...does it cut off the engine?
...does it cut off the engine?
Well, lots of cars have a fuel pump cutoff or similar that will shut the fuel pump down after a high inertia event.
I dunno if the Miata has something similar.
I don't believe so. From memory, the airbags are on a completely self-contained harness. That's based mostly on NAs, I'd have to check wiring diagrams for NBs but I don't think so.
No inertia sensor, the fuel pump shuts off if the engine stops running.
Hmm...
Engine looks unharmed after my wreck (other than busted things like intercooler piping and radiator).
Trying to figure out why it won't start...
Cranks but no start? Any impact near the crank pulley? Anywhere else?
In reply to Keith Tanner :
Yes. Cranks but no start.
Still trying to figure out impact. There was impact near crank pulley, but it does not appear it was hit. Accessory belt was knocked off, but none of the pulleys appear bent or misaligned.
LH chassis horn was folded against the hoses pushed into the accessory pulleys. Impact was diagonal, not straight back into engine.
The alternator pulley had contact, so I can't rule it out.
The crank sensor may have been bumped enough to move it more than 0.040" from the teeth, which means no signal and the ECU won't try to start the car. I know you have both a factory and an MS2 for it, which one is installed? I'd be tempted to plug in to whichever one it is and do a sanity check on what it sees.
In reply to Keith Tanner :
That's an excellent thought!
I won't be able to check for a few days. I'll get back to you...
I'm out of state right now, but just checked my pics...
Keith, you may have nailed it.
I've got access to my manuals now, I can confirm there is no connection between the airbag system and anything else of note. Weirdly, there's a connection to the TNS (tailight/marker light) relay that I'm going to have to chase down. But nothing to the ECU or anything related to running the engine.
Here's the list of reasons Mazda gives for "cranks but does not start" with a stock ECU. Interesting things in there: the camshaft sensor is on the front of the valve cover and is a little fragile. If you're running a stock ECU, I would expect no MAF signal to be a cough and die situation instead of a no start, but I could be wrong.
No battery power supply to PCM
Air leakage from intake‐air system
Open PCM ground or vehicle body ground
Improper operation of IAC valve
EGR valve malfunction
No signal from CKP sensor or CMP sensor due to sensor, related wire or incorrect installation (note: crank or camshaft sensor)
Low engine compression
Vacuum leakage
Spark leakage from high‐tension leads
Poor fuel quality
PCV valve malfunction
Air cleaner restriction
Restriction in exhaust system
Disconnected electrical connector
Open or short circuit in fuel pump and related harness
Inadequate fuel pressure
Fuel pump mechanical malfunction
Fuel leakage from injector
Fuel injector clogged
Purge solenoid valve malfunction
Luckily crank sensor air gap is pretty easy to check. IIRC you should also see an RPM count while cranking if you have an OBD-II scanner reading real-time engine speed, or an equivalent signal from an MS2.
If you want to really mess with a Miata troubleshooter, install the trigger wheel behind the crank pulley backwards. Everything will look totally normal but the teeth will be in the wrong place and there's no way it'll run. Unlikely to be the situation here as it requires disassembly and reassembly, you've only done the former :)
In reply to Keith Tanner :
Keith Tanner said:Weirdly, there's a connection to the TNS (tailight/marker light) relay that I'm going to have to chase down. But nothing to the ECU or anything related to running the engine.
Could that be to trigger the 4-ways? I know a lot of cars will automatically turn on the blinkers if they get into a collision that triggers airbags, but I don't know if they need to be modern enough to do it over CANBUS...
You wouldn't need CAN to do that, but not in this case. Back to the manual because I want to know.
Ha, it's to make the "passenger airbag deactivated" indicator light dim when the lights are on.
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