starter voltage

[aafc]

Question
I was checking the voltage at the purple wire while cranking and noticed that
the voltage was 8 volts while cranking engine. With volt meter on battery
reads 12.6 volts at rest. Then while cranking it read 9.5 volts. Is this normal
or do I have a problem.
Thanks
John
1990 white/black #2546
one of a few 4l8OE eq ZR-1's
147,xxx miles

[Paul Workman]

That is "a bit" low. Two things come to mind:

1) battery is tired OR needs a good de-sulfate charging cycle and then check voltage while cranking. It should be closer to 10.1V (Marc Hiabeck can be more specific. IIRC, the ECM gets "iffy" if the voltage drops below 10V).

2) corrosion of the battery terminals. For sure if you feel heat on the terminals when cranking, YOU HAVE CORROSION that needs to be cleaned! Same goes for the connection to the frame (negative cable). Be sure all connections are clean (and I use dielectric grease on the batter terminals to stave off corrosion. Or, there is battery terminal spray-on protective coating - avail @ most auto parts stores. (Also dielectric grease is usually available there too. Comes in handy for wire harness connections to keep them from oxidizing AFTER they are first shined up!)

[mlipmd]

Dielectric grease is an insulator, if you want a conductive grease, use No-Ox-Id. Both are water/moisture barriers but act differently. You can coat the terminals and connections with a small amount of dielectric grease (silicone) to try and insulate them from water and stave off corrosion, just like you can use plain vasoline or any other grease, but if you coat the terminals and connectors themselves with enough of it, you can actually prevent your car from starting because of all the insulation you are applying between them there.

[aafc]

Those are some good points to check. I'm in the middle of some upgrades to
my new address (Home) and get distracted by the contractors. So the car
sits inside the garage where i can work on it when I have time.
I will find out what's going on sooner or later and report back.
Thanks
John

[Paul Workman]

QD Electonic Cleaner.jpg

Originally Posted by mlipmd

Dielectric grease is an insulator, if you want a conductive grease, use No-Ox-Id. Both are water/moisture barriers but act differently. You can coat the terminals and connections with a small amount of dielectric grease (silicone) to try and insulate them from water and stave off corrosion, just like you can use plain vasoline or any other grease, but if you coat the terminals and connectors themselves with enough of it, you can actually prevent your car from starting because of all the insulation you are applying between them there.

Not to take exception to what you've said, except to consider practical reality (experience) to the argument of "dielectric" grease potentially impeding electrical connectivity where battery terminals are concerned. In practice, dielectric grease (in practice) does NOT appear to impede metal to metal contact within the body of the connector(s).

Although (theoretically I suppose) a conductive grease may be better, it doesn't appear to make a practical difference in the specific application (battery terminals). Furthermore, if one accidentally (or otherwise) applied a conductive grease to a multi-pin connector, the possibility of shorting between the pins would be a real concern.

A whole chapter could be devoted to automotive batteries - and the reasons for them to fail - specifically. But, to cut to the chase, a LOAD TESTER is an inexpensive tool to have to quickly sort out "what is what" in an automotive battery. Once a car battery is fully charged, one can know in 10 seconds if the battery is "up to snuff". (if NOT up to snuff, sulfate and other things come into play - food for another topic).

And, as far as connector oxidation and other crud goes, an electronic connector solvent/cleaner goes a long way to refurbishing "iffy" connectors.

Just sayin!

[aafc]

OK no update as the home improvements have taken over the garage and the
car sits under an outdoor cover on the inside of garage (no room to work on
it. Will get back to working when the dust settles.
John

[aafc]

Final update,
This past weekend (Jan 28-29) construction slowed down allowing me to
work on the starter (slow crank) without being interrupted.
Once I got to the starter I did some voltage measurements. Starter ground
circuit - voltage 0.23 volts normal reading 0.2 to 0.6 v0lts. Next circuit
starter power circuit - 0.05 volts normal reading 0.2 to 0.6 volts.
when I tried the next reading sparks came out of the starter. So in my
mind (drag racer) Oops their is my problem the starter was going bad very
slowly. Local auto parts store (O'Reilly's) was able to get a NOS Delco
starter.
Installed starter put everything back together . now cranks like it should
the voltage at the starter solenoid now reads 9.9 volts while cranking with
Battery voltage reading showed 12.7 volts before cranking.
thanks for the help that made me think.
John
1990 white/black $ 2546
one of a few 4l8OEeq ZR-1's