Datsun Roadster Forum-311s.org

I need some help figuring out if I have a bad coil. !970 SRL311, the car runs great for close to an hour of driving, then just suddenly bogs and dies. I feel the coil and it is very hot to the touch. I let it cool down and it starts right back up. BTW, it is a new coil purchased from DatsunParts.com if I remember correctly. Also a new set of points, cap, rotor, plugs, wires, condenser, and voltage regulator. I've read that a coil that heats up is defective. Any advice how to check if this is the issue ?

Do you have a ballast resistor in series with the coil? If not, you need one if you do, verify that the wiring is correct on it. With the key on but not in start, there should be power on the end of the ballast that is not connected directly to the coil.

Peace,
Pat

Habitat.pat wrote: Tue Feb 01, 2022 3:42 pm Do you have a ballast resistor in series with the coil? If not, you need one if you do, verify that the wiring is correct on it. With the key on but not in start, there should be power on the end of the ballast that is not connected directly to the coil.

Peace,
Pat

Yep the only component not mention was the BR, although generally not needed to replace as part of preventative maintenance / tune up IMO. Still available from Nissan P/N 22460-14615 just in case.

Yes, new BR as well. With key in on position, 12v at battery positive. 6.3v at BR side connected to coil. 11.3v on other side of BR

Is there an oily residue on the bottom side of the coil?

No, it is a new coil as well

Have you checked for spark when it won’t start? While I agree that it sounds like an electrical problem, it could also be a fuel problem. Best to check for spark since it’s easy, just so your not chasing your tail for a non existent problem.

Is it points or EI?

Yes BR ,
if your alt is leaking ac voltage , diodes leaking ,( and many did you saw it scoping the electrical )
that does that quick
What's the ohms read on - to +

It is a standard dizzy

jayedeluxe wrote: Tue Feb 01, 2022 8:47 pm It is a standard dizzy

Usually, the simplest explanation is probably the correct one (read: just a bad coil). However, might also check/adjust the points gap and then reset the ignition timing. Wrong points gap (too much dwell) and incorrect timing can over-energize a coil and cause it to overheat quite easily causing it to fail.

As an aside - I’m assuming you didn’t do any rewiring of the ignition switch, starter solenoid, voltage regulator, alternator, etc in between the coil replacements, correct?
Let us know!

No rewiring, just component replacing. What should I be seeing as far as voltage with the engine running ? At both posts of the coil ? And both posts of the BR ? Thanks !!! BTW, I'm not ruling out a fuel issue. Yesterday, I drove it for 45 min, then it died. Pulled over. Waited 30 seconds, it fired back up, ran crappy for a few seconds, then ran fine. Two more times of this before I got home. If the coil was overheated, I'm guessing it would take some time to cool down and perform normally ?

I don't think I've ever had a bad coil, but faulty fuel pumps can, and do, have intermittent problems, like those you describe...I won't go into my personal experience with them, but I believe it is so...
Mike

With points, you should see 12v when starting and 8v when running. If it’s much higher than that, it’s likely due to a bad BR.
Out of curiosity, how many volts are there at the battery when running?

13.8v when running. Today I ran it for 2 hours straight with no issue. I did put 6 gallons of gas in, I usually keep the tank down to a couple of gallons, maybe I am picking up some tank bottom funk when I keep it low.