PUZZLED, NO SPARK

[Mark Merritt]

Guys;I am A little stumped here,I get 12.75volts at the + side of the coil and the same at the - side,(key on),power at the points(test light),12.75volts coming out of the coil wire to the distributor,but I lose the voltage out of the coil wire at the distributor when I "crank" the engine.the solenoid wire yellow is hooked to "I" the nueteral switch wire is hooked to "S" is that correct? Bad coil? I know it needs higher voltage during the cranking as the starter draws more,but does not after the start and gets lower voltage due to the resistor,the resistor is bypassed during cranking,I think after it starts it only needs around 8 volts,am I wrong?Just wondering if the solenoid is hooked up right,or if it is bad.Everything worked ok before the engine rebuild,and I have not had anything beyond the firewall apart(ignition wires /switch etc.)Does the engine need it's own ground? All the grounds look ok.In short I know it is getting power to the points / battery to solenoid,key switch to coil,negative side to points and at points (no breaks in the wires)but I am loosing something when I crank it,any thoughts? Mark M

[rogerh]

If I follow that all correctly, you say there's power to coil when the key is ON, but not when you turn it further to crank it over, your ignition switch is faulty.
Maybe try hot-wiring the coil directly, bypassing the IGNITION part of the key switch??
I don't recall the ballast resistor going out of the circuit at any time, but you can bypass that thing too, it''s only there to keep the points from burning, I think.
Yes, the engine has its own ground, from back of engine-to-firewall.

[Mark Merritt]

Roger; The coil will not have power if I go and turn the key to on,but will have A little over 12v after it has been cranked and will remain the same after I stop cranking and put the key back to on.It will lose it after the key goes back to off.It's like I get in turn the key on(nothing at coil),crank,return key to on(power at coil),turn it off,back to on(no power at coil).The only ground I had seen when I pulled the motor was connecting the firewall to the frame(passenger side below the heater core),I did not see anything grounding the motor to the frame,just the - battery ground near the water pump.I know that when A car starts it byepasses the resistor to get full voltage to the coil,maybe bad coil? Thanks Mark M

[RICKYMOPAR]

Mark, Make sure the engine, body and frame are all grounded, or expect to be repairing/replacing some expensive drive train components. Bad Grounding could cause the problems you are now experiencing.

[rogerh]

You get power at coil AFTER cranking, not before. Then the power goes away next time you turn to ON.
I think it's a bad ignition switch, and I would try hot-wiring it, maybe w/ a helper in case some wire starts getting hot.
At although its been years, I still think there needs to be aground wire from any bolt in the rear of the engine to the firewall.
Needless to say, I could be talking thru my hat, as I am not a backyard mechanic and I do not have any manuals to look at which might show which way the neutral safety switch and such are to be wired.
If you make sure your car is in neutral, you can disconnect that wire, if you suspect it.

[Mark Merritt]

Guy's I'll correct myself,(negative) side of coil (the wire that goes to the points) I connect A volt meter turn the key to on and get over 12v,as I slowly keep turning to crank position I lose the power to "0".Then I disconnected the nueteral switch wire,put A meter on it and at the same point I lost over 12v at the negative side at the coil I got over 12v from the wire that connects to the nueteral switch.The car does not crank over when the nueteral switch wire is disconnected.I have an additional ground cable I put from the frame to the block(ground and cleaned the connection and have good metal to metal).Is the nueteral switch bad? How does it work with only 1 wire (hot when cranking) going to it,the solenoid might be bad? I also have A good ground body to frame.

[Mark Merritt]

P.S.The wire in the picture with the rubber boot at the left side terminal is the one going to the nueteral switch,the yellow bare one on the right goes to the key switch

[RICKYMOPAR]

Mark, You are wired correctly from what you have written. The negative side of the coil reads zero if the points are closed and full supply voltage when points open. The coil fires when the points open, with a good capacitor, Coil charges with points closed. You can fire the coil yourself as a test, when the negative side of the coil has full supply voltage, just momentarly 'Just a fraction of a second' ground it and the coil will fire when you remove the ground.. Be carefull it can lite you up and a fire as well! Coils do go bad, usually damage, but very rarely. P.S. I am a front yard mechanic, being my back yard is car storage garage.

