1st post ever! Johnson 140 no spark in one cylinder

Kaibrock · Jul 16, 2011

My dad has a 1978 v4 140 outboard that doesn't have spark in one plug. It's the top right as you look at the back of the motor. I changed the coil and power pack on the right side but still no spark. A test light shows pluse coming from one wire out of power pack but not the other. I'm now stumped. Any suggestions?

Added: The other side coils and power pack seem to work fine.

crestlinermusky · Jul 16, 2011

Re: 1st post ever! Johnson 140 no spark in one cylinder

Try taking a coil and power pack that does work from the motor and switching it with the new one, just to eliminate that
you don't have a faulty new part.

Kaibrock · Jul 16, 2011

Re: 1st post ever! Johnson 140 no spark in one cylinder

I thought about that. I will try that in the morning. Any ideas if that doesn't work?

TD_Maker · Jul 16, 2011

Re: 1st post ever! Johnson 140 no spark in one cylinder

I have an idea for you. Find the rubber two pin connector ( black or dark brown in color) which has a single wire leading to each coil on that particular bank of the motor. Make sure the connection is solid and not corroded (or missing.) I have seen these little metal pins inside of this connector bend, corrode, or break off; thus, keeping the coil from firing. I once had to eliminate this connector all together, and solder and heat shrink the wires together. There is connector on each side of your V-4. I am going off memory here, but I believe the coil wires were orange in color.

Kaibrock · Jul 17, 2011

Re: 1st post ever! Johnson 140 no spark in one cylinder

Thanks. I actually swapped the power packs side to side but no change. Of the two wires coming out of the power pack, using a lead light, I can see one flashes while the other doesn't. Turbine that flashes has a spark. I've now eliminated the power packs and coils for sure as a problem. Just not sure where to go from here.

guy74 · Jul 17, 2011

Re: 1st post ever! Johnson 140 no spark in one cylinder

Well, if you have ruled out the coil and powerpack, and the other 3 are firing good, that leaves the trigger assembly. The trigger has 4 seperate circuits, one for each cylinder, so that could be a source for a single cylinder misfire.

sterndrive tech · Jul 17, 2011

Re: 1st post ever! Johnson 140 no spark in one cylinder

correction, the trigger only has 2 bobbins, each fires 2 cylinders, leave both blackyellow wires disconnected from the packs as these act as a biased cicuit,, they return grounds to their source,, on pack can block the other,, try this , then swap the 2 packs and see iof fire changes to the other side

guy74 · Jul 17, 2011

Re: 1st post ever! Johnson 140 no spark in one cylinder

sterndrive tech said:
correction, the trigger only has 2 bobbins, each fires 2 cylinders, leave both blackyellow wires disconnected from the packs as these act as a biased cicuit,, they return grounds to their source,, on pack can block the other,, try this , then swap the 2 packs and see iof fire changes to the other side

Reguardless of how many "bobbins" there are, each cylinder has its own wire from the trigger to the powerpack. If he has already substituted the powerpack, changed coils around, and the misfire has stayed with the one cylinder, the only thing left is the trigger or the wiring to it.

sterndrive tech · Jul 17, 2011

Re: 1st post ever! Johnson 140 no spark in one cylinder

then he should be able to swap the timer base/sensor leads and the problem go to the other bank.
altho i have never seen a sensor pick on one cylinder,, but always a first for everything..

guy74 · Jul 17, 2011

Re: 1st post ever! Johnson 140 no spark in one cylinder

sterndrive tech said:
then he should be able to swap the timer base/sensor leads and the problem go to the other bank

Good idea! The side he is working on is the long lead side, so he can plug it into the other pack and see if it causes spark to go out on one of them. Of course the motor won't run and checking for spark will have to be done while cranking, but it would help find the issue. A resistance check between terminal A-B and A-C (30-50 ohms), then ground the meter at the timer base, and check all 3 terminals (should be infinity). The timer is an expensive part and needs to be checked out well before replacing.

emdsapmgr · Jul 18, 2011

Re: 1st post ever! Johnson 140 no spark in one cylinder

The cdi.com website has some good ignition troubleshooting tips specifically for your engine if you don't have a factory service manual.

1st post ever! Johnson 140 no spark in one cylinder

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