#4 plug misses...

[keithems]

nstalled a new carb about 3 yrs ago...

runs well - when it runs..which is not always..

1. often the #4 plug [trans end of the engine] does not fire..usually if i fool around enough and replace the plug ..and/or the wire...i can get it to go.. : )

recently noticed that if i pull the wire and then lay it loosely on the plug..i can see a gap between the wire and the plug and then it fires..so i am wondering why...

do i have to do a complete tuneup? or maybe it's just the cap and/or rotor?

pls let me know, as i'm not getting any younger, and i remember last time i did condenser, points, etc. it was a real pain..i'm only using the motor 50-100 hrs / summer [year], and mostly for in and out of the harbor..no long cruises..

there are more questions but i'm over the limit -- so let's solve this one and then i can post more

[Dave Neptune]

When you hold the wire away and get the plug to work indicates a few things.
First question is what plug are you using and is the gap set?

Another indication of the above is a poor spark which leads me to the points. Did you set the points by gap or dwell? These old distributors are really old and the cam that moves the points is probably worn so setting by "gap" can result in poor coil saturation and a weak spark. The #4 plug is problematic to this issue as it tends to run rich because it is a downhill feed and gets the excess fuel.

Third it could be fouling so have you tried to lean down the carb idle by opening the air screw?

Dave Neptune

[keithems]

see next -- still relearning how this site works

[keithems]

Thank you for the quick reply!

Quote:
Originally Posted by Dave Neptune View Post
When you hold the wire away and get the plug to work indicates a few things.
First question is what plug are you using and is the gap set?

yes -- i've tried them all -- champion 12 yc and also the auto lite 85 and ngk..which were recommended because they are hotter..

gap is set at .035

u can't believe how many plugs i have lying around cuz i've tired to clean the old and install new....mostly not helpful for very long..

Another indication of the above is a poor spark which leads me to the points. Did you set the points by gap or dwell? These old distributors are really old and the cam that moves the points is probably worn so setting by "gap" can result in poor coil saturation and a weak spark.

haven't touched points since motor was removed and reinstalled in 2012...don't use the motor much -- 50-100 hrs per year - in and out of the harbor only....and wanted to avoid fooling with the points..but i will if i have to..not getting and younger, u know...

The #4 plug is problematic to this issue as it tends to run rich because it is a downhill feed and gets the excess fuel.

interesting...always learn something from you...i assumed it ran cold cuz when i redid engine i reinstalled water spray per don's instructions, so i think it's getting lots of cold lake erie water sprayed on it..motor typically runs fairly cool

Third it could be fouling so have you tried to lean down the carb idle by opening the air screw?

no -- the opposite...air screw has to be almost full rich to get a good idle..so i richened it to hopefully cure the fouling..to no avail...but i can't lean it very much---1/4 to 1/2 turn out from full rich to get a smooth idle...

and that was my 2nd question!

keithems

[Dave Neptune]

Do any of the plugs have an "R" in the plug number. That indicates a resistor type. What you are doing by holding the plug wire away is increasing the resistance which backs up the current a bit until there is enough energy to spark across the gap. I recommend Champion RJ12C or equivalent.

Might be a good time to convert to an EI as converting it is easier than adjusting the points until the proper "dwell" is achieved.

Another point is since it has been so long since you did the points the timing is probably a bit off too. This too is another reason to go EI.

Have you checked to see that the C-advance is working smoothly?

Dave Neptune

[keithems]

Do any of the plugs have an "R" in the plug number. That indicates a resistor type. What you are doing by holding the plug wire away is increasing the resistance which backs up the current a bit until there is enough energy to spark across the gap. I recommend Champion RJ12C or equivalent.

Might be a good time to convert to an EI as converting it is easier than adjusting the points until the proper "dwell" is achieved.

Another point is since it has been so long since you did the points the timing is probably a bit off too. This too is another reason to go EI.

Have you checked to see that the C-advance is working smoothly?

Dave Neptune

yes-- i usually have used rj12yc, i think--they're the plugs moyer recommends

like i said some of the auto stores recommended i try the autolite 85 or the ngk plugs because they are hotter...nothing seemed to make any difference. also can't always get the champions around here.

haven't checked the c advance at all..i always assumed it was the problem with that cylinder or the valve causing the plug to foul

only recently noticed that it fires when wire is only laying on or near the plug

i guess i'll have to consider that e i, but i don't want to make that investment until i'm pretty sure it will fix the problem

also -- if it needs new points / timing, etc. why do the other 3 cylinders run fine?

thank you again for your help.

[keithems]

where do i get the electronic ignition?

[Dave Neptune]

You can get one from MMI or Indigo, both are excellent units. I do like the new Indigo unit a bit better only because it has an LED indicator on the unit that shows it is switching which eliminates some guessing as to it working.

Ten years on a set of points is a very long time and they must be really worn by now.

Dave Neptune

[Dave Neptune]

The #4 cylinder gets the least cooling and thus more wear as well as the fuel that puddles goes "down" to that cylinder. It is kind of a weak link or the first to cause problems. Is the #4 fouled wet, sooty or oily? Often a hotter plug will help with the fouling and so will a better ignition spark from an EI.

Check the C-advance by twisting the rotor, it should move smoothly against the springs and return just as smooth. It should be lubed from time to time to keep it so in a marine environment.

