Mercruiser 454 MPI 1989 fuel in cyls 6 and 8

[OleBoater]

I have a 1989 Merc MIE 454 MPI that is flooding cyls 6 and 8 with fuel. Disconnected injector harness and cyls still flooded. Replaced both injectors to no avail. All other cyls functioning properly. Any help on troubleshooting this would be appreciated.

 

[E4ODnut]

Re: Mercruiser 454 MPI 1989 fuel in cyls 6 and 8

I don't have any direct experience with this engine, so just a couple of general questions and suggestions.

First of all, how much flooding? Just enough to drown the plugs, or is it hydro locking the cylinders?

If it's just drowning the plugs, are you sure the ignition system is good? Plugs, Wires, Cap?

If it's hydro locking, and it still locks with proven good injectors and no connection to the harness, I have no idea where to turn.

 

[Don S]

Re: Mercruiser 454 MPI 1989 fuel in cyls 6 and 8

Do you have spark on those two cylinders. Bad plugs or plug wires ?????

One note, Merc didn't use MPI in 89, so what year engine do you really have?

 

[OleBoater]

Re: Mercruiser 454 MPI 1989 fuel in cyls 6 and 8

Thanks for the reply Don. My bad... it is a 1996. I'll be checking spark later today and advise.

 

[OleBoater]

Re: Mercruiser 454 MPI 1989 fuel in cyls 6 and 8

Thanks for the help... Engine runs, but very rough. I will check wires, plugs et al later today and advise.

 

[OleBoater]

Re: Mercruiser 454 MPI 1989 fuel in cyls 6 and 8

Started to hydro-lock due to excessive fuel. Also some fuel in oil gallery. Finally figured it out. The problem was a bad diaphragm in the vapor separator tank which allowed raw fuel to go into intake manifold. The engine is a v-drive so it tilted forward which allowed fuel to collect in cyls 6 and 8. New diaphram and all is well. Many thanks to all who helped on this.

 

[E4ODnut]

Re: Mercruiser 454 MPI 1989 fuel in cyls 6 and 8

Thanks for the update. Glad you got it fixed.