No spark on cylinders 2,4,6,8

[92sc400]

I bought a 92 Q45 about a month ago .It didnt have a motor in it but it came with a jdm engine and transmission.I swapped the engine and transmission in about two weeks ago got everything all hooked up.But Im not getting any spark on cylinders 2,4,6,8, throwing code 21 ignition signal circuit.I checked all connections. I have four igniters that I have tried and still nothing.The driverside bank of cylinders is getting spark.I tested all the igniters and coil packs on that side and they all work.I was wondering if there is seperate relays or something for the left and right banks of cylinders.I have been reading on here for the past month and have found a lot of info.But I cant find anything about my problem.This is my first post on here.So any information would help.Thanks

[goody90q45]

Did you bolt down the ground wire which is part of the ignition (spark plug) coil harness? IIRC, it bolts in at about #8 cylinder.

[Q45tech]

Just like injectors all coils [both banks] are feed +12 from a common point. The other side of each primary coil winding supplies power to each transistor inside ignitor. Measure to make sure +12 is getting to passenger bank pull a connector off coil look for +12 [if not a harness/connector problem].Try a replacement ecu............I believe that there is an IC for each bank on ecu board to drive igniter?

[92sc400]

Yea all the ground wires are hooked up.I checked the voltage coming out of the ecu.Pins 1,2,3,11,12,13,14,15.I havnt used a multimeter very much so im not sure I did it right ,but there is a difference between them.Pins 1,3,11 and 13 are LH and my readings were really low they barely moved the needle,this is while Im cranking the engine.But the other pins made the needle jump pretty good.The motor was already out when I got the car.Maybe the messed something up while they were pulling out the engine that messed up the ecu. I dont know.But thanks for the replys.

[Q45tech]

Like for the injectors the ecu just provides a ground pulse to the ignitor circuit which does the same for coil..................70-140 millivolts depending on rpm from ecu. to ignitor.

[92sc400]

if I check the plug thats coming from the ecu that plugs into the igniter, what am I looking for?Volts?

[Q45tech]

Not the way to do it as the voltage flows back from ignitor to ecu [ecu transistor acts as a switched ground].

You need to tap the circuit intact and look at dwell............visualize how an old points ignition worked [ecu acts as the points]. Except that it feeds the base of an NPN transistor [in ignitor] which handles the 6amp switching of coil.

Remember the coil fires when the points are opened and the primary current collaspes.

If these ecu transistors blow open in their junction the never can close to tell the transistor in ignitor to switch. or even to charge coil.

[92sc400]

So do you think it could be the ecu.Do you know of anyone that has a spare?

[goody90q45]

So do you think it could be the ecu. Do you know of anyone that has a spare?

Here's a couple for sale in the Infiniti Parts Forum:

zerothread/276440

[92sc400]

So the coils have a constant 12v and the ecu provides the ground right?Well I took a tester light and provided a 12v power source to the clamp and used the pointer and tested the pins on the ecu and four out of the 8 pins barely lit up the tester.I tested it with just the key on and while turning it over. 4 of the pins are dim even without turning the engine over. Is there any electrical components between the igniter plug and the ecu. I checked the plugs that plug into the igniters and the readings were different between the left and right banks.I dont know if this is normal or not.

[Q45tech]

Looks like it's an ecu failure.........................when dealing with transistors the term provides a ground is some what appropriate.

Actually as I mentioned earlier the ecu terminals should provide +100 millivolts 1/10 of a volt to the transistor base terminal in ignitor. This voltage causes the transistor in ignitor to conduct [like grounding the coil].

A test light tells no nothing I need accurate voltage readings from ecu terminal.

[92sc400]

I checked the volts on the driverside bank plug that plugs into the igniter and they read about 18v and when I crank the engine the needle bounces. When I did the same thing to the passenger side bank the needle reads 18v on 3 of the pins and about 12v on bottom far left pin its copper colored.The bottom and top far left pins(white wires going into the plug) barely read at all.But the needle dont move when I crank the engine on any of the pins the volts just stay the same.I really apreciate the help so far.Thanks

[92sc400]

I think I got the ignition thing figured out.There is three wires on each of the coil plugs.A positive a ground and the one coming from the ecu is the signal wire.The positive one comes from the ignition relay and provides the power to the coils,and the ecu and the igniter control the coils.Does this sound right?

