[SOLVED] Starter voltage question

You could also measure from battery positive to the s post and read the voltage drop over the cable. I hope that the s post is what I think it is. The crank position wire from crank relay to starter?

Anybody able to verify if that 20 amp spike is normal for the "S" post wire while cranking? Or if it's an indication of a failing solenoid? Again, this was on a good crank. Haven't been able to catch one of it's "no cranks" as it's terribly intermittent and is almost always overcome on the very next key turn.

RobBrown wrote: Anybody able to verify if that 20 amp spike is normal for the "S" post wire while cranking? Or if it's an indication of a failing solenoid? Again, this was on a good crank. Haven't been able to catch one of it's "no cranks" as it's terribly intermittent and is almost always overcome on the very next key turn.

I'm OK with a 20 amp spike on the solenoid wire on initial starter engagement.

There have been a couple times this week when the starter has failed to crank on the first attempt. But it always fires up immediately on the next one. Making it really hard to get any sort of reading (voltage, amperage, or otherwise!) on the failing system:-(

Frustrating, I hear ya. I don't suppose there's a way you could semi-perminently wire in a test light, or other similar small bulb, into the solenoid circuit? Then, position the bulb somewhere visible from the drivers seat. This'll enable you to catch that intermittent first attempt.

I applaud you sticking with this one, sir, given how random the symptom is. I'll be honest, if this was my vehicle, I probably would have tried a starter by now. :blush:

Okay. So I caught it not cranking this holiday weekend. Had my powerprobe in the car. Hooked it up to the battery, unhooked S post terminal and applied battery voltage directly to the s post (with the key in the run position). Starter cranked the engine without popping the breaker in the probe. However, I noticed that when I initially attached the PowerProbe, it was reading 11.9v at the battery. Then, while applying that battery voltage directly to the s post, the voltage read out on the probe was at 9.5v.

Of course, immediately after cranking it with the probe, I shut if off and tried cranking with the key....and it cranked fine. And cranked fine the rest of the weekend. So...after this test, my thoughts move away from the starter and back to the battery/charging system. I'm going to test the battery using my Solar BA-9. I'll let you know how that turns out.

Thanks for your help and patience!

9.5v is an acceptable cranking voltage if the battery voltage starts at 11.9v A instant drop to about 6.5v when the engine is cranked indicates the battery may have a dead cell, a slow drop in battery voltage when the engine is cranked is a sign that the battery needs a recharge,
A battery voltage of 11.9v with no loads on it generally indicates a battery that is about 60% discharged and requires charging. A normal battery "resting" voltage ie load off charge with no loads is in the range 12.4v to 12.8v.
A good fully charged battery will normally crank an engine at about 10.1v to 11.5v depending on the relative size and age of the battery and state of charge, ambient temperature and oil viscosity.

With the engine running at normal idle speed the voltage across the battery should not be less han 13.1 volts, at fast idle speed ( say 2000 RPM) look for over 13.4v but less than 15.0v, then repeat the fast idle test with the headlights and heater blower on the voltage should not drop below 13 volts.
Then with the headlights and blower on increase the rpm to 3,500 and switch all electrical loads off the battery voltage should never rise above 15volts at any point.

Just a small addition. I find when using my powerprobe in high current situations, the voltage indicated will be lower than battery voltage due to losses within the tool. That's the idea behind the red and green LEDs on the tool.

Ok! I was FINALLY able to do an amperage reading during a no-crank on the S post wire. A solid 20 amps of current while holding the key in the crank position. Replicated this on several occasions. Does this condemn or vindicate the starter? Or does this continue to leave some abiguity?

As always, I was able to coax a crank and start at almost any time by quickly turning the key off and then back to the crank position.

I think I would have had the starter off early on in the saga. You could try cleaning and lubricating the fork pivot and drive gear with WD40 working them back a forward to ensure they move in and out freely this can sometimes work as a short term fix.
On some starters the link between solenoid and the fork can be adjusted.
A full starter rebuild is probably the real solution.

RobBrown wrote: Ok! I was FINALLY able to do an amperage reading during a no-crank on the S post wire. A solid 20 amps of current while holding the key in the crank position. Replicated this on several occasions. Does this condemn or vindicate the starter? Or does this continue to leave some abiguity?

As always, I was able to coax a crank and start at almost any time by quickly turning the key off and then back to the crank position.

YAY! This is the feeling I get when I finally get a customers car to act up after hours of driving, lol.

I personally believe this clears the wiring and condemns the starter. I don't see the solenoid control circuit could drawing a steady 20 amps with a resistance problem. Like Andy said, rebuilding is an option. I'd probably just buy a quality parts store starter.

Just a small addition. I find when using my powerprobe in high current situations, the voltage indicated will be lower than battery voltage due to losses within the tool. That's the idea behind the red and green LEDs on the tool.

I'm glad you mentioned this, 'cause I just noticed the same thing while manually powering some cooling fans yesterday. Looks like my PP3 is still working

A new starter has fixed the issue...so even though there were only 6v present at the S post during cranking, the steady 20A of current present there, too, (during a no-crank) indicated an internal issue. I'm still a bit shady on where those other 4 or so volts were being dropped...somewhere inside the starter...but I don't know enough about their internals to hazard a useful guess.

Thanks, as always for your help, all. Feels good knowing I replaced ONLY the needed part.
Rob

Sweet! Super glad to hear this one got fixed.

The missing 4V... I got nothing. The current measurement was key, though, IMO. Well done!