electrical problem CRX, intermittent lights, won't crank

My 91 CRX HF won't crank, and the lights won't come on sometimes. It
seems that the lights WILL come on after I have disconnected the
battery. Then if I turn the ignition to ON, the dashboard lights up
normally. If I then proceed to turn the ignition to the start
position, the engine does not turn over and the dash is dark. After
that, the lights won't come on, apparently until I disconnect the
battery again.

It first refused to turn over when I was in the process of starting
it. It turned over maybe once, then stopped turning over and the dash
went dark.

I have checked some of the fuses, the main fuses and some others.
Tried a known good battery from another car.
Cleaned the battery posts and checked a few of the many ground
connections.
The engine is NOT seized.

I tried jumping a hot wire to the starter solenoid, and it did not
crank the engine. So I took the starter (a Mitsuba one) out and had
it apart. Tested the solenoid separately and off the car it seems to
thrust the pinion and make the connections to the starter motor
terminals like it should. Could not find anything wrong electrically
with the starter moter (but don't have an armature buzz tester.)

I can't understand why the lights come on sometimes and why attempting
to crank would make the lights off thereafter.

My dad suggested it is a high-resistance connection somewhere, like
the frame ground.

Just disconnected and reconnected the battery yet again. Now the
lights and wipers work again. Don't want to try to start again until
I understand this.

Maybe the starter is bad, drawing a lot of current and affecting
something computer-like, eg the ICU.

 

I'm with your dad on this one. If by lights you mean headlights, tail
lights etc., then there is no ecu or other computer that has any control
over these. They don't go through the ignition switch either, so it
would not be the problem.

I would check very carefully the connections to the battery. I have seen
problems where the battery contacts stretch a little over the years, so
even if you tighten the nut all the way, the contacts aren't tight on
the battery poles (on one car I had to wrap a few turns of aluminum foil
around the battery pole in order to get the contact to fit properly). If
the terminal is too loose, it may work just fine for moderate loads
(lights etc.) but once you try to crank the starter, you get sparks and
oxidation and you loose the connection. First check both battery
connections. See if you can twist loose the terminals from the battery
poles, you should not be able to. Then check where the battery negative
connects to the chassis. Also see if the terminals on the ground cable
are firmly attached to the cable.

 

I agree. It's most likely a battery cable. Check under the cable
insulation near the connector. I've seen cables corroded down to a
couple of strands of copper by battery acid at that point. Disconnect
the ground end of the negative cable and put a star washer under it.
Clean the lug down to bare copper with a file and scrape the metal
it's bolted to to make sure there's no corrosion there. Is the braided
bonding strap between engine and bodywork present, in good shape and
well connected?

 

Yep, you're all correct. The problem was as you say, the junction at
the cables to the positive terminal. It was an aftermarket type, a
metal plate with two bolts to a lead (pb) terminal. It was full of
corrosion.

I learned that even though it seemed like a tight connection when I
pulled on the wires, it really wasn't tight at all. It loosened up
quick once I started to unbolt it. It practically fell apart.

Also I learned that my internal model of electrical connections is
bad. I assumed that if it measured a few ohms or less, it was a good
connection. As you say, that could be just one hair thin wire making
contact. Enough to carry the current of say the lights, but when the
starter draws current, it must quickly vaporize that one thin contact.
Jiggle the wire and it establishes another hair thin contact and you
have the same problem. I also assumed that rust and corrosion wasn't
that good of an insulator. Apparently it is.

Thanks to all. Pure-D geniuses.

 

In a 110 volt circuit where one amp is flowing, an extra 1 ohms
resistance will cost you not much more than a volt.

In a 12 volt starter cable where 100 amps are flowing (and lots of
starters draw more) an extra ohm will cost you more voltage than
you've got!

Starter motors draw a lot of current and are enormously powerful
for their size. They'd burn out in minutes if they had to run
continuously.

Oh yeah!