Well here is what you have going on a mefi 4 ecu running a mef 3 component setup..the only thing i can tell is its been repinned and the mefi4 has 2 more grounds you need to find a schematic to understand how this is done and its done quite often. And one more thing the mefi 4 module has bee reprogrammed to fit your engine or better said tuned to your engine...was that done right.... there is no way to know for now...that is why i asked you if this boat was ever running right in your possession. For now find out the pin out diagram for the conversion and then follow it down i posted a site link where they do this type of work and should have a pin out.
http://www.gmpartsdirect.com/result...ber=88963118&singlepart=1&partnumber=88963118
Theres the harness you have now i cant find a wiring diagram
Thank you so much for all the help. I just said screw it an put my fuel pump back together today, threw the computer in, and started doing checks. Below is a list of what I checked today.
Battery voltage at injectors - Good
Injector resistance 1.5 Ohms - Good
Injector ground wires to end of MEFI III harness - .3 Ohms - Good
Injector ground wires through conversion harness - .2 Ohms - Good
Ignition module ground through both harnesses - .3 Ohms - Good
Then I tried to start it, and got the SAME result I always do. The engine roars to life for 2 seconds, then cuts out just as quickly as it started, and never starts again. If I wait 24 hours it will do that again.
I then changed the ignition module and coil - no change in condition.
Checked codes again (realized I have been reading them incorrectly since it only has to flash codes twice, not three times). I got codes 34 - Map Low, 41 ignition circuit open, and 81 (which I have no idea what it is). I did disconnect the knock sensor today while cranking, thinking maybe its detecting knock, could that throw code 81?
Code 34 is probably due to me disconnecting the map again. Code 41 is probably due to me forgetting to reconnect the ignition module leads after installing it, and then trying to start it. Code 81 from what I understand can be tons of things, from no oil pressure, to bad injector drivers. Seeing as OBD Diagnostics just confirmed my ECM is functioning, how do I find out what code 81 means?
I ran out of daylight, but I am going to clear the codes again tomorrow, and then try like hell to get them to reappear, but without me disconnecting any sensors.
Honestly guys, I am getting desperate. Is there a way to rule out any bad sensors, like the oil pressure sending unit (which is brand new), or the MAP?
Is there a possibility that OBD Diagnostics tests falsely flagged my ECM as good, when in fact it is not?
Again, just to recap, it was running perfect last fall. I pulled the engine to do an oil pan, and other misc items. The engine runs if supplemented with fuel, and has good compression, so its not mechanical.
And Tail Gunner, I have checked all the MEFI 4 grounds, I noticed that it has one extra ground as well.