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Engine returns to idle over 2400 rpm.

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Rick 64

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I have a 1996 volvo penta 5.7gi . My problem is after engine has warmed up (about 9 miles) the engine will die but remain running at idle. i can run it up to 2400 rpm and it will run fine. I have replaced the fuel filter and checked the lines to the tank including removal of the suction tube, also i have replaced the distributer and coil. same results. it seems that something is telling the ecu to power down.
I trailer this boat and its a hour and a half ride to the ocean. I would apreciate all the help i can get.
 
Hello Rick 64,
It appears that I have a very similar problem.
Did you find the cause, if so I would be grateful if you could let me know the details.
Thanks.
 
I’m very please to report that he problem I was experiencing has been resoled. Essentially, the risers had become partially restricteddue to build up of corrosion. Under heavyoperating conditions the exhaust riser temperatures gradually increased to thepoint that the ECU would force the engine into RPM Reduction Mode. Apparently, this is a normal operatingprotection feature on the Volvo Penta engine control system. However, the engine alarm/buzzer should soundprior to this event to warn the operator that there is a problem but in mycase, the alarm/buzzer was not working and I had no warning that the ECU wasabout to force the engine into RPM Reduction Mode.

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

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

A scan of the ODB codes revealed a general code for theexhaust temperatures indicating a higher than normal reading from the riser tempsensors. 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 andother debris. I also inspected the exhaust manifolds; they appeared to be clearand in good condition. I re-installedthe risers and again went back to a sea trial. The problem has been resolved, no alarm/buzzer and no more returning toidle without warning.

I hope this thread will be useful to others.
 
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