Forums/Z31P/z31-performance-upgrade-forums electronics-aa/No Ignition spark from Coil
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NewJerseyZ: (2014-08-18 14:44:48)
Hello,
OK, I'll admit it … I need some help. Perhaps some serious help. As the thread title suggests, I have no spark coming from my ignition coil, as I pulled the main high tension cable off from the distributor cap to see if it would make a spark to ground on a frame bolt. Nothing. So obviously, no plug is getting any spark. Overall, here's what's been done on the car so far:
1) The ECU has been upgraded to a Jim Wolf unit for my make/model. (1985 Turbo 5-speed GL)
2) A/C unit has been completely removed.
3) Still has factory turbo but waste gate re-adjusted mechanically to 12 lbs boost. (Higher flow injectors installed --- 420. Matched to ECU)
4) Power transistor upgraded to PRW-2 and re-wired correctly. (2-wire swap)
5) Electric water pump. (Direct drive unit with PWM controller --- no conventional thermostat)
6) Electric fan (switched on/off via thermostatic switch in radiator)
7) Engine cooldown circuit installed (SS Delay-relay controlled for water pump and fan)
8) Euro cams
9) Ported heads
10) Titan alternator
11) 3-Bar fuel pressure regulator
Things I have checked so far:
1) I am getting +12V to the coil's primary (voltmeter on green/red wire)
2) Engine cranks just fine
3) Fuel pump works just fine (stock as of now --- to be upgraded)
4) Cooldown circuit works just fine as well (works as designed --- timing and shutdown)
A friend of mine (who's an electrical engineer, I'm a physics/math instructor) helped me with all electricals and mods. Basically, I'm at a a loss, so any suggestions would be greatly appreciated.
Thank you.
les_joey_paul: (2014-08-18 14:51:58)
Ohm check the coil. Confirm that the ignition control module (prw2) is working. It needs to get signal through that to fire the coil. Also make sure if that's how you are checking spark, that you are putting a small Alan key or something into the lead of that boot. Then watch it jump from the lead to your ground.
NewJerseyZ: (2014-08-18 15:10:22)
Thank you for the quick reply.
Here's what I measured …
Coil primary resistance ~1.3 ohms
PRW-2 ground to chassis bolt ~ 5.3 ohms
As for checking for spark, the boot end that came off the distributor does expose some spring metal which when placed right up to a chassis bolt should make a spark --- but nothing.
Not exactly sure how to test workings of ignition module (PRW-2) other than swapping it out. I have nothing right now available to do that.
les_joey_paul: (2014-08-18 15:22:20)
Hmm. Are you using the factory fsm to trouble shoot?
Also are you sure the wires are installed properly on the prw2? I had this issue when I swapped mine in. Have you touched anything else?
NewJerseyZ: (2014-08-18 15:32:08)
Yes, I in fact have the original 1985 FSM … got it a month after I bought the car. (Yes, you've got an original owner here.) My friend and I were extremely careful in re-wring the PRW-2; triple checked everything. I am using the +12V input to the coil as a signal switch for the SS delay relay --- so that is being pigtailed, but the splice checked out continuity-wise. The ECU (I believe) is what grounds out the coil according to engine RPM in order to produce the primary going from 0 to +12 to 0 over and over to achieve an induced high-voltage to the secondary. So in other words, I don't believe the pigtail (which only draws a few milliamps) does anything detrimental.
les_joey_paul: (2014-08-18 15:42:41)
Try bypassing your splice. Current will want to flow the path of least resistance. Everything should work if it's how your describing, except this delay relay your talking about
NewJerseyZ: (2014-08-18 15:49:34)
Sounds reasonable and would lay to rest if tapping off the primary is an issue. But just one thing … this will stop my cooldown circuit entirely, and my water pump and fan will no longer work at all. I'll need to obtain another source of +12V to trigger the system --- a +12V tap that is hot ONLY when the engine is in running mode, not accessory.
