Why would a '65 18 HP FD-19 backfire trying to start it?

[cntrllglnn]

I have another (older) thread on this motor and instead of adding a different, but similar topic of discussion thought it'd be best to start a new thread. I've rebuilt the carb with a kit minus the float bowl. The coils each ohm at 4.69, points have plenty of padding on them and gapped at .020 at WOT. It had a NOS mag plate put in yesterday because the other had a significant amount of side to side and up and down slop that I believed to either not be opening or closing the points correctly or properly. Plug wires have quite a bit of resistance plug cap to end (out of the coil for a truer reading); now mind you these are automotive (fiber) plug wires and all I had at the time and WANTED to go fishing. O'Reilly's is getting in a new roll of copper cored plug wire in the morning so it'll get the plug wires that are suggested to be used. The motor ran rough before I believe due to the mag plate, but had never backfired when trying to fire her up. I got in a hurry and didn't pay attention to whether the front coil (by the carb) goes to the top or bottom plug. So i have two questions for the experienced OMC members. Thanks in advance for your time and knowledge it's truly appreciated guys.

1) What would cause the backfiring. Everything being the same with it running prior to changing the mag plate?
2) Which plug gets assigned the front coil by the carb?

 

[oldcatamount]

Re: Why would a '65 18 HP FD-19 backfire trying to start it?

The coil closest to the carb is the top cylinder coil. As far as the backfire goes, have you done a link and synch adjustment that coordinates the timing advance with the throttle plate opening?

 

[Chinewalker]

Re: Why would a '65 18 HP FD-19 backfire trying to start it?

First, get rid of tha graphite core wires. Motor simply will not run on them. Period.
Second, once you've replaced the wires, confirm that you have the FRONT coil wired to the TOP plug.

 

[kfa4303]

Re: Why would a '65 18 HP FD-19 backfire trying to start it?

+1. You have to use 7mm copper core spark plug wires along with Champioon J4C, or J6C plugs in order to get proper spark. The front coil, found above the carb should fire the #1/upper cylinder. There is usually a small metal clip on the #1 wire to differentiate it. I would also go ahead an replace the old cork carb float with a new plastic one if you have not done so already. Here are some great overall maintenance links for your motor including a great step-by-step ignition rebuild link with lots of pics. It's for a different model, but all of the steps will be the same for your motor. I also noticed a slight discrepancy in your model/year number. A '65 model would actually be an FD-19, and a '64 would be an FD-18, but it doesn't make much of a difference as virtually all of the parts are interchangeable. I have a '66 20hp Johnson myself, which is practically identical as well.

Maintaining Johnson E & FD Serie

3 HP Evinrude Lightwin Ignition System Tune-Up 1952-1967

 

[cntrllglnn]

Re: Why would a '65 18 HP FD-19 backfire trying to start it?

I have synced the brass mag plate cam to just start to open the carb's butterfly with the timing mark on the cam. I'll have the 7mm copper core plug wire in the morning. The cork float has been replaced prior to acquiring the motor. Been running E3's in it for kicks because I hate Champion plugs with a passeion and prefer Bosch or NGK. I've been under the flywheel so many times for the ignition system I could more than likely do it blind folded. The backfiring COMPLETELY throwing me off though. Thanks for the coil and plug correlation; that clearly makes sense based on their respective location alone and I should've known based on that alone. Once I get the new plug wires put in hopefully she'll act right and quit all the back talking

 

[cntrllglnn]

Re: Why would a '65 18 HP FD-19 backfire trying to start it?

In regards to year and model that's what I was told by a guy at J/E in Sturtevant, WI according to the numbers off the welch plug from photos I emailed him.

 

[kfa4303]

Re: Why would a '65 18 HP FD-19 backfire trying to start it?

If you look on the transom clamp there should be a small riveted tag with the model and serial number on them. My motor is a '66, FD-20, which would make your '65 an FD-19, a '64 would be an FD-18 and so on. I would suggest you use the Champion plugs as well. They're the factory spec and I've never had an issue with them, but some folks have had issues when using equivalents from other brands. I suspect the backfire has to do with the incorrect plug wires. Make sure you twist the new copper core wires on to the coil posts to ensure a nice snug connection.

 

[cntrllglnn]

Re: Why would a '65 18 HP FD-19 backfire trying to start it?

How would one go about twisting the wire around the coil post its short and makes that task difficult? I've been fooling with this thing and have excellent fire on the bottom cylinder.

 

[kfa4303]

Re: Why would a '65 18 HP FD-19 backfire trying to start it?

