Alright, so I have a few things to run by you guys, mainly to check my train of thought, but also for advice.

Today I experienced a strange occurrence. With dual terminator pumps, I'm not used to seeing about 50% duty cycle (running a max of 3500 icp). My issue is today I spotted the rare occurrence of 70% DC! Oh and it hit this at a measly 2700psi. Noticed that if I kept RPM's up, DC stayed within acceptable levels, although no where near where I'm used to seeing. IPR seems to be acting fine, just incredibly high DC when under 2200 RPM's. I've replaced my LPOP before with a melling due to a similar issue, have since changed IPR's and some other stuff. Basically I know its not a high pressure issue causing the high DC% (or at least as sure as I'm going to be without throwing a bunch of new parts at it).

This brings to me what I did. I have a fuel pressure gauge (isspro electric sender) so I pulled it out of my regulator, plugged the resulting hole obviously, and used an adapter fitting to mount it into the HPOP Res (through the fill/service port). My idea was an easy way to verify low pressure oil without buying a new gauge, and without a lengthy process. It worked. Fired the truck up, and "fuel pressure" gauge came up to 20PSI. Thought to myself, hmm that seems normal if not good, maybe it is the IPR. Revved the engine up just to verify low pressure oil was good, and was shocked when I watched the gauge rise slightly (to 30psi) as RPM's came up, but then drop to 10-12PSI as ICP came up. Checked under the hood expecting to see massive oil bleed from my make shift adapter and sender. There was a little oil around it, but not the spray I was expecting as bleed off.

Ok this is at idle with 0 load (stickshift in neutral) so lets see what happens running down the road. Logical thinking made me pretty sure it wouldnt change (mechanical oil pump on the crank, RPM's are RPM's), but what the hell. Floored it down my street, meaning I would see MAX ICP, and sure enough, low pressure oil came up slightly, but as soon as ICP started coming up, low pressure oil DROPPED to about 5-10 psi. It slowly came up as I kept driving with the throttle depressed, but never touched the 20psi I was seeing at Idle. As soon as I let off the pedal (ICP drop) low pressure bounced up to 35-40 before dropping back down to 20. Repeated the test 2 more times.

My train of thought is that something is up with my low pressure pump, and the demand of dual pumps combined with not adequate low pressure, is causing me to see WAY lower oil pressure in the res than I would expect. Meaning, I see a oil pump replacement in the near future. In my book, if the low pressure pump cannot keep 40+psi in the res, its only a matter of time before I have a problem caused by this. Not to mention its starving one if not both of my pumps, which as we all know are not cheap.

Anyone have any ideas what my issue could be other than low pressure pump? Oh the melling that is in there is less than 2 years old. Have spoke with Joey and I know he is against the melling. It will be getting a ford OEM replacement pump if I replace. I simply dont want to do the work of replacing the pump without doing due diligence and making sure that there isnt another issue that this could be.

 

some body can correct me, but I though the res had a drain into the case and didn't have full oil pressure? Checking LPOP should be done at the stock sending unit before condemning it.

 

Res itself does not have a drain. HPOP drains into the standpipe which is built into the res, but not connected to the actual res that supplies the HPOP

 

I believe it's your HPO. Say your LPOP is happy as clam just providing the same ol' oil it always has... then comes the order from upstairs "Dude! More oil!" While the little pump that could is wondering what the hell is going on up there, he's barking "I'm givin' ya everything she's got" - as Scotty would say.

Taking the transport tube to the next deck up, we find the HPOP feeling just like "Elly" below. "Dude! More oil!" is screeching in his ears, but he's got nuthin' left in the well... and the chorus of "I'm givin' ya everything she's got" continues.

One more hop through the transport tube to the heads and here is where the voice is loudest - "Dude! More oil."

Basically, while us peons under Deck 500 recognize an oil leak under the VCs, twin HPOPs and a Melling can really confuse the symptoms. You are losing oil up top, and you have the hardware to suck on the straw pretty hard, where we just have to wait for the bucket out of the well.

Direct talk: A pump only builds pressure when the demand does not exceed the pump capacity. The upper pump is exceeded, which can then ask too much out of the lower pump... but the symptoms can easily look like a failed pump.

I have a Melling on the bench if you need one... but I think you'll need some of my spare O-rings more than the pump.

