Author Topic: CA20E ignition queries  (Read 111 times)

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Offline Mister_T

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CA20E ignition queries
« on: May 12, 2019, 03:03AM »
A while back I used a timing light to figure out that the the exhaust side spark plugs were not getting spark. The intake side works fine.
The timing light showed that the exhaust coil lead was triggering the light but none of the exhaust plug leads would trigger the light.
Once the dizzy cap came off I could see that the rotor was rooted. The divider just outside of the exhaust contact ring had big holes eroded through it. Uh oh!
There is a bit of oil in the bottom of the dizzy and the shaft has more play than I think it should but otherwise it's not too bad inside.
So I bung in another rotor and no change. So I bung on another dizzy cap and no change.
That is when I pull off the exhaust coil lead to try to find a spark between the exhaust coil lead and ground. Oh dear, no spark. Why does the timing light trigger?
Just for fun I pull out the spark plugs for a look. The previous maintainer had put in Bosch spark plugs. While I don't like Bosch plugs after seeing how they fail in Z cars, these one looked ok. However I notice that the plugs are not consistent in heat range. So I research the Bosch plugs and figure out that all the FR8DCX are supposed to go in the intake side and all the FR7DCX are supposed to go in the exhaust side.

Out of curiosity I flip the coil leads around and try to run the engine on the exhaust plugs. It runs, sort of, but even when cranking it sounds like it is way too advanced. I flip the coil leads back to correct position and the engine is back to its normal.
Is that expected behaviour when the coil leads are swapped around?

While fiddling with the coil leads I notice that the exhaust coil is not the same as the intake coil. I guess somebody has replaced it in the past, perhaps hoping to make the exhaust side fire. The plot thickens.
I guess my next port of call will be the exhaust side "Spark Output Module" which in Z31 parlance would be a just a Power Transistor.

Once I get the ignition sorted I'll have a look into setting the timing by the book. Currently without going into "maintenance mode" the timing is sitting around 15 deg advance at idle. Does this sound about right? The whole diving under that dash to jump the terminals in a connector just to get codes and set the timing seems a bit excessive. It's probably simpler to put a simple compact switch in the dash somewhere and wire it to the connector.

Offline Pringles

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Re: CA20E ignition queries
« Reply #1 on: May 12, 2019, 02:05PM »
Have a squize at this for the coil and ECU operation conditions for the older model ... it's mostly the same.. just for the idea of operation

It's a trick of having all input into the ECU as happy.. ie correct levels and then the ECU in theory switches in and out your exhaust side coil.. That and if the coils themselves are wired backwards it will twist things up.. in that link above is a basic schematics of the signal path. By memory the ca20 fires that second set of coils (exhaust side) as a clean up for emotions.. thus it's a little later in The rotation.. potentially after DTC.. thus the poor running on the 2nd bank only..
..a fun trick is to disconnect the signal wire from the exhaust side coil and run a link from the signal wire on the intake coil... effectively a more consistent spark condition.. attempting to removing the coded spontaneous nature of the Boosh ECU in the ca20.. pwr1!
« Last Edit: May 12, 2019, 02:10PM by Pringles »
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Offline Mister_T

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Re: CA20E ignition queries
« Reply #2 on: May 13, 2019, 01:27AM »
Hi Pringles,
Thankyou for your time.

Yeah, between the Corsair FSM and the Gregorys manual that came with the car, the ignition system seems simple enough.

With the prospect of some overtime in this week's pay, I engaged in a fit of expenditure at Pick-A-Part wrecking in Campbellfield. A colleague of mine had spotted a Corsair there and the Pick-A-Part website still listed it.
Just a few weeks ago there had been a couple of Pintaras at DIY Auto Parts in Camp Road Broadmeadows, A Pinty T manual and an Exec auto, but those have apparently now gone. Jeez you have to be quick.
Some Melbournites may think of DIY Auto Parts as the wrecker formerly known as Andy's Autos.

Anyway, I scored a dizzy and whole coil/power transistor assembly. I like the way the whole lump comes of with 2 bolts and 1 connector.
It was reasonable weather to burn a log book day on the club rego'd bike but curiosity got the better of me and once again I lifted to bonnet of the 50-Shades-of-Brown Pintara, this time to swap out the coil/PTU assembly.

I now have spark on the exhaust side plugs. Howevar, I'm still not happy.  ::)
Using the timing light, the intake plugs fire as expected. The exhaust plugs fire way too fast, pretty much like having the timing light pickup on the coil lead. There seems to be some serious crossfire going on with the exhaust side. That should not happen with new a Bosch rotor and cap, unless the wobble in the dizzy shaft is a factor.
Admittedly all the leads are factory and may well be the original parts out the factory door 28 years ago. I have some spare leads sitting around so I'll give those a shot next time I get around to it.
I don't see any difference in timing between intake and exhaust, before or after the coil/PTU swap.

The spark out of the coil leads seems sort of ok. The spark is orange out of both coils and can stretch out to at least 10mm. I expect a bit better out of electronic triggered ignition. The spark out of my Z31 is blue and can easily stretch out to about 12mm, and that is a single coil feeding a 6 cylinder distributor.
So the old exhaust side Mitsubishi J121 Power Transistor is suspect, which is no surprise since I've seen similar J119's fail in first gen Mazda rotarys.
At least now I have a spare known good J121 and coil.
Also, it is easy to overlook the 2 condensers on the coils/PTU assembly which could be dubious. (Condensers? With electronic ignition? Sheesh.)
I'll have to figure out a way to test the condensers.

Offline Mister_T

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Re: CA20E ignition queries
« Reply #3 on: May 19, 2019, 11:43PM »
Once after work the car would not even start due to the crossfire so I had to disconnect the exhaust coil to get running.

Today the Bosch inductive leads that came with the spare dizzy came in handy. I fitted those leads to the exhaust side. The engine started fine and I checked all the exhaust leads with the timing light. All flashed exactly as they should. Win!
I let the engine warm up a bit and compared the intake timing with the exhaust timing. They are pretty close if not the same. just maybe 1 degree difference.
For shits and giggles I tested the old (original?) exhaust plugs leads with the multimeter. All but one were open circuit. The bad ones must be burned to shit inside if the spark preferred to jump around inside the dizzy and erode holes in the rotor instead of going down the leads.

Now that the high tension bits are running to spec, I figured I might as well check the timing and set it to spec. So I take off the panel on the passenger side of the console and go hunting for the check connector while keeping in mind the pictures and drawings I have seen in the Corsair FSM and Gregorys. Nup, can't find the check connector. Bugger.

I got antsy for a ride on the bike while the weather is still good so I called it a day on the 50-Shades-of-Brown Pintara with a solid win under the belt.
Maybe next time I'll pull the console panel off the driver side and have a look. The car has an aftermarket stereo so maybe the installer did something unwarranted back there in the dash.

The stereo itself is a decent Sony with USB input which I like. I've had to recode the music I want to travel with since this Sony does not handle "theoretically lossless" WMA sound files, not that I would hear the difference yet since the rear shelf speakers are cheapo rubbish and the front door speakers are totally rooted originals. I have a plan to replace the shitty rear speakers with a pair of old Pioneer TS-E1695's I have sitting around. They are pretty hefty for 6 inchers.

Onward and upward.