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Back in November I tucked my dohc away in the garage for the winter. The engine was in a non running condition, it had NO spark. I tinkered with it breifly but then just left it be and decided I would fix it in the spring. Well spring is here. I'm trying to find out if my understanding of the DIS/Coil system is correct.
As far as I know, if the DIS module has power and ground and a crank signal then it will make spark. It is my understanding that the ECM has no manipulation over spark at crank speeds under 400 rpm, so by that logic I've ruled the ecm out as a factor.
Before kicking the bucket entirely the engine would miss a beat while driving, even stall sometimes, but would start back up. Then other times I could start it and idle for 10 minutes but when I moved the car it would stall. This scared the hell out of me because I thought it might be the thrust bearing in the engine allowing the crank to move and throwing the CPS out of alignment - when I moved the car. BUT, I realized that as long as I didnt actually move the car I could press the clutch all I wanted and it wouldnt stall. So that had me thinking a loose wire somewhere. Other times it would run just fine. This all took place over a single day before it just died completely. I tried the DIS and Coils from my running 3.1 and that did nothing. So DIS and coils arent a suspect. I replaced the CPS for the hell of it, nothing. By my logic (and assuming the new CPS is good) that leaves me to believe that the crank signal is not reaching the DIS: bad wiring. The harness carrying power and ground to the ecm tested good with a digital volt/ohm meter. So I have been suspecting the wiring all this time. I tested the harness carrying the crank signal with the same digital ohm meter. While someone cranked the motor I used the low scale AC voltage setting and got a reading but it varied too much to actually read (even in analog mode it was too wild for me to read). I havent resumed work on the car just yet (last final on thursday and then I get to go home for summer), but does anyone think it could be something else? Is my understanding of the conditions required to generate spark correct? (if the DIS has power and recieves a crank signal those are the only factors required for spark?)
As far as I know, if the DIS module has power and ground and a crank signal then it will make spark. It is my understanding that the ECM has no manipulation over spark at crank speeds under 400 rpm, so by that logic I've ruled the ecm out as a factor.
Before kicking the bucket entirely the engine would miss a beat while driving, even stall sometimes, but would start back up. Then other times I could start it and idle for 10 minutes but when I moved the car it would stall. This scared the hell out of me because I thought it might be the thrust bearing in the engine allowing the crank to move and throwing the CPS out of alignment - when I moved the car. BUT, I realized that as long as I didnt actually move the car I could press the clutch all I wanted and it wouldnt stall. So that had me thinking a loose wire somewhere. Other times it would run just fine. This all took place over a single day before it just died completely. I tried the DIS and Coils from my running 3.1 and that did nothing. So DIS and coils arent a suspect. I replaced the CPS for the hell of it, nothing. By my logic (and assuming the new CPS is good) that leaves me to believe that the crank signal is not reaching the DIS: bad wiring. The harness carrying power and ground to the ecm tested good with a digital volt/ohm meter. So I have been suspecting the wiring all this time. I tested the harness carrying the crank signal with the same digital ohm meter. While someone cranked the motor I used the low scale AC voltage setting and got a reading but it varied too much to actually read (even in analog mode it was too wild for me to read). I havent resumed work on the car just yet (last final on thursday and then I get to go home for summer), but does anyone think it could be something else? Is my understanding of the conditions required to generate spark correct? (if the DIS has power and recieves a crank signal those are the only factors required for spark?)
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