If you would like, I can post the circuit for the engine cooldown which allows for the fan/water pump to run at speed for a set time after the ignition is off. This pretty much eliminates the need to sit and wait for cooldown after a long hot run since the engine is completely off, yet coolant (being cooled by the fan through the radiator) circulates through the block and turbo without any exhaust heat in the housing.
les_joey_paul: (2014-08-18 15:53:10)
You can probe around the engine bay, try the egr control solenoid connector or the fpr solenoid connector. Or just wire it to the battery with a fuse in line (if you wish for it to run with the car off (I'm not 100% on what the circuit is for)
Just make sure if your tapping a solenoid or something, that your creating a parallel circuit by grounding it too.
les_joey_paul: (2014-08-18 15:55:04)
I've heard of this being an issue with using ignition 12v signal to power a fan control module.
les_joey_paul: (2014-08-18 16:26:33)
Does your controller have a hard wire to the battery to keep it running when the ignition is off? Or capacitors? O:
les_joey_paul: (2014-08-18 16:27:58)
Sounds reasonable and would lay to rest if tapping off the primary is an issue. But just one thing … this will stop my cooldown circuit entirely, and my water pump and fan will no longer work at all. I'll need to obtain another source of +12V to trigger the system --- a +12V tap that is hot ONLY when the engine is in running mode, not accessory.
If you would like, I can post the circuit for the engine cooldown which allows for the fan/water pump to run at speed for a set time after the ignition is off. This pretty much eliminates the need to sit and wait for cooldown after a long hot run since the engine is completely off, yet coolant (being cooled by the fan through the radiator) circulates through the block and turbo without any exhaust heat in the housing.
Lol I don't mean to be spamming. If you want to post or pm the schematic that will help.
NewJerseyZ: (2014-08-18 16:45:58)
OK … some updates.
I eliminated the splice with it having no change in anything, except for the fan/water pump not running.
I have tried to find a +12V tap prior to using the primary coil feed. The most I found was an occasional +7.2V here and there. But I will try your solenoid suggestions. (The EGR solenoid would be nice, since I blocked off the valve port --- it's still electrically/vacuum connected to prevent a fault code.) The pump controller does use a hard wire to the battery (+12 and ground) and is chassis star grounded along with the relays and fan. Basically, all my electronic mods are isolated from everything else, except for the +12V signal tap on the delay relay. Below is the schematic for the cooldown circuit --- the "ignition switch" is the +12V tap. Hope all this helps.
300ZX Cooldown Circuit.jpg
les_joey_paul: (2014-08-18 16:58:32)
Next try switching some of the connectors on the prw2
jaqattack02: (2014-08-18 19:04:20)
If you pull the distributor and spin it, do you get any clicking from the injectors firing? If not, you most likely have a bad CAS. The CAS (crank angle sensor) controls both the spark and opening of the injectors.
NewJerseyZ: (2014-08-18 19:18:00)
I believe the injectors are squirting, as after 10 or so seconds of engine cranking one can smell gasoline fumes out the tailpipe. Faint, but clearly noticeable.
There not being any spark at all going to the cap/rotor seems to me to be the major issue.
les_joey_paul: (2014-08-18 19:36:57)
Can you run self diagnosis with that ecu?
NewJerseyZ: (2014-08-19 00:19:25)
Good question. I wish I had as good an answer. I don't recall anything about JWT ECU's having self diagnosis, but I will be trying this series of tests. (It includes the CAS among others.)
jaqattack02: (2014-08-19 02:19:02)
The CAS is what tells the coil to send a spark to the cap. Seriously, pull the distributor and spin it with the key on. If the injectors click and no spark it's something else. If you get no spark and no injectors clicks then it's the CAS.
NewJerseyZ: (2014-08-19 02:24:35)
OK … will try that tomorrow and give an update on results.
Thanks for all the suggestions. [archived image: smile.png]
NewJerseyZ: (2014-08-19 21:33:19)
Distributor has spun …
Well, it certainly sounded like the injectors were clicking (and squirting?) as I rotated the rotor by hand with the unit out of its gear. I guess this means it's the PRW-2 module, eh?
PS: I made a mark on the distributor's inner shield relative to the rotor's initial location and re-inserted it so that it was in the exact same spot. Is it possible since the crank angle sensor is in the distributor head, that it's 360 degrees off? … given that the crank rotates 720 degrees for every 360 for the distributor. Does it matter? I didn't count how many rotations I made with the rotor. (Insert Homer Simpson DOH)
les_joey_paul: (2014-08-19 22:01:40)
You should set the engine to tdc on cylinder 1 and just install the distributor per the fsm. To rule out the possibility of it being installed incorrectly to begin with.
C.Gesler: (2014-08-20 00:44:50)
did you happen to check the secondary side of the coil.
