle only. I plugged in a Snap-on brick scanner to watch the engine data streams to see if it was shutting with the same values. Watching the ICP pressure it is bouncing between 382 and 1053psi. the IPR % is bouncing between 15 and 31%. I just replaced the ICP sensor do to it leaking, and am getting the same pressure readings. The truck is stalling an ICP pressures between 382 and 953psi. If anyone can help it would be great. Thanks, Will

 

has you oil pressure gauge in the truck dropped when its at idle?? ive been haveing problems with very rough idle but no stall havent been able to get scanner plugged into it yet im gonna put new orings in the ipr but havent yet,, im thinking my hpop is dying on me

 

what is hpop?

 

boy you are getting an education today.
HPOP= high pressure oil pump
Ford Powerstroke engines, introduced in 1994, employ a unique fuel injection system, commonly termed HEUI, short for Hydraulic Electronic Unit Injection.

As the name implies, the HEUI injection system uses hydraulic energy to actuate the unit injectors. Not many people realize this, but a Powerstroke engine has TWO oil pumps: a low pressure lubrication pump, located near/in the front engine cover below the water pump and a high pressure hydraulic pump, located at the front of the engine vee, underneath the fuel filter assembly. If this is the first you've heard about the high pressure oil pump, don't feel bad: many times we've talked to Ford parts people that have no idea a Powerstroke has TWO oil pumps.

Pump Purpose

The purpose of the high pressure (HP) oil pump is to provide high pressure (up to 3,000 PSI) motor oil to the injectors. The pump is a seven piston axial (swash plate) design, of fixed displacement. Here are some links to swash plate pumps:

(Maintenance Resources Library)
The axial piston pump with rotating barrel by R. van den Brink
Axial Piston Pumps by Integrated Publishing

There are many more available on the internet. The Powerstroke HP oil pump is fed low pressure oil from the lubricating pump via the HP oil reservoir, located at the front of the engine. Contrary to popular belief, the HP oil reservoir does not store high pressure oil: the oil in the reservoir is at lubrication pressure, 15 to 45(?) PSI , not injection oil pressure (500 to 2700ish PSI.) A more correct term for this reservoir would be HP oil pump reservoir, but everyone seems to leave out the "pump" part, thus leading some people to think the reservoir is holding 3,000 PSI oil.

The high pressure oil pump feeds two high pressure oil rails, one in each head, via two hoses. The output pressure of the pump is controlled by an electromagnetic pressure regulator mounted in the body of the pump, commonly termed the Injection Pressure Regulator (IPR), although it has other names. (Rail Pressure Control Valve, RPCV, if I remember correctly.)

There are at least 2 different high pressure oil pumps used on 99+ Powerstroke engines:

1999 engines built before December 12, 1998 use a pump common to the A250 T444e engines. 1999.5+ engines use a very similar pump, albeit with about 30% more displacement and a different swash plate/rear cover assembly. There is some confusion as to the part numbers of these respective pumps, but it appears the 99.5+ pumps have a part number ending in "CRM" International appears to use a better part number system than Ford does.

A 1999 Powerstroke engine runs better with a 1999.5+ pump installed, although the parasitic power loss will be higher. A 1999.5 engine will run with a 1999 HP pump, but it will be somewhat performance limited. The same IPR assembly is used with both pumps.

Recommendation: if you ever get the HP oil pump replaced on a '99 PSD, attempt to get the '99.5+ pump. It will bolt right in.

The HP oil pump has a built in pressure relief valve factory set at 3800 to 4000 PSI to prevent damage to other HEUI components in the event of a short circuit to the IPR control circuit. (The IPR is controlled by a PWM low side driver.)

 

Awesome explanation wlihntr!

 

Ok guys, want to ask you guru's if the 99.5 and newer HPOP will bolt right in to the 95 PSD, or will something need to be changed?
Also, are the International HPOP cheaper and if so, anyone know what motor number does International use or part number on the better HPOP?

 

Damn dude, I guess thats why your classified as a 'Guru'.