First Start of the year and High Oil Pressure

[Trueblue95gt]

I just started my 2004 EFI 5.7 Mercruiser engine for the first time this year and I immediately got a warning buzzer and the oil pressure gauge was pegged at 80 psi. It's always been in the 40 psi range. I did not hear any mechanical tapping noises like starvation of oil from a blockage. Nothing has changed since last year. Should I start out by checking the oil pressure sensor or is that more likely a culprit of a bad gauge?

 

[QBhoy]

I just started my 2004 EFI 5.7 Mercruiser engine for the first time this year and I immediately got a warning buzzer and the oil pressure gauge was pegged at 80 psi. It's always been in the 40 psi range. I did not hear any mechanical tapping noises like starvation of oil from a blockage. Nothing has changed since last year. Should I start out by checking the oil pressure sensor or is that more likely a culprit of a bad gauge?

Be quite unusual for a gauge and a pressure switch to be both faulty, but perhaps more relevant, might be that it would be almost unheard of and also unusual to have an alarm for high oil pressure perhaps.
You sure the alarm isn’t for gear oil level or otherwise? The gauge being pinned high may be caused by the wrong oil filter or restricted perhaps, but all things being assumed ok that way, more likely would be a fault with the circuit feeding it. Your oil pressure will be higher than 40 for sure, in a cold start circumstance. Until the temperature comes up and oil thins. More so if you have anything above idle rpms after cold starting. Not quite 80 perhaps, but something not a great amount less.

 

[Trueblue95gt]

Be quite unusual for a gauge and a pressure switch to be both faulty, but perhaps more relevant, might be that it would be almost unheard of and also unusual to have an alarm for high oil pressure perhaps.
You sure the alarm isn’t for gear oil level or otherwise? The gauge being pinned high may be caused by the wrong oil filter or restricted perhaps, but all things being assumed ok that way, more likely would be a fault with the circuit feeding it. Your oil pressure will be higher than 40 for sure, in a cold start circumstance. Until the temperature comes up and oil thins. More so if you have anything above idle rpms after cold starting. Not quite 80 perhaps, but something not a great amount less.

I'm not exactly sure how the alarm works. Does it use the same output as the gauge and therefore the sensor could be the issue? Or, if the gauge is used and that causes the alarm?

 

[Bt Doctur]

sender is for a gauge, sensor for alarm circuit

 

[Trueblue95gt]

sender is for a gauge, sensor for alarm circuit

Is it a different sensor or the same?

 

[QBhoy]

It’s different. Two different and separate things.

 

[QBhoy]

I could be wrong in this case of course, but I can tell you that I’d be not much wrong in suggesting that by far, the most numerous reason an alarm goes off on an engine like yours, especially after just starting cold and after a service, intervention or storage, is almost always caused by low gear oil in the header tank. Odds on usually.

 

[stresspoint]

let the motor warm up a bit IE: idle , and see if the pressure comes down before jumping to conclusions of something bad being wrong.
it most likely will be fin once the oil thins a bit and circulates.

 

[Fun Times]

What does the oil gauge read with the key on, engine off? < Any alarm too?

Just making sure there isn't a certain type of ground issue though it could be a ground issue too.

Was the oil and filter changed since last years run to this years run?

Engine serial number is?

 

[04fxdwgi25]

Super high oil pressure sure sounds like a stuck oil pressure relief valve in the oil pump, from sitting over the winter.

Is the oil in the engine fresh oil, or last years? Maybe a little Marvel Mystery Oil in the engine oil may help "unstick" it.

On the alarm.... low oil pressure, low drive oil tank and high engine temp will set that alarm off, if it is the standard merc alarm system. All 3 are connected in parrallel, so any one of them will set it off on same alarm buzzer.. Also, all 3 of those use their own alarm switches, not gauge senders.

 

[Scott Danforth]

fresh oil, or did you not change oil before winter storage?

pressure relief on SBC is 78 lbs. with bearing clearances, etc. a gauge normally reads less

not uncommon to see high oil pressure on cold start up as oil viscosity is higher. 80 psi is nothing to worry about. let the motor run.

gauge could have a corroded connection on the ground wire

 

[dubs283]

I'm not exactly sure how the alarm works.

Being an efi engine the alarm could be for any number of issues, low oil pressure included along with afore mentioned coolant temperature and gear lube monitor level.

The only way to know for sure the cause of the alarm is to use a diagnostic tool that can read fault codes. It's possible the high reading oil pressure guage has nothing to do with the audible alarm.

Oil pressure reading has more to do with volume vs viscosity. I'd be curious to know the oil level/quality as you haven't mentioned this. Also, as mentioned an engine serial number so folks can know closer to exactly your setup.

 

[Trueblue95gt]

Wow, thanks for all the replies! I was strapped for time last year and didn't get to changing the oil. I was actually starting it yesterday to try and get the oil warm so I could change the oil. I did have low gear lube so I'm betting the alarm is on for that instead. Hopefully an oil change will help unstick anything and fix my oil pressure.

 

[Scott06]

Wow, thanks for all the replies! I was strapped for time last year and didn't get to changing the oil. I was actually starting it yesterday to try and get the oil warm so I could change the oil. I did have low gear lube so I'm betting the alarm is on for that instead. Hopefully an oil change will help unstick anything and fix my oil pressure.

You can unplug the wires at gear lube bottle to see if alarm goes away.

If once you change the oil you still have pressure concerns go to auto parts store and by a inexpensive mechanical gauge to can pullout the sender (above oil filter) and screw the gauge in temporarily to confirm oil pressure is ok. It is cheap peace of mind.

 

[stresspoint]

Wow, thanks for all the replies! I was strapped for time last year and didn't get to changing the oil. I was actually starting it yesterday to try and get the oil warm so I could change the oil. I did have low gear lube so I'm betting the alarm is on for that instead. Hopefully an oil change will help unstick anything and fix my oil pressure.

i would address this before moving on , that oil does not just disappear into space.

 

[Trueblue95gt]

So I just did the oil change and unfortunately the oil pressure gauge is still pegging at 80psi plus. I wiggled the leads on the gauge and I wiggled the leads on the sensor. I did fill yup the drive lube and the beeping did not go off. I can barely reach the oil pressure sensor but what would resistance need to be on this engine and would failure cause a low reading or a high one? I do have a mechanical gauge but I don't want to pull out the sender just yet without checking the sender first (possibility of causing a leak plus it's in a horrible place).

 

[Trueblue95gt]

This is the engine info

 

[Trueblue95gt]

Update: I pulled the single wire off the sender and key on engine on I'm at zero. Plugged it back in and I'm still at 80+ so I think that rules out the gauge right?

 

[Trueblue95gt]

Update: I pulled the single wire off the sender and key on engine on I'm at zero. Plugged it back in and I'm still at 80+ so I think that rules out the gauge right?

Another Update: I was able to take the sender out and I installed my mechanical gauge (what a pita). Started up and 40-50psi at idle which is perfect. Is that a nail in the coffin for the sender?

 

[dubs283]

Update: I pulled the single wire off the sender and key on engine on I'm at zero. Plugged it back in and I'm still at 80+ so I think that rules out the gauge right?

Maybe, testing the guage/wiring means abating the sender from the circuit during the test, i.e. grounding/applying 12 volt (+) to the sender wire and reading guage

Your info reads as including the sender as part of testing. Hard to convict the sender when your test doesn't remove the sender during testing