Good news is that the compression test results were great: 190/180/190/190
This is on a 1995 Miata with an FMII kit.
I performed the compression test by unplugging the CAS and pulling the fuel injector fuse. Where I fear I may have screwed up, I pulled the fuse circled in red, and not the 30A Fuel injector fuse. I left the spark plugs and wires connected on the 3 cylinders I wasn't testing to minimize strain on the coil packs.
I double checked all the connectors and grounds. All spark plugs are wet and smell like fuel. I held one of the wires, with a plug inserted against the block and got zero spark. I figured somehow that I burned out the coil pack, so I replaced it with a known good pack with no change. All fuses are intact. Jumping GND and TEN, it throws code 12 for the TPS, which it's been throwing for a year or so. At this point my battery started getting weak so it's back on the charger...what am I missing?
What's your ECU? An FM II should have an aftermarket ECU, which means there should be no codes from jumping GND and TEN.
What you pulled was the main relay, not a fuse. When those fail, you get a car that will crank but won't do much else. I'm not sure if you'd get a prime squirt. Check for power on the white/red wire on an injector when the ignition is on.
I'm going to guess it's a problem with the CAS wiring - that harness is prone to failure from vibration, and you may have broken a wire when you disconnected it. You'd still have wet plugs due to the prime squirt, but no spark or fuel when cranking.
Running stock ECU with Bpipes band aid
Just to avoid confusion in the future, that's not what we'd call an FM II. It's a DIY kit that's closer to our Stage 1 (aka Voodoo II) kit. The important thing is that stock ECU, which is not found in an FM II. Just FYI.
I'd start by checking power at the white/red wire on an injector. Should be 12v with the ignition on.
Copy that. I actually thought it was a Voodoo kit when I purchased it. I just recently opened up the unmarked box and I was surprised to find it had "bpipes" stamped on the circuit board. I'll check the injectors next, thanks Keith!
Bipes, perhaps? That's a fairly old piece of kit, but decent. IIRC it only does timing, you may have something else going on with fuel. In the Bipes era, that would be a rising rate fuel pressure regulator. Care to share a pic?
So a few interesting things from this morning:
Swapped the injector relay with a known good relay. No joy.
After cycling the ignition, the engine runs roughly for 2-3 seconds and then dies. Every similar case I've found online points to the coil packs still being bad. Is there a chance the CAS itself died?
Went to go check the 12v wire on the injectors and of course my multi-meter is dead.
This was the original coil pack. Fairly certain that's bad. Kind of shocked considering all the precautions I took while testing compression.
Pics of the engine bay, no rising rate FPR. As a data point, when the car was running, it was absolutely pig rich. It also started the instant you turned the key.
From what I understand about Bpipes, it intercepts the CAS signal to retard timing, so it could be the culprit. For kicks I unplugged the battery for 10 minutes to see if anything would reset, still stumbles for 2 or 3 seconds and then dies.
Here's the bpipes itself. It looks like fueling is handled by this card from "Dobeck Performance" though the website doesn't list any Mazda applications and the board was printed in 2013.
Resolution: I bypassed the stock coil packs completely, stole a Toyota COPs setup off one of my other Miatas, and it immediately fired up. Guess my "good" spare coil pack, wasn't. Thanks again for all your help Keith!
That's a weird failure mode for coils. You were describing what happens when the ECU doesn't realize the car has started, so it turns off the fuel pump. The car runs for 2-3 seconds on the leftover fuel pressure from cranking before stumbling and dying.
I suspect you still have dodgy wiring at the CAS, but when you swapped the coils you got lucky and the broken wire is currently connected. I would strongly suggest a wiggle test on those wires near the CAS and coils when the car is running. MAF wiring is also possible but you didn't touch that when you were in there. You can also check the connections where the Bipes is patched in. More information here.
What you have there is an older Voodoo Box. And now you know who manufactures the boards :)
If it were an old Civic, a compression test is an excellent way to kill a coil...
Keith,
I had originally printed these instructions out, but it only bears a passing resemblance to the voodoo box that I have installed. Is there any more technical literature available on this older voodoo box (particularly what those two blue pots do)?
edit: Wiggle jiggled the CAS wiring before and after a shakedown run with no negative effects
Note to self: Don't do a compression check on any of my vehicles unless required.
With the main relay disconnected, there was no power to the coils so it's unlikely it caused a failure.
Email our CSR guys for the older Voodoo Box instructions. Those pots control the slope of the extra fuel and the onset of the O2 signal modifier.
Coincidentally enough, I emailed y'all last week and Mr. Anderson just responded a few minutes ago. He sent me a link to the Voodoo_Box_new.pdf and said the box itself shouldn't need any adjustment. I'll ask again
Feedyurhed said:
Note to self: Don't do a compression check on any of my vehicles unless required.
I've always done it by manually triggering the starter. So key nowhere near the ignition, computer off, no danger of this sort of trouble. Clip a switch to the starter solenoid and crank!
You obviously let the compression out....
