When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission. Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.
Hey all. I just got a battery yesterday, installed new terminal clamps, and when I put the negative on after the positive, I heard a whirring sound, and realized it must be the fuel pump. But, the key wasn’t in the ignition, so I was curious what you guys thought might be causing this? It’s not the stock fuel pump, and I didn’t buy it either, but I believe it’s this same one:
Also replaced all fuses the other day, checked what I believe is the fuel pump ground wire in the trunk, and made sure all connections are clean, if any of that info helps lol.
Thanks for looking
Last edited by OilyRotor16; 05-15-24 at 10:11 PM.
Reason: Clarity
Haha, sorryyyy, I just fixed it! It was probably that ground wire in the back or something, I messed with a whole bunch of things, but anyway, we got pop ups and light!!!
Well, I found I hadn’t fixed the fuel pump lol, I just happened to remove the relay box pictured below, in an attempt to find a ground issue that might cause the fuel pump to go all wacky, and that was truly a lucky guess because, when I reconnected it to the chassis, the fuel pump kicked back on, so it’s definitely something to do with the relay box…
Another thing I just remembered is that, when the relay box was disconnected and the fuel pump was silent, I accidentally turned the key forward to “on” instead of just “accessory” and that turned the fuel pump on… but when the key is out of the ignition and the relay is grounded to the chassis and its wires hooked up, it turns on with the negative terminal…
And one last thing, initially I found the bullet connector (pictured below) disconnected, and yet the fuel pump still turned on, so I reconnected that; but with that 6-pronged connector, I disconnected it while the fuel pump was running and that immediately cut the fuel pump’s power. And again, when the entire relay is disconnected from the chassis, no fuel pump unless the key is in the “on” position.
Any thoughts and ideas on how to fix this would be much appreciated
I found another potential lead. I’m only beginning to understand wiring diagrams, but if I’m reading this correctly, then maybe the regulator/relay normally gets power from the alternator? Which would mean the relay only gets keyed power in the “on” position, including the fuel pump… so maybe that entire relay is getting direct power instead of power from the alternator, allowing the pump to turn on instantly?
Really just a wild guess lol, but anyway here’s the diagram I was looking at:
Oh also there’s no gas in the tank, idk if that could change anything for the fuel pump or not lol.
Okay, more seems to be pointing toward this alternator thing…. I just happened to check its power wire and it BROKE 😭😭😭
The Black/Yellow wire must’ve twisted itself to death when I was moving things around lol; it was already getting close to breaking anyway :/
Can I just use some of the 22-16 AWG butt connectors to fix this? I checked the spare engine block harness I have and it’s the wrong plug for the alternator… These are the only ones small enough I have, and are crimp-style:
What you calling a relay is the location of the voltage regulator on a 1979.
Ah okay, I thought so when I was looking at that starting/charging system diagram, as it said regulator below it. Any thoughts as to what’s causing the bypassing issue? Do you think it could be the alternator wire?
Btw I don’t have any solder seal connectors at home, so when I’m in town tomorrow I’ll get some so I can fix the alt. wire and see if that solves the issue.
I believe this is what he's referring to, in the Navy they were call "environmental" splices and were used in areas like aircraft wheel wells, noes gear, and speed brake wells where wiring is exposed to the elements.
Have you looked in the rear bin area where the fuel pump connection is to confirm someone didn't rewire the pump to a 12V constant power?
It doesn’t appear to be rewired. I was in there a while back taping up the wire because the outer rubber casing was chewed away