60 Amp Alternator upgrade....now dead battery

[Weasel73240Z 0]

I recently installed my 60-amp, internally regulated alternator. After driving the car a few times, now my battery has died, and doesn't want to take a charge. I charge it, start the car a few times, then park it over night, dead. I have tried diagnosing, but I am pretty useless when it comes to electrical issues. I am wondering if there could be some type of drain on the battery, possibly related to the plug that I inserted when eliminating the voltage regulator? Or is it just a coincidence, and my battery just happened to be dying as I was making the upgrade. I have never had to charge the battery before, except after the Winter hibernation. The battery is about 4 years old. Thoughts? Thanks for all the wisdom......

[SteveJ 1,196]

Yes. Search on here. There is a long thread on the subject. I haven't analyzed the 73 wiring as much as I should on this subject to give a blow-by-blow. For the 74 260Z, I have. In the 260Z, the fuel pump relay is wired between the alternator and voltage regulator. I suspect the 73 is wired in a simlar manner. Dave Irwin (Zs-ondabrain) might be able to confirm. I've attached a simplified schematic of the 260Z fuel pump wiring.

When you jumpered out the voltage regulator, you energized the coil. While it's a relatively low draw, it's there.

[Weasel73240Z 0]

I did search for a while before asking. But with any search, you need the right keywords to get the right answer. I got 7 pages of answers, and read for over an hour without finding the info I needed. I guess I'll just have to keep reading until I stumble upon it, unless someone can guide me to the correct post.

Edited August 23, 2011 by Weasel73240Z

[Weasel73240Z 0]

And thanks Steve! I figured it had to be something to do with the upgrade, but again, electrical is not my bag. Maybe the best work around is just to install a battery cut-off switch, which I've been planning to do anyway?

[SteveJ 1,196]

Here is the thread. The key for me was finding that there is another 6-pin connector between the wiring harness and voltage regulator. It's been a few years, but I think it's not too far from the plug for the voltage regulator. I unplugged it and put the jumpers in that plug. My battery stopped draining after that.

[Weasel73240Z 0]

Thanks Steve! You saved me several more hours of searching. I'll check out the FP relay when I get home.

[SteveJ 1,196]

Consider it a freebie.

Searches build character. You may also find out information on something else that you'll need to know later.

[Weasel73240Z 0]

Consider it a freebie.

Searches build character. You may also find out information on something else that you'll need to know later.

LOLLOLLOLLOL

I'd search all day, but for some reason my boss considers it a waste of my time!

Thanks again...

[240ZGL 1]

The yelow power wire going to the relay needs to be cut, then put a Bocsh relay in line on that wire and trigger that relay with a power wire off the ON side of the ignition switch. Mine works great all automatic.

[SteveJ 1,196]

To elaborate on the solution from Steve, you could use a standard automotive relay to interrupt the fuel pump circuit. After opening up the yellow wire, one end would to pin 30 on the relay, and the other end would go to pin 87. You would need to use a switched source, such as the circuit for the radio and put the ends on pins 85 & 86. The circuit would be completed when the ignition is in the run position.

There is a downside to this solution. In the event of an accident, the coil could still be energized. If you have an electric fuel pump, it would still have power. The original circuit (external voltage regulator) is energized only when the alternator is providing power. Some people have utilized an oil pressure switch as a fallback. Modern cars also employ a shock sensitive switch to cut the fuel pump.

[pbarcher 0]

My '73 had the same problem after the 60 amp alternator upgrade. I unplugged the electric fuel pump relay under the dash on the passenger side. This is not an ideal solution, because the electric fuel pump doesn't work.

My car was delivered without an electric pump when I bought it in August of 1973. The electric pump and underhood fuel line insulation were added as part of a recall for vapor lock a few years later. The car runs fine without the electric pump, and since there is no air conditioning I don't drive it on hot days.

[Weasel73240Z 0]

I only run the mechanical fuel pump anyway, so it seems like eliminating the FP relay is a simple solution. The car had both when I bought it, but after some reading, I decided I didn't need the electric pump. I have never had any problems running the mechanical pump alone. I felt around for the fuel pump relay last night after work (looking for a "warm" one), but I had some things to do so I was never really able to locate it. I'll get back at it today. Thanks again everyone for the help.

[Weasel73240Z 0]

Okay....I think I found it! I found one very warm relay on the passenger side. I disconnected it and it was getting 12 volts with the key off. The number on the wiring harness was 24034-N3300. Since I don;t use the electric fuel pump, I disconnected it. I'm now charging the battery and hope I found my problem. Thanks again to everyone for the wisdom.

[Weasel73240Z 0]

So just to close this out, the fuel pump relay was definitely the problem. I charged the battery, drove around a bunch yesterday, parked it over night, and no battery drain at all. Obviously this is a much more difficult problem if you are still using the electric fuel pump, but thanks again for pointing me in the right direction guys!

[djdavies 0]

To elaborate on the solution from Steve, you could use a standard automotive relay to interrupt the fuel pump circuit. After opening up the yellow wire, one end would to pin 30 on the relay, and the other end would go to pin 87. You would need to use a switched source, such as the circuit for the radio and put the ends on pins 85 & 86. The circuit would be completed when the ignition is in the run position.

Why add another relay to control it with the IGN, and leave the fuel pump relay controlled by the battery (which is what it's doing), and not just drive the fuel pump relay with IGN?