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346 Flathead -no spark

Started by jsmithtss, June 27, 2014, 06:53:16 PM

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jsmithtss

    I'm stumped!! >:(  My 346 flathead began running rough a few weeks ago , so I decided to check the timing and maybe check the points too.  I found out that my #1 cyl. was not firing at all.  I then figured I'd convert to electronic ignition .  Bought a Pertronix kit and followed the instruction. After putting everything back together the #1 cyl. still was not firing.   Since then I have done the following:
            Changed plug wire----- changed rotor----  changed cap------ I've even changed the distributor.  There are no visible bad signs on either cap, both rotors appear good, and even the distributors seem great. Yet, I get no spark to #1 .  I should say most of the time, no spark . On occasion the engine will bark and shake and #1 will fire but it is not constant.
              Do any of you have any suggestions on my problem?  Is there any possibility the coil may be bad?
I just have a hard time understanding why only one cylinder is the affected.  It would seem to me that the rotor may not be good-- but why on one and not all. 
              My ability has almost reached it's end and I could sure use some input. 
                         Thanks ---     Yea, I'm shak'n my head too.   

Fred Pennington 25635

You list everything but the plug. Have you tried another plug. They do go bad a tiny crack in the porcelain under the metal is all it takes.

Good luck.
Fred P.
Fred Pennington, CLC 25635
1940, LaSalle 5019
1940 LaSalle 5019 parts car
1968 Ford Bronco
1973 Mustang Convertible
2012 Shelby GT500

jsmithtss

 Yes sir, I swapped out the plug also.  I know the timing light works too.   It is a real puzzle why only one cylinder wire is not getting juice to the plug, with all that I've done.   The new electronic ignition does not require a condenser, so that too is eliminated.

John Washburn CLC 1067 Sadly deceased.

Does the distributor turn when you crank it? It could be a timing chain/gear issue. Either slipped or broken. Or perhaps the coil is bad?

As always just and opinion...

The Johnny
John Washburn
CLC #1067
1937 LaSalle Coupe
1938 6519F Series Imperial Sedan
1949 62 Series 4 Door
1949 60 Special Fleetwood
1953 Coupe DeVille
1956 Coupe DeVille
1992 Eldorado Touring Coupe America Cup Series

Bill Ingler #7799

When you say that #1 cylinder is not firing have you proved this by pulling #1 plug wire and holding it about 1/8 of an inch from the plug and get someone to crank the engine. You should get a spark from the wire to the plug. If the spark happens all the time and number #1 cylinder is still not firing then maybe that cylinder is not firing normally because the valves in that cylinder are not opening or closing correctly because of a weak or broken valve spring. This condition directly affects compression. I would do a compression check on the engine which then will let you know if you have an internal problem affecting the combustion in a particular cylinder or several cylinders.  Bill

joeceretti

#5
I really hope you missed something and you don't have spark OR the spark is weak due to a failing coil otherwise what Bill said is just about your last possibility. A weak spark can still cause the timing light to fire.

jsmithtss

 Bill and Joe---  That was probably one of the first things I did.  While the engine was running (very rough ) I pulled the plug wire and put it next to the plug with no spark. I then tried putting the wire to ground -- no spark.  It was after this, that I replaced wire from the cap to the plug and retested. ---- same thing, no spark.  My thoughts were, that even if the complete piston was not working, I was dealing with an electrical problem. Wouldn't the wire spark to ground with or without it being connected to the plug?  I never thought about compression since I was trying only to get spark.  I figured that compression and valves would only matter after the plug fired.  However, I'll try to check my compression and get back .
                             Thanks a bunch for giving the tips!!

joeceretti

I had numurous problems and ended up soldering all my plug wire clips on. Fixed my random spark loss.

Jeff Rosansky CLC #28373

I think it was somewhere on this forum where someone had a problem like that.  Look in the cap under the rotor.  Are all the lobes in good shape?  If 1 lobe is worn down it would not allow the points to open and then you would have a dead cylinder.  I know you converted but the principle may be the same for the magnetic pickup.