[Q45tech]

Just like all the drawings and written explanation in the FSM............recreating the wheel without an FSM is time wasteful.

[mxr662]

I think I got the ignition thing figured out.There is three wires on each of the coil plugs.A positive a ground and the one coming from the ecu is the signal wire.The positive one comes from the ignition relay and provides the power to the coils,and the ecu and the igniter control the coils.Does this sound right?

Black is ground. Black/Yellow is +12v when key is on. The other wire, which is a different color at each coil, comes from the power transistor. The power transistor then is connected to the ECU.

I would try swapping the power transistor from the other side to see if the problem goes away. But also would like to here from some of the experts here before I tried swapping it.


Modified by mxr662 at 7:44 PM 1/12/2008

[92sc400]

I got the ignition thing figured out.I had the plugs switched around that went to the igniter. I didnt think they would have made the plugs interchange like that.But now it backfires through the intake.The only code its giving is 34 the knock sensor.But thanks to everyone that has replied.I learned a lot about the ignition system.

[Q45tech]

That's pretty amazing since one plug has 4 and the other plug 5 pins

[92sc400]

The plug that got switched was one of the 3 plugs above number 8 cylinder.I adjusted the crank angle sensor all the way counterclockwise.It doesnt backfire through the intake as much but I can still here it a little.

[Unnatural1]

Just a suggestion for later automotive electrical problems. Ditch the test light and the analog voltmeter. They are nearly useless on modern electrical systems and can damage sensitive modules if you probe the wrong wire. Buy an auto ranging DIGITAL multimeter that can read volts, Ohms, and amps. These can be had for a reasonable price. I think the Sears Craftsman version is about $25. It will save you some time and guess work.

As for the test light...don't replace it at all. I've never used one at work and I'm guessing Q45Tech doesn't use them that often.

Get the factory service manual for the Q also. It's like trying to drive blind with out one. Good work though getting everything running. It can be frustrating to put everything together and have it not work. Sounds like you've got the problem beat though.

[92sc400]

I have the workshop manual.The short thick one.It came with the car.It just takes a while to go through it to find exactly what your looking for.This is the first time I have ever worked on an infiniti and this kind of ignition with the seperate coils and everything.But Im still getting a little bit of a backfire through the intake.The crank angle sensor shouldnt have to be turned all the way to the left.Any ideas?

[Q45tech]

Use a timing light to set CAS correctly as the very first step to diagnosis.

THE CAS should never need adjusting once set at factory. and then only a microscopic movement of a few degrees out of 45 degree range!

Without ignition on that bank running engine would fill cylinders with fuel and really mess up oil...............wet plugs...............usually takes a few minutes of running to clear

[92sc400]

So why do you think its backfiring through the intake with the CAS turned all the way to the left?Its firing while the intake valves are still open right?Can I just unplug one coil at a time and see what cylinder is causing the backfire?Any suggestions would be great.Thanks

[Unnatural1]

It sounds like you've got the ignition timing fully retarded. This is a guess on my part because I have not had to set timing on my Q45. But, judging from the rough running and back firing engine, this seems to be the case. You also said the sensor is turned fully to the left. Again, not the expert but I'm betting that is the wrong angle for the sensor to be at.

Regardless of any of that...have you checked the current engine timing with a timing light? Is at 15* +/- 2*? If not you need to adjust the cam sensor to obtain the correct base timing per the service manual. Then, you need to allow the engine to burn through the excess fuel that is left over in the cylinders. Only after getting the timing correct should you worry about diagnosing any other component as Q45Tech said.

[Q45tech]

The engine coolant must be warm before the final ignition advance set. Because the cooant temp sensor signals ecu to advance timing during warm up!

CAS is one sensor you never move without expert knowledge!

[scs13]

im having this same problem in my vh45 s13, just posted a thread in the vh forum.