runs good then no spark

[wildcard_55]

hello I am new to the forum and have been reading and trying to learn all i can about no spark. I have a 1972 50hp johnson. At times I can hit the key and it starts right up. and the next timew it wont do a thing. can the key switch,the power pack or coils only work when they want to? thanks for any help!!

 

[JB]

Re: runs good then no spark

Ahoy, wildcard.

Welcome to iboats.

If "not do a thing" means that the solenoid clicks but starter does not run you probably have a poor connection in the starter wiring circuit. Classic case is where the ground wire from the battery to the engine block has invisibly corroded at the connection to the block. All connections to the battery and the engine are suspect.

If that is not it, please be more specific about what "not do a thing" means.

 

[tashasdaddy]

Re: runs good then no spark

90% of starter problems are bad connections. remove and clean both ends of the battery cables, so that they are shiney, also the cable from the solenoid to starter. check for nicks in the cables. and make sure the connectors are on the wire good. the cable tend to corrode from the inside out, if nicked, corroded wires, and connections, heat up and cause resistance to the follow of electricity, thus the starter doesn't get enough. you can also take jumper cable pos battery post to large post on starter. with a good connection, the engine should spin. then if the starter is good clean everything and retest. then trouble shoot solenoid. starters can be rebuit at a starter/alternator shop, much cheaper than a new one.

also have the battery load tested at the auto parts store, free, i've had new batteries go bad

 

[wildcard_55]

Re: runs good then no spark

hello guys thanks for your replies. what I mean about it wont do any thing is that it doesnt get any spark. turns over great and all. But today after reading more in the forum I disconnected the main wireing plug that goes from the engine to the controls. when i unplugged it then I had good blue spark. when i plug it back in again then no spark again. I am thinking that maybe the ignition switch itself? will it run with the main plug unpluged and not damage anything? Thanks for your help

 

[wildcard_55]

Re: runs good then no spark

Thank you for your reply JB. What I meant was that it runs good in the barrel. then sometimes when I shut it down and try and restart I have no spark. I read here in iboats anthor sailor said to try and unplug the big red plug.(mine is kinda yellow,maybe faded) but when i do that I have good blue spark. when i plug it back in ,then no spark again,unplug then spark. I am thinking that it is the ignition switch engine is a 1972 50hp john. am i on the right track? thank you again...

 

[tashasdaddy]

Re: runs good then no spark

you are on the right track, it is between the motor and the controller, could just be a bare wire shorting, or the ignition switch. becareful of the wiring, the insulation is going to be brittle.

yes your plug is yellow,

 

[lutin2]

Re: runs good then no spark

Thank you for your reply JB. What I meant was that it runs good in the barrel. then sometimes when I shut it down and try and restart I have no spark. I read here in iboats anthor sailor said to try and unplug the big red plug.(mine is kinda yellow,maybe faded) but when i do that I have good blue spark. when i plug it back in ,then no spark again,unplug then spark. I am thinking that it is the ignition switch engine is a 1972 50hp john. am i on the right track? thank you again...

wildcard_55 did you get this problem fixed if so what was it ? i ask because i have the same problem with my 1972 50hp johnson . would like the help.