Next, have you changed the plug wire? 
Then take the plug wire out and stick another wire in its hole on the cap.... Just a random piece of house wire or something and then ground it.  See if you get spark there.  Next, rotate the cap 180 degrees (if possible) and see if the problem follows the cylinder or the place on the cap.
Jeff
Jeff Rosansky
CLC #28373
1970 Coupe DeVille (Big Red)
1955 Series 62 (Baby Blue)
Dad's new 1979 Coupe DeVille

Bill Ingler #7799

#9
I went back to search and brought up a posting I did in 2009 on what is called ghost firing or cross firing. It might help your problem.  If I am reading the article on cross firing correctly then it could be that the reason you are getting no spark from #1 wire is that #1 wire is cross firing with another wire to another cylinder.       Bill


« Reply #8 on: May 28, 2009, 10:54:38 PM »


This might be completely off the wall but have you considered you might have some induction firing, some call it ghost firing between cylinders. As you know induction firing can happen when long plug wires are running parallel and close to one another causing the spark energy from one cable to induce a current in the other which in turn causes two cylinders to fire at the same time. Try switching the position of plug wire 4 with plug wire 6 in the wire loom holder. Do the same thing with 3 & 7 on the other side.  Just a thought. Here is a good article on induction firing.

http://www.jasperengines.com/pdf/SparkPlugCross-FireTB.pdf

jsmithtss

 Bill & Jeff--- 2 very great ideas  :D!!!    I may start up the engine in my garage in complete darkness. If there is a jump between wires, I may get lucky enough to see it. The inside of the cap is a different bird, so I really like your suggestion Jeff on rotating the cap. Both of you deserve a big thanks for taking the time to help me out, I really appreciate it.
                         THANKS   j.smith

Jeff Maltby 4194

#11
http://autorepair.about.com/cs/troubleshooting/a/aa090602a_2.htm

An easy and simple way to check spark plug wires for cracks is to use a spray bottle to spray the wires with water. If there are cracks in the wires you will see and hear the sparks jumping to ground. Doing this at night makes seeing the spark much easier.

   Spark plugs can go bad internally as well. Inside most spark plug wires is a carbon core. After a while this core can crack and small gaps develop in the core. This makes the resistance in the spark plug wire increase to the point where the spark won't travel to the spark plug, or get to the spark plug greatly weakened.
Jeffo 49er chapter

CLC 1985
Honda Gold Wing GL1500

Jeff Rosansky CLC #28373

Correct on the electrode/porcelain.  When working on the airplane, they say if you drop a plug it makes 2 sounds.... The first is when it hits the floor, and the 2nd is when it hits the trash can. 

And you're welcome on the help--Lord knows we've all been there, in fact, I'm still there.  That's the fun of having these old cars.  Working on them and learning about them.

If you start removing plug wires, be sure to do them 1 at a time and/or mark them very well.  You don't want that headache, believe me.  By the way, the firing order is correct, right?

Keep us posted on what you find.
Jeff
Jeff Rosansky
CLC #28373
1970 Coupe DeVille (Big Red)
1955 Series 62 (Baby Blue)
Dad's new 1979 Coupe DeVille

Dave Burke

I'd also look at the distributor cap and make sure that there isn't a bit of corrosion or something there that is preventing the spark from going from the coil to the wire.  But seeing as how you have tracked most of the issue, you have really narrowed it down: the coil doesn't care what wire is being fired, nor should the rotor, so you are left with the distributor cap, the wire, or the plug.  Good luck and let us know what it turns out to be - some knowledge applies to most cars, and can be helpful to all!

Dave Burke
1957 Sedan Deville
1963 Series 62 - Project LUX
1983 Maserati Quattroporte

"Who loves ya, Baby?" - Kojak