Ok, I seem to have a very odd problem, at least I think it's the problem! Car won't start after rebuild, different engine, loom coils etc from before. I didnt have a cas ne signal. Now sorted by replacing the wires in the loom and verified using a scope. Both cas signals now fine. Sparks on all plugs but won't start. Thought I'd put timing light on all plugs to check. What seemed very odd is that both front plugs and lower (leading?) rear were all firing with the timing mark lighting up at about 10 o'clock on the pulley (marker is at 11 o'clock). But the rear upper (trailing?) plug fired at 180deg to this, around 4 o'clock. I don't fully understand the firing sequence but I thought the 2 lower plugs seemed ok (bearing in mind timing at cranking is probably alot different to idle). The fact that the front upper was identical struck me as being strange though. Can anyone tell me what I should expect to be seeing from this please? I know this isn't a standard method but I think someone may have done something strange with the wiring at some point. Any help would be much appreciated. Thanks
Pete

 

This may be a question better off to get answered in 3rd Gen Specific Pete.
If you have any MODS on the car, it should be mentioned..like a aftermarket ECU.

 

Hi, thanks for replying. Unfortunately I cannot post anywhere else yet (not done enough posts). The car is standard 93 twin turbo manual. If someone could just tell me whereabouts each spark plug should show up on the crank with a timing light it would be enough for me to troubleshoot from there. Reading between the lines from what I have read I believe it should be this:

At idle:
Both leading (bottom) plugs 20atdc which is in line with the only markings.
Front trailing plug 5atdc
Rear trailing plug 185atdc

Does that look right? Because I am at cranking, not idle, I believe these values may adjust but I dont know by how much. Any idea? I just want to use this as a reference to make sure everything is wired up right. Thanks again

Pete

 

Stock ECU then?

Have you reversed the wires to either the G or NE signal?

 

Yes stock ecu. I haven't touched the g cas but I did rewire the ne cas. I did check. Still the same way but I noticed the signal drops negative first then positive on the scope. I assumed it would be positive to negative wave but it's still yellow to yellow so wiring must be correct polarity. I did reverse the signal out of frustration to check but it didn't fix the problem so I put it back. I have to admit I have made a fairly major oversight after getting so involved fixing the faulty cas wire.. I forgot the fuel in the car must be 3 years old! So drain fuel, refill fresh and try to fire hoping the timing pattern is a quirk of the Mazda ignition system at cranking speed! Thanks!