Volvo Penta 5.0 GXIC-P Will not accelerate over 1250 RPM

[familymanbob]

2012 Regal 24 FasDeck 24’
Engine- Volvo Penta 5.0L GXIC-P (40869138)
Outdrive- Volvo Penta DPS-B 1:95 (21615543)

Team - thanks in advance. I can’t seem to find this issue on the forums, but happy to read a link if anyone knows of one.

I purchased this boat used last year and ran all season with no problem. In the spring, I replaced the gimbal bearing, bellows, and aligned the engine when reinstalling the lower unit. We had a hard time getting the lower unit off because alignment was out significantly in my opinion.

For the first several trips of this season, everything was perfect, no issues.

I have no check engine lights on, and the regal engine diagnostic (onboard system) shows no errors. When the boat is in the water and engine is NOT in gear, I can easily exceed 1250 -1350 RPM’s. However, under a load, the boat will not exceed 1250-1350 RPM’s.

I can kill the power to the entire system (via battery off switch) and then restart the boat and it will start, run and plane just fine. But after about 5 seconds of plane, it will drop back down to 1250 RPM’s.

I’ve considered the throttle arm, but it’s a little more money than I want to spend with ‘hit and miss troubleshooting’. Not sure how to test it. But then it doesn’t make sense because I can exceed the low RPM’s when not in gear in gear (with hose connected out of water). Engine seems to accelerate when low resistance on prop. Lastly, if I turn the wheel sharp right, the boat will exceed 12-1350 RPM.

Could this still be an alignment issue? As a side note, this is not my first boat, nor my first lower unit job, I’ve repowered boats, rebuilt wiring harnesses, etc. that said - I am teachable and willing to admit my own errors

I do not have an engine scanner, but again, it seems the built in code reader would tell me something if it were sensing a problem.

Appreciate the guidance.

 

[alldodge]

Check the fuel system
Pull the fuel filter and dump the contents into a clear container and see if there is anything other then clean gas

Connect a fuel pressure gauge to the fuel rail and see what the pressure is

 

[QBhoy]

Did you have the distributor out at all ? If so did you align it up again between the timing marks ?
is the diz cap ok ? You almost certainly know about the well known issue with these ? At very least check it inside and look for cracks. But much better to replace it every year.

 

[familymanbob]

Thank you team, i’ve ordered a new cap and fuel filter (might as well replace it if I am removing it anyway) and will check both this weekend. I was unaware of the distributor cap issue. I do run 100% petroleum fuel, no ethanol in all of my watercraft, but not sure why first owner did. I will check back in and report findings.

 

[muc]

Your serial numbers don't have enough characters.

This is a catalyst engine so be careful and don't do anything stupid, like run it out of fuel.

 

[familymanbob]

Muc-
Thank you for the responses. I ended up putting the boat away for the season after I realized I didn’t have tools to look for data. I purchased the Diacom software and adapter for the boat. Hoping some of this data will help, or that you can guide me as to what to look for in the software. I currently have The following active faults:
1. SPN697 ECT gauge driver fault
FMI: 5 temp gauge driver voltage low
2. SPN698 Oil pressure gauge driver fault
FMI: 5 oil pressure gauge driver voltage low

the engine is a 40869138
serial number is A177943
ECM is 2050001-A
ECM software 2336006-A
engine has 228.5 hours

I replaced the fuel filter (fuel was in good shape)
I replaced the distributor cap

thank you!

 

[QBhoy]

Still think it’s somewhere between bad fuel, your tank pick up being blocked (when more throttle demands more fuel flow) and the well known crap cap diz cap issue these motors have.

 

[muc]

There are 3 types of codes for OBD-M (catalyst) engines. They are “active”, “previously active”
and “pending”. Have you checked for the other 2? If you do have fuel or spark issues you should have a bunch of other codes.

I'm a little surprised to see those codes without the trim gauge code (SPN699) with them. Do the oil and temp gauges on the dash work? Those 3 codes normally come up when the boat has can bus gauges installed and in that situation they don't mean anything. It's possible that both wires (engine temp and oil pressure) to the dash have an open or short to ground in them. If so, that is pretty easy to troubleshoot. But these codes don't have anything to do with your low RPM problem.

The won't reach W.O.T. issue is somewhere else so I recommend 2 more steps.
1. hook up a fuel pressure tester and see what the pressure is at idle and when the problem is happening. My guess is these reading will be good because you are able to get the boat on plane for a short time. But fuel pressure is ALWAYS something that is tested with a WOT situation.
2. take the boat to the lake and do a Diacom recording that you can post here or PM me..Seeing a GOOD Diacom recording will answer 30-40 questions that I would otherwise have to ask you one at a time.


