Oil pressure gauge all over the place.

[GeneralDisorder]

Is the recommendation to clean and reseat or replace as they are old?


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I replaced all of mine. But note that my truck was in Kuwait and El-Paso till late 2021 when I drove it home. Only 2,750 miles, but all three of my engine transducers have failed or thrown codes. It's worth the peace of mind to replace the 15 year old sensors - the boost pressure in particular had a nasty habit of throwing the truck in limp mode with no boost. Very hard to drive with no power.

 

[GCecchetto]

So, when I was back in Maryland helping the guy I bought my truck from do all the maintenance on it before driving home, one of the first things he had me do was install a new oil pressure sensor. He said the oil pressure gauge was periodically acting weird, and would drop to 0 PSI. That obviously wasn't actually happening since it's a HEUI motor and they won't run if there is no oil pressure and the truck was running as normal.

Once the new sensor was installed the gauge was rock solid. On a cold start pressure would be above 80 at idle and then drop to around 25-30 when warm, and would run at 45-50 at cruising speed on the freeway. I wasn't watching the oil pressure gauge constantly on the way home, but I was frequently checking all of the gauges and never saw anything weird going on with the oil pressure.

Yesterday on my way back up the hill after dropping off my windshield defrost diffuser to be sandblasted and powder coated, I noticed the oil pressure was only at 20 PSI when it should have been above 40. When I stopped at the stop sign at the top of the hill and the engine was at idle, it was showing 0 PSI on the gauge. Drove the remaining 1/2 mile home, shut it down, checked the oil level, then started it back up and it was again idling at 25-30 and would rise to it's normal 45-50 as the RPM was in increased. Pretty sure I actually have oil pressure when the gauge drops to 0 or the motor would die, but still want to make sure there isn't some oil pump weirdness happening. Thinking about putting a tee fitting in under the oil pressure sensor and adding one of these so I always have an easy mechanical double check on actual pressure. Don't like adding anything that could be a failure point or cause of a leak, but the piece of mind may be worth it.

Cure as to what you all think about the likelihood that the gauge may be going bad, or if it's more likely a ground issue or something? I haven't checked wiring at the gauge yet, but everything seems fine at the pressure sensor end. Of course it could also be anywhere along the way between the two as well. Guess it's time to pull the steering wheel and get behind the dash and start checking wiring to the gauge and the grounds.

 

[ramdough]

So, when I was back in Maryland helping the guy I bought my truck from do all the maintenance on it before driving home, one of the first things he had me do was install a new oil pressure sensor. He said the oil pressure gauge was periodically acting weird, and would drop to 0 PSI. That obviously wasn't actually happening since it's a HEUI motor and they won't run if there is no oil pressure and the truck was running as normal.

Once the new sensor was installed the gauge was rock solid. On a cold start pressure would be above 80 at idle and then drop to around 25-30 when warm, and would run at 45-50 at cruising speed on the freeway. I wasn't watching the oil pressure gauge constantly on the way home, but I was frequently checking all of the gauges and never saw anything weird going on with the oil pressure.

Yesterday on my way back up the hill after dropping off my windshield defrost diffuser to be sandblasted and powder coated, I noticed the oil pressure was only at 20 PSI when it should have been above 40. When I stopped at the stop sign at the top of the hill and the engine was at idle, it was showing 0 PSI on the gauge. Drove the remaining 1/2 mile home, shut it down, checked the oil level, then started it back up and it was again idling at 25-30 and would rise to it's normal 45-50 as the RPM was in increased. Pretty sure I actually have oil pressure when the gauge drops to 0 or the motor would die, but still want to make sure there isn't some oil pump weirdness happening. Thinking about putting a tee fitting in under the oil pressure sensor and adding one of these so I always have an easy mechanical double check on actual pressure. Don't like adding anything that could be a failure point or cause of a leak, but the piece of mind may be worth it.

Cure as to what you all think about the likelihood that the gauge may be going bad, or if it's more likely a ground issue or something? I haven't checked wiring at the gauge yet, but everything seems fine at the pressure sensor end. Of course it could also be anywhere along the way between the two as well. Guess it's time to pull the steering wheel and get behind the dash and start checking wiring to the gauge and the grounds.

Do you know what sensor they installed stock?


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[GCecchetto]

Do you know what sensor they installed stock?


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I assume just the typical CAT C7 part.

 

[GCecchetto]

By the way, when the gauge would drop to 0, the stop engine and low oil pressure lights did not come on, so the ECM must have still been seeing oil pressure. I'm guessing the issue is with the gauge or wiring behind the dash.

 

[GeneralDisorder]

The gauge itself is CANBUS to the MMDC so a low reading is not likely to be a connection issue since the signal is digital.

I had nothing but problems with the pressure sensors and connectors so I replaced the engine wiring harness and in the process also found an injector wire rubbed through on a valve spring:

Updated C7 injector harness PSA

I replaced the ECM to engine wiring harness on my 2008 M1079 A1R due to multiple occurrences of connection issues with all three of the pressure sensors - the oil pressure, boost pressure, and atmospheric pressure sensors would throw codes and the boost pressure sensor in particular would put...

www.steelsoldiers.com

My other concern is the oil pump on these engines. It's on my short list. Too many failures of the pump and idler gear and then coincidental failures of the HEUI pump, etc. That's why they introduced the HEUI pump pre-filter. Nice that it's $200 in parts, but not nice that it requires removal of the compressor to install.

 

[ramdough]

The gauge itself is CANBUS to the MMDC so a low reading is not likely to be a connection issue since the signal is digital.

I had nothing but problems with the pressure sensors and connectors so I replaced the engine wiring harness and in the process also found an injector wire rubbed through on a valve spring:

Updated C7 injector harness PSA

I replaced the ECM to engine wiring harness on my 2008 M1079 A1R due to multiple occurrences of connection issues with all three of the pressure sensors - the oil pressure, boost pressure, and atmospheric pressure sensors would throw codes and the boost pressure sensor in particular would put...

www.steelsoldiers.com

My other concern is the oil pump on these engines. It's on my short list. Too many failures of the pump and idler gear and then coincidental failures of the HEUI pump, etc. That's why they introduced the HEUI pump pre-filter. Nice that it's $200 in parts, but not nice that it requires removal of the compressor to install.

I have an A1….. I think mine is analog.


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[GeneralDisorder]

I have an A1….. I think mine is analog.


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Correct. I was referring to @GCecchetto's post for his A1R. Totally different gauge system.

Same concerns about the 3126b oil pumps though. Same issues with the 3126b and the older C7's. CAT redesigned the pumps a couple times. And our application exposes that issue much sooner than say a pusher RV due to running at redline basically all the time. Must watch: