TAMD22P-B Oil Pressure woes

[JST]

Hi,

I'm new here, new boat owner, and looking for some reassurance/guidance, because I am running in circles.

I have a boat with a Volvo Penta TAMD22P-B. I bought the boat a couple of months ago, and so far everything was great. Last weekend I wanted to go on my first offshore fishing trip (20 miles). After loading the boat, and starting the boat as normal, the low oil pressure alarm went off.

I checked the oil level, which was on the lower side. I bought some oil (15W40), and restarted the engine. The alarm went off again. I called a mechanic who came three hours later. When he arrived, we started the engine, and the alarm did not return. He checked some basic things, and said the engine runs fine. He looked at the wiring, but there was no real obvious issue. I took the boat out for a couple of short tours, and the alarm did not return. I am now wondering what can explain the oil pressure alarm going off after I refilled, but three hours later everything seeming to be fine.

Since the event, I lost some of the confidence I had in the boat, which is not a fun feeling. I am a very anxious person (like medically diagnosed, under treatment), and I am looking for some thoughts and feedback. I had prepared well to go offshore, and still want to do these trips, but I am a bit unsure now.

I rechecked all the wiring (electrical engineer by trade), tested the alarm, etc. All seems fine. The boat did not have an oil pressure gauge. I installed one (some generic 0-10 Bar). The oil pressure reads around 1 - 1.3 bar when the engine is running, regardless of RPM. When have seen higher numbers (around 2 bar) when I was manually revving the engine.

The engine is from 2001, so 24 years old. I read online that this can explain the low pressure. On the other hand, it is still the original oil pressure sensor, which are known to fail. I bought a new one, which I will install next weekend.

Can anyone with more experience provide me with some feedback/guidance/reassurance? I don't want to be "that guy" who has a preventable engine breakdown and needs to call the coast guard to be rescued by doing something stupid.

The engine has always been well maintained, and the turbo has been rebuilt two years ago according to the previous owner (whatever that means). I do not have maintenance invoices.

I look forward to some input from more experienced boaters on how to proceed.

[skipperpete]

G’day JST, welcome to the forum. There are a whole range of “preventable engine breakdowns” that are specific to your engine but low oil pressure is worrying. The MINUMUM oil pressure at max rpm is 36 psi and the relief valve opening pressure is 60 psi. But before doing anything else, you need to check the actual oil pressure with a master gauge, preferably mechanical. Your engine is likely to be wired above ground and consequently not as easy to figure out electrical problems as ground wire to engine block systems are, so the alarm and low pressure on your aftermarket gauge could be electrically related.
If you have no logbook history ( or date on the belt) regarding the timing belt replacement, assume the worst and get a new belt and the idler/ adjuster bearings as well as a circulating pump then at least that’s a couple of items off the critical list. Good luck with it.

[JST]

Thanks for the reply

What do you mean with the motor being wired above ground? I connected the ground pin of the pressure gauge to the central ground point of the batteries. Should I connect it to the black wire coming from the oil pressure sensor?

That could explain the low reading of course.

[skipperpete]

Originally Posted by JST

Thanks for the reply

What do you mean with the motor being wired above ground? I connected the ground pin of the pressure gauge to the central ground point of the batteries. Should I connect it to the black wire coming from the oil pressure sensor?

That could explain the low reading of course.

Above ground means that every electrical component or sensor has its own negative cable. Most MD22,s and Perkins Prima’s were wired this way , yours might or might not be, if the oil pressure sender has only one terminal it’ll be grounded to the block by the threads and if the block isn’t connected to the negative post the gauge won’t work…. Or won’t work properly. I only use a mechanical master gauge that I know and trust.

[GordMay]

Everything SkipperPete wrote [and may write], and I know you're an EE, but...


Did you mount your new gauge sender on a "tee' fitting [rather than directly n the block]? This could provide lower pressure readings, than actual.


When you Disconnect the wire from Sender on Engine Block, and test continuity, you should read Zero Ohms [or VERY near], from Block end to Gauge end.

When you Measure Resistance from Sender Terminal (on Block) to Ground on Block, you should read [either] 10 or 240Ω as below*.

When you Disconnect Sender Wire from Gauge, and turn power ON, the Pressure Gauge should read ZERO Scale [indicating Low Pressure].
When you Short the Gauge Sender [centre] Terminal to Ground [or Negative terminal], the Gauge should deflect to FULL Scale [indicating High Pressure]

* When you measure Resistance from [centre] Sender Wire to Ground, you should read:
American Press. Sender: 240 Ohms [Zero Pressure; or 33.5 Ohms when running [Full Pressure @ 80 psi].
European Press. Sender: 10 Ohms [Zero Pressure]; or 180 Ohms [Full Press. @ 150 Bar].

Alarm Switches are "On-Off" devices, either Normally-Open or Normally-Closed; which switch 'On' or 'Off' in response to a pre-set condition. Switches are utilized to operate Warning Lights and/or Buzzers.

See also: “Basic Engine Gauge Theory and Testing” ➥ https://www.cruisersforum.com/forums...sting-645.html

[JST]

Sorry, was offline for a couple of days.

@Skipperpete: The oil pressure sender has 3 terminals: WK (warning light), G (gauge) and a ground. However, when I trace the schematic, it seems it is connected directly to the motor block. I will measure the connectivity when I am back at the boat next weekend.

@GordMay: Thanks for the additional explanation. I did use the existing gauge sender. The sender that was installed has the three pins (gauge, warning, and ground). I will do a full set of measurements on resistances of the sender like you suggest. The alarm contact is shorted to ground in case of low oil pressure. Under normal conditions, it is left floating. Unsafe, as it will not detect a broken cable, but nothing I can do here.