NewJerseyZ: (2014-08-20 04:13:40)
Here are resistance values for the coil and ignition module (PRW-2):
Primary input - Primary return = 1.3 ohms
Primary input - Chassis Ground = Infinite
Primary return - Chassis Ground = Infinite
Primary input - Secondary output = 9.17 kOhms (9170 ohms)
Primary return - Secondary output = 9.17 kOhms (9170 ohms)
Secondary output - Chassis Ground = Infinite
PWR-2 Ground - Chassis Ground = 5.3 ohms (not a perfect ground, but should not be the issue)
So basically, the coil is isolated from the chassis; no shorting to ground. Both the primary input and return against the secondary output are the same, which is expected given that the coil is technically an autotransformer. Anyway, everything seems to be within spec.
C.Gesler: (2014-08-20 13:21:09)
Correct me if im wrong but primary positive and secondary positive should be open only the ground from primary and secondary should utilize the same connection
if you are getting a closed circuit from primary + to secondary + then I would say you have a bad coil
NewJerseyZ: (2014-08-20 15:10:17)
Ooops, I believe you're right. It was late when I took the readings (I'm in NJ, as my name suggests).
Going to check again and get back to you --- but if my numbers were correct, then I do have a bad coil.
C.Gesler: (2014-08-20 15:19:09)
1408547770809.jpg
Sorry I have that backwards primary and secondary + share the same connection, primary - and secondary - should be open
NewJerseyZ: (2014-08-20 15:52:22)
On second/third thoughts I'm not so sure about your comments above (and my previous Ooops comment). Both the Primary positive and Primary return (negative on primary) do go to the Secondary output (from coil to the plug), but differ only by the primary's internal resistance, in my case 1.3 ohms. (That's why the meter showed basically the same 9.17kohms for each --- too small a measurable difference on that scale.) Look at your diagram (and mine from 2 comments ago). An ohmmeter placed between the switch and the end of the primary (primary negative) and the output of the secondary (before the plug) will see the majority (99.99%) of resistance through the secondary; continuity is achieved by going in reverse through the primary. However, compared to the secondary, the primary winding is like a piece of wire. (Remember, it's in some ways an Autotransformer, not a basic transformer.) About 10 amps or so will flow through the primary yet none through the secondary since the spark plug gap makes it an open DC circuit --- this basically makes the battery's current negligible in the secondary, essentially isolating it. This then allows the secondary's windings to charge accordingly to the turns ratio between the two (primary/secondary). The "switch" is in the ECU as I pretty much thought from the beginning.
C.Gesler: (2014-08-20 19:54:13)
Ok I see what you are saying. Shouldn't you be getting more than 9.17k ohms if you are going from primary return to secondary return or if that is through both windings then you should have less than 9.17k ohms in the secondary windings.
Shouldn't you be getting three different readings
primary
secondary
primary+secondary
sorry if im making this confusing this helps me learn a thing or too. [archived image: wink.png]
NewJerseyZ: (2014-08-20 20:26:07)
The difference is going to be the internal resistance of the primary, which is only 1.3 ohms ---- so you are correct in that there will be different resistances. But take note that when using the kilo-ohm scale, a mere 1.3 ohms won't show up. It's no different that a piece of ordinary wire attached. Negligible. It's 9170 vs. 9171.3 ohms.
C.Gesler: (2014-08-20 20:39:23)
Ok I see that does make sence
You might be right about the prw-2 then
NewJerseyZ: (2014-08-22 02:28:52)
Before I go and spring for another PRW-2 ignition module, I recall having a similar problem with another car … my 1991 Acura Integra. It too is a manual 5-speed, and over time it slowly began having starting problems. It would crank longer and longer (over the course of several weeks) before starting. It turned out to be something called an Ignition Relay. Once replaced, it started every time like new. Does the 1985 300ZX Turbo 5-speed have a similar relay? And if so, exactly where is it located?
Thanks.
les_joey_paul: (2014-08-22 02:37:01)
I think under the driver side steering column area. By the fuse box.
NewJerseyZ: (2014-08-22 02:37:10)
OK … a little research led me to this page at Courtesy Parts.
It appears to be part 25220G … about $22. Not bad for an exact OEM replacement.
Any thoughts on my conclusion?
NewJerseyZ: (2014-08-22 02:38:15)
I think under the driver side steering column area. By the fuse box.
Yes, that seems to be correct from the diagram on the website.
Thanks. [archived image: smile.png]
NewJerseyZ: (2014-08-23 19:21:50)
Well, I tried swapping the ignition relay with another similar relay (next in line on the bracket) and the result was no different than before … no spark.
I think the only possible solution at this time is swapping the PRW-2 module with another one. I wish there was a way to determine if it is malfunctioning before springing for another one.
