86 N/A spark issue
09-18-17, 12:27 AM
#1
Braptastic
Thread Starter
86 N/A spark issue
Hey guys, I've got a mildly modified '86 GXL (RB Headers and presilencer, Corksport cat-back, 'cold air' intake, modified actuator valves (like the smoother atkins 6 port actutor valves), and then OMP, air pump/emmisions, A/C, etc delete) but for the most part I've left it pretty stock, since it is a "daily" (I also have a Ford Ranger so I drive that a lot, but still drive the 7 almost every day and have put some good mileage on it).
Well up until now I've had virtually no issues with it, and any questions I've had so far were almost immediately answered by digging around on these forums a bit. However, I currently can't find anyone who has had quite this same issue and am looking for a bit of advice going forward to help me focus my efforts.
A couple weeks ago it died on me out of the blue on the freeway and I haven't gotten it to start since. Up until then I had been dailying it for almost 2 years with virtually no issues outside of normal maintenance.
I'm getting spark for about 2 or 3 seconds when I crank the engine, but then it just stops sparking on all 4 plugs. Tach stops bouncing as well (which makes sense since the tach runs off the trailing igniter right?).
First thing I did was checked both the leading and trailing coils. The leading coil was showing 0 ohms so I replaced it with a known working one off a running engine I got from a friend when he did an LS swap (don't worry, I gave him a lot of **** for that. Couldn't complain too much though since he gave me a free motor). Went ahead and swapped out the trailing coil/ignitor assembly that came with that engine too just for good measure. They both ohm out to .8-.9 ohms. Both are getting a good 12v (on all three B/Y wires) with the key to on as well.
Next thing I did was check the resistance of the CAS. That checked out good, so then I took the CAS from the other motor and plugged it in and turned the gear with a timing light hooked up to each of the spark plug wires and I'm getting a consistent spark on all four when I turn the gear.
I've also tested voltage at the check connector and it gets 12v and I checked all the relevent fuses for continuity and they all check out good.
I checked to make sure the igniters are grounded well, and no matter where I stick my multimeter lead on the mounting brackets or bolts I get a solid 12v.
Checked my main grounds and they all seemed perfectly fine (last owner who is a good friend of mine completely tore down and rebuilt the engine about 40,000 miles ago and cleaned the whole engine bay including any ground points while the engine was out, and I've done a good job of keeping it clean since I've owned it. It's definitely gotten an expectable amount of dirt build up from 40,000 miles of driving, but compared to most cars with 100+ thousand miles on the body it is very clean).
The only ground I haven't checked is the main ECU ground connected to the rotor housing, since I would have to take off the intake manifold to get to the grounding point.
I plan tomorrow to go out and check the grounds at the connector on the ECU and the three wires between the ecu and the trailing coils for continuity. Is there any easier way to test those then checking for continuity? (I'll have to have some pretty long leads to reach the whole length of those wires). Should those three wires have a certain voltage when the key is on or when the engine is cranking?
I also tried to get my CAS out today to try throwing in the other one but even with the main pulley perfectly lined up on the yellow leading mark I can't get it to budge. Could it just be a really tight O ring or something more serious? The other one came out super easy.
Would it be worth it to take off the intake manifold to check that ECU ground? Would a bad ground even cause this kind of issue? I know it could cause hesitation or erratic spark, but I wouldn't consider this to be erratic since it does the exact same thing every single time and since it happened so suddenly? What are the odds that my CAS is bad (those things are pretty bullet proof aren't they?) Could my ECU be fried? Anything I'm missing?
I'd love to hear someone else's opinion. I've never been good with electrical stuff so I don't really know what I'm doing to be honest, besides what I've read on these forums. I'm certainly learning a lot, but I'd love to hear what some of you guys think.
Thanks!
Well up until now I've had virtually no issues with it, and any questions I've had so far were almost immediately answered by digging around on these forums a bit. However, I currently can't find anyone who has had quite this same issue and am looking for a bit of advice going forward to help me focus my efforts.
A couple weeks ago it died on me out of the blue on the freeway and I haven't gotten it to start since. Up until then I had been dailying it for almost 2 years with virtually no issues outside of normal maintenance.
I'm getting spark for about 2 or 3 seconds when I crank the engine, but then it just stops sparking on all 4 plugs. Tach stops bouncing as well (which makes sense since the tach runs off the trailing igniter right?).
First thing I did was checked both the leading and trailing coils. The leading coil was showing 0 ohms so I replaced it with a known working one off a running engine I got from a friend when he did an LS swap (don't worry, I gave him a lot of **** for that. Couldn't complain too much though since he gave me a free motor). Went ahead and swapped out the trailing coil/ignitor assembly that came with that engine too just for good measure. They both ohm out to .8-.9 ohms. Both are getting a good 12v (on all three B/Y wires) with the key to on as well.
Next thing I did was check the resistance of the CAS. That checked out good, so then I took the CAS from the other motor and plugged it in and turned the gear with a timing light hooked up to each of the spark plug wires and I'm getting a consistent spark on all four when I turn the gear.
I've also tested voltage at the check connector and it gets 12v and I checked all the relevent fuses for continuity and they all check out good.
I checked to make sure the igniters are grounded well, and no matter where I stick my multimeter lead on the mounting brackets or bolts I get a solid 12v.
Checked my main grounds and they all seemed perfectly fine (last owner who is a good friend of mine completely tore down and rebuilt the engine about 40,000 miles ago and cleaned the whole engine bay including any ground points while the engine was out, and I've done a good job of keeping it clean since I've owned it. It's definitely gotten an expectable amount of dirt build up from 40,000 miles of driving, but compared to most cars with 100+ thousand miles on the body it is very clean).
The only ground I haven't checked is the main ECU ground connected to the rotor housing, since I would have to take off the intake manifold to get to the grounding point.
I plan tomorrow to go out and check the grounds at the connector on the ECU and the three wires between the ecu and the trailing coils for continuity. Is there any easier way to test those then checking for continuity? (I'll have to have some pretty long leads to reach the whole length of those wires). Should those three wires have a certain voltage when the key is on or when the engine is cranking?
I also tried to get my CAS out today to try throwing in the other one but even with the main pulley perfectly lined up on the yellow leading mark I can't get it to budge. Could it just be a really tight O ring or something more serious? The other one came out super easy.
Would it be worth it to take off the intake manifold to check that ECU ground? Would a bad ground even cause this kind of issue? I know it could cause hesitation or erratic spark, but I wouldn't consider this to be erratic since it does the exact same thing every single time and since it happened so suddenly? What are the odds that my CAS is bad (those things are pretty bullet proof aren't they?) Could my ECU be fried? Anything I'm missing?
I'd love to hear someone else's opinion. I've never been good with electrical stuff so I don't really know what I'm doing to be honest, besides what I've read on these forums. I'm certainly learning a lot, but I'd love to hear what some of you guys think.
Thanks!