I bought a new sender with WK and G pins, which is grounded to the motor chassis.

The plan for the comming weekend:
1) measure the resistances of the sender unit
2) connect the ground of the gauge to the black wire from the engine wiring loom instead of the central ground connection in the electrical cabinet.
3) if all else fails, replace the sender.

If the low oil pressure then continues, I will have a mechanic diagnosing the motor in more detail to fix the issue. I also requested the maintenance log from the previous owner, I hope he will give it to me if he still has it.

[wholybee]

1 bar = 14.5 PSI
1.2 bar = 17.4 PSI
2 bar = 29 PSI

Rule of thumb for most ICE is 10 PSI per 1000 RPM. Skipperpete states for this engine the minimum PSI for MAX RPM is 36 PSI. I have the MD22 version, and I don't recall exactly the pressure on mine, I think it is close to 40 at any RPM-mine is pretty low hours for an engine this old and well maintained.

So the specific RPM you were operating at is really important here. The low numbers are worth further investigation, but aren't all that off what would be expected on an old engine with high operating hours.

14.5 PSI at idle (600 RPM ish?) is low, but well within safe buy the 10 PSI per 1000 rule. It only indicates a worn engine.
29 PSI, if that was applying a bit of throttle to 1500-2000 RPM, again, well within acceptable. If that was MAX RPM, which if I recall for this engine is around 3500 RPM (maybe higher because it is the turbo version) then that is pretty low.

Ultimately, there isn't anything you can do about it. If the oil pressure is low, the engine needs rebuilt. You can (and should) check your gauge against a good mechanical gauge, but you can't fix low oil pressure. If a mechanical gauge concludes low oil pressure, it's still probably fine for many more years as long as you go easy on it. If it starts making unusual knocking noises, that is time to pull it and rebuild or replace.

With all that said, at one point I did chase a gremlin which I could only conclude was a bad connection on my sender. There is a fair chance you had the same. There is also a reasonable chance that your generic gauge isn't matched to the sender on the engine, and is reading incorrectly.

[JST]

Thanks for the nice reply Warren!

[JST]

So, I have bought a mechanical pressure gauge. I will try it out this weekend. Is there any special procedure to test the oil pressure besides screwing on the right fitting and connecting the oil pressure gauge?

It is one of those types:


How does this work? Will the hose fill with oil, or is it air coupled?

[skipperpete]

Well, that gauge in your photo IS advertised as an oil pressure tester…. And I guess that’s an air bleed valve on the side, but it’s going to be messy. My tester is just a length of high pressure hydraulic hose , ⅛ bsp male threads on both ends and a tested calibrated oil damped gauge….. plus a few loose adapters in a little lunchbox. My one is also messy but I have a sealing cap for the engine end of the 2metre hose after removal…. And a box of tissues.
I think your gauge will hold at peak pressure and you’ll need to push that button if you drop back to idle or else you’ll still be seeing the higher reading, that’ll be messy so keep a bucket nearby…. my gauge constantly reads the system pressure as it varies, your gauge may not.

[JST]

Some feedback. It turns out, it was the oil pressure sensor that was broken. When measuring with the mechanical gauge I got around 3 bar when the engine was on operating temp. With a new pressure sensor, I get the same when I measure the resistance of the sender pin. The gauge reads something different, which can be explained by a mismatched sender/gauge, or some wiring loom issue.

The wiring loom issue is something I feel comfortable tracing down. I am really relieved that the engine is working fine. Thanks for all the people who suggested the mechanical gauges, that was the big changing factor in solving the problem which never was a problem after all.

I am relieved, and can enjoy my boat now so much more, because 1) I am reassured with the knowledge that oil pressure is solid, and 2) that I can find solutions to these problems involving grease and oil (which, as an EE, is exciting).

My first experience with this community is awesome, thanks so much!

[hpeer]

FWIW, I had a similar problem.. original sender was reading like 45. Replaced that sender with a new compatible sender when I replaced the control panel. The new gage read around 65. But after some time was reading either 65 or pegged out high. So I got a new sender and it now reads about 50. When researching senders it seems they have a fairly large amount of discrepancy, they are like +/- 10% and maybe more. Or at least that is what I read.

I now look at in a more subjective manner. Highish until warms, then comes down a little, still over 10PSI at idle so I an good. Variations from this routine would bring alarm. I think oil type and very significant operating temp changes may give some additional variation.

[Icarus]

Sounds like a wiring problem..you either have low oil pressure or not..gauges and senders can give false readings ..when they fail.
If the fault is intermittent I would look for a bad connector and ground issues.

[Markhunter1097]

Check your engine mounts! Yes I know weird, but I had a gauge that was going to zero, checked everything, mechanics etc.
Then the mounts broke, and subsequent reading I found somewhere that sketchy oil pressure readings could be a symptom on mount issues. I wish I had fount this story before mine broke

[Shaneesprit]

Hi
See it’s fixed but I didn’t read an important piece of information, just how much oil you used to top-up?

Oh and someone said if the oil pressure is low you need to rebuild the engine, no not really, I mean possibly but to fix low oil pressure,
Change
Oil filter - check oil pick up if you can.
Pressure relief valve
Oil pump
Probably in that order - Oil pressure has nothing to do with Engine condition, you can have good oil pressure on a badly worn engine and, low oil pressure on an engine in good condition. (A part from the obvious lack of oil pressure.