Hi there, welcome to iboats, Do you happen to know the full engine model? Here's where to look if needed:
How to identify your engine or drive
Just wondering who inspected the ECM as I remember the thread below,
http://forums.iboats.com/volvo-pent...utdrives/ecm-volvo-penta-5-7-gi-e-622341.html
Most engine models did not utilize a fuel pump pressure sensor to cause a fault code and I "believe" your engine would not have one either ?.
Looking through the service manual you will not typically find a code 81 listed to be able too start a typical diagnostic procedure. But code 81 does exist and there is a list of codes but the problem is they are not published. They only show up on the scan tool when some sort of problem arises. And if I have this correct, code 81 would be a list of internal issues the ECM may see either from internal ECM problems or a non "sensor" type problem such as a power supply turning on and off intermittently and the ECM does not recognize this as normal and sets a code 81 with information of what it's seeing as abnormal.
Since you seem to not have 12v power to the fuel pump/s intermittently, that could be a reason code 81 is coming up if the ecm is recognizing something unusual such as the fuel pump relay or relay driver within the ECM shorting out or not receiving full power. But again that is not a typical sensor to go bad as we know it like a TPS for example. Something like a loose or corroded power or ground wires, cables or connectors not allowing the ECM to see full 12v power internally may set code 81.
The ECM controls the fuel pump power relay by way of ignition key up for 2 seconds then it looks for a reference signal starting at the pickup coil under the distributor cap and rotor, then to the ignition module under the distributor cap.
If the pickup coil or ignition module or even the fuel pump relay was to be intermittently bad or bad wire connections, etc... I could foresee them turning off the power to the engine and fuel pumps till things cooled off once again. Relays and the ignition module are known to be either sticky or heat sensitive at times. Can't rule out the fuel pumps, fuel pump wires, or fuel pump circuit breaker running hot either.
If you are using wing nuts on the battery, that would allow the power and ground cables to have a loose connection and run hot, quickly / intermittently turning on and off the 12v power just enough for the ECM to see it. Also check the ECM ground wires and the back of the engine.
Code Description:
13 Oxygen Sensor 1 or 2 Malfunction
14 Coolant Sensor Voltage High (cold)
15 Coolant Sensor Voltage Low(hot)
21 Throttle Position Sensor Voltage High
21 Throttle Position Sensor Voltage Skewed High
22 Throttle Position Sensor Voltage Low
23 Manifold Air Temperature Sensor High (cold)
24 Speed Sensor Inactive (if installed)
25 Manifold Air Temperature Sensor Low (hot)
31 Governor Not Tracking
32 EGR Valve Not Tracking
33 Manifold Absolute Pressure Sensor High
34 Manifold Absolute Pressure Sensor Low
41 Electronic Spark Timing Open Circuit
42 Electronic Spark Timing Grounded Circuit
43 Electronic Spark Control Detects Continuous Knock
44 Knock Sensor 1 or 2 Inactive
51 Calibration Checksum Error
54 Oxygen Sensor 1 or 2 Lean
55 Oxygen Sensor 1 or 2 Rich
61 Fuel Pressure Sensor High
62 Fuel Pressure Sensor Low
63 Fuel Temperature High
64 Fuel Temperature Low
81 See Scan Tool*
* Scan tool will display specific details on the type of Code 81 that is
set. Code 81 is associated with a variety of system faults.
Hope you find something, let us know and good luck.
