Could a weak battery cause oil pressure indication issues?

[Chooko]

All,

I am having two problems with my '10 Tahoe, and am hoping that someone smarter than I am will tell me that they are related.

The vehicle is a stock 2010 Tahoe LT with the 5.3, and about 210,000 on it. It has been sitting since early February because I have been in Afghanistan. When I left it was running great and I was driving it every day. My trip was supposed to be much shorter, but COVID made it difficult to get home and it ended up being 5 months.

When I got back the battery was dead, dead, DEAD. After leaving it overnight on a trickle charger I got it to where it will (barely) start the car. I was hoping that if I drove it the charge coming from the alternator would wake the battery back up, so I took it for a drive yesterday. At first all was well, but about 10 minutes into the drive I noticed the oil pressure very slowly dropping. By the time I got it home I was only showing 5-10 PSI. Once the Tahoe was in my driveway I turned it off and then immediately turned it back on and had 20PSI at idle.

I figured maybe the sender was unhappy about siting for so long, so I changed it out this morning. I also put some Seafoam in the oil. I took it for another drive and had the same oil pressure issue. And again, as soon as I was home I shut the car off and then immediately started it again, and again, 20 PSI at idle, approaching 40 at 3000 RPM in neutral on the driveway. This is instant, I turn the key off and then start the car again immediately without ever releasing the key from my hand.

As I was sitting pondering this with the engine off but the key on and the radio on I got a "Low Battery, Start Vehicle" or something similar on the DIC after the car was off for less than a minute. If I start the car and run it I see 14.5-15 volts on the gauge, but as soon as I turn the car off I get no more than 12V across the terminals on my multi-meter, and I can literally watch the voltage on the in-dash gauge drop if the engine is not running. So clearly this battery is toast.

In researching this, I have come across other brand vehicles where people report gauge issues, and specifically in some cases Oil Pressure issues with a very weak battery, but so far none that I have found are GM vehicles.

The oil level is right in the middle of the hashed part of the dipstick, I am running Moibile 1 Synthetic, with their filter as well. I also changed the small filter under the sender about a year and a half ago.

So, what say you all? Has anyone ever heard of a weak battery causing indication issues in a Tahoe? If not, any other ideas about the oil pressure issue? I don't really want to spend the money on a new battery if, for example, the oil pump is bad, but I doubt that is the case since it recovers immediately upon being restarted. Any Ideas?

Joe

 

[Joseph Garcia]

Having 14-15 volts when the engine is running is normal. Having 12 volts across the battery terminals when the engine is off is also normal. If you haven't already done so, I suggest that you have the battery load tested at a local auto parts store, usually performed for free.

Poor electrical connections can cause all kinds of havoc on these trucks. If you have not already done so, I suggest that you check the electrical connections at your battery terminals and engine block to ensure that they are clean and tight. Look closely at the points where the wires are crimped into the connectors themselves, as there can be corrosion under the wire's insulation that may not be readily visible, except under close inspection. Also, check the ground connections on the firewall, within the engine well.

Other folks more knowledgeable than me will chime in with their suggestions.

 

[avalonandl]

Your oil pickup tube O ring may have disintegrated. Put in 2 extra quarts and start it up but don't drive it if it warms up and keeps pressure then you have your answer. You need to drop the pan....

Look at the Low oil pressure thread in Engine section....

 

[OR VietVet]

Agree with Roger about the possibility of the pickup tube o-ring may be bad. You certainly have enough time and mileage on that engine to have that problem. Next check all ground connections and clean/tighten as necessary. If you did not have a battery tender on that battery while you were gone, I would not even mess with the battery you now have. I would change it asap and go from there.

You did not say but if you are active duty or a vet, thank you for your service. Maybe you are a contractor though but you got big ones for just going over there. Good luck with this and stay safe. By the way, change out that oil asap as well. Don't save it and put back in if you drop the oil pan. New quality filter of course as well.

 

[avalonandl]

His oil pressure is up at 40 psi at 3k rpms. I doubt its eletrical, but u nevrr know at 210k miles.

 

[Chooko]

Alright gentlemen, thanks for the input and here are the updates:

First, the battery was done, as expected. I now have a brand new battery in the car (courtesy of Autozone's no-questions asked replacement) and further reason to expect electrical issues.

However, the problem persists. I had already read quite a about the O-ring issue on the pick-up, but I didn't really think it seemed to explain the issue I am seeing, because the car will tun and idle with reasonable pressure and the problem only seems to manifest after a few minutes of driving. But, figuring I didn't have anything to lose I just parked it facing downhill and added two extra quarts. Started the car up and pressure seemed normal. Let it idle until the temp gauge showed 210, and everything was fine. But again, this is not where the problem has been showing up. Decided to take it for a drive (I know, I know, oil aeration/bubbling due to crank shaft slappage). Initially all seemed well, but, after about three miles of driving the pressure started dropping, just as it has been doing all long. I had to turn the car off several times to limp it home when the low oil pressure warning started to go off. Each time it came up to at least 20PSI as soon as I restarted it. The last time, in my neighborhood, I though maybe I could keep the pressure up by increasing engine RPM, so I started it, put it in first, and came through my neighborhood at 3200 RPM. Initially this yielded around 30-35 PSI, but over the course of about 30 seconds, it decayed down to around 10, at which time I was pulling into my driveway.

So, I think the O-ring is ruled out since there was no change in behavior with the overfill, and I think it HAS to be submerged. This doesn't seem like a pump issue to me, as I feel like pumps either work or they don't. Doesn't seem like the little mesh filter below the sender, because that thing should either be clogged, or not. Same with the primary filter. I am open to any other idea's. I am also open to the idea that I am wrong in my assumptions.

Joe

PNW-VietVet - I did 15 years on Active Duty in the USMC, including multiple Afghanistan and Iraq deployments. I am still in the USMC Reserves, but, as you correctly guessed, I was actually a dirty contractor on this most recent trip. I appreciate the wishes, and thank you for your service on the KittyHawk.

 

[avalonandl]

Then you have a failing oil pump IMHO....

 

[OR VietVet]

Then you have a failing oil pump IMHO....

I would also attach an oil pressure gauge and drive it to see if it could be a sender/gauge problem. We are all assuming the gauge is correct. Can a Tech 2 do that. I know it can the fuel but forget if can do the oil.

 

[Joseph Garcia]

I would also attach an oil pressure gauge and drive it to see if it could be a sender/gauge problem. We are all assuming the gauge is correct. Can a Tech 2 do that. I know it can the fuel but forget if can do the oil.

@swathdiver Is Tech 2 capable of doing this?

 

[OR VietVet]

@swathdiver, inquiring minds want to know.