Here is my recommendation on how to do the recording.
Start with a cold engine and the boat in the water.
1. Connect Diacom
2. Turn on batt switch, turn on key switch -- but don't start engine
3. Start Diacom recording -- let run for 30 seconds to one minute
4. Start engine
5. Check that Diacom is still recording, it's not uncommon for it to have lost communication during starting. If it did, save that recording and start another one.
6. Run the boat gently at idle to 1500 RPM until up to operating temp
7. Run the boat up to full speed --- take your time, looking to get data here so advance the throttle slowly (spend one to two minutes) now slow back down to minimum wake and idle in neutral for awhile. Use the trim as you normally would.
8. Do a "ski start" -- full throttle all the way to full speed and trimmed out, now back to idle fairly quickly.
9. Drive boat back to the dock/ramp and shut off engine.
10. Stop recording and name the file

 

[familymanbob]

Thank you for the detailed response. I will work with the software a little to make sure I am ready to properly use the software to record. We are still under a lockdown for boating here in Virginia. I will run the tests as soon as I can get on the water and post (or PM) the results. Thank you so much!

 

[muc]

Your welcome. Happy to help when I can.
Thanks for the update.
Stay safe.

 

[familymanbob]

Muc -

I've created a shared one drive folder with the data.

Here is a link ( https://1drv.ms/u/s!Ag28SKmv6FyQgb8Q...BOL7Q?e=UtZwxH ).

Thank you so much for the review. I do not have a fuel pressure gauge, so I am working to get one.

The first recording file is the engine at idle

the second (extended recording) is start, idle, reverse from dock,
slowly increase idle to 1500 until engine warm-up,
slow increase to plane (never gets on plane as idle limits at 1250),
then back to neutral
Next is two ski starts
next is two right ski starts while turning hard to the right (we get up to about 2800rpm
next is a ski start while turning hard to the left
next is a hard start in reverse
head back to dock. Son stops recording, so I had him start again

Third recording (trip back to dock and shutoff)
remainder of the trip back to the dock and engine shutoff.

I think we captured the recordings correctly, but it was our first time. When we started the engine, it took some time for the system to reconnect. I'm guessing this is relatively normal.

Thanks again for the help!

 

[muc]

The files don't work for me.
They appear to be .txt files
Think I need the .rec files

Fuel pressure is very important.

 

[familymanbob]

Sorry about that - I had tried to rename them to allow uploading on the forum, but it wouldn't allow me. I just uploaded the .rec files for you. Thanks again!

 

[muc]

I have only had a short amount of time to review the files. Just wanted you to know that I haven't forgotten you.

First thing the jumps out at me. In the ECM Data screen, there is no info on the catalyst. That info should be there. Are you sure your Diacom software and cable version is up to date per the Rinda website?
On the system info screen. I see empty adaptive learn tables and very low misfire counts. This is unusual. This should be a catalyst motor.
I also see 500 engine starts and 230 total engine hours. So that's like a 30 minute average usage time? Does that fit with how you usually use the boat?

You have 2 active codes, but I'm guessing they are because you have can bus based gauges. Do you know what type gauges you have? Either way they aren't faults that would affect performance.

I can see that engine is trying to reach target RPM and isn't able to. But I don't see why it can't. Fuel pressure readings at full speed and load. Plus catalyst information would really help with this diagnosis.

Your cam retard is a little out of spec. You might try adjusting it between 12° to 15°.

 

[familymanbob]

We are using the 94073 cable with the CAN BUS 94029 adapter which is what the website says to use (website says 94023 or 94029 for 2008+ VP engines).

We checked the software version and were running 3.1.4. We've updated to 3.17 and will take the boat out again tomorrow as we have storms passing through this evening. I will also check to see if we are seeing the I will also head to O'Reilly and grab a loaner fuel pressure gauge tomorrow and test that at the same time.

I do have CAN BUS gauges (RegalVue Display) good or bad... Its slow, and I'm not overly impressed.

As for usage - thats probably about right - 30 minutes or so at a time when we take the boat out. I've had the boat for three years now (fourth season).

Thank you.

 

[familymanbob]

Muc-
Same folder link above. https://1drv.ms/u/s!Ag28SKmv6FyQgb8Q...BOL7Q?e=UtZwxH

I called Rinda today and they advised me I needed to run separate tests on each data set in order to get the rest of the data you are looking to view.

I went out this evening and recorded two starts for every data set without restarting the engine.

After I did that - I killed the power to the boat, reapplied power, turned the key switch on, selected the data set and then started the engine and immediately did a ski start. The boat gets up on plane and the engine runs correctly for 20-21 seconds from the time the engine is started. I did this once for each data set.

Fuel pressure -
@idle - solid steady 16 psi on the low side and 57psi on the high side
@WOT (after battery disconnect cycle) 59.5psi then briefly to 54 when the engine begins to drop off, then jumps back to 57 as the engine slows down.

Thanks again!

