1995 4.3 engine stops when starter key released

[NZMERC]

I have a 1995 Bayliner 1850 Capri with the 4.3 V6.
It has been very reliable until a few days back.
The engine starts with the key turned as usual but upon release of the key back to the 'run' position, the engine stops. It will only run with the key held in the start position (and the starter motor is turning). With the key turned on to the normal position the instruments all light up OK so there is power there. The coil must work because the engine does run - that is until I let go of the key.
It's like the ballast resistor is faulty but I understand this was only fitted to much earlier models. Any suggestions please?

 

[Bondo]

Ayuh,..... Welcome Aboard,..... On the back of the key switch, is there power on the purple wire when in the run position,..??

How 'bout the purple wires on the motor,..??

If there is power at the back of the switch, but not at the motor, pull the big cannon plug where the boat's wirin' meets the motor's wirin', 'n check there,....
The cannon plug is on the motor,....

 

[NZMERC]

I'll look today at what you have suggested. Thanks.

 

[Rinker95]

Take a look at #8, the oil pressure cut-off switch. It provides power to the fuel pump after the key leaves the start position, but only if there is oil pressure. (There is no power to the fuel pump from the ignition switch in the run position but there is in the start position. The oil pressure cut off switch switch stops the fuel pump if the motor quits or loses oil pressure. If this switch is bad or you have run out of oil, you would get the symptoms you are describing.)

 

[Rick Stephens]

Take a look at #8, the oil pressure cut-off switch. It provides power to the fuel pump after the key leaves the start position, but only if there is oil pressure. (There is no power to the fuel pump from the ignition switch in the run position but there is in the start position. The oil pressure cut off switch switch stops the fuel pump if the motor quits or loses oil pressure. If this switch is bad or you have run out of oil, you would get the symptoms you are describing.)

The wiring diagram is important, but the symptoms are of no power to purple (ignition circuit) except when cranking. So you're almost there... when cranking the starter motor provides power to the purple wiring harness backwards from the purple/yellow fuel pump circuit. If purple is not getting power, then when the starter is disengaged the purple ignition circuit goes dead.

This isn't a fuel pump power problem. It is an ignition power problem.

 

[Rinker95]

The wiring diagram is important, but the symptoms are of no power to purple (ignition circuit) except when cranking. So you're almost there... when cranking the starter motor provides power to the purple wiring harness backwards from the purple/yellow fuel pump circuit. If purple is not getting power, then when the starter is disengaged the purple ignition circuit goes dead.

This isn't a fuel pump power problem. It is an ignition power problem.

Gotta agree...ignition power. Thanks Rick

 

[NZMERC]

Hi,
Thank you very much for the help so far.
Here's where I am at.
There is power to the purple wire on the back of the ignition switch with the ign on.
With the ign on, there is no power to the terminal on the coil that has the purple wire attached to it. Except when the starter motor is engaged with the key turned to the start position. With the engine running (& the starter motor still engaged) there is 11 odd volts at the coil purple wire terminal. The second the key is released back to the run position, the engine stops and the voltage reading goes to zero. I have pulled the main electrical socket off on the engine. All appears clean and undamaged.
While I am cranking over the engine (and it's running) there is normal oil pressure shown on the gauge.
Something else - the day I had this problem I did note that the audible warning buzzer wasn't working, the first time ever. However this ign problem didn't develop until the end of the day, after numerous start/stops throughout the day without issue.
Next clues please! Thanks.

 

[Rick Stephens]

You won't get anything more - the power going through the purple wire coming off the ignition switch is not making it to the motor and the coil/elec choke/fuel pump. Start looking. Read what was posted by Bondo. He told you exactly what to do.

 

[NZMERC]

I'm thinking of running a temporary wire from the ign switch direct to the coil and see if that fixes it. Then I'll know for sure that there is fault somewhere in the loom.

 

[alldodge]

There is power to the purple wire on the back of the ignition switch with the ign on.
With the ign on, there is no power to the terminal on the coil that has the purple wire attached to it.

Kill Switch?

 

[NZMERC]

Yep, kill switch. A bad connection.
Thanks for all the help.
Back to the lake!