[Mark Merritt]

Ricky;I put A test light at the pos.side of the coil and noticed it seemed dim,placed it on the neg. side and was equally dim,so I ran A jumper from the pos.side of the battery to the pos.side of the coil(the side that leads to the key switch) and it was very bright,as is also the neg.side going to the distributor points,I cranked it and it wants to fire.I put A timing light on the number 1 cyl.wire, cranked it, and it is firing.Will need to check the wires coming from the solenoid and make sure there is no breaks,also I am going to take the distributor out and check the advance plate for proper ground(maybe it is not grounded at the distributor.Will check back, Thanks Mark M

[Mark Merritt]

Guys; Seems to be indicating A problem with the ballast resistor(original),have good power before it and wire continuity after it to the coil,I have replaced the solenoid(also original) today but had to order the resistor,it will be in tuesday,I also am ordering A new coil (appears older),was going to replace this stuff anyway,however before the engine rebuild the motor did run that is what is puzzling to me.Bye running A wire straight to the pos. side of the coil I am bypassing the resistor and I did get spark,will know more later,bye for now, Mark M

[rogerh]

While I DID say I have no idea what I am talking about, I DID suggest you hotwire the coil, and I DID suggest you bypass the ballast resistor.
I'm glad you are making progress!
Once upon a time, I had my car at a repair shop. I picked it up after they closed, but the car died at the first stoplight. I had to walk 8 miles home. I figured out the next day that the firewall-mounted ceramic ballast resistor had quit. No external signs. All I had to do is put a jumper across its terminals and the car started right up. After that debacle, i carried a spare.
Another time,after some home repairs, the car would crank but it simply wouldnt catch. It took me quite some time to realise I had put the sparkplug wires in the cap correctly, but one space off.
Another time I forgot which way the distributor rotor turned (I think the 318 turns counterclockwise).
Just saying, sometimes it pays to follow the book directions and not your instincts!

[Mark Merritt]

Guy's ; Well it runs!!!!!!!!!! However,it was not as I thought,in fact it was my mistake.The 3 wires coming out of the fire wall(oil pressure,temp sensor,pos.coil) some how got mixed up,earlier I had A broken wire at the pos.coil(wire clip) and went to repair it and also some cracked missing insulation going to the temp sender,the factory tape is like A potato chip very brittle,the color wire is extremly faded,and being somewhat color blind and you guessed it I mixed up the temp sender with the pos.coil that explains the dim test light and going out in start mode but on when key is on.I pulled the wire schematic from the manual and sanded lightly with scotch brite the wires and exposed good color.I am going to contact YNZ to see if I can get A new harness,mine is toasty with previous owner splices. When I am wrong i'll admit it,this goof was mine!! Thanks for the come backs!!!!!!! Mark M

[rogerh]

That's hilarious!...and totally understandable.
There are several companies making wire harnesses..maybe shop around for best price?
From your description, you sure don't need the wirng you have now!

On all the '50s Mopars I've owned, the coil wire coming out of firewall grommet went straight to the ballast resistor. Another wire then connected the ballast resistor to coil. Thus I could plainly SEE and KNOW the coil was wired correctly. Sounds like yours has been altered by previous owners.

[Mark Merritt]

Roger; I called Ynz they are out in California,talked to A fellow named Chris,he said no problem and send it out in A day or two,he said it is part of the complete harness but can section the one out,he told me $35.00 i'm ok with that.Will also have t connector and all terminated with correct color code. over time I will probably replace the of the rest of wiring as I go. Later Mark M

[rogerh]

Can't argue with that price, or delivery time! Nice that they will sell you only what you want. The under-dash and under-hood wiring is what most often gets dried out/brittle.