1998 VP 5.0Gi looses power, maybe in protection mode

[Monterey296Twin5.0Gi]

Raw water cooled, and lives in a slip. First thing I want to ask is if you can check or change an impeller in the engine pump with the boat in the water?

It is only the Port engine with the problem. It starts/idles great, runs fine in lower rpms, and as you accelerate, it gets all the way up to 2400-2500 RPM and then it cuts to 1600 RPM. When it first happened I was able to pull back and reapply the throttle and "get past" that point in the RPM and throttle up to get on plane, but I don't want test run again until I have it looked at or check some things myself.

All gauges look fine, temp and oil. Oil is a little high in the Port engine, I thought about pulling some out to get it at the top line or below. When we changed the oil we were very careful with the amount we put in, so seeing it reading a little higher than the line was odd. I changed fuel w/s filters and drained the old ones into jars and they looked fine. The Port engine's filter did look like it had been leaking or sweating fuel, it had a varnish baked on the outside. Stbd engine's filter was still white.

I thought I would first try to check water pump impeller, sensors, and pulling out a little oil. The problem doesn't seem fuel related, but I only say that because it seems to occur at a predictable RPM point and be a deliberate cut in power like a protection mode. Any ideas and answers to my impeller question are appreciated.

 

[alldodge]

Yes the impeller can be changed with boat in the water. Don't know how low the boat sits in the water, but remove the hose coming from the drive and raise it up to stop the flow. The hose should be 1 1/4 ID hose (do verify) and can make up a plug out of a piece of 1 inch PVC and cap or similar

As for the motor, I would check fuel pressure first, and see if it stays up during throttle up

Edit: have a serial number?

 

[Horigan]

There should a limp (SLOW) mode that receives signals from a dedicated oil pressure switch and a water temperature switch that kicks in at 2500 rpm. The gauges for these run off separate sensors. I believe the switches go to ground when activated.

 

[Monterey296Twin5.0Gi]

Thank you I appreciate the help, I was able to get some pictures of the raw water pump and it looks like it is needing service or replacement.

I am trying to figure out the part number for this VP raw water pump.
Where would I find the serial number for a 1998 5.0 Gi ?

 

[bruceb58]

Its probably a BY or an LK. Either one of those will use the same water pump.

More than likely a BY. I don;t think they used the GM engine in LK model.

Volvo part number 3857794

Pulley-Driven Raw Water Pump | Volvo Penta 3857794

OEM pulley driven sea water pump with V-belt pulley fits many different Volvo Penta gasoline marine engines from 1995 to 1999.

marinepartssource.com

https://www.amazon.com/3857794-3851982-3855079-3852399-Genuine/dp/B073WZC92R/ref=asc_df_B073WZC92R/?tag=hyprod-20&linkCode=df0&hvadid=312151608179&hvpos=&hvnetw=g&hvrand=16087683707807211581&hvpone=&hvptwo=&hvqmt=&hvdev=c&hvdvcmdl=&hvlocint=&hvlocphy=9032735&hvtargid=pla-570558653455&psc=1

 

[alldodge]

Its has rust but might be able to repair/rebuild

 

[Monterey296Twin5.0Gi]

UPDATE: Thank you, I wanted to give an update. We took some oil out of the Port engine, it was a little high on the dipstick. Then we took it out for a test run and it ran smoothly through the RPM range. No more protection mode.

We tested the engine harness for fault codes and it never read anything other than '12', which is OK. So it appears it is possible to trigger a sensor and an ECM reaction and still not set off a fault code. I don't want to speak too soon, we tested it for a few minutes and tries, but haven't tested it since and decided to replace the belts, hoses, and impellers.

Below is sort of the order of things since we first got the boat:
-Port engine oil reads low on stick.
-We add a little oil, a few times to Port engine.
-We never notice anything weird about checking the dipstick.
-We end up changing oil in both engines.
-Similar amount of oil is pulled from both engines.
-We replace oil with multi-viscosity oil recommended & on sale at WM
-Engines seem happy, and run fine most of the year.
-Notice oil creeping up dipstick tube when cold checked (capillary action due to lower viscosity oil?)
-I don't remember adding any oil, but might have, but we notice Port engine reads a little high on the dipstick cold or warm.
-Never notice a problem running up on plane until one time I can off the throttle too quickly and from then on the Port engine would 'cut out' at 2500 rpm and drop revs.
-Having never experiencing that before, I was able to play with the throttles and get 'past it' in the RPM/throttle and get back on plane.
-On later trips Port engine would do same 'protection mode' rather predictably and so we started looking for answers.
-So the first trip out after draining some oil saw no 'protection mode'.

So I will have to figure out if I added too much oil. Or do you think it is possible that the engine (980 hrs) is "making oil"? Any tips on checking oil are appreciated. Or changing oil with the vacuum canisters, how to get all of the oil.

 

[alldodge]

Making oil usually means fuel is leaking into the pan. If the injectors are leaking, then this could be the reason for the other issues. Oil coming up the dipstick is caused by engine blow-by.

There is no tricks for changing the oil and using a vacuum pump or other pump, 100% will not come out. There will always be a little left, but that isn't much

 

[Monterey296Twin5.0Gi]

Making oil usually means fuel is leaking into the pan. If the injectors are leaking, then this could be the reason for the other issues. Oil coming up the dipstick is caused by engine blow-by.

There is no tricks for changing the oil and using a vacuum pump or other pump, 100% will not come out. There will always be a little left, but that isn't much

Thank you, since we have TBI and only 2 injectors I am hoping we don't have a problem with an injector or fuel. We don't notice any bogging or flooding, only the more predictable Engine Protection Mode RPM change.

