77 Chrysler 105 no spark to # 4

[deangun]

Set timing and points. Runs but am not getting spark out of distributor for cylinder 4. Ohm test from inside cap to end of plug wire and have good resistance. Replaced cdi box with a used 1 and same problem. Looked at lobes inside distributor and took flywheel off to make sure all clean and good magnets. Any ideas what else to look at?

 

[Nordin]

Are you getting spark at #1-3 cyl. but not at #4?
What do mean by good resistance at wire #4? It should be infinity or very close to 0,0 Ohm.
Check the #4 post inside the cap for dirt and crack. The cap has a top that is mounted with screw and the hightension wires are knited to the distcap by this top and a typ of rubberseal.
Check the #4 wire connection to the #4 post, the strands in the hightension wire are just spread and pressed by the top to the posts.
Check the spring in the plugboot for rust.

If no luck, change the hightension wire.

There is nothing under the flywheel that has something to do with the ign.system except for the flywheelkey. If the key is shared or damage the timing will be off/wrong
There is a alternator that charge the battery under the wheel that is all.

 

[deangun]

Yes 1-3 spark nicely and run the engine. In comparison to the other plug wires the resistance is very close. Don't remember exact # but being it's just a bit longer it seemed right to me. I have tested wires on auto's many times. I swapped caps and wires just to be sure. Sorry forgot to mention that. Flywheel key is good nas well. Thanks for the info on whats under the flywheel.

 

[Frank Acampora]

You should have the Motorola ignition. If you get spark on any one cylinder, the unit is good and you should get spark on all cylinders. Thus your coil and high tension lead are good. The problem would most likely be with the #4 plug or associated wire.There should be very little resistance in any of the plug wires. This engine uses solid core stranded wire. SO: Check the plug itself, check the plug terminal. Finally, remove the distributor cap. Check the contacts inside. Look for carbon tracking which would short out the #4 terminal inside the boot. The plug terminals are spring steel clips that simply stab into the wire. They frequently rust and break.. Split the cap and remove the top (two round head screws, one on either side of the high tension lead.). Then pull out the rubber seal. see if the #4 wire is seated fully on the recessed prong

 

[MickLovin]

As Frank mentioned more than likely a rusty steel spring clip under the boot of the plug wire.

 

[deangun]

I changed cap and rotor and wires and plugs. Tested from inside cap to inside plug wire boot. Have good resistance. No spark yet.

 

[MickLovin]

No Title

You should have a very low resistance on your leads if they are the copper/wire core ones. Also you should be using surface gap plugs on these motors.

May I ask what resistance you have on all your wires? Also with the belt on the top of your dizzy, at top dead centre does the top of the dizzy marked with a T, line up with your flywheel?
Have you had it running and tried to pull one lead out at a time to see what difference it makes while running?

 

[deangun]

I will have to retest ohms on wires. Been awhile since I have had time to look at it. Yes the timing mark is lined up. I went through timing procedure and also did pull 1 lead at a time from cylinders 1-3. Can tell a difference with each 1 when pulled off. I replaced the plugs with the same ones it had when I bought the boat.

 

[NYBo]

How are you checking for spark?

 

[deangun]

Have pulled the plug and used an in-line spark tester.