Not around the coil post, on to the coil post. Each coil has small, recessed pin that the core of the new plug wires will need to make contact with. If you blindly jam the new wires into place you may not make a good enough connection which could lead to intermittent spark. Instead, you'll want to take the new wire cut it flush on one end and twist it onto the coil pin such that the metal core of the wire and the pin on the coil make a strong connection. You'll then need to attach a 90 degree boot to the other end which will connect to the plug itself.

 

[lindy46]

Re: Why would a '65 18 HP FD-19 backfire trying to start it?

To put new wires on, and do the job right, you really need to remove the mag plate. The wires are secured underneath by brackets and you must loosen the screws on the brackets to free up the wires. I usually feed in excess wire through the hole where the wire meets the coil, so I can twist the coil onto the wire. Once secure, I pull the wire/coil back into the proper place and secure the wires under the brackets.

 

[cntrllglnn]

Re: Why would a '65 18 HP FD-19 backfire trying to start it?

That's exactly how I did this one. I'm surprised the screw heads aren't worn completely out yet because it's been off so many times. Both coils are ohming out the same and I've swapped front to back, have continuity on the new plug wires and still no fire from the front coil/top cylinder. By twisting the wire on the coil posts I thought you had a short length of bare wire and wrapped it around the post and twisted it Its hot here in East Texas and its showing!

 

[Chinewalker]

Re: Why would a '65 18 HP FD-19 backfire trying to start it?

CLEAN the points! Very critical.

 

[OptsyEagle]

Re: Why would a '65 18 HP FD-19 backfire trying to start it?

Are you sure the coil wire for the top and bottom cylinders are on their respective spark plugs of the correct cylinders. If you switch the spark plug boots on any motor you will get spark when the piston is at "bottom" dead center and you can get backfiring like that, and of course the motor will never run. I am not sure if you got the motor to run or not when it was backfiring, so I thought I would add this suggestion. If it was running then ignore it.

 

[Mr. Asa]

Re: Why would a '65 18 HP FD-19 backfire trying to start it?

Are you sure the coil wire for the top and bottom cylinders are on their respective spark plugs of the correct cylinders. If you switch the spark plug boots on any motor you will get spark when the piston is at "bottom" dead center and you can get backfiring like that, and of course the motor will never run. I am not sure if you got the motor to run or not when it was backfiring, so I thought I would add this suggestion. If it was running then ignore it.

Similar to getting a car engine wired 180 degrees out? I was reading this and thinking, but didn't want to post as I'm just learning the differences between boat engines and car engines

 

[cntrllglnn]

Re: Why would a '65 18 HP FD-19 backfire trying to start it?

Right you were Chinewalker! Something so simple funks up the whole firing chain of events! Got the the tester out no continuity on the #1 cylinder with the points closed. Quick couple/three swipes with a small file and wipe with acetone and VIOLA. I'd just swiped some Emory cloth through both sets the day before too. Apparently there was enough build up to prevent them from working as they should. Getting good fire again on EACH plug wire now. (( I was pouring sweat, hot, and aggravated. Something so tedious; yet all too important. Took it Lake Holbrook and ran her a bit, she loves having fresh air stuffed in her throat and flat out runs better with the cowl off. Beached her to move the bolt (original hardware is missing) to change the tilt and one plug wire had been nicked all but completely through. Only a small sliver of the outter jacket holding it together. I took the slack out of the wire by turning the plug boot 180 degrees and that was a no no! Cut and spliced it back together with several turns of electrical tape for the evening. I will replace it again tomorrow; it's only .69?/foot and a lesson learned. I want to thank all for their contributions and suggestions they are truly appreciated guys.

 

[kfa4303]

Re: Why would a '65 18 HP FD-19 backfire trying to start it?

SWEEET!!! We love pics

 

[cntrllglnn]

Re: Why would a '65 18 HP FD-19 backfire trying to start it?

Hey that's the least I could do. We are actually getting rain here in East Texas today. So when it clears up I'll get some of the motor and fishing rig to post up. Thanks again everyone. have a fantastic weekend, happy, and safe boating to all.

 

[cntrllglnn]

Re: Why would a '65 18 HP FD-19 backfire trying to start it?

Keep getting upload file failed messages

 

[kfa4303]

Re: Why would a '65 18 HP FD-19 backfire trying to start it?

:/ You can try the "Go Advanced" in the bottom right corner of the reply box which will take you to a screen where you can upload and attach a pic, or you can set up a photobucket account and copy and paste the img code.

 

[Mr. Asa]

Re: Why would a '65 18 HP FD-19 backfire trying to start it?

:/ You can try the "Go Advanced" in the bottom right corner of the reply box which will take you to a screen where you can upload and attach a pic, or you can set up a photobucket account and copy and paste the img code.

For what it's worth, on imgur.com you don't have to set up an account (although you can), and it's slightly easier to navigate