Wife tried welding while driving... now it wont start
 

Hey guys.

Here's what happened. Wife is driving the car, and the tire jack winds up contacting both terminals of the battery, at the same time, unknown to her. Car quits. I come help, I can get it moving running, but as soon as I take the ebrake off (and light disappears on the dash) it stalls. Got it towed.

Car is 1999 Miata 1.8L 5spd.

Symptoms:
Car turns over strong, doesn't fire up anymore
Dash has no lights
No check engine light comes on
Power mirrors, windows, etc do not work
Will not jump start

Ive tried:
Checking "room fuse" & "engine fuse" in interior fuse box
Checking and replacing main efi relay (green one)
Checking all fuses, including big ones under hood.
Checking that ECU connection is tight
Replace battery and check cables for damage


Followed this set of processes, only step 2 because everything else seems to be fine. I have not tried pulling codes, but doubtful due to no dash lights.

I would love some thoughts. I'll clarify anything I missed.
My miata cranks but it won't start - ClubRoadster.net

Perhaps the batterie cables melted the insulation and they are grounding on the chassis somewhere?

That is certainly a possibility - however unlikely at this point. I've started to narrow things down a bit...

I know I've got power to the interior fuse block. The "engine" fuse does have voltage, and the fuse was tested for continuity. That fuse runs juice to the main EFI relay, which also is receiving power. I replaced that relay (just because I wanted to drop $30 of a relay) - which did nothing for me.

Checked all the big engine fuse-block fuses... all intact, all good. Next thought is fuel relay or ECU. I'm going to verify that the ECU is receiving juice... if it is, then the ECU might be toast. That would explain the dash lights not running and having no engine light (leaving me unable to run a diagnostic or get "flashing light" codes from the CEL.

So, I've got an ECU on the way... any other thoughts, something I'm missing?

If it comes to that! (Hope not!) - Thank you

How does the big 80a fuse look under the hood - the one you have to unbolt to replace?

That was my first thought... after the main relay. Pulled the fuse - continuity was good. Installed a new relay as well, didn't do any good. Might not be a bad idea to re-visit some of these basic things before I go crazy on it.

page 17-19.

good luck.


http://www.miataforumz.com/1990-200-...g/2000wire.pdf

AWESOME resource - Thanks!

Well guys, a little bit of an update.

The car does start cold. It cranks for a moment, and starts rough, but it DOES turn on, warm up and idle just fine. I can blip the throttle and its ok.

But if I shut the engine off when its warm, it will crank endlessly and not fire up. When cranking, no lights show up on the gauges, and the heat gauge is pegged at "hot".

I have installed new:
Coil packs (both)
CPS on the top of the engine.
Main 80amp fuse with new, and several of the other main fuses.
Installed verified good ECU but no change
New battery
Main engine relay (green one)
Verified all other fuses in the car
Several other random bits.

I need to:
Check that fuel is at plugs
Check spark plugs
Replace crankshaft sensor
Check ignition switch

Anything else, or any other thoughts? Don't bother with yelling at me about new parts, the car has a lot of miles and was in need of a good tune up anyway.

Thanks guys

Check MAF sensor.

The water temperature sensor circuit will cause some strange effects. The sensor is wired from the back of the engine to a connector in the front of the engine. The connections in the front of the engine will corrode and cause an intermittent signal to the ECU and the temp gauge to go full up. Check the sensor and the wiring back to the ECU.

I apologize for the delay guys. Your input (would have been) invaluable.

Long story short - it was my fault. When doing work on the car, I had removed the grounding strap located by the battery... however this was nearly 4 months previous! My wife had been driving the car, and it had been doing great that long!

Then, one day, nope, no more!

So - moral of the story... ... don't do what I did : D

thanks for the update.