RedZ31

Hey there folks, haven't posted in quite awhile due to the car running pretty good for once! But all good things must end, been having some issues for the last couple weeks, in general the car runs like crap. Started to check and make sure i didn't have a dead cylinder cause of the random misfire iv'e been having and noticed my spark (from distributor) is straight red and orange, no hint of blue.

Grounded the plug wire from the coil and its still orange/red, so i check all my grounds ,even run a fresh one just to be safe and still no better. I figure it must be the coil and replace it...still orange. So my question is, and i have looked, what else controls how STRONG the spark is? To my knowledge the ignition control module just regulates when the coil and plugs fire, correct me if i'm wrong? I'm hoping this isn't some wiring problem the past owner ran himself. Thanks in advance!

Mods are: Intake, exhaust

RedZ31

Btw could the diode for the distributor ground have failed? I experience no change in the engine when unplugging this ground wire.

rogerz

there is no diode for the dizzy. poor battery and battery cables will do that as you are not getting full 12v. you are right the ignitor is just like a set of points in the old days just causes the field to collapse which causes hi voltage to the spark plugs. try looking at the engine in the dark and see if you see odd sparks going on. new dizzy cap and rotor might be in order.

RedZ31

Battery and terminals are 2 days old lol, I will wait for tonight to look for a "light show" under the hood. New plugs and wires also but again the spark is weak coming right out of the coil. Any idea exactly how this is grounded, aside from its bracket? I looked in my chilton but it proved to be useless yet again! Thanks for the reply.

RedZ31

Checked last night, no sparks to be seen, which would be a good thing but doesn't help me solve my problem. Checked battery voltage this morning, 12.25 steady. Then I checked voltage at the coil, 12 flat. Could a .25 voltage drop be enough to cause a weak but steady spark? Thinking of doing the whole "hot wire" thing that I hear on the 240 forums but I don't want to screw anything up!

Big Slappy Z

Check your PTU, or just go ahead and get this:

Upgrade to PRW-2 Ign. Control Module (Power Transistor Unit))

RedZ31

Hmm seems relatively simple. Thanks for the link! Ill see if I can't test this thing somehow, never heard of ptu before but the symptoms do match, though in rare occasions. Thanks for the input. Hope this thing doesn't just quit on me one day lol but I guess I'll know what's wrong then.

rogerz

pull the connector off the low side of the coil and be sure it isn't corroded. assuming you looked at the high side for corrosion. download the fsm from xenon z31. take the wiring diagrams on a thumb drive to kinkos and have them blow it up 11x17. makes it a lot easier to read. then you can trace down grounds and wires much easier.

RedZ31

Wow can't believe my luck, my brother has an old Prw 2 from his 240 laying in a "misc parts" box! Think ill do mod just for avail abilities sake.

RedZ31

Will look at the fsm and double check my grounds, thanks rogerz

RedZ31

Did the mod, worked but unfortunately didn't help the spark strength and still running like crap but at least now I have a little more pep and a 55 dollar part instead of 140 if it ever goes. I'm at a loss for what this could be ill post back if I find out anything, thanks for the help

rogerz

also possible the new coil you installed is bad. when I was a young pup and put new points into my 49 ford. it wouldn't run. my dad says well how do you know those points are good. so says I they are new - Ok but are they good. on close inspection found a manufacturing defect. Moral just cause new doesn't mean it is good. you could try just bumping the secondary with a hot wire off the battery an see what the spark looks like. if good then you got another problem if the same probably bad coil. beyond that I go back to is the battery good (load tested not just it is a new battery) Cables. corrosion free both ends. does the ground strap go to a bolt into the body first and then to the starter. grounding thru the starter is not a reliable connection. Z's no likee low voltage causes all sorts of gremlins.

RedZ31

Got me working 8 hours till Teusday, ill see if I can't rule at least some of that out. I'm really glad my rebuild has turned out successful (fingers crossed) so far, now I can concentrate on getting rid of the "gremlins" one by tedious one. For the hot wire, which one would be the secondary the blue or green wire?

RedZ31

Okay I had off today so I did some digging. Negative battery terminal goes directly to a ground on the firewall which grounds the starter, I believe. Did the whole Hotwire mod with some help from my bro, and still no change in spark strength! Again, car had a bit more pep but still missing at idle and slight hesitations while in the throttle. Might go get another coil (I returned the one I bought last week). 1 question, is the ecu grounded through its bracket at all?

RedZ31

Got ANOTHER coil from a different parts store...still orange! I'm literally at a loss. Starting to think I have a slight electrical problem any more suggestions anyone? Again all help is welcome at this point if someone said check my blinker fluid I'd do it!

trulywitit

did u ever get good spark again?
3 months w same prob but 280zx non turb.
Denise