no fire on top cyl 4hp 1971 evinrude

[crosbyman]

yep same thing …

btw Mumbles……thanks for that picture showing the cable routing I was wondering if the 2 plug wires should jump the edge or needed to be tucked under the throttle hook up bar just to the right of where you have them clamped down .

I even grounded myself to the top plug wire…and felt nothing when hand spinning the flywheel ….. I certainly did not try it with the bottom plug 🙂

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[Mumbles]

Even though they are new, you might have a bad plug wire. The core could be broken internally giving a good ohm reading but not being able to handle the voltage needed to fire the plug.

An ’59 18 horse almost drove me over the edge trying to figure out what was wrong. it had a whole new electrical system but it missed badly at the lake under load. I finally figured out it was a bad/broken plug wire. The solid core wire I used was at the end of an old roll of FoMoCo wire and I remembered I could hear it cracking as I took it off the spool. It checked out OK with a meter but the core wire must have broken as I unwound it and it wouldn’t fire the plug. After several trips to the lake I decided to try some fresh wires and that was it. Problem solved.

[crosbyman]

this is what I am using and I replaced the first wire with a second one in the pack of 8

https://www.napacanada.com/en/p/BMX700175

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[Mumbles]

That is resistance wire, not solid copper core and carbon cores are known to break if they are mishandled. Just saying.

[crosbyman]

look closely at the wire ends in the picture … these are not carbon core (resistive) they are solid metallic wires and I have used them on several rebuilds with no issues . Actually they measure a solid 0 ohms en to end

bottom cyl fires fine with the same wire type

they call it Low Ohm Distributed Resistance Core giberish for 0 ohms …about as low as you can get 🙂
they use the same giberish on bmx700715 wire

NAPA part number 700715.
Application Guide:

Low Ohm Distributed Resistance Core
Marine Spark Plug Wire Set

but now you got me worried……

see this one.. FIXED RESISTOR WIRES

Lastly, there are fixed resistor wires. These are often found on European vehicles and feature steel or copper wire and a resistor inside the plug boot to control interference.

I will try a straight piece of wire NO BOOT at the end and see what happens A.S.A.P. makes no sense all my other rebuilds worked fine as does my lower cyl plug on this 4hp 1971. and it measures 0 ohms

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• This reply was modified 4 years, 9 months ago by crosbyman.
• This reply was modified 4 years, 9 months ago by crosbyman.
• This reply was modified 4 years, 9 months ago by crosbyman.

[rudderless]

…too much air gap on one coil?? I use 1 pc. duct tape stuck on the magnet. It should miss on both coils. If no hit use another piece and try again. Keep adding tape until one or both coils hit.

My rule of thumb…one piece should miss…2 should just hit.

Don’t trust the mag plate boss at this point. It is not a magical mystery why it does not spark.

I bet if ya really spin it up it will spark…

Put your analog meter on the point terminal screw and one on ground. 0 ohms points closed…primary ohms with points open. Ya will need to get the cap out of circuit either by removing the wire or remove attaching screw in plate and sliding a piece of cardboard or equivalent under cap so it is not conducting the mag plate.

• This reply was modified 4 years, 9 months ago by rudderless.
• This reply was modified 4 years, 9 months ago by rudderless.

[JOHN HOLBIK]

I had a problem same as you years ago.A good friend was taking a small engines course at the college.I gave John several motors from our resort.When I got them back all were good except for a 20hp Johnson no spark on one cy;inder.John had changed all the magneto parts even the mag plate as it was really worn.I must have tore that flywheel off a hundred times .I finaly found the problem by fluke. I reached down and picked up the flywheel with my right hand and I had my fingers curled on the magnet I felt a small bump under my finger .Stuck to the magnet was one of the tiny points washers .I put the flywheel back on and she purred like a kitten.One coil must have had enough clearance to let the washer pass by.
So I learned something that day look for the obvious easy stuff first I still automaticaly look too far into the picture.
I guess I should practice what I preach.

[rudderless]

So did the missing washer cause the point terminal screw to be grounded or did the washer mess up the mag field? Or too much air gap? Inquiring minds need to know..

• This reply was modified 4 years, 9 months ago by rudderless.

[crosbyman]

Rudderless………

Don’t trust the mag plate boss at this point. It is not a magical mystery why it does not spark..

. I will try to “bring out” the coil to see what happens

my FW magnet is clean and strong on a screwdriver blade..and works fine on the bottom cyl….

I tried with and without the capacitor in the cct. nothing

whomever (shady man) had this engine must have had lots of reason to sell….including the cracked up coil I found 🙂

thanks all for your patience and hints… glad I have a few months to ” ice out ” 🙂

Joining AOMCI has priviledges 🙂

[crosbyman]

update… I moved out the top coil closer to the FW…. no fire

i’ll report back when I have sparks …

I will start over from scratch…. all over again ………. in a day or two of mental rest

xcrsxrtxcc !

Joining AOMCI has priviledges 🙂

• This reply was modified 4 years, 9 months ago by crosbyman.

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