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No spark

Beer Snob

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So I attempted to return home from work when my 620 failed to start. After a quick attempt to pull start it (its kind of a hooptie,this aint the first time ive had to help it get going), anyway I discovered one of the wires to my matchbox had had come loose only to discover that the male prong coming out of the match box had broken off. This will be my 2nd problem to fix, as I also discovered no spark from the coil. When I turn the key to the on position the wire to the coil is hot, but when I attempt to fire the motor up I dont have any spark out of the coil. Figuring I may have a bad coil I changed out the coil for one I grabbed out of my parts bin. Still no spark, but when cont. to try got a buzzing noise out of one of the relays on the pass. fender. I think it may be the ign relay as ive only ever had two relays installed and the other is the horn. Since the supply wire to the coil is hot with the switch in the on pos. but no spark when i try to start I am guessing the ign relay may be at fault. Anyone agree? Anyone not? thanks.

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I appreciate the help, the attitude not so much. If it occured to me the broken wire was my problem I probably would have just fixed it without asking what I can only assume must seem like a stupid question. But seriously Thank you, I do appreciate your imput. I have always struggled with auto elect. probs. Some day I hope to have a better understanding, but till then I guess ill just have to ask questions. Have a great day guys and thanks again

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You're right, my bad.


The distributors job is to connect and disconnect the coil to ground. That's all it does. If there is power on one side of the coil then the distributor simply switches it off and on to ground to fire it. If anything interrupts this there is no spark.


No power from the ignition switch.

A broken (open) coil.

Points in distributor not making contact or electronic module failed.

Distributor not grounded to motor

Any loose wiring connected to any of these parts.


If you still have your old coil keep it. You have a known good spare.

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Thank you man , I probably didnt need to get butthurt and throw back any attitude. once i thought about it after reading your reply it occured to me that current must have to flow through the coil, to the dizzy, and back to the coil, then back to the cap and plugs some how. your explanation gives me more understanding yet and helps me to fill in the gaps in my knowledge of these things. so im off to pull my dizzy out fix the prong on the matchbox if pos., or swap out to another dizzy from the bin-o- datsun parts that seem to never stop growing. Sincerely thank you again, I do very much appreciate the help from you and others and shall pay forward all I learn. Peace!

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To further your knowledge....



The coil is simply a transformer. There are two sets or coils of wire inside. The primary which has power on one side and the distributor on the other, and a larger secondary coil with one end grounded to the primary on the distributor side and the other the high voltage cable coming out of the top.


When the points or electric distributor ground the coil and current begins to flow through the primary windings, a very strong magnetic field is formed. When the points open and current stops flowing, the magnetic field collapses very fast and induces a tremendous and much higher voltage in the secondary coil. This high voltage is directed to the proper spark plug and easily jumps the small gap.

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So after swapping out the control mod. on the dizzy, i have spark out the coil, seems a little weak but i dont know anyway, no spark coming out the cap. unknown condition of the control mod and have not swapped cap and rotor yet (there both pretty new ) if the spark out the coil is weak would this hamper its journey through the rotor and cap? can a bad control mod weaken spark? Keep in mind everything ran ok yesterday before i discovered the bad prong on my contr. mod

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The distributor must be solidly grounded. What coil are you using? The best coils are those intended for use on the electronic distributor. Points coils must use a ballast resister or the extra current through them will burn them up.



What motor and vehicle is this on?

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I dont have any extra dedicated ground wire from the dizzy, and im unsure how the dizzy is grounded from the factory. My coil is a points coil I believe because it does have the little resistor on the side( if i understand things right). I am in the process of finding a E.I. coil from a E.I rig,(Late model 620,720 or 280z). All this is just running my junky little 620. Its a 75 with all elect harness swap from a 79. L20 with a set of su's. Nothing is adjusted 100% correctly (carbs/timing/ havent ever checked the valve clearance) as its a 500.00 truck that burns more oil than fuel and is in need of some major love. However its not one of my project cars its just haulin my ass to work and back right now so as long as it runs good enough im happy enough right now.  Im happy to say that with your help I didnt have to waste a bunch of time guessing what to try next and its back to running like its old clamped out self once more. Ill try keep checking back with ya if you have any more wisdom to share as I can use as much as i can get! Thanks brother have a great day

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The dizzy has always been grounded by the mounting bolts to the timing cover. Later EI dizzys had some problems with the increased current flow and a separate ground lug can be found on the side of some.


Points coil is fine as long as the dropping resister is used. This set up will have the same spark energy as a points dizzy but minus the points. For the full higher output an EI coil and removal of the ballast resister is required.

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