 

[familymanbob]

Hello, wondering if anyone has any feedback. Thanks in advance.

 

[muc]

Sorry it took so long to respond, I've been busy.

The first thing to understand about your engine. It is a "speed" based system. What this means is that when you move the throttle the ECM converts that throttle setting to a "target RPM" this is the RPM that it thinks you want. This is very different from earlier EFI systems. Here is a little bit from Volvo tech school that explains how this works.

In the speed based throttle system the TCP is still the driver’s “throttle
request” and is still “hardwired” to the ECM. What’s different is that with this system the ECM
sees the “TCP Actual %” and converts that percentage to a “target engine speed”. The
ECM then controls the throttle blade to either increase or decrease engine speed until the
engine speed (from the CKP sensor) indicates that it has reached the target. This occurs
anytime the engine is not in idle mode. If the TCP is advanced to 100%, the target engine
speed is set to approximately 100 RPM higher than the maximum rated speed for that engine.
To the customer, this speed based system causes the engine to seem to operate differently
than ETC engines in the past because the engine is governed to an engine speed not a lever
or throttle blade position. As an example: the boat is cruising at 3000 rpm and the driver
doesn’t move the helm lever but he starts turning to port. This will cause an increase in load on
the engine. In the past and with lever based systems, the engine would start to slow down due
to the increased load and the driver would have to add more throttle to maintain the same
engine speed. With a speed based system as the driver makes the turn, he did not move the
helm lever so the “target engine speed” did NOT change. So as he makes the turn, engine
load increases, rpm starts to drop below the target so the ECM opens the throttle to try to
maintain the target engine speed.
Likewise; if the boat is cruising and the drive is under-trimmed (bow down), as the driver trims
the bow up, engine speed will NOT increase. Boat speed will increase. If the driver continues
to trim the drive up, the load on the engine will decrease and the ECM will not need to open
the throttle blade as far as it was to maintain the target engine speed. As the driver continues
to over-trim the drive (bow up), the boat will also start to slow down but engine speed will not
change.

So, knowing that this is how your engine operates. We look at the target RPM and can see that after about 20 seconds the target RPM starts dropping rapidly. In all the other engines I've diagnosed this has always been because the ECM has a reason to derate engine speed --- overheat, low oil pressure, loss of sensor feedback etc. With your engine I'm not seeing any reason for the target RPM to be decreased and the amount of the decrease is different from what a derate #1, #2 or forced idle would be. But it is close to a derate #2.

In reviewing the files you posted. The ones that show whats happening right at the point the engine begins to lower the target RPM are the important ones..Unfortunately some of those files are missing.
The injector monitor, gauge monitor and misfire monitor don't have that info.

I do see a few things that lead me to guess that they won't show the problem. When watching the injector driver off volts I see spikes up over 20 volts and I see the off volts dip to zero volts. Neither of these volt readings are normal. I also see that the relationship between MAP, TPS and injector pulse width are unusual at certain RPMs.

At this point my guess is there is something wrong with the ECM. But if you were a customer of mine I would sure be doing more tests before ordering a ECM ---- they are very $$$$$$

If you would like to run more tests, I would recommend the 3 I listed above and also the O2 sensor test.

Click on the Tests tab and then click on the Oxygen Sensor Test bar
This test can be run in or out of the water. Do the test in neutral because the engine speed will increase to about 1200 rpms.
Save the results and post them.
I will do my best to respond, but the Marina I consult for has to take precedence. I think we are over the hump but I never know when the phone will ring.


Another option you might try is to send your ECM out to be tested. This is something I rarely recommend because they can't be tested 100% but in this situation they maybe able to catch something. The only company that I'm aware of that can service your model of ECM is in Texas called Boats Unlimited Performance. You might want to Google them and give them a call.

 

[familymanbob]

Muc,
Great information and that definitely explains the increase in RPM's during the right turn!

I've uploaded the requested tests and data. Its in the same folder link above. https://1drv.ms/u/s!Ag28SKmv6FyQgb8Q...BOL7Q?e=UtZwxH I added folders to sort by test data to make them easier to find. I've also been in contact with the team at Boats Unlimited Performance. Good guys and once you've had an opportunity to review the files, I will send the ECM to them if necessary.

I hope the files I uploaded are the ones you need. In rereading your post above - I'm not sure if you wanted the injector monitor, gauge monitor and misfire monitor or didnt need those. We also ran the O2 test as well. Thanks again for the help.

 

[muc]

I've been through the files many times and don't see any reason for target RPM to drop like it does.
The only thing I see is can retard is low. Suggest that you run engine at 1500 rpm and using Diacom to monitor cam retard, turn the distributor until cam retard is about 13°. Spec is 12 to 15 degrees so shoot for the middle.
I don't think this is what is causing your problem, but it is out of spec now so it should be adjusted.

Got to go now, I'll try to finish this post when I can.