LLY: Oil Pressure Acting up

[BGuinn]

Couple of weeks ago I was cruising along and had the info thing ding ding at me and looked down and it said low oil pressure, looked at the gauge and she was bouncing back and forth. Changed the oil and filter and put a new pressure sender in, problem went away, mind you this has been VERY intermittent so I never have a chance to actually test anything. Just the other day I was cruising up the hill and literally in the EXACT same spot as when this previously happened and DING DING DING....and it went away. This happened a third time yesterday and I was going up a different hill but it all seems that every time it happens is when I am headed up a hill. I have plenty of oil in the sump when running, oil was changed less than 1000 miles ago. Any thoughts?

Again, I already did a new sender and oil change. Next thing I am doing is putting a aftermarket O/P gauge in to see if it acts the same as the factory when I hit a hill. But it is also fairly intermittent.

If anyone has any suggestions I am listening because as of now I am stumped unless I pull the motor and tear it down to find out whats going on and I really don't want to do that because I do NOT have the time at the current moment.

 

[THEFERMANATOR]

On an 05 my guess would be guage cluster. 03-05 had ALOT of problems with the cluster, so many in fact GM issued an extended warranty policy on them(doubt any are still covered though). Chances are it's just a bad steeper motor in the cluster.

 

[BGuinn]

I wish I could agree, but it reads on my CS off the OBDII so it has to be coming from the ECU signal.

 

[whitetrash21]

My oil pressure guage took a dump randomly one day.....scared the shit outa me, seeing it fall to zero. Turned out, stepper motor went dead. CTS still shows good pressure. When my guage went to 0, i never got a CEL or dinging, it just quit. Id think your prob is elsewhere, not the cluster.

 

[BGuinn]

My oil pressure guage took a dump randomly one day.....scared the shit outa me, seeing it fall to zero. Turned out, stepper motor went dead. CTS still shows good pressure. When my guage went to 0, i never got a CEL or dinging, it just quit. Id think your prob is elsewhere, not the cluster.

I concur, I just want to know where. if this is something that I can fix without pulling the motor I would be a very happy camper. but it is looking more and more like I need to yard it. I think I am going to pull the lower pan and see if anything is floating around in there.

 

[duratothemax]

Its not the cluster. The DIC only shows "OIL PRESSURE LOW" and dings at you if its actually getting a data message from the ECM that the oil pressure is actually low.

Low oil pressure warnings arent dictated by the physical position of the needle/gauge. If your stepper motor fails and points to zero but the ECM is still sending a normal oil pressure reading to the cluster over Class 2 data, its not going to ding at you.

Either the sending unit is bad, or you have a spun main bearing or something. Put a mechanical gauge on it and see if it corresponds with what the ECM is reading for pressure.

 

[BGuinn]

UPDATE: So last night I drove around putting the truck up some hills and found that the steeper the grade the more the O/P acts up. If I am going up a mild grade the needle just bounces around a slight bit, if I am headed up a nice steep hill she is going wild. the only thing I can think of is that the pick up has come loose from the oil pump and when I am not level the pick-up is struggling to suck oil. I never lose oil pressure it just becomes erratic. I am thinking about welding a bung in the lower oil pan and putting a back-up electric pump on a check valve and a switch. If anyone has any thoughts please chime in because I am about to drive the damn thing off a cliff. I am thinking about pulling the motor but I don't want to do that and then not be able to find a cause for the effect.

 

[Cheyco]

Can you get at the oil pump without removing the pan. Is the sum in the small section or do you need to lift engine to remove the whole pan to access the pump and pick up.. My guess would be the loose pick up tube or even partial blockage

 

[leehype]

My money is on something screwy with the oil pump or pick up. I haven't pulled apart a 6.6 so I don't know how the oil assembly is set up, but if your only getting intermittent readings in a circumstance where the oil in the pan could cause it, I would start there, Someone with more experience should chime in. Would it be possible to overfill the oil pan and see if the problem lessens or goes away, with out causing damage?

 

[Sledhead]

The thread is a few months old, probably been resolved?

 

[duratothemax]

Can you get at the oil pump without removing the pan. Is the sum in the small section or do you need to lift engine to remove the whole pan to access the pump and pick up.. My guess would be the loose pick up tube or even partial blockage

No. Basically, the engine has to come out to replace the oil pump.

If you insist on replacing the pump with the engine still in the truck, then you'll still have to pull the trans, front diff, crossmember, oil pans, etc...

 

[kidturbo]

High RPM Pressure Bouncing

Hi Guys, I have a similar oil pressure bouncing issue that I've logged with EFI. Posted it in another topic with no replies. So here is the screenshot of it again.

