No spark except when turning flywheel by hand

[shoepike]

I have an old 1971 85 hp Chrysler outboard motor that is helping me learn more and more about engine ignition. I am at a point now where I can't figure out how to proceed. The problem is that if I try to start the motor, the engine will turn over but will not produce a spark in any of the spark plugs. However, with the key turned to the on position, the spark plugs will spark if I turn the flywheel by hand. I had read something on here from a while ago that suggested this is a problem with the ignition switch, but I wanted to make sure before buying a new switch. I am confused about why a bad switch would cause the starter to turn the flywheel and at the same time stop the plugs from firing when turning the flywheel by hand does cause them to spark. Thanks.

 

[Frank Acampora]

Yes, It could be a bad ignition switch. It is a difficult concept unless you have seen a switch taken apart but there are several discs of copper inside the switch. If a portion of the disc for ignition is corroded, then that portion will not pass current. If it happens to be the portion in contact at the start position, then you will get no spark at start but you will get spark at run.

A simple check is to jump at the engine terminal, blue to red This will power the CD box. Now crank the engine. If it starts and runs, the switch is bad. To stop the engine, disconnect the blue at the engine terminal and buy a new 6 pole, push-to-choke switch. They run from 17 to 35 dollars. they can be purchased here at iboats store, at your local marina store, or from Sierra at your local NAPA store.

 

[shoepike]

Thanks for the reply and check. I did as you suggested and jumped from red to blue. I did get 1 spark in the beginning and then nothing. So I checked the voltage going to the ignition (blue) when trying to start and it goes from 11.8 V when in the on position down to around 5 V when the starter is engaged. Is this normal? Is it too low to activate the coil? If so could it still be the ignition switch or is it just that I need a new battery? Thanks again for your help.

 

[Nordin]

It can be a bad battery, BUT first check all connections in the starter circuit. From battery to starter solenoid and to the starter for bad contact.
The power pack (CD module) on this old Chryslers need power from the battery to charge the capacitors in the pack. If the voltage drops under 10 volts it would not fire.
You can have bad connections in the starter circuit or a bad starter. This will cause the starter to draugh to much current and the battery will not be able to hold the voltage up. It drops and the CD module will not produce power for sparking the plugs.

 

[shoepike]

Finally got around to working on the motor again and wanted to update this in case anyone else had a similar problem. I checked all of the connections and also used a newer battery and the ignition system is working now (unfortunately I have compression problems to deal with now). Thanks to all that provided advice.