Any suggestions?
jaqattack02: (2014-08-24 02:09:24)
I assume you've already verified that your PRW-2 is wired correctly? I'd honestly be surprised if it's bad, as I've yet to see one go bad yet.
NewJerseyZ: (2014-08-24 02:39:43)
I assume you've already verified that your PRW-2 is wired correctly? I'd honestly be surprised if it's bad, as I've yet to see one go bad yet.
No offense, but my friend, who's an electronics engineer, and I were very very careful when doing the 2-wire swap on the connector. We triple checked everything.
I do understand your questioning this as nothing else would seem to be the problem, it's just that after making the connections we sealed everything up really well and all that careful work might have to be done from scratch as it would have to be ripped apart --- and then (of course) to find that it was all done correctly. Remember, I do get +12V to the coil primary when the ignition is switched to the "run" position. Is there any way to determine if the unit is good without taking things apart? Like connecting the terminals to a scope? --- my friend has one, but it might be a while before he can get it over to my place.
NewJerseyZ: (2014-09-03 01:47:15)
OK … back from vacation and back to the Z.
I'm going to try and get my friend to come out my way either this coming weekend or next with some testing equipment.
I will update on any news (good/bad) as soon as I delve deeper into this mess.
Thanks again for all the help/suggestions.
NewJerseyZ: (2014-09-08 02:43:20)
Well, I think the problem is solved --- the problem being the PRW-2 transistor module.
I took it this weekend out to my EE friend and did some basic tests. We found it to be an N-P-N transistor showing continuity from Emitter (center pin) to Base (right pin, facing module pins with lettering topside) in both directions (reversing tester polarity). This junction (Emitter to Base) is a diode junction and should only show continuity in one direction. It displayed test current both ways. All other junctions tested correctly (as per the 1985 shop manual page EF&EC - 46 accounting for different pin locations 2 and 3), however the E-B junction failed. And that's all it takes to know the unit is … fried! I guess I should be happy … the shop manual indicated that if the module tested good, the fault is in the E.C.C.U. and needs to be replaced. So it's off to get a replacement … this time a good new one from a reputable establishment, not eBay (which is where I bought this one). [Go ahead … I deserve it!]
One other thing … my friend noticed something on the underside of the unit I never paid attention to. A small white cross made with a white marker. I said to him jokingly, "That's an X to indicate it's no f--king good." Then I realized, that's probably exactly why it's there.
NewJerseyZ: (2014-09-11 19:10:22)
Maybe not …
Preliminary testing of the new Bosch PRW-2A (arrived today) from Rock Auto shows the same continuity values as the older unit … which (when accounting for the contact swap between it and the old power transistor) is in need of replacement according to the Nissan shop manual for my model year car. So what gives? Either both units are bad (how likely is that?) or the noted wire swap is somehow in error. No combination of continuity testing shows the units to be in any way electronically different. Does anyone here have (or know of) the detailed schematic of either the old OEM power transistor or the PRW-2?
C.Gesler: (2014-09-18 17:38:38)
Any luck yet
jaqattack02: (2014-09-19 03:15:45)
Why don't you get someone to send you a tested, known good transistor/prw-2? That way it will eliminate that as a possibility.
NewJerseyZ: (2014-09-28 13:36:44)
OK … it's been a while and I'm sure some are wondering if I fell off the planet. But truth be told, my electronics friend was on vacation and finally got back yesterday … to my place, that is. He brought his scope and other various tools of the trade. Here's what we found out …
1) There was a pulse signal to the PRW-2 transistor. This confirmed that the ECU was at least working in that regard. It also meant that the distributor was working properly; crank-angle sensors, etc. (tested while cranking)
2) We saw +12V going to the positive side of the coil. (checked for with ignition on as if car was running)
3) We did not see however +12V on the negative side of the coil. (checked as in step 2)
This made us suspect that the coil was defective. My friend suggested we check the connector 2-wire plug on the coil --- we removed the rubber boot and it looked fine. We placed it back on to check and see if the ground was good in the power transistor (emitter). I don't know why, but my friend asked me once more to crank the engine to see if any sort of pulse could be detected. The car cranked … and then started up. It started up for the very first time after all the mods and, tests and checks.
The problem was simply that the connectors on the OEM coil were somehow either lose or oxidized enough to prevent a good connection. All our testing with needle probes being shoved into the plug contacts here, there and everywhere in-between must have either removed enough corrosion and/or tightened up their spring tension.
To quote Toyota .. "Oh what a feeling!"
(It's OK … I used to own a Celica) [archived image: biggrin.png]