7.3 Loses base pressure

[6.0 Tech]

This is a customers truck, havent really dug into it yet, but am looking for some input. Seen it a lot on 6.0s, but not really 7.3s.

Trucks a 2000-01Ex has about 88k on it. Has a banks power pack with the wastegate, gauges, exhaust, and im guessing tuner. Came in dropping dash pressure at rpm, typically dropping out around 2500-3000. Found oil very thin, and had some aeration. Customer said only had about 1500 mi, but unknown time and was guessing on mileage. I changed the oil and filter real quick before going home. On start up it drained the rervoir, then stalled, and had to crank the hell outta it to start it. After the oil change, it still drops dash pressure at approximately same rpm. If its held on the limiter for about 30 sec, it runs rough on return to idle for about 5 sec then smooths out.

I have not checked base pressure yet, but will a hi pressure issue cause this? I am thinking something with the base pump like something went through it, like a 6.0, but with the low mikes, im not sure.

Thanks and sorry for the long post. :toast:

 

[dthompson]

I believe some people had some issues with a cracked pickup tube, therefore causing it to suck air. I believe you can overfill it with oil to see if this is the issue.

 

[m j]

whats 'dash pressure'? is it the idiot gauge? if so that is extremely low oil pressure

 

[dsberman94]

If it's draining the Rez you are looking at something on the low pressure side. Cracked pickup tube or bad LPO pump. Possibly from running the very thin oil and it's scored now or something like that. The dummy gauge on the dash I believe reads LPO. Hpo shouldn't cause the issue unless the LPO system can't keep up.

 

[ghohouston]

Could be as simple as injector o rings along with a faulty oil pressure switch on the lpop side. Could be a worn lpop/front cover, could possibly be a cracked pickup tube/ o ring, anti drain back valve, etc. Hpop reservoir is the highest point in the oil system of these engines. There could be a leak anywhere below the reservoir.

 

[cbf9703]

You're guessing it has a tuner?

Based on that first post, it sounds like you're getting air in the system.

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[6.0 Tech]

You're guessing it has a tuner?

Based on that first post, it sounds like you're getting air in the system.

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Yes, i did not drive it, but there was no smoke.when i was running it up and verifying the concern.

Thank you all for the replies, i was leaning towards air/low pressure, buat i know with the six liters a.blown out injector to rail seal will cause low to no base pressure due to the size of the leK. Truck usually starts fine hot or cold customer said and it had been starting with no issues hot, until i changed the oil. I will try overfillng it in the morning and go from there. The thing thats kinda throwing me is the lack of mles, at least for a gerotor issue. I guess the pick up oring could have rotted out. Customer said truck hardly gets driven, will sit for months at a time sometimes.

 

[6.0 Tech]

Ok, so i added 3qts of oil to it for a total of 18, concern is still present. I then pulled the gerotor pump off, and while it didnt look happy, i have seen way worse on 6.0s with no issues. Both gears had wear marks on the teeth like they had been hitting eachother pretty hard. The outer gear had a weird wear mark on the outside of it, and there is some very light scoring on the front cover. It can be felt with a finger nail, but not terrible. The pump housing looks fine. The inner gear has some marks where it goes on the crank, almost like its been sloppy on the crank, ther is some play, but agin not a chit ton. The front cover and pump will more than likely get repkaced due to the issues seen, but myself, and a couple guys i work with, feel that these issues seem to be caused by low pressure, not so much the cause of the low pressure. I am going to pull the oil pressure regulator on monday, but is there anything else i should check as well? Thanks again for the help.

 

[6.0 Tech]

Quick update

Got motor pulled today, and it looks like someone had resealed the oil pan and left the pan in the parts washer too long. The paintbhad started peeling and plugged the pick up, there was also a pile of copper in the bottom of the pan though too....

 

[DEEZUZ]

None of these flakes came out when you changed the oil?

 

[6.0 Tech]

Didnt see any, and used a really dirty pan on the ground. Should have paid more attention, yes. Guy is looking like he is gonna unload it instead of fixing.

 

[DEEZUZ]

Yea. that's what they all say... Then 6 months later it's at another shop and the story is the last shop(you) didn't fix it right....

 

[webb06]

We recently had a truck in with a similar situation. Recent rebuild by the custom himself. Had Oreilly do all the machine work and he put it together. After rebuild it showed no oil pressure on the gauge but started and drove fine. When we got it we immediately check oil pressure with a manual gauge and at idle it was like 4psi and at 2000 rpm it was at 14psi. After pulling the engine out we found the freeze plugs for the lifter galley on the rear of the engine had been left out causing a HUGE low pressure oil leak but it was inside the rear cover that's siliconed and bolted on. Installed freeze plugs and checked all bearings in the lower end, removed heads and pressure checked valves to make sure valve guides and stem seals were okay and put it all back together. Problem solved. Oreilly ended up paying for that bill.


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