Mercruiser 4.3 will not start

[frig770]

2004 mercruiser will not start, turns over starts and as soon as starter is released engine shuts down. If I keep the starter engaged engine will run. Replaced and checked oil pressure switch, Switch is working fine. Power to fuel pump drops off after dissengaging starter. Ingnition switch replaced also and tested. Anyone have any ideas?

 

[alldodge]

Welcome
Could use a bit more info like a serial number to help but being a 2004 is it fuel injected ?

 

[Scott Danforth]

Check the key switch and MOB switch

 

[frig770]

not fuel injected. Serial number 0W020874

 

[alldodge]

Thanks
Being it's a carb it should be your key switch

 

[nola mike]

Gauges work with ignition on?

 

[Bt Doctur]

your losing the power from the "I" ignition wire to the motor

 

[frig770]

New key switch. First thing i tried. Going to check wiring from switch again.

 

[alldodge]

Unless someone changed the wiring (doubtful) it has only the one purple wire powering the ignition.

 

[dubs283]

Still no confirmation of the lanyard, run/off, man overboard switch at the remote

First post sounds exactly like a situation where the switch is in the "off" position

 

[Scott06]

2004 mercruiser will not start, turns over starts and as soon as starter is released engine shuts down. If I keep the starter engaged engine will run. Replaced and checked oil pressure switch, Switch is working fine. Power to fuel pump drops off after dissengaging starter. Ingnition switch replaced also and tested. Anyone have any ideas?

This is the symptoms of the man over board switch being tripped. Red toggle on shifter cycle it

 

[Bondo]

2004 mercruiser will not start, turns over starts and as soon as starter is released engine shuts down. If I keep the starter engaged engine will run. Replaced and checked oil pressure switch, Switch is working fine. Power to fuel pump drops off after dissengaging starter. Ingnition switch replaced also and tested. Anyone have any ideas?

Ayuh,..... Welcome Aboard,...... Another possible problem spot could be corrosion in the cannon plug, specifically the purple wires pins,....

 

[nola mike]

Still no confirmation of the lanyard, run/off, man overboard switch at the remote

First post sounds exactly like a situation where the switch is in the "off" position

Agreed, gauges should be unpowered with ignition switch on if so

 

[stresspoint]

i saw a failed ignition module cause the same issue.

 

[frig770]

Yes lanyard, run/off, is good and works.

 

[frig770]

And we have a winner, OMG cleaned Cannon plug and all is good. Thank you Bondo and everyone else. Thank you!

 

[alldodge]

Check voltage at coil for 12V with key ON and motor OFF.
If power is not present then trace the purple wire back to the key

For a quick test, run a jumper from the purple wire on the key to the coil, it should start and run