So I have a strange issue occurring on my 72 240z.
I have been driving the car without issue for the past 2 months since I bought the car. The car has triple Weber 40s, l24 block, n42 head, mechanical fuel pump still, etc. I didn't drive the car for about 9 days, and I am used to needing to pump the gas a bit and modulate the throttle to get it running once it has sat a bit.
I went to go start the car and the car is completely dead. The car is acting like the battery is 100% dead. Well I have an Optima redtop in the back of my miata (that's in pieces) that fits just fine so I dropped it in. I got a couple 15 second cranks out of it, but then the battery acted like it was dying too. I first attributed this to the battery having sat a bit so i threw it on the trickle charger for 5-6 days. I took it back out and the car could only crank for maybe 20 seconds total before acting like the battery was dead again. I repeated this one more time, same results.
When I first put the Optima the battery into the car fresh of the trickle charger it cranked really fast, but slows down to the point it can't even crank the motor with in 30 seconds or less. The lights dim, the dash dims, the head lights barely function. 100% symptoms of a dead battery.
This is where it gets odd. So I take the Redtop down to my local Autozone. The guys there have this fancy load tester and it has a specific setting for Redtop Optimas. The two guys at this location really seem to know their stuff BTW, I know some locations have some rather shady unknowledgeable guys behind the counter. Well the battery tests better than new. Read 12.87 volts, passed the load test with flying colors.
The guy there suggested that it could be either the starter solenoid or the starter, but he was kind of guessing at the problem because that is the only thing the battery is directly connected too. Now I am inclined to try swapping it out, but I wanted to check if this is a common issue or if anyone has had such a weird situation happen before.
TLDR: Car acts like battery is dying very fast, cranks full speed down to a near stop in 20-30 seconds. The battery is testing out perfect. What could be another cause?