why do i get no spark from coil?


Asked by Jan 25, 2015 at 12:59 PM about the 1985 Buick Grand National

Question type: General

rebuilt motor
no spark to plugs from coil

10 Answers


First you need 12v on the B+ side,When key on or cranking, and a switching signal voltage on the distrib. side., when cranking. If the key springs back to run, and B+ voltage drops to half that shows a proper resistor wire function. and if these readings change out of spec with temperature, it is a sign of corroded switch , wires, or connections. A coil that cannot pass ohm checks according to spec is also to be considered no good . The service manuals are free at the library, reference department.


Once you have a known good available spark voltage, the rotor should be inspected for the voltage seeking a ground through it, and grounding to the distributor shaft. Secondary ignition resistance in wires and plugs can be high enough to make it arc there. A/C delco makes the best ignition wires and plugs for your vehicle, but maintenance may require their replacement.


Since you have an 85 GM HEI ? You may want to replace your module and pickup coil with some fresh A/C delco parts. The testing can lead you there if you cannot see obvious spark arc evidence.


it has a coil pack not a distributor


Please review your question. Then tell us what you are actually working on, provide a schematic, or describe all the changes you made so someone with that type of specific experience can answer you as simply as possible. Thank you.


If a car has a coil pack ? it still has a module, if you used some specific system, it can be helpful to describe it, the Gm cars I have worked on that had coil packs had modules mounted underneath. If you hear spark arcing or not, it may still have found a short path to ground. all the things i was telling you so far are still true. but the arrangement of the parts could be different. instead of arcing through the rotor, it can blow a hole in the module, but then who made it, anyway.


I looked up your coilpack, it looks like the 3800 engine used in pontioldsmobuicks I have seen, They eat aftermarket modules. I recommend A/C delco module wires and A/C delco plugs. 547 of those were made ? You really should say what it is. Since it had that system all the way back in 85 ? Stands to reason it has been seen by very few people. The bulletins for other cars with that system may be helpful to you also. for hard starting and timing chain wear issues when mileage starts to add up. Have a nice Buick.


Your timing is off. It can be off by as little as one degree and these engines WON'T fire. It is not like a distributor that you can fudge with a bit one way or the other. It has to be exact. Do yourself a favor and google Buick Grand National timing tool. It will be a little box with an led that will come with a sticker showing where the timing marks should be.


Thanks chad for the info. hopefully your info helps those who read this. The system was a confuser because you had to have books for the cars with and without it to have the books for the rest of the car. The last one I had, the guy was so confused and overrought, he pre ordered a pile of parts to throw at it but refused any diagnostic time. Since I heard the spark ticking, I went to the u-pull-it yard and found him a used ac delco module, then his cold start issue was pcv hoses, grommets, etc........ If your cam timing issue is happenning ? I am glad to hear it has a tool to adjust his cam sensor? It would affect his injectors. But he has not replied with his info in a long time to say what fixed it back then.


When you have a 30 year old car that 547 were made trying to make them legal for nascar, a good portion of them can be found stored or in a car collection somewhere. I notice that system is used on the 3800 wherever I find it. and similar coil pack equipped 6 cylinders. It is difficult to diagnose a spark loss issue because of the part locations on many applications. The bulletins for cam angle can help explain issues with that sensor, and higher mileage units may be up for regasketing and timing chain wear. Using A/c delco parts has been solving the repeat failures of ignition parts on the ones I worked on. Hope the timing tool is necessary if you have to buy one. we did not have that when I worked for GM, so chaduski is your helper on that one. Years of time and wear or hot and cold can change how your system needs may change.

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