Intermittent Loss Of Power ...
 

happy spring, fellas!

almost immediately after I put a fresh 462 in my car last October, I starting experiencing this PITA issue where car suddenly loses ALL electrical power. it's never occurred when motor hasn't been running at least 15-20 minutes. once power's lost I have to wait 20-30 seconds when suddenly power returns and I can re start engine.

even though I was losing all power as opposed to only the motor shutting down, I foolishly thought it could be the pertronix module. obviously when I put points back in problem would still occur. I thought I had it licked when I realized since block was freshly painted, the ground between block and firewall wasn't as clean as it should be. It realllllly seems that since going over this ground, frequency of occurrence has diminished. when this first started occurring last season I could lose power/restart 2 or 3 times before getting car home. today I took two separate 5 mile jaunts and it was only during second time out that after 5+ miles problem occurred. doh!

ive gone over connections at the starter and over every ground. I don't think it's any of the fusible links as the M&H engine and dash harnesses are only a few years old. I've gently twisted and torqued entire length of engine harness while motor is running trying to instigate issue. I've carefully inspected where engine harness joins fuse block. both battery cables are well made 1/0 AWG and battery is brand new.

it's worth mentioning that previous iteration of motor never once lost power like this ... the same engine and dash harnesses were in use btw.

it seems it's temperature related as it hasn't occurred when motor wasnt at temperature. but if it is temperature related would power come back so quickly, within 30 seconds?

voltage regulator on car is original to 1969. last season I did attempt to adjust it's voltage-out to keep pertronix module happy. wonder if I screwed something up there?

sorry for such a long winded post, any help is greatly appreciated!
mike
MA

Does it have the same battery as it had with the previous engine?

Almost sounds like some kind of over-current or over-temp circuit protection. If it's not in the harness, maybe the battery?

last season was a really short one for me as it took longer than expected to get motor built .. only got 200 miles in.
the first 150 miles were on previous battery .. same as previous motor was using.
this stuff was occurring with that first battery too.

another thing I think is worth mentioning: when I lose power I lose headlights too. if issue was the ignition switch, pretty sure I'd still have headlights.
so issue is between battery and fuse panel?

besides checking grounds a-gain, I'll run a cable between neg. on battery directly to firewall. if that licks it I'll know its a ground issue. if not I'll know its the positive side.

I remember after engine went in and I hooked up battery, i very quickly touched + cable to battery , just in case it was grounding somehow..
sure enough I got a really juicy spark but it was super quick. I wonder if that grounding stressed positive side somewhere? it was really quick tho.

thanks for thinking on this.

The voltage regulator is the original one?
:confused:

I'd change it and see what it does.

Is the wiring basically the same as factory, like battery cable to starter, wire from starter to harness main power joint (in harness wrap), wire from there to regulator, etc?

:confused:

hi, John ..

yes, the same. if regulator was bad would I lose all power? not just ignition?

thanks,
mike

It might be a very short loss, but enough to stop the coil/spark, with the main power being just a quick 'flicker' that wouldn't be noticeable?

I wonder if it's not a loss of ground or something in regulator, possibly a loss of voltage but not all of it.

:confused:

Where/what was the short that caused the spark?

Clay

hi, clay,

one of the stacked positive terminals at the starter was grounding against starter body, not sure which one was the culprit. I was careful and quick when putting + cable onto battery I thought. got a juicy spark tho.

I just tested continuity between negative battery terminal and block and to firewall and it looks fine. I'll go over ground connections again tho.

I'm about to go out there and also re check everything + at starter.

re- regulator .. ive poked around and it appears a bad regulator wouldn't cause a total loss of power? if I'm mistaken please let me know.

appreciate the help, fellas,
mike

With loss of battery power the engine should continue to run on alternator output.

Makes me think you could have a bad/poor/loose connection in a master splice between back of alternator and firewall. Could be in the firewall plug itself.

Clay

yes, clay, it's a total blackout not just loss of battery

everything looks real good at starter stack. eyelet terminal for fusible links is soldered and crimped, it looked fine. I re arranged terminals and snugged up.

patch of block where braided strap bolts to looked very gnarly from winter so I got back down to metal. even tho meter was showing continuity this morning maybe connectivity weakened when block heated up?

I popped into a local speed shop nearby thats been around for 20+ years. owner seems to think its not any fusible link, says they either work or dont.

that leaves where harness plug meets fuse block.

cause I know everyone's dying to know outcome here ; )

the <tiny> little tab that's supposed to lock the female connecter into the dash-side block that mates w/ engine harness block ...
that tiny little tab was bent outward and in half so that when the two halves would meet, the thick red power wire that meets battery wire would merely push out of dash-block.

I'll miss losing all power in the middle of downtown traffic

Nice job figuring it out and thanks for updating.

It's always something that no one would ever figure out without a lot of investigating!


:D