7.3 Low Oil Pressure on Rebuild

So, without getting into a big drama filled ordeal, most who know me know that I've been in the process of having an engine built for my truck that had all the goodies I'd ever want. Basically, it's been a nightmare. It's taken far far far too long and I've had nothing but problems with the build and it's only been ran for a few minutes.

That being said. Last weekend I got the engine in the truck and ran it. Only ran for about 30 min and puked a rear freeze plug. Improper install. It was barely drove in. Got everything back together and fired it up. Ran great. Took it for about a 5 mile drive. Up to operating temps. Good oil pressure. Came back, installed the hood and got ready to go to a family reunion about 30 miles away. Figured it would be a good time to drive and work on breaking it in. Had the truck idling in the driveway for about 5 min while I changed clothes. Came back out and the oil pressure gauge was at 0 and the "CHECK GAUGE" light was on.

If you reved it up, it would register, then it would fall at idle. I pulled it back in the shop and turned it off. Turned back on and the gauge was working again. Free revved it to about 2700 RPM and back to idle and the gauge would drop then popped back to normal. I'm told the factory gauge is basically a glorified idiot light.

Went to NAPA and got a new sending unit and a cheap mechanical gauge to plumb into the sending unit port for a temporary check. Swapped sending units and the gauge wouldn't register ever. Might have been the wrong one. Plumbed in the mechanical gauge on the top of the HPOP reservoir, there was like 2-5 PSI when the oil was hot. Rev it up to 2000 RPM and it had like 45 PSI.

Being pissed off, I went in the house for awhile to cool down. Went back out and plumbed the gauge in by the oil filter housing. Engine was cold then. Fired it up Idle pressure was like 25-30 PSI cold and then as it warmed up, it kept falling to down around 5 PSI at an idle when warm. When the truck was fully warm, I revved it to 2000 RPM and the hot oil pressure was about 55-60 PSI at the filter. I put the ford sending unit back in and the gauge would drop to nothing when the engine was fully warm. Rev it slightly and the light would go off and the gauge would register.

Truck doesn't die. Runs pretty well. It kind of romps a little when you come down to idle after revving it up on the "modified stock" tune of DP. I'm thinking the romps are a tuning issue. Mailed tunes can be difficult with all the mods I've done. Nothing to do with this issue though.

Mods:
Carillo Rods
Swamps Girdle
Coated and Machined Dyno Proven Pistons
350/200 FFD Injectors.
Swamps IDM
Twin 15 Degree Terminator Pumps
Partial Block Fill
DP Tuning
Melling LPOP
Ported Heads
DI Headers
Riff Raff Reservoir Spacer
Irate Comp Fuel with Irate T4 and S468

I know most of that stuff doesn't have implications on oil pressure, but I'm just giving all the info. As you can see, I've spent too much money to walk away now, but I literally am ready to take it to the dealership and walk away. Too much heartache with this thing. Every time I have something good happen, something bad follows it up. :shrug:

Anyone have any advice on the oil pressure? What's my next step? It's obviously pumping oil because it keeps the HPOP supplied. Truck never dies. 60 PSI when hot at 2000 RPM seems good for oil pressure. Very little haze comes out of the oil fill tube for blowby even with it being only a 60 min old engine.

Any help is truly appreciated.

Thanks,
Ryan

I mean I don't know, but maybe an issue with the filter bypass valve or the other regulator thing in the oil cooler header.
Definitely gotta suck after all that work.
Pretty strange that it still makes good pressure up high.
The factory idiot gauge is ran off a 7 psi switch.

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How did the front cover look prior to the rebuild? Any scarring or indication of abnormal wear?

Other than the few things like the pump and regulator the main factor in oil pressure is bearing clearance..

backwoodsboy said:

How did the front cover look prior to the rebuild? Any scarring or indication of abnormal wear?

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I put a Melling on my old PMR engine about 6000 miles before it blew up. At that time, it was fine. I took the pump and front cover off of my old PMR engine to the engine builder. He was supposed to have used my front cover. He said my Melling was no good and had to buy a new one. I question the truthfulness of that, but I'm not sure. So he put the new pump on and went on our way.

That being said, I never physically inspected the front cover for this motor.

I noticed this morning that there is a drip of oil coming from the bottom bolt of the LPOP.

Just confusing that it makes really low pressure idling when hot, but at 2000 RPM, the pressure is up to like 55-60 PSI.

I would think something to do with the oil filter housing that has two diffrent springs and valves in it. Did you take this apart and assembled wrong.

There also a spring and check ball down in the front part of the block under the hpop res.
Did you remember to install this ?

Swaan said:

I would think something to do with the oil filter housing that has two diffrent springs and valves in it. Did you take this apart and assembled wrong.

There also a spring and check ball down in the front part of the block under the hpop res.
Did you remember to install this ?

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The ball and spring In the driver's side of the block by the reservoir was installed. I checked it because the o-ring wasn't replaced as I asked. I thought this was only to keep the HPOP reservoir from draining down. :shrug:

Yes, I put new o-rings in the oil cooler and we pulled both the oil filter bypass and the oil pressure regulator out of the cooler housing to clean.