The oil coming up the dip stick seemed to only happen the first time you check it, after the boat was sitting for weeks in the water, we assumed it was just a well sealed dip stick tube and as the engine cooled maybe oil was drawn up since we saw it happen on both engines.

Thank you, that is how we changed the oil, I might change it again on both engines just to be sure and I can close ly monitor what is added back. Hopefully it was just our error of adding slightly too much oil.

 

[Monterey296Twin5.0Gi]

UPDATE: After hunting down our problem we seemed to focus in on fuel delivery, in other posts I was made aware of the Vapor Separation Tank, and so we had a mechanic come out to check. He ran it up to RPM in the slip and it did hesitate on occasion. He was able to remove the Flame Arrestor part way, even with the stud out it won't remove completely. When watching the injectors fire off, the STBD side injector of the Port engine was intermittent. He switched the wiring harness between injectors and then the other injector did it, so it doesn't seem to be the injector. He said it was a "signal issue" and was going to ask for advice from others in his company, apparently he can see the signal drop on his tester.

I am hoping it will end up being a wiring or ground issue and not an ECM issue. The problem was intermittent for us on the water, and at times we could "get past" the bog position in the throttle, but other times it was fairly consistent and would never get past the bog.

Any ideas are appreciated. Thank you.

 

[alldodge]

Its either a loose connection or the ECM
There is 2 wires (one from each injector) that the ECM grounds to turn the injector ON.
The pic may not be yours but the wiring to injectors is the same

 

[bruceb58]

In protection mode, it turns off or cycles half the injectors

 

[Monterey296Twin5.0Gi]

Thank you @alldodge and @bruceb58!
We will check the wiring for any obvious damage or corrosion.

The mechanic said he wanted to come back a run a test on engine oil pressure. He didn't give me any feedback on his first check when he saw the injector firing intermittently and said we had a "signal issue" with that injector.
Could he be thinking that oil pressure is causing Engine Protection Mode to intermittently affect the injector?
Could a bad oil pressure sensor be triggering the ECM to make that injector fire intermittently?

 

[alldodge]

If pressure gets low enough it will go into protection mode as Bruce mentioned. If it did that it should throw a code which could be seen on a scanner

 

[bruceb58]

Thank you @alldodge and @bruceb58!
We will check the wiring for any obvious damage or corrosion.

The mechanic said he wanted to come back a run a test on engine oil pressure. He didn't give me any feedback on his first check when he saw the injector firing intermittently and said we had a "signal issue" with that injector.
Could he be thinking that oil pressure is causing Engine Protection Mode to intermittently affect the injector?
Could a bad oil pressure sensor be triggering the ECM to make that injector fire intermittently?

Your engine has an oil pressure sender and an oil pressure switch. It's the switch that determines if you are in S.L.O.W. mode. I can't remember if the switch is closed with low oil pressure or high but you can easily test that. Take the wire off the terminal and check resistance to ground and then start the engine and do the same.

 

[Monterey296Twin5.0Gi]

Our power loss problem is intermittent, but it can be consistent at times, other times it seems like we can "get past" the 'iffy' area of throttle position and get it up to 3200 rpm. Can 'protection mode' be intermittent if a sensor is on the edge of failing?

When the mechanic showed me what he saw on the injectors, the 'left' injector in video (STBD injector of Port engine) seemed to stop spraying at certain points as he revved the throttle, while the 'right' injector in the video seemed consistent. He said he swapped wiring and then the 'right' injector did it, but I didn't see that myself.

So I went back to shoot a video, but I didn't see the 'left' injector stop spraying as I revved it, it does look a little sloppy though compared to the 'right' injector (see video in link). I didn't swap wiring since the mechanic is coming back tomorrow and I wanted to leave it as he left it. Here is a link to my Google Photo album with a video of the injectors firing:

BOAT - Troubleshooting Injectors

7 new items added to shared album

photos.app.goo.gl

 

[alldodge]

Looks like a lot of fuel coming out of the injectors
Thought about having the injectors cleaned and flow tested?

 

[Monterey296Twin5.0Gi]

Looks like a lot of fuel coming out of the injectors
Thought about having the injectors cleaned and flow tested?

It looked pretty "wet" with fuel to me too, but I don't have a lot of experience with EFI in general and I should have looked at the STBD engine to compare. I will report back what the mechanic says tomorrow since we already have him scheduled. I will look into an injector service in the meantime.

I appreciate the feedback. Getting closer to figuring it out.

 

[Monterey296Twin5.0Gi]

UPDATE: Well we think the mechanic fixed it. He just replaced the oil sender mounted off of the filter housing. I assume that is the oil pressure switch @bruceb58 mentioned above.

So it does seem possible for that "switch" to have a soft-fail, where it would only trigger EPMode at certain RPMs or pressures and not every time. And when it did trigger EPM, it didn't set an error 'flag' in the ECM otherwise we would have been able to read the error code.

I feel good that it seems fixed now after running it around for a bit this weekend, but I need to understand how a switch can soft-fail unless the ECM is looking for a certain voltage or resistance and the oil pressure switch couldn't produce whatever signal the ECM needed to flag the error code.

Here are the 2 'extra parts' we found in the bilge that we hope are not critical (eyeroll), we left them for him when he came back, but he left them again for us. The brass part looks like it came off of his tester, the middle Nut is for the flame arrestor and is back on the engine, but the spring is still a mystery. Any ideas on the spring?

 

[bruceb58]

The part on the left is a scraeder valve stem cover.