M-Tuned

iTrader: (6)

Okay.. Here is the story.. Don't laugh!

I was out at a Time Attack event with my Miata and the car was running very well. I was coming into a corner and suddenly I lost all power to the engine. I coasted onto the grass thinking nothing of it.
Look into my rear view and saw Black Fire like smoke. Ran out of the car and my Dual exhaust was like a pair of Flame throwers. Got the mini-fires out and tried to start the car. NOTHING!
So I went to grab my laptop behind the seat and when I grabbed it I found the plastic connector (2 Piece) on the $5 DB9 Cable had come apart and the wires on the DB9 had shorted out.

So here is my first guess.. This shorted out my Megasquirt and the computer just started dumping fuel into my motor. When I removed the plugs and cranked the motor I had a ton of fuel coming out of the engine.

Sooooo.. I was planning to put the car away for the winter this week, so I might just re-install the stock injectors and ecu and fire it up to make sure all is okay.
Where would you recommend I send the Megasquirt for testing/repair? DIYAUTOTUNE?

Oh well.. Towed the car home, sitting in the driveway with a little clearcoat damage on the back bumper due to the flames. Easy Fix! Hopefully the ecu issue is as easy to fix.

BE CAREFUL WITH YOUR DB9 CABLE. MY $5 cable cost me a $120 Lapping/Time Attack Day, never mind my costs to get the Miata running again.

Any thoughts or suggestions would be great!

jwarriner

Where did you buy the components for the 'Squirt? They should at least be able to give you steps to test the components, I'd think.

M-Tuned

iTrader: (6)

I bought it pre-built and i'm not an electronics guru.. I think I am going to put the stock ecu and injectors in. If the car runs then I know it is the MS unit.

Matt Cramer

If you bought it pre-built from us, we can take care of it although probably not under warranty. Send us an email at websales@diyautotune.com if you want to set that up.

M-Tuned

iTrader: (6)

Matt.. I just emailed you, but was wondering if you have heard of this type of thing happening before? Might save me putting my car back to stock to make sure everything is okay.

Just want to get it running again before it gets very cold here.. I hate putting cars away for the winter broken

Matt Cramer

Sorry, but this is the first time I've seen "death by shorted DB9 cable" happen. It's definitely a theoretical possibility, but the failure rate on the cables is so low that yours may be the first reported case.

M-Tuned

iTrader: (6)

Just installed the stock injectors and ecu and the car started right up! I guess the Megasquirt really did have "death by shorted DB9 cable"

Time to send it out to get fixed!

- Intake Manifold was full of fuel as were some of the intercooler pipes. Wideband is running very rich since I probably have to drive the car to get all the fuel out of it. Atleast the car is idling nice at 850rpm.

Rafa

iTrader: (22)

That's good news Marc! Pretty simple fix.

M-Tuned

iTrader: (6)

Yeah.. I'm quite happy that the car runs on the stock ecu and injectors.. Good Piece of Mind and I can actually drive the car up my driveway and into the garage for the winter

Toddcod

iTrader: (8)

Did you pull the case off to see if anything was melted?
I had a faulty usb adapter. It sent the info in a little crazy and it shut the whole thing down. I thought it burnt up!

Nothing worked it was dead. But I did a boot jump, reinstalled my firmware, and everything was fine.
Worth looking into. If the wire comming apart messed up any signal going into it. It could happen.???????

M-Tuned

iTrader: (6)

Nothing looks burnt... I was able to communicate with the megasquirt, but did not try to reinstall the firmware. The car is going away for the winter, so I am just going to send it out to get checked out. Don't want to risk hydrolocking the motor again. Already happened twice, but the motor still seems to run fine since it was only as 300rpm (Starter power)

Toddcod

iTrader: (8)

I bet you just need to reinstall your firmware. Before mine shut down. It was getting rich as well. Like 10afr rich on idle.

I returned the adapter cable and bought a used laptop with the 9pin. Problem fixed.

I had a wierd thing going on last week. I re-installed the firmware again and now I'm fine.

Its worth a shot to save a few bucks.

M-Tuned

iTrader: (6)

Ok.. So it was actually a bad Crank sensor on my 2000 NB MIata. Seems that even though I run a Megasquirt, my stock ecu needs to get a reading from the Crank Sensor in order to power up the coils.

Nooooooow....

Car died on Sunday night and showed the same problem. Ended up having it towed as it would not start on numerous occasions.

Towed the car home, tried to start with a no go!

Attempted it in the morning and it started! Getting a little frustrated with these crank sensors. The tows are free, but this is becoming a pain in the ***...

Any thoughts..????

Marc D

iTrader: (7)

You must be using a retrofitted NA CAS to use MS correct?

If you are, you dont need to have any of the stock sensors on your car, but they should be there to keep the stock ECU happy. If they werent, the stock ECU would just throw a code. Check your OBDII ports for codes too. If you get a P0335 (IIRC), then its your crank sensor (but i highly doubt that its the problem).

I had a problem like that driving normally. My ecu cut all of a sudden, and it ran like **** and bogged. Before my CAS died, a week before, the car would bog so much, it was almost undriveable; I had to keep the revs up to keep my engine from dying.I think the CAS signal could have lost sync or something of the like. From what youre telling me on the symptoms of your car, it's most likely your NA CAS is about on its way out.

Joe Perez

iTrader: (8)

?

Power to the ignition coils on your '00 comes in on the black/white wire which comes from the "Engine" fuse. That fuse is supplied with +12 whenever the key is in the start or run positions (terminals ST and IG1 in parallel).

The stock ECU will want to see a crank signal, but this should have no effect on the ignition coils, assuming they are being driven by the MS.

M-Tuned

iTrader: (6)

Hmmm.. I know that if I unplug the stock CRANK or CAM sensor the engine will die and the megasquirt will crank fuel only. Basically a no spark situation. The stock ECU must do doing something funky here.

Any thoughts Joe?

Joe Perez

iTrader: (8)

Some details on your setup would be necessary. I take it you're using an NA CAS to drive the MS, and the crank and cam sensors are connected only to the stock ECU? And that the spark driver wires (brown and brown / yellow) have been disconnected from the stock ECU and are wired only to the MS?

If the above are true, then the scenario you're describing would seem impossible. Here's the relevant wiring:




As you can see, the coils receive power whenever the key is in the start or run position. They don't even rely upon the Main Relay. So I assume that the issue here is one of signalling, and there's just no way for this to be interrupted if they're driven only by the MS, and the MS is not looking at the stock cam or crank sensors.

Somethin' just ain't right.

M-Tuned

iTrader: (6)

Weird.... I'm going to try unpluging the Cam Position sensor while running again and see what happens. I was quite shocked the first time it happened, but just learned to accept it and figured it was the way Chad wired up my boomslang harness.

Correct.. I am using an NA CAS for the Megasquirt.