How do you know if the regulator is stuck?

I'm just trying to figure out my next step in diagnosis.

I'm not much help but I'd try to get in touch with Dave at Swamps.

I think I'd start at that oil cooler header.
Make sure everything is in right, or just replace it to be sure.
Those springs can wear out.

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I would lean towards the front cover being scared up. When my motor blew metal went through the lpop trashed it and scoured up the front cover pretty bad. Could pull the lpop and inspect the front cover.
I would think if the bypass valves in the oil cooler/ filter head where installed incorrectly or stuck it would maintain that high of pressure at 2000rpms

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The hpop res is staying full yes? Series with FC scoring that is an issue with drain back. The oil from the oil pump housing old make we want to dig in there giving your symptoms and the history.

It's hard but try to keep your emotions out of it so it's not going to help neater what the case I.

On the bright side.... as long as the pressure comes up off idle the truck will actually run just fine. I drove for years with no pressure at idle and a max of like 20 or so. So you've got that beat by double, lol. Bearings all looked fine.

Sometimes oil pressure can be a real whore on these with extra pumps/turbos and crap. Makes me want a gilmer drive to a belt pump...

One thing to check is your oil cooler for blockage. If the coolant tubes are filled with crap then the truck will overheat the oil and pressure will plummet. What's your EOT?

There was a guy fighting low oil pressure after a rebuild, and after much headache , he found out his engine builder left a rear oil galley plug out. Just food for thought

Charles said:

One thing to check is your oil cooler for blockage. If the coolant tubes are filled with crap then the truck will overheat the oil and pressure will plummet. What's your EOT?

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I don't have an engine oil temp gauge yet.

The oil cooler is brand new from Riff Raff. The ends are from my old engine.

TARM said:

The hpop res is staying full yes? Series with FC scoring that is an issue with drain back. The oil from the oil pump housing old make we want to dig in there giving your symptoms and the history.

It's hard but try to keep your emotions out of it so it's not going to help neater what the case I.

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The HPOP is staying full. Well, it's about 1/2" down from the top. I thought maybe the Riffraff HPOP spacer was causing an issue, but it wouldn't manipulate oil pressure. The truck fires up after about 3 cranks every time now.

Last night I went out and hooked the mechanical gauge to the top of the HPOP reservoir for s and giggles. I ran a long enough lead so I could read the gauge the entire time.

Upon startup, pressure went to 25 psi at this location. I let it idle for about 30 seconds. After that, I gradually raised the RPMs up to about 2300. By this RPM range, the oil pressure was over 70 psi.

Within 5 minutes of idling, the idle pressure had dropped to around 5 psi and the pressure at 2500 rpm was around 45-50 psi.

After 15 minutes, the gauge barely moved at an idle.

Really strange that the pressure would fall off that quickly.

This is so frustrating. Its not like this was a $500 wrecking yard motor. Looking back, that's probably the route I should have went.

Is the LPOP in the right way? I have seen this happen before. Easy mistake to make. If for some reason the pump was installed wrong it will more then likely ruin the front cover as well. Just a thought

cjfarm111 said:

Is the LPOP in the right way? I have seen this happen before. Easy mistake to make. If for some reason the pump was installed wrong it will more then likely ruin the front cover as well. Just a thought

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I thought a Melling didn't matter which way the rotors were installed.

Black 02 said:

The HPOP is staying full. Well, it's about 1/2" down from the top. I thought maybe the Riffraff HPOP spacer was causing an issue, but it wouldn't manipulate oil pressure. The truck fires up after about 3 cranks every time now.

Last night I went out and hooked the mechanical gauge to the top of the HPOP reservoir for s and giggles. I ran a long enough lead so I could read the gauge the entire time.

Upon startup, pressure went to 25 psi at this location. I let it idle for about 30 seconds. After that, I gradually raised the RPMs up to about 2300. By this RPM range, the oil pressure was over 70 psi.

Within 5 minutes of idling, the idle pressure had dropped to around 5 psi and the pressure at 2500 rpm was around 45-50 psi.

After 15 minutes, the gauge barely moved at an idle.

Really strange that the pressure would fall off that quickly.

This is so frustrating. Its not like this was a $500 wrecking yard motor. Looking back, that's probably the route I should have went.

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You have an issue there... Thats pretty bad... (I know capt obvious...)

I'm thinking pump issue... Its a pain to swap, but pick up another melling and swap it.

Yea strange cause reved up pressure is good. Mines about 50 hot reved but 5 hot idle no good. Should be about 20-25. 15 min. I agree with joe may wanna pull lpop off and have a look. My gen3 is gettin kinda like that. I run high d/c at hot idle but it does awesome reved but its like 8or more years old.

I dont know about the melling pumps but i know that it will ruin the cover if it is installed wrong. Then when you replace the pump with a new pump it to wont hold oil pressure.