5.7Gi-E (3869258) suddenly returns to idle.

[What Boat?]

This is a desperate cry for help. My 8.4m cruise is powered by a Volvo Penta 5.7Gi-E driving a SS duo-prop out drive (stern drive).
Engine starts well, idles well, accelerates well, achieves good fuel consumption but recently developed a strange problem.
While cruising (up on the plain) for no apparent reason the engine suddenly returns to idle. The engine continues to run, eng temp is Ok.
I've had the Volvo Penta service technicians look at this problem but no fault found.
Fuel pressures are fine.
If you know anyone who has experienced the same problem, I would be grateful to know how to fix this problem

 

[Fun Times]

Hi there, welcome to iboats!

When the engine suddenly returns to idle, does the engine sound like when you'd pull the throttle back to idle or does the engine have a bog type sound when the event happens? And is the throttle handle in the same spot as your cruise speed? if so, what happens when you try to push the throttle to wide open throttle?

Bear in mind that should a sensor like the throttle position sensor for example have an intermittent problem, it does not necessarily mean you're going to find a fault code because should the sensor not fall out of it's operational range, it wouldn't set a fault but could get close enough to make the ECM think you're trying to slow the engine down.

To find sensor issues, sometimes you have to watch the live data on the scan tool to see if there are any changes to the sensor values when the problem happens.

I'm sure your service techs know all this but have they personally experienced the problem yet while testing?

 

[What Boat?]

Thank you for your reply. Essentially, when cruising the throttle lever is in the forward position (approximately two thirds) and speed is 18 knots and no apparent reason the engine returns to idle. There is no warning, ie engine lugging or misfiring. After this happens, I move the throttle lever back to the neutral position, the engine continues to idle. I check engine temp gauge (reads normal operating temprature) and volt meter, no problems here.
After I regain my composure, I push the throttle lever forward as per normal, the boat gets back up on the plane and all is fine until it happens next time.
There is no corrolation in terms of time (when the event occurs) or cruising speed (happens anywhere between 15 and 30 knots). The maximum boat speed is 30 knots and the boat cruises comfortably at 18knots.
The dealer technicians have no answers at this stage, their diagnostic tools are not revealing any faults.
I'm currently searching for another boat owner that may be able to loan me their ECU - maybe it's a process of elimination from her on in unless someone reading this post has experienced the same issue.
Any further advice or comments would be greatly appreciated.
Thanks.

 

[alldodge]

Appears to me to be a electronic throttle control issue. Loosing connection between the throttle control and the CAN bus. Check your connections on the throttle control to the ECM on the engine

and :welcome:to iboats

 

[What Boat?]

Thanks AllDodge, I appreciate your suggestion and will check accordingly.........

 

[kmarine]

Had a similar problem wit my friends boat ended up as a week fuel pump. I would have the fuel pressure checked.

 

[What Boat?]

Hello kmarine, I was thinking the same. Volvo Penta technicians checked low and hight pressures and assured me that they were within spec. The thing here is they only checked pressures while running engine with boat on a cradle not actually cruising on the water.
I'm looking at fitting tempory pressure gauges that I can monitor from the helm.
I appreciate your comment - thanks.

 

[Fun Times]

I'm looking at fitting tempory pressure gauges that I can monitor from the helm.

That's really the only way you're most likely going to find or narrow down/out the problem. Also you may want to invest in a marine scan tool by rinda technologies or mefiburn.com so you can watch the live data to see what changes if any.

Also mefiburn may have the capabilities of testing your ECM should you believe you need to test it. Call them to be sure though.

http://mefiburn.com/mefiscan.asp

http://www.rinda.com/marine/marine.htm#merctool

 

[What Boat?]

Hello Fun Times. Thank you again four your comments and the links......
I'll keep searching for the cause and once I know for sure, I'll be happy to post the details so that others may benefit..
Thanks again everyone for your comments and suggestions.

 

[JustJason]

Does your alarm system work in the boat? Does it do the self check beep every time you start the engine up?

 

[What Boat?]

No beeps on start up.....never had reason for alarms to sound so I can only assume that system is ok.

 

[JustJason]

It's supposed to beep every time you turn the key to run. That is the self check, telling you the alarm system works. (Kinda like every time you start your car all of the engine lights come on)

So you need to get your alarm fixed, that's first.

After that, the engine cuts power in self protection mode for 3 reasons. Low oil pressure, engine overheat, and exhaust overheat. You don't have a gauge for exhaust temperature, only engine temperature. So chances are this is what it is .

 

[What Boat?]

JustJason, thanks for your comment, you make a good point. I'll followup with the Volvo Penta technician and ask a few more questions.

 

[What Boat?]

Just an update.
I found the alarm/horn behind the helm dash, I check it with direct power and it works fine. I'm now in the process of checking continuity between the ECU pin/wire back to the helm.
Once that circuit is re-established, I will be able to continue with trouble shooting to original problem.

 

[What Boat?]

I?m very please to repost that the problem I described at the beginning of this thread is now resolved. Essentially, the risers had become partially restricted due to build up of corrosion.

Under heavy operating conditions the exhaust riser temperatures gradually increased to the point that the ECU would force the engine into RPM Reduction Mode.

Apparently, this is a normal operating protection feature on the Volvo Penta engine control system. However, the engine alarm/buzzer should sound prior to this event to warn the operator that there is a problem but in my case, the alarm/buzzer was not working and I had no warning that the ECU was about to force the engine into RPM Reduction Mode.

Thanks to the comments and advice above, I focused on fixing the alarm/buzzer problem first.

The alarm/buzzer was installed and tested OK when check manually. However, I was not able to achieve circuit continuity between the alarm/buzzer terminal back the ECM (connector J-1, pin #8). For those of you who are familiar with the Volvo Penta 5.7Gi-E wiring harness, I tracked the fault to the main engine control connector (10 pin M/F fully sealed plug). The Tan/Black wire leaving the ECU (connector J-1, pin #8) had become detached from the female #4 pin at the main engine control connector (10 pin M/F fully sealed plug).

After I re-established this circuit with a bypass around the plug, I went back to a sea trial and sure enough, the alarm/buzzer sounded (5 long beeps) well before the ECU was forced into the into RPM Reduction Mode. This provided me with plenty of time to reduce speed and steam home safely.

A scan of the ODB codes revealed a general code for the exhaust temperatures indicating a higher than normal reading from the riser temp sensors. I removed and inspected the risers; there was some obvious build up of corrosion. I used a domestic high pressure cleaner to blast away the corrosion and other debris. I also inspected the exhaust manifolds; they appeared to be clear and in good condition. I re-installed the risers and again went back to a sea trial. The problem has been resolved, no alarm/buzzer and no more returning to idle without warning.

I hope this thread will be useful to others and again I?d like to thank everyone for their comments.

Happy boating everyone.

 

[Tail_Gunner]

Well done and thankyou for the reply.

 

[Fun Times]

Well done and thankyou for the reply.

X 2, And a nice job goes out to Jason too.:encouragement: