“Who killed the power?” - Intermittent dead condition

[SP3]

Low Windshield 1600 with SU’s.

Cars will lose electrical power and everything dies - no lights, ignition switch or anything else. After 15-20 minutes power restores, can start car, lights etc. I drive off and maybe make it 10-15 minutes and then car dies, everything off again. Condition repeats.

Also when car does start and I take off car misses intermittently to point I have to pull the choke all the way out to retain speed, while moving. When miss clears, choke can be pushed in and engine pulls fine until miss occurs again. If try to increase RPM while car is missing, either from under hood at carbs or while trying to drive, motor stumbles to almost shutting off unless I let it return to idle.

I wanted to confirm does this sound like a defective coil? I thought that would impact car running smooth - miss, latter condition described but not kill all the electrical power to circuits, described in first paragraph.

Battery tests 12.7 volts and increases with RPM increase.
Also re-placed clogged fuel filter, cleaned sediment out of float bowls and re-placed one float with leak (brass). Topped off dashpots in carbs with Marvel Mystery oil.

Was wondering if both conditions are tied to a single item that is bad?

[notoptoy]

Check your wiring and connections to the Ammeter. This acts like a fuse to the rest of the car (A very expensive one). If the connections are loose, or if one comes off, you get no power to anything. The missing rough running etc., could be the same cause, and intermittent or bad connection.
It does not explain a steady pattern of power on for 15 minutes and then off - unless the intermittent connection heats up and breaks contact, then cools down and returns.

[Curtis]

Sounds like a loose connection. Power goes from the battery to the starter then to the dash harness. Need to check connections all the way up the line to the fuse box, ammeter and ignition switch among others.

Maybe this will help. http://kendo-usa.org/datsun/datsun_char ... _66_67.pdf

[SP3]

Thanks! This is very helpful. Can you point out where the 2 plus downstream from fuse box will be on car? Is the first under dash near amp gauge or other side of firewall near starter area? Is the 2nd one near the brake master cylinder/rear carb location?

Car is ‘67.5

[SP3]

Also would this unstable voltage condition prevent oil pressure and temp gauges from working. New senders installed on both.

[Linda]

The starter harness is by the rear carb, goes from starter to a connector coming from the dash.Here is what can happen there:
viewtopic.php?f=2&t=32930
Then check the 3 connectors under the dash at the firewall on driver’s side.Look for any wires backing out or connectors coming loose.
The ammeter wires mentioned are on the combo guage on the 68, and from the back, under the dash, connect at about 10 and 1 o’clock. Both should be tight and are hard to get to. If previously burned they will just be spliced together, off the guage.
Coil, as mentioned.
Maybe pigtail wire in dizzy as well as a faulty condenser?
Be sure to clean all grounds, there should be one from the starter to frame.
Check ballast resistor to be sure it is not rusted out in back
Good luck
Linda

[baxtersit]

This is a longshot but I have a 1979 Yamaha RD 400 with glass fuses like the roadster. I lost power while riding and it came back 20 minutes later and then dropped again. I checked everything out and then went back to the fuse box, pulled the main fuse again and one of the end caps separated into my hand.

[david premo]

The alternator should putout about 13.7 to 14 volts when the engine is running. Sounds like you have a bad alternator.

[nismou20]

Dave makes a good point. A representation of a good alternator would be reving to about 3K and see what vdc is. Should be up in the 13 or low 14s.

[Linda]

Why would the car keep restarting if the alternator was bad and not recharging the battery?
Linda

[Curtis]

What year is the car?

[redroadster]

Take it to a pro

[Linda]

Take it to a pro

We are the pros, Red, the collective group, can if engaged, and with adequate info, can figure this out.
Where is your DIY spirit?
However if referring to the alternator, Autozone can test it or most rebuilders can test it for you too of course.
Linda

[Curtis]

Thanks! This is very helpful. Can you point out where the 2 plus downstream from fuse box will be on car? Is the first under dash near amp gauge or other side of firewall near starter area? Is the 2nd one near the brake master cylinder/rear carb location?

Car is ‘67.5

The drawing shows you where the connections are. Battery, starter, starter harness to dash harness plug, ammeter, ignition switch, fuse box. There is only the one plug for this part. The rest are terminals, blade or ring.

Layout for 67.5 is the same as 66-67.

[SP3]

Curtis,
Wanted to update you/group on progress or lack there of. I bought all new ignition components to try and resolve the misfire condition- points, condenser, ballast resistor, rotor button and coil. I found all the parts on Amazon. STMP parts and coil was a 40k volt 1.5 ohm coil.

I have a condition now where can’t get car to start. It appears no fire. Pulled a plug from cylinder and placed on valve cover and turned car over and no spark. I measured the coil with meter and it is 1.5/1.6 ohms across negative to positive terminals. What’s interesting is that I have NO resistance across the coil wire. Would this represent an open or break somewhere inside wire?

Attaching pictures of wiring to coil, ballast resistor and distributor for confirmation I did not get wires crossed. Also note there appears to some type of mini condenser mounted to firewall in addition to the usual condenser mounted on the distributor. Is this normal?

In the pictures, the negative terminal on coil is at 12 o’clock and positive at 6 o’clock (red and blue wire attached).

Disregard mis-match plug wires. Ends came off one when removing wire and other wire had a split, dry rotted plug boot. Ordering a new set of wires. For a points setup, with future intention to move to Pertronix does it matter if plug wires are 7mm or 8mm. I like the nostalgic Accel Yellow jacket wires. Silicone or Copper core?

Thanks