If you stick with the points do get ahold of a dwell meter if you can still find one. It is a pain to set the points by dwell and the only way to get truly good results. With the EI you install and set the timing. The timing needs to be set either way and every time you touch the points as well as compensating for wear as the wear changes the timing. There is no wear with an EI so once set your done and the timing won't change as time goes by.

Have you ever checked the compression?

Dave Neptune

[joe_db]

The trick of making a gap between the plug and plug wire is one way to get fouled plugs to fire. I found that out many years ago.
In my experience #4 isn't the hottest plug, it is the coldest and most prone to plug fouling and sticking valves. Also if there is any way water is leaking into the exhaust or intake, it ends up in #4.
Electronic ignition will certainly help, but it might be covering up a problem that may just keep getting worse. I have been there and done that

[keithems]

The trick of making a gap between the plug and plug wire is one way to get fouled plugs to fire. I found that out many years ago.
In my experience #4 isn't the hottest plug, it is the coldest and most prone to plug fouling and sticking valves.

so can you suggest a way for me to make that gap that would keep the plug wire on in rough seas?

Also if there is any way water is leaking into the exhaust or intake, it ends up in #4.

how would i determine if that is the problem?

Electronic ignition will certainly help, but it might be covering up a problem that may just keep getting worse. I have been there and done that

also fwiw...the next suggested thread is from someone with a problem identical to mine:

https://www.moyermarineforum.com/forums/showthread.php?t=1241

[Sam]

All good advice. If it were me I would do one thing at a time and usually inexpensive. First find TDC and change and set points. At high point on cam set gap at .025 and then see if #4 fires. If it does then dynamic time the engine and then possibly upgrade rotor and cap and you are roughly right. Next or first I would change out #4 wire - may be old and have developed more internal resistance requiring the bigger coil load ie air gap.

If this doesn't work you have great advise to follow. If you go the EI route remember to get new coil with proper resistance.

[keithems]

The #4 cylinder gets the least cooling and thus more wear as well as the fuel that puddles goes "down" to that cylinder. It is kind of a weak link or the first to cause problems. Is the #4 fouled wet, sooty or oily?

yes -- all of the above...but the motor does use a bit of oil, and i load the #4 with mmo to keep it working

Often a hotter plug will help with the fouling and so will a better ignition spark from an EI.

yes -- i may have to follow your suggestion and get EI

Check the C-advance by twisting the rotor, it should move smoothly against the springs and return just as smooth. It should be lubed from time to time to keep it so in a marine environment.

will do...

If you stick with the points do get ahold of a dwell meter if you can still find one. It is a pain to set the points by dwell and the only way to get truly good results. With the EI you install and set the timing. The timing needs to be set either way and every time you touch the points as well as compensating for wear as the wear changes the timing. There is no wear with an EI so once set your done and the timing won't change as time goes by.

in the moyer manual, don says i can replace points without removing the distributor -- seems easy enough -- hope it is...so today i intend to remove the cap to see if it's damaged [my first inclination], check the advance & springs as you suggest, and probably replace points, condenser, rotor and cap as soon as i come up with the parts...also per the thread i cite below, i may try champion rj-8c's, which in fact are the ones the original a-4 manual recommends..[i understand, there were no rj-12c's at the time]

here's the url for the thread cited above...

https://www.moyermarineforum.com/forums/showthread.php?t=1241

Have you ever checked the compression?

nope -- hopefully that's not the problem, cuz i'm not up for doing another rebuild...


Dave Neptune

thank you again

[keithems]

All good advice. If it were me I would do one thing at a time and usually inexpensive. First find TDC and change and set points. At high point on cam set gap at .025 and then see if #4 fires. If it does then dynamic time the engine and then possibly upgrade rotor and cap and you are roughly right. Next or first I would change out #4 wire - may be old and have developed more internal resistance requiring the bigger coil load ie air gap.

If this doesn't work you have great advise to follow. If you go the EI route remember to get new coil with proper resistance.

yes -- i've replaced wires a zillion times...have a whole pile of them, plus a box with a new set...doesn't solve the problem, unfortunately...have also replaced plugs a million times..will try some rj 8's today per the following thread [looks like a problem identical to mine]:

https://www.moyermarineforum.com/forums/showthread.php?t=1241

thx for the advice re. a new coil...didn't realize i'd need one if i get the e i

[TimBSmith]

One request...do you have an in-line spark plug tester?

I would be very curious to see what the #4 results are using an in-line spark plug tester before and after the plug switch with clean gapped plugs. Perhaps you would see a difference in the test light pattern which will help with your decision making?

https://www.youtube.com/watch?v=UymD_i_9Q9Y

I understand the interest in a hotter plug in number 4 for fuel pooling there, though the cooling ports may make this a hotter than average cyclinder (usually seems to be the first cylinder to show temp increase on my A4). Not sure how this is for engines with the Thatch(?) mod.

If a hotter plug fouls less, the 8 vs 12 swap is baffling assuming the 12 is a hotter plug. And you are treating #4 regularly with MMO so that could cause faster fouling with a cooler plug right?

I just want to know more about the pattern of spark reaching the #4 plug either way. And I have not yet seen this explored here. Test across plugs even make a phone slow mo video and compare. May help you with next steps. Cheaply. Even though you are not getting any younger : )

Best with isolating the problem.