2006 Mercruiser Has power to fuel pump with ignition off

[Logic186]

Had a problem last week where engine (mercruiser 4.3 L serial number OW617116) would crank but not fire. After two or three attempts, 15 amp ignition fuse under dash would blow. visually checked all wires under dash, and those that were in plain sight in engine compartment. Remembered the fuse back by the starboard side of the carb (20 amp mini blade type). That fuse was blown. I put a new fuse under dash and inserted a new mini fuse and could hear the fuel pump turn on and run even though the ignition was off. Had my wife try to start the engine and she fired right up. After 15 seconds or so, I told her to turn it off. She turned off the key but the engine just kept running until I removed the mini fuse. I disconnected all wires under the dash, but I still have power to the fuel pump all the time. Does anyone have a wiring diagram for this engine? Any obvious places to look for the short that is causing this problem?

 

[ssportsmfg]

Just a guess because I am not a marine mechanic, but sounds like you have a short in your ignition switch.

 

[Logic186]

Thanks ssports, that was my first thought, but I took all the wires off the ignition switch and the problem is still there.

 

[Fun Times]

Hi there, welcome to iboats!

Sounds like you have a bad diode like described in this bulletin, http://www.google.com/url?sa=t&rct=...9IGQBw&usg=AFQjCNF7aoDOfwVo_jbVPB5UIDMW-Atz-g

Mercruiser part number 83-865913A01.

The diode assembly kind of looks like a red fuse holder and can be seen here in this photo posted below next to the distributor cap area.

Also the fuse under the dash should be a 20 amp fuse not 15 amp.

And you may need to be aware that there "might" be a hidden 15 amp fuse next to the cannon plug area like this guy finally found.
http://forums.iboats.com/forum/engi...68105-hidden-fuse-on-4-3-tahoe-q4-please-help


http://forums.iboats.com/filedata/fetch?id=7042815&d=1339374999

 

[achris]

Merc want $18 for that thing!! You can buy any diode with a rating higher than about 4A and it will do the job. In the land of rip-off (Australia) I can buy a 6A 1000V diode for $1.95.... If you do find the diode has failed, just go get one from and electronics shop... Save yourself a heap of cash...

Chris.....

 

[Logic186]

Thanks Fun Times, I will try to find that diode and check it out tonight. The 15 amp mini fuse that I found blown is the cannon plug fuse (I believe).

 

[Logic186]

Thank you Fun Times, you nailed it. I checked the diode and it would pass current both ways. Installed a new diode this morning and she is back up and running normal again. I can't imagine how much time your post saved me in tracking down this issue.