RX744CSP

iTrader: (4)

This is driving me batshit.

I am running an S4 turbo with a stock N333 ECU and have *no* spark on the trailing ignition on the rear rotor, leading is fine on both and I have trailing on the front rotor (more on that in a moment). So far, I have:

done a 'pinout' on each wire multiple times to include wiggling the wires to see if there's a bad spot, no joy,

swapped a known good trailing coil/igniter,

swapped another ECU (an N332),

verified voltage on each wire at the trailing coil/igniter (the one weird thing: the FSM says the blue/red wire should have ~2 volts, it has battery voltage with both ECU's)

swapped two different knock boxes and knock sensors just in case there's a limp mode,

swapped a CAS,

and the problem is still there. Once or twice in all my fiddling I have lost trailing spark on the front rotor (i.e. no trailing ignition at all) but it's come back each time. This happened with both ECU's.

It's my understanding that S5's kill the trailing spark and drop the fuel pump voltage to go into 'limp' if the electronic OMP quits. S4's don't have the electronic OMP and as far as I know don't have a limp mode. Am I wrong? If so what puts it in limp?

Anybody have any ideas? I'm stumped.

monty11ez

Have you checked the grounding block right under the coils?

misterstyx69

iTrader: (142)

are you premixing?

satch

iTrader: (1)

When you checked the Blue/Red wire did you check the voltage at the coil plug or at the ECU? Mine reads 1.3 volts while idling as measured at the ECU. Also, the igniter in the coil requires good contact w/the fender to assure a proper grounding or the coil will not fire. Perhaps sanding down the contact point is needed.

RX744CSP

iTrader: (4)

I'm not premixing, this being an S4 it has a mechanical OMP and shouldn't be able to go into limp, when S5's do that they lower the fuel pressure and kill the trailing ignition.

There's some confusion out there concerning the possibility of a bad knock box making the ECU go into limp. It's my understanding S5's will do that (the knock box is integrated into the S5 ECU though) but on S4's it's unclear.

So is there anything at all which will make an S4 go into limp?

I checked the red/blue at the coil plug, a buddy with an N/A car checked his and got the same reading, i.e. approx battery voltage. His trailing ignition does work.

I was reading up on aaroncake's ground stuff, I'm going to do that.

There is a possibility the RPM side of the CAS is wired backwards, that means the pickup's signal would be incorrect. I'm at work now so can't check it. But that is on my short list of things to check.

satch

iTrader: (1)

Did you have the coil plug unplugged to take a reading? The wire is a feedback signal to the ECU so it needs to be plugged in and idling to get the same reading as stated in the FSM (below 2v).

And do you have a spare CAS?

RX744CSP

iTrader: (4)

Ah, that makes sense now.

I have two spare CAS's and swapped a known good one last night, no joy.

I did verify power to both trailing coils, popped the plastic covers off and checked directly at the power terminals.

The really weird thing is how I have no spark on the trailing rotor only. That makes ~no~ sense. When running the engine, I do get ~2.5 volts at the 'select signal' wire (IIRC that's blue/yellow but not looking at it right now), the aforementioned blue/red had battery voltage (but that was with the plug disconnected), almost nothing on the yellow/blue (tach trigger, the tach does work) and approx .08v on the brown/yellow.

satch

iTrader: (1)

Your problem could very well be caused by a fouled spark plug and or plug wire though you could switch out a known working plug and wire to test this. Also, the select signal wire, Brown/Yellow-pin 1U, could be problematic. This signal tells the trailing coil whether to fire the front rotor or the rear rotor.

And the timing signal, pin 1x-Blue/Yellow wire, should have 0 volts w/key to on and then as the engine is rotated by hand via rotating the alternator pulley, the voltage should rise to 5 volts briefly before returning back to 0 volts. When the voltage is one reading the select signal decides whether to fire the front or rear rotor. When the timing signal changes then it causes the select signal to fire the opposite rotor.

RX744CSP

iTrader: (4)

Very good information on the voltage rise/drop, thank you.

On the spark plug/wire, I've swapped them as well. When I use my inductive timing light it will flash on the front trailing plug wire but not the rear. I swapped the trailing wires and trailing plugs from the front to the rear rotor, no change.

I'm wondering if perhaps the wires for one of the pickups in the CAS are swapped in the connector, this would mean the signal would be incorrect.

satch

iTrader: (1)

Perhaps pulling the rear trailing coil wire boot from its bore and placing the plug wire within a fraction of the coil bore and turning the engine over is the best way to test for spark. Timing lights are rather finicky w/respect to rotary engines especially as it relates to the trailing side of things.

RX744CSP

iTrader: (4)

Well, after running through the checks again I now have spark. I must have inadvertently fixed a bad connection somewhere along the line (probably on the select signal wire), it sure would be nice to know where it was in case this happens again. Thanks for the replies!

Turbonut

iTrader: (1)

Unusual that the trailing spark returned, so keep an eye on the problem and check occasionally with the timing light, as long as it's the normal run of the mill light, but if a sophisticated light, e.g., Snap-On, the light will light, but the plug isn't firing.

Been a long time ago, but the S4's were know for the trailing plugs not firing after a very short period of time because of a design flaw.