Igintion Problem w/ 70hp Johnson

I am new to the board so bare with me. I have a 1975 Johnson 70 hp outboard, that has been running fine for about a year now since I purchased it. Yesterday morning, come to start it up, no fire on all three plugs. Started troubleshooting the problem, removed the black and yellow wire from the pack, to check key switch, still no spark. Did sensor coil resistance check according to manual, within range. Charge coil checks ok. Started to suppect the power pack was back. However, after a few hours of fooling around with wires, to my surprise I had fire on all three plugs. Installed plugs, and engine fired right up. Ran it for 10-15 minutes in driveway with water to lowerunit, running great. This morning come to start engine, no fire again. Pulled red plug apart, did continuity test on conductors from harness, all okay. My question is could a conductor be broken inside the insulation or could the conductor fail under load? Any ideas please let me know? Thanxs guys

Re: Igintion Problem w/ 70hp Johnson

Hey Linkin'....<br /><br />Yes you could have a broken conductor someplace and not see it. If you can remember what wires you were messin' with right before you got fire back, that would be the place to start. Also check the condition of the insulation on the wire harness. Look for a ground or dead short that would cause the problem.<br /><br />Keep us posted.

Re: Igintion Problem w/ 70hp Johnson

Also, forgot to ask if anyone know how much voltage should the power pack output to the coils? Also, I unplugged the red plug wire harness and jump started the engine to eliminate any problems from the front end, still no fire on any plugs. Grounds seem to be in order, tight, no loose connections or corrosion. If anyone has any ideas as to what is going on, I would appriciate it, thanks fellas

Re: Igintion Problem w/ 70hp Johnson

Thanks for the reply OutboardJim, gonna go look again at Dem stinking wires, is there any other test or place I should look for this seemingly nutty intermittent problem? How can I test the charge coil on a multimeter, and is there any way to test the timer base assembly?

Re: Igintion Problem w/ 70hp Johnson

You can check the charge coil with an ohm meter.<br /><br />Set the meter to high ohms and disconnect the brown and brown/orange wire from the power pack. Across the wires you should read 630 ohms +/- 50.<br /><br />To check the timer base, disconnet wires from terminals 8, 9, 10, 11 on the power pack. Set the meter to low ohms and connect the black meter lead to the common wire, black w/white stripe. Take the red lead and touch the timer base leads one at a time. Should read about 8.5 ohms +/- 1ohm.

Re: Igintion Problem w/ 70hp Johnson

The charge coil should put out about 230 V. Check wires on stator that they have'nt come in contact with flywheel, and rubbed through . Check wires from sensor assembly where they make a sharp bend as sensor rotates. Sensor ground to pack may be broken.

Re: Igintion Problem w/ 70hp Johnson

Charge coil checks out good on the ohm meter, 620. The sensor coils check out good also on meter, around 8 ohms on all three. Mr. Johnson, I checked the bends and sharp angles to both the sensor and the charge coil wire and both groups look ok, didn't see any chaffing or wear. Going to check charge coil voltage as soon as the battery is charged up again, ha. Thanks for the quick replies Outboardjim and Rjohnson. By the way, what reading on the meter should I get on output from the power pack the the three ignition coils to the plugs? Thanks for the help!!!!

Re: Igintion Problem w/ 70hp Johnson

You should have 220 v. from charge coil, 230 v. from pack. You will need a peak reading volt meter for these tests, regular volt meter won't work. When you check the sensor wires for a break where they make the bend, disconnect all 4 wires. With your ohm meter, place one wire on sensor,any one will do. Place other on common black lead, then pull on black lead to see if it parts at the bend.When you do the voltage check for output, also do a short to ground test on sensors, and charge coil. Remove black & yellow from pack for final test. Spark should jump about a 1/2" gap

Re: Igintion Problem w/ 70hp Johnson

Alright fellas, think I've found the culprit. After checking everything else, I decided to try and turn the engine over while wiggling some wires around. Since, I don't have three hands, I had a friend come over and help me. Well, first things first, started with the wire harness (Big red connector), twisted and wiggled a bit and BAMM!!! she fired up. I think one of the pins or conductors maybe broken inside the plastic mold. Gonna reterminate all 8 conductors and hope and pray. Thanks for the quick replies and the advice, even though the other things checked out fine, still liked to confirm everything else was still ticking and they are. Thanks a lot fellas.