jumping coil cause engine to run

[gair]

I am working on a 4cylinder mercursier 224 cu. in. 1978
the wires to the coil measure 12 volts both from the resistor and the regular wire.
won't start till I jump 12 volts from the battery to the coil, remove jumper wire. 12 volts is 12 volts right? Once I do this it always starts till the next day then I have to jump the coil again.
Changed the points, condensor and plugs. Removed the ballast resister wire and replaced with a block ballast running off of the choke hot wire as suggested on this site.
strange thing is that testing across the ballast resistor I expected 6 volts but is always twelve, used a chevy auto ballast.
Motor runs good when running.
another strange thing is the tach quite working about the same time this problem started, once when I jumped the coil the tach worked again, hasn't since though.
one last comment should the starting in gear switch always have power to it? then when you pull the handle out it should close the circuit and power the other wire. Mine only has power to it while the engine is cranking is this right?

gary

 

[Don S]

Re: jumping coil cause engine to run

What model engine do you have?

Where are you jumping the coil from and to?

 

[gair]

Re: jumping coil cause engine to run

mercruiser model 470 170 hp 224 cu in
jumping straight from battery to coil + post.

does not make sense that this should help because voltage tester says wire to coil is putting out 12 volts when I hit the starter.

gary

 

[bruceb58]

Re: jumping coil cause engine to run

Often, there is a secondary connection to the coil from the starter solenoid to give the coil 12V during start and bypassing the ballast resistor.

Also, voltage measured at the coil with the engine not running and the points open will be 12V.

 

[Don S]

Re: jumping coil cause engine to run

does not make sense that this should help because voltage tester says wire to coil is putting out 12 volts when I hit the starter.

It should show 12V while cranking, and the engine probably sounds like it's running but when you let of the key off, the engine dies. Is that correct?????
If so, that means the resistor wire in the harness is probably open.
Turn the ignition switch run position (not start/cranking position) and check for voltage at the + terminal of the coil.

 

[bruceb58]

Re: jumping coil cause engine to run

Turn the ignition switch run position (not start/cranking position) and check for voltage at the + terminal of the coil.

You also want to make sure the points are closed during this test. If you have a bad connection somewhere, you can still measure 12V. You want the points closed to load the circuit.