Looking for some help with my thinking. I was chasing excess fuel consumption even though engine seems to run fine. Might be a squeak bit rougher idling, but starts fine and runs fine. Here is what I have so far:
Ended up using a Techmate to pull data from engines. Boat has twins, so easy to compare. Starboard engine is using more fuel, pulse injector width is wider. I replaced the MAP sensor on that engine since manifold pressure was higher (less vacuum???), but it was not causing the issue. Data below shows the Starboard with old MAP (cold), Starboard with new MAP (hot) and Port with 21 year old MAP (hot). Port engine is all Volvo Penta original (except fuel cell). Starboard has had the IAC changed plus new fuel cell and now MAP.
So - at the moment - I think I have a vacuum leak. I tried to educate myself on MEFI4 (mine is actually MEFI-4B). Because the manifold pressure is high, I think the engine thinks it is under load so it is enrichening the mixture. If it is a vacuum leak I think there can only be 4 sources?? - throttle body gasket, intake manifold gasket, pressure regulator vacuum line and PCV line. Am I missing something else? Also - could this be something besides a vacuum leak?
Hot data was after running for 15 minutes and gauge displayed 175. Spark advance at idle was hopping all around from 2 degrees to 10 degrees. This seemed to calm down a lot as RPM's went above 1000. This was the same for both engines.
Thanks in advance for your thoughts.
Ended up using a Techmate to pull data from engines. Boat has twins, so easy to compare. Starboard engine is using more fuel, pulse injector width is wider. I replaced the MAP sensor on that engine since manifold pressure was higher (less vacuum???), but it was not causing the issue. Data below shows the Starboard with old MAP (cold), Starboard with new MAP (hot) and Port with 21 year old MAP (hot). Port engine is all Volvo Penta original (except fuel cell). Starboard has had the IAC changed plus new fuel cell and now MAP.
So - at the moment - I think I have a vacuum leak. I tried to educate myself on MEFI4 (mine is actually MEFI-4B). Because the manifold pressure is high, I think the engine thinks it is under load so it is enrichening the mixture. If it is a vacuum leak I think there can only be 4 sources?? - throttle body gasket, intake manifold gasket, pressure regulator vacuum line and PCV line. Am I missing something else? Also - could this be something besides a vacuum leak?
Hot data was after running for 15 minutes and gauge displayed 175. Spark advance at idle was hopping all around from 2 degrees to 10 degrees. This seemed to calm down a lot as RPM's went above 1000. This was the same for both engines.
Thanks in advance for your thoughts.
| | | | | | |
| Starboard | Cold | Starboard | 175F | Port | 175F |
| Old MAP | | New MAP | | Original 2004 MAP | |
| Idle | | IDLE | | IDLE | |
RPM | 650 | | 595 | | 595 | |
Desired RPM | 643 | | 600 | | 600 | |
IAC | 34 | | 60 | | 68 | |
IAC Follower | 0 | | 0 | | 0 | |
Barometric Pressure | 30 | | 30.3 | | 29.8 | |
MAP Volts | 2.68 | | 2.88 | | 2.31 | |
Manifold Pressure | 19.8 | | 21 | | 16.4 | |
TPS Volts | 0.62 | | 0.6 | | 0.58 | |
Throttle % | 0 | | 0 | | 0 | |
Coolant Temp | 90 | | 155 | | 154 | |
Manifold Air Temp | 81 | | 116 | | 109 | |
Inj A on pulse | 3.2 | | 3.4 | | 2.2 | |
Inj B on pulse | 3.2 | | 3.4 | | 2.2 | |
Fuel Flow GPH | 0.9 | | 0.94 | | 0.62 | |
Battery Voltage | 14 | | 13.7 | | 14.1 | |
Spark Advance | 2 to 10 | | 2 to 10 | | 2 to 10 | |
Cam Retard | 65 | | 66.7 | | 66 | |
Knock Retard | 0 | | 0 | | 0 | |
Octane | 100 | | 100 | | 100 | |
Knock | 0 | | 0 | | 0 | |