 

Rich as per our discussion on the phone, I would agree O rings (most likely sticks) would be the apparent culprit if it werent for the fact that RPM nullified the original symptom (high DC%). Just cruising I have not seen the same DC at HIGHER icp pressures. To me that does a few things:

Proves it is not injector O rings, because this would create higher DC% across the board, as well as a multitude of other issues. (see hard starts, noisy sticks, etc)

It is not the pumps simply not being able to supply demand (they are happily supplying the same pressure under different conditions, IE higher RPM as well as on flat ground)

Most glaring evidence to me of a low pressure (IE supply) issue is the numbers I got when checking pressure in the res. The fact that when I go WOT then let off, while monitoring low pressure, I see an immediate raise in pressure the instant I let off the throttle tells me that the DEMAND of dual pumps is overcoming the SUPPLY of oil.

High pressure on = major drop in low pressure
high pressure off = return of low pressure to respectable levels

In addition, I would say that the o ring failure idea would make sense, except I find it EXTREMELY improbable that less than a year old allient o rings would fail, especially with 2 steel rings. For that to happen, and not be catastrophic failure, (IE hard starts, horrible running, across the board significantly higher DC%, or the dreaded NO start condition) it would mean that high pressure oil is bypassing 2 o rings, 2 steels, and properly torqued injectors, ONLY at low RPM, high load, high psi operating conditions.

The simplest answer is this. The low pressure pump is supplying volume x at say 50psi, but the dual high pressure pumps require 2(x) volume while maintaining the same pressure. While we know the melling is a suitable pump to supply a single HPOP (even when modified IE T500, SRP1.1, etc) supplying 2 pumps at the same pressure as 1 may be beyond the scope of the Melling. I'm not saying the Melling is not functioning as designed, or is a sub par pump, but the task of maintaining pressure with the draw of dual pumps may make any minor problems appear as much worse than with a single pump.

I have located a known good Ford OEM pump from a friend that will be going in the truck when I get it. Personally, I believe this will solve the problem, or the problem will become much more evident during the procedure or afterwards. I will say that after further examination of the patient, there appears to be a decent leak at the bottom of the front cover/behind the crank pulley. Pic is being uploaded.

 

 

The post I made was before our phone conversation... and after additional info, I agree with 2000ca250. There are so many factors to this that are beyond normal that it takes a great deal of study to absorb the dynamics at play:

250/200s "Farmerized" to a larger capacity.
Twin HPOPs.
Melling LPOP.
Personal tuning (he has Minotaur).
The latest clue being a great deal of oil leaking around the LPOP.
IPR drops at higher RPMs (more demand, but more oil from the LPOP as well).

Overhead oil leaks usually show themselves at higher RPMs, not lower. My confusion began when an RPM increase from idle saw a decrease in LPOP pressure.

 

To the OP in your original post im assuming that was on a hot engine that you got those psi numbers from. I run a lpo gauge all the time and granted I don't have half the set up you have (which I wish I did) but I have never seen my truck at 20-30 psi... Ever. It almost never falls below 40 psi. Cold its around 70 psi and very little input will peg out my 100 psi gauge. Hot at wot I'll see 55-60
So right away your post was telling me your lpo pump has seen much better days. How recently did you add the duals and big sticks?

 

It should be pointed out that the Melling LPOP shows a reduction in pressure at idle that makes most people freak out.

While I was thinking of the HPOP pulling quicker than the LPOP can deliver, I jumped to a conclusion before I had more information. I'm leaving my original post there to show how easy it is to fall into this trap if one does not ask enough questions.

 

Big difference between pressure and volume. We start to ask a lot of a system that wasn't designed for two HPOP's. If you have any internal leakage at all I think it would compromise your pressure.

That being said, are you sure your IPR is functioning correctly?

 

He conducted many tests with the throttle under load while monitoring his gauges... a real plus when seeking the loss of power. The IPR was normal at higher RPMs and would climb at lower RPMs... the opposite of normal oil problems we see with our trucks.

 

Duals have been on for almost 3 years I believe? sticks have been big in one form or another about the whole time. Had a similar issue before that I believed to be caused by low oil pressure, so swapped in the melling. Truck started faster, and the problem went away.

Judging by the picture, I have a leaking seal around the LPOP housing at the very least. Not saying there might not be another leak (front oil cooler mount doesnt look amazing, and neither does the rear, but the oil is only showing on the block not on the cooler itself at all).

Like I said, I will be putting an OEM pump in, and will make sure to update along with some pics of what I find.

 

I'm curious to know as well. I put a melling on mine a few years ago.