A couple months ago my 91 Civic broke down while I was driving. No bad noises or anything; it just quit quit running. I tried to start it back up and it cranked. It backfired a couple of times, but wouldn't start. After 2-3 attempts, each slower than the last, it would no longer crank at all, and the battery was dead--barely enough juice to get the windows up. So, I got the car towed home, and the next day try to jump start it, it cranks without issue but backfires and makes all kinds of noise. It started one time, and ran badly for several seconds before it quit. I didn't have much time to work on it then, so I decided to leave it alone for awhile and come back to it in the fall with cooler weather.

Today, I took a look at it, finally. I started at the distributor. unless it jumped time, this seemed like the likely culprit. Plus, the car had broken down in similar fashion once before, and the issue in that case had been the small bolt that holds the rotor cap had backed itself out. This turned out to be true again. So, thinking this is an easy fix, I get some light duty thread locker, and get it all put back together. I hook up the jumper cables and let it charge for several minutes. When I try to start it, the car cranks a couple of times but sounds slow, so I let charge some more. I can get a decent crank or two sometimes but no start. At least it's not backfiring and cross-firing like it had been.

So, get my battery charger out and drag it and a 100' cord up the hill to the Honda. I set it to the 200amp Start setting and give it a shot. The results are about the same as with the jumper cables: just slow cranks (but with some electric humming). Now, I put it on the regular charging setting and leave it hooked up for a bit more than an hour to see if the battery will charge. Then I try to to start it, with the charger still hooked up on a 6volt 100amp jump-start setting, and there's no change. the car just slowly turns over as if the battery is almost dead.

This is where it gets weird, to me at least. I take the charger off the battery and turn the key just to see what it does. Nothing. It's dead. No crank, no start, as if the starter is bad or the battery is totally dead. I put the charger on it, and it cranks slowly. Take it off--nothing. I checked the battery with a multi-meter (with the charger disconnected) and the battery is sitting between 12 and 13 volts. So, maybe it's a little low once the surface charge is gone, but it might not have ever gotten fully charged. Still, even at 10 volts, it should be able to engage the starter and give it a shot. Maybe the cranking amps aren't there?

The day the car broke down, it had failed to start once, and I had gotten someone to give me a jump and it started right up, and it started twice more without issue in the couple hours before it broke down. The battery and alternator are both fairly new, less than a year old, but I drove that car quite a bit during that time, so probably has 15k miles on them. I had replaced the alternator belt the week before.

I'm stumped. Why would the car crank slowly with jumper cables or a charger, and not at all with a charged battery? Is this separate from the distributor issue, or connected somehow?

 

Turns out it was just a really bad battery. Still under warranty, swapped for a new one for no money, and the car cranked really well. Took a long time to get started, which this car has been known to do any time it sits for more than a week without being started (the one exception being when I rebuilt the head. Car started on first crank after I got it all back together. That's a great feeling.)

 

That battery was long gone. This is just a ballpark, since there are way more variables at play than just voltage. You should consider getting a battery tender if you're not using the car for long periods at a time.

I've seen super dead batteries prevent cars from starting before. But why were you trying to jumpstart a 12v battery with a 6 volt jumpstarter?