67 911 charging/battery issues, It's why I can't make WCR! Options

[FlacaProductions]

@bdstone914 - you asked - here it is! (posted here because you guys are smart and hands on - the 911 board is less hands on...)

1967 911 coupe. Just completed a “wake-up” after sitting rarely used by the previous owner for a few years. Main issue was gummed up carbs, but all suspension/running/stopping gear restored/replaced generally to OEM/stock specs.

I picked it up April 17 after 2 months of restoration. Ran like clockwork until June 9.

My overall suspicion with this issue - a bad voltage regulator (although I never get an alternator warning light unless it’s at initial start and until the revs have been up for just a bit and then the light goes out as expected/normal) - and/or heat induced high resistance around starter wiring.

Except as noted, headlights/dash lights/accessories all work as expected - even when battery acts dead and won’t turn over the starter.

first incident - Monday, June 9
cold starts fine and drive to anaheim. about an hour - freeway all the way. lights, radio on all the way. no performance issues or dash indicators.

Parked - went to move 5 mins later and it wouldn’t start. slow turnover until battery finally died. portable jump start brought it back and I moved about 50 yards. I thought I’d just jump it again if it failed to start but that wasn’t possible. jump box finally depleted. Clay from Scott’s Independent was about 15 minutes away and brought me a charged battery. Put it in and car fired right away.

to the shop - tested charging system and all seemed well - including swapping of a couple of voltage regulators with no real difference noted to voltage/charge numbers at the battery.

Wrote it off to a battery failure, installed new Interstate and away I went.

After that day, I’ve done multiple small, 10-30 minute “exercise” runs around my area without incident. Including multiple drive/stop/park/start/drive scenarios. Groceries, fuel, errands, etc.

friday June 20 - angeles crest - again - no issues
started fine - ran continuously/aggressively on the freeway and up the hill for 60+ minutes/60 miles. stopped at the top for an hour. Started fine for return. stopped for gas near home - started back up fine.

lights on all the way.
charging phone (rennline iPhone charging mount)
radio on
no issues

saturday June 21 - latest incident
started fine
ran slow up PCH (30 mph for 60 mins) to canyon run at highway speeds, back down 101 to malibu canyon again at highway speeds, stopped for dinner.

on that last leg, I noticed that the the phone didn’t charge and I didn’t have the horn - but did have the horn at beginning of ride. (I always honk coming out of our condo garage as it's somewhat blind to pedestrians)

After dinner, it seemed to crank JUST a bit slower after dinner but started easily. phone charged and had horn.

ran 30mph down PCH (30 mph) just fine for 45 minutes. Lights on. Radio on.

On Sunset, started to stumble (40mph) - especially when going past half throttle. big backfires. finally stumbled and quit.

Side of the road. wouldn’t turn over. lights etc all work. wouldn’t jump start. Left it - came back after an hour - turned over slowly - wouldn’t start. started with jump box. drove home without incident. wouldn’t crank when i got it home.

Sunday june 22 - wouldn’t crank - acts like dead battery. starts with either jump box or after trickle charger applied for a while.

Any input is appreciated - sorry for the long post - just trying to do a stream of consciousness of the details....

[jim_hoyland]

FI or carbs ?

[FlacaProductions]

Carbs

[Chris914n6]

Sounds like turning the headlights on is the problem. Don't do that (IMG:style_emoticons/default/biggrin.gif)

But seriously, a battery will last a long time on a running car even if not charging as it's not alot of current draw.

Check battery voltage. Check that it is charging at 13-14v. Check again with headlights etc on.

[FlacaProductions]

It's funny - I turn the lights on every time - can't be too visible, now can we?! But the "failure" doesn't happen every time. Intermittent problems are the worst.

Charging voltage checked ok at the shop when we changed the battery.

[Superhawk996]

I’m not a 911 guy

“Side of the road. wouldn’t turn over. lights etc all work. wouldn’t jump start. Left it - came back after an hour - turned over slowly - wouldn’t start. started with jump box. drove home without incident. wouldn’t crank when i got it home.”

Sounds a whole lot like a bad chassis ground between body and engine (aka - what is the equivalent of 914 trans ground strap?) and/or the battery negative to body. Could also be the positive battery cable but less likely given your symptoms.

Lights etc. are all very low current draw (tens of amps) compared to the stater motor draw (100 or more amps). Sounds an awful like it can’t support high current and it’s intermittent nature would prevent alternator from charging battery if there isn’t a good ground between engine and the chassis.

Just a hunch and where I’d start troubleshooting.

[FlacaProductions]

The more I think/read about things, the more I agree that this is the right track, @Superhawk996 - and all my lighting is LED so it's pulling even less.

I posted this here not so much as a 911 topic but as one centered around classic automotive power/ground issues. It's a topic that has always proven important in 914's for sure.

[infraredcalvin]

Don’t count on the shops trouble shooting on intermittent issues, start from square one, especially when you are having the issue. Batt voltage and charging voltage are so easy to check.

I agree with bad grounding as an issue…

[Spoke]

In your description of the issues, I didn't see any measurements of voltage. Any idea what voltage you see at idle or raised idle or while cruising?

It is very useful to have a voltmeter on your 911. I have a USB ciggy plug-in with built-in voltmeter. Measuring at the cig lighter isn't ideal but does help indicate if something is really wrong.

[FlacaProductions]

I don't have a voltmeter on the 911 but the cig lighter version just landed from Amazon.

Plan for the coming days is to check/clean/tighten grounds at the battery and at the engine/trans and watch the voltages via the new meter and then test voltages if/when I get the fault again.

[rhodyguy]

On the 21st both the horn and phone charging? circuits appear as though they are dead. Are they on the same circuit? How altered is the stock circuitry? This issue might be a contributor why the car saw limited action.