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

[muc]

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

I don't think I did a good job of explaining how a speed based control works if you think an RPM increase during a turn is normal. The idea is that RPMs should stay the same during changing loads like turning or trim change.

I don't know why your ECM is lowering the target RPM like it does.

Here is my best guess.
When I look at your injector off volts, I see injector drivers 2,4,5,6 and 8 will have voltage spikes above battery voltage. Sometimes as high as almost 24 volts. These are cylinders 8,3,6,5 and 2.
The wire that the ECM is monitoring also feeds the coil, ignition module and 4 O2 sensors. So it's possible one of those 6 components is creating these spikes or you have a problem with EMF. But I don't think that these spikes alone are causing the target RPM to be lowered.
My guess is that these are caused in the ECM and are just another symptom of a failing ECM.

I'll be honest with you. If this was a boat at the marina I do most of my consulting with. I would be on the phone with Volvo Penta tech support. As a Volvo dealer we don't send ECMs out for repair, we only install new ones. Mostly because there is a 2 year parts and labor warranty. Because this is a $1,750 part I always want to be as sure as possible before asking a customer to spend that kind of money on a guess. I have had a few ECMs over the years that had weird symptoms and most of them, factory tech support had seen those exact symptoms before. One of them was a Mercury outboard that had problems very similar to yours. I had spent the time to record all the files to email to them and during the first 30 seconds of the phone call he stopped me and had me go take a ohms reading. Told me if ohms were above a certain number to call him back and if ohms were below that number to just order a new ECM because they had seen this problem enough times to be certain. Sure enough Ohms were almost zero and the new ECM fixed it. The reason I bring this up is because sometimes there is some value to working with a dealer. The choice is yours. I'm just trying to give you as much information as I can so you can make an informed decision.

 

[muc]

Just looked up a new coil and module. $500 part. Pretty expensive part to guess at.

 

[familymanbob]

Adjusted the CAM retard today to 13, took it for s test run and as you suggested - no change. In looking at the recording today - I saw that the TCP percentage drops just before the manifold pressure drops.

 

[muc]

Per the PM you sent me. Please doubt everything I say. I'm human and I do make mistakes. I won't take much offence, just maybe get a little "snippy".
Yes I didn't think the cam retard would help, but you never know with the strange problem that you have.


I was surprised by your ECM part number. This is what I find when I look it up. You will want to discuss this with Volvo.
ECM (21461925) is the correct part number for your engine. But I show it as "no longer produced" and the ordering system tells me it's on "back order"
ECM (21652642) is a good ECM part number, but I show it as fitting a 5.0GXiC-270-R. This is a newer version of your engine.

 

[familymanbob]

Ran leak down test and no issues indicated. Very tight engine, all well within spec. Spoke with VP today about the part number discrepancy and was advised the part 21461925 is the old part and was superseded by 21652642. He advised that part number shows in their system as superseded but would not show in the online version. Planning to order a new ECU today. Will update this board after the new part is installed and tested.

 

[familymanbob]

Well, I replaced the ECM and no luck. Still same issue.

 

[alldodge]

Man that is a bummer and a lot of money.

 

[familymanbob]

Man that is a bummer and a lot of money.

Happy wife = happy life. Some things are priceless >>> for other things there is MasterCard ;-)

My hope is that someone else can benefit from this issue and (someday) resolution...

 

[muc]

In your first post you mentioned that the engine will accelerate in a hard right turn. How much? Can you catch that on a Diacom recording?

can you think back to when this engine ran properly? Have there been ANY changes? No matter how small. New stereo, battery changes, light bulbs. Anything. I’m wondering about a possible EMF issue in your wiring.

One of the the things that I noticed when reviewing your files was the misfire counter. Sometimes there would be a few misfires logged and sometimes none. It’s my understanding that the misfire counter won’t clear it’s self. Are you clearing it or is it happening on it’s own?

Something to try is to try and separate the engine from the boat as much as possible. Disconnect the can bus cable going to the dash at the engine, disconnect and jumper the 14 pin boat harness at the engine. Use Diacom to monitor oil pressure, temperature and RPMs.

Have you contacted Volvo with the results of the new ECM?

 

[muc]

One other thing. Have you done anymore Diacom recordings with the new ECM?
i understand that your symptoms haven’t changed, but the ECM might be recording something that wasn’t there before.

 

[familymanbob]

Good point. I will check them this weekend. I did order a new coil and

 

[alan ber]

Sounds familiar

My boat is a 2004 , 30 footer with Twin volvo penta 4.3 gxi 2004 , fuel injected

My symptoms , At times boat gets up on plane , then cant get out of its own way , max rpms 2000

At dock put into N ,able too hit high rpms
in water , slow rpm, ok ,
open it , could not get up on plane , digging in so deep swim platform was getting covered by water ,,

Long story short ,
Fuel pump cells , Common issue , Earlier pumps paint chips , VP pump which is a Carter pump painted internal and breaks down clogging ,

If your questing a cable cost , wait until you shop around for a VP fuel pump

6 years , later , I have gone thru a number of fuel cell pumps. .

Gave up on costly Volvo Penta , tried cheap o from china , $ 179..00. amazon 2 years later still ok ,
I boat local , inland
Long journey via ocean I would question china quality but for local use I see no difference except 1500 savings on pumps I break down , 1- 800 SEA TOW

 

[familymanbob]

Thanks Muc and Alan - Well, previously, I replaced the distributor cap, the ECM, and yesterday I replaced the coil and the fuel pump and took new DIACOM readings to see if anything else popped up. I do still have the ECT Gauge Driver Fault and the Oil Pressure Gauge Driver Fault. The recordings are here: Diacom Files under the 2021 April folder. Thank you for looking!