Johnson 70hp 1978 outboard ignition problems

[davehull]

Hi there,

I have a johnson 70hp that was running fine but have been away on six weeks holiday and now turning the key does nothing. Trim controls were still working but tried a booster on the battery and still nothing so I thought I would try jumping the starter directly and the engine starts and runs fine.

Looking for help to trouble shoot this.

Thanks

 

[trendsetter240]

Re: Johnson 70hp 1978 outboard ignition problems

Two possible issues come to mind.

1) Battery cable: Loose or dirty battery cable connections either at the battery or the engine could cause this. Remove, clean and fully tighten the connections on both ends. Check the cable for breaks as well.

2) Starter solenoid is burnt out.

My money is on the battery cable connections.

Cheers

 

[durban]

Re: Johnson 70hp 1978 outboard ignition problems

make 100% sure you have it in neutral position first a little off the neutral position you will get these syptons too

 

[davehull]

Re: Johnson 70hp 1978 outboard ignition problems



I tried all you suggested but I came across what seems like a damaged wire, its a grey wire ( circled) that seems to run all the way back to the engine. would this be the reason?

 

[Steele329]

Re: Johnson 70hp 1978 outboard ignition problems

I would definitely repair that connection just because if it isnt a problem now, it will be later. If you still have an issue, check the starter solenoid. I had the same problem on a 77 70hp and I was out on the water! Its easy to check it if you have a meter. Find where the positive cable comes in, and then where the lead to the starter is. with someone turning the key to start, check for 12 volts both where the positive comes in, and then at the starter. If you arent getting 12 volts at the starter but you are before the solenoid 99 percent its the solenoid. Cheap part, easy fix. Good luck!

 

[Will Bark]

Re: Johnson 70hp 1978 outboard ignition problems

You didn't mention checking the fuse next to the starter solenoid; is it good?

 

[Steele329]

Re: Johnson 70hp 1978 outboard ignition problems

Good point, I forgot to mention that as well. My choke solenoid grounded once causing a similar situation. Check the fuse. If it is good revert back to what I mentioned before. If not start looking for a short. (It is possible that wire you circled grounded at one point and moved before you removed the cowling.)

 

[davehull]

Re: Johnson 70hp 1978 outboard ignition problems

You didn't mention checking the fuse next to the starter solenoid; is it good?

Looks like this solenoid fuse is done for. I am in Australia so dont know how easy these are to get. Its a 1AG 20Amp 32V fuse in there?

Cheers

 

[Will Bark]

Re: Johnson 70hp 1978 outboard ignition problems

Most auto parts stores here in the states have them. Good luck

 

[davehull]

Re: Johnson 70hp 1978 outboard ignition problems

Hi there,

I have now replaced the fuse to the solenoid, when I turn the key still nothing happens. But now when I push the key it will work the choke. I have tested and the solenoid is getting 12V too it. Is there any other test to see if the solenoid is bad?

cheers

 

[emdsapmgr]

Re: Johnson 70hp 1978 outboard ignition problems

The broken wire is grey. Probably the signal wire for the tach. Has nothing to do with the running of the engine. If the starter turns over the engine rapidly with automotive-type jumper cables it is probably ok. It's either a bad ignition switch or the starter solenoid. The solenoid is easier to get to and probably cheaper to replace. The internal contact tips in those solenoids do wear-such that they won't transfer high current loads. FYI, the power trim system is separate from the engine wiring harness on that year engine. It has it's own fuse in the box under the boat's rear splashwell. When the main engine fuse goes, the trim will normally still function.

 

[davehull]

Re: Johnson 70hp 1978 outboard ignition problems

Yeh broken grey wire is tach. Whats the best way to see if its the solenoid or the ignition switch?

Cheers

 

[davehull]

Re: Johnson 70hp 1978 outboard ignition problems

I have replaced the solenoid and it seems its still doing exactly the same thing as it was before. When you push the key in it initiates the choke but when you turn the key fully nothing happens. Any help is much appreciated. Thanks

 

[Steele329]

Re: Johnson 70hp 1978 outboard ignition problems

If the solenoid is good, and you replaced the fuse its most likely your ignition switch, BUT, recheck the fuse there could be a short. If both fuse and solenoid are good then its got to be the switch. Easy to check with a meter as stated before. The only other thing that I can imagine is a broken wire somewhere but unlikely. Check it all again from the start. If you start pulling your hair out WALK AWAY! Come back and recheck from the start again. The dumbest of things can be overlooked I do it all the time... Good luck