Hi,

I've had my 2001 Mazda MX-5 mk2.5 / NBFL for a little over a year and it has been working great the entire time.
Until last week.

The problems started appearing on friday.
When trying to start the car it cranked fine, then fired up and then died within a second. This happened several times. I tried removing all fuses and replacing them in the engine fuse box as well as doing the same thing with all connections to sensors that I could see. Don't know if this had any effect but after a couple of tries it fired up and kept going.
Drove the car to a restaurant, and no problem starting, to a shop and no problem. The next day we drove the car for only a couple of hundred meters, no problem.

Then on sunday when trying to start the car it didn't even crank.
The clock on the stereo, blower, lights on dash etc all started fine, but no crank. I went through the fuses again and then we had crank, but no start, not even start and stall as the first time.

We went though all fuses and connections with electrical spray and no difference. Then, after a while we got to the first problem. Start and stall.

Then I went to measure the battery while cranking. I saw a huge drop from 12.45 volts to somewhere around 7-8 volts while cranking. Then it suddenly started and stayed running. Once running it was fine and we drove it home (since we were away for the weekend) without turning it off.

When I got back home the MX-5 was fine again. I tried starting 3-4 times after shutting off and waiting for like 30 mins and it was fine.

What seems like a plausible explaination?
Bad battery, i.e. to much voltage drop, but then why the no crank situation?

Glitch somewhere? Where should I look for a bad connection?

Thanks,
Mike

 

Check your battery terminals are tight. Check your main earth's. Get the battery properly tested. Also check the alternator output. Maybe go to the dealership & get a code check.
( before disconnecting anything)