This is a LLY in a boat, and I have several logs of the same bouncing on extended WOT runs.

It typically varies a pound or two at cruise, but above 3400 it gets pretty nasty. I don't think it's a sender cause the pattern is rhythmic, but the analog pressure gauge doesn't show it.

Oil temps are normally in the 160-185F range, and it has a remote cooler / filter setup. Pump was replaced on a rebuild 150hrs ago. The piston sprayers are drilled out over size, but the check balls and springs were left alone. To me it looks as if it's sucking some air in the pick up somehow. I smoked a crank and 2 pistons before due to an oil restriction, so I'm all about solving this issue...

What ya think?

-K

 

[JoshH]

I would consider a dry sump for your application. Have you verified what you're seeing with a mechanical gauge as well?

 

[kidturbo]

Dry sump would be nice, but realistically not in the budget. It doesn't do that much bouncing around to cause this type of starvation issue. Purely RPM related, all the logs match up.

Not ruling out pumping the pan dry, but you'd think the windage tray would contain the splashing enough avoid that.. The analog gauge is an Autometer electronic pick up. It's not showing this bounce.

-K

 

[JoshH]

Dry sump would be nice, but realistically not in the budget. It doesn't do that much bouncing around to cause this type of starvation issue. Purely RPM related, all the logs match up.

Not ruling out pumping the pan dry, but you'd think the windage tray would contain the splashing enough avoid that.. The analog gauge is a electro-mechanical, my bad on wording that above.

-K

I'm not sure what an electo-mechanical gauge is, but does it use a sending unit? If so, is it the same one as factory? My thinking is an electric gauge could have some sort of built in damping to prevent needle bounce. A straight mechanical gauge should show a pretty strong flutter when you see the swings on the log.

The only thing I can think of that may be causing your problem, other than sucking air, is a problem with the oil pressure relief valve. There's one in the front cover and another in the oil pump itself. The one in the front cover is very easy to get to. It may be worth removing it and checking it out.

 

[kidturbo]

I'm not sure what an electo-mechanical gauge is, but does it use a sending unit?

Bad wording on my part, corrected it before you replied.

Agree I should probably dig up a true mechanical and port it in to be certain this isn't "ghost signals" from the wiring harness or something.

As to your pressure relief valve point.

She is spraying a little oil out on the belt in this same time-frame from somewhere I've yet to find.. First thought it was the filler cap[not], possibly front main seal [can't see to verify], leaving ? Faulty relief valve maybe??

If so, I'm betting someone has witnessed this before.

Thanks

-K

 

[BGuinn]

Found It!!

I finally found the origin of the problem. The truck has not been my daily for a while now but in the last couple weeks we have been doing some remodel at work and I have needed the truck. Problem persisted, it was not a true fluctuation in pressure rather a wire intermittently grounding. Today on the freeway it was dinging the "low oil pressure" indicator in the console, gauge was bouncing as was my edge insight...Finally gauge went dead but the insight still showed fluctuating pressure. We ended up tracing the harness through and when I pulled the engine connectors apart just for ease of a continuity test I just happened to notice a VERY minor rub through on the wires in the lower engine harness connector. The two engine connectors are mounted to a bracket that has mounting of one above the other(most of us know this but for people that are hunting) and the lower connector was barely rubbing the upper connectors mounting location. There is a piece of foam adhered to the wire of the lower connector for chaffing protection and it didn't do its job, it was just shy. The three oil pressure wires are the first wires towards the fire wall on that lower connector (gray, tan w/white tracer, black w/ green hashes) and the gray wire continually grounded causing the erratic gauge behavior. haven't been able to get my hands on a wiring schematic but I am going to take a shot in the dark and say that gray is either the 5 volt reference or the signal to the PCM. I think the gauge going dead is coincidental since the PCM still shows a value for that PID on EFI Live and insight monitor. Pictures are attached. Keep in mind that foam that was on there left a residue that made this hard to spot.

 

[kidturbo]

Thanks for that update.
During the total rebuild a couple years ago I started cleaning up the wiring harness by moving the PCM to the engine and ditched that bottom connector. But haven't finished the job yet, still need to remove that top connector. I'll check it when I bypass that one and let ya know if it matches yours.
I've since logged over 200hrs without any oiling related issues, so I know it's a false reading. Since I last posted about the oil leak at high RPM above, replacing the bypass valve didn't fix it, but a new front seal did the trick. Lesson learned there, never reuse a front crankshaft seal....

 

[Mike_Champion]

I missed it or did not understand did u fix the problem because I have the same problem and if fixed it please give me more details tks

 

[kidturbo]

I finished the custom harness and the problem disappeared....