2003 6.0L Max Pump Pressure

Keith Browning · January 22, 2013

Anyone know how high the pressure should be with the HPOP dead headed and the IPR fully closed?

Aaron · January 22, 2013

If I recall rightly it should be around 3000, but it has been awhile.

I got told if the pump doesn't build pressure quickly/past 5-600psi hooked up as it should be, and you dead head it and it makes pressure almost instantly, the pump is weak/failing.

The last one I only dead headed the one side just to see if I was headed in the right direction, and it went from right around 500psi cranking hooked up normally to 1500 almost immediately as soon as it started cranking.

Hopefully this helps.

Keith Browning · January 22, 2013

I found it. 4,000 PSI is the opening pressure for the relief valve in the IPR valve.

Matt Saunoras · January 23, 2013

I believe a healthy running stock 6.0 should make 3800-3900 PSI at WOT. I don't think I've ever seen ICP desired go above 4000.

I do know that I've been in some heavily tuned trucks that make a lot of power by tricking the PCM into thinking ICP is much lower than it actually is, hence it never gives out an actual ICP reading(they'll run in the neighborhood of 1500 psi WOT which we know is not correct). Some of these trucks have one hell of a surging problem at WOT and I always remember thinking I wonder if it's the internal relief valve in the pump causing this.

Alex Bruene · January 23, 2013

Don't quote me on this, but I'm pretty sure I've seen them in excess of 7000 psi when dead headed. It's been a long time since I've had to do it.

Bruce Amacker · January 23, 2013

I don't know for sure about the 2003 pump, but I deadheaded a 2006ish with a V4 pump idling and got 4700psi on a gauge. (I did post pics and a full writeup on this several years ago) Here's my opinion: When you ground the IPR return it should make enough for the relief valve to open in the HPOP. When the relief valve opens the sound of the engine clearly cycles in a very nasty way very audibly about 2-3 times per second.

IIRC, IH says 4100PSI min deadheaded and does not specify what pump. I'm pretty sure none of them make 7000psi. As for ICP at WOT I've seen a variety of pressures from low 3's to high 3's and I suspect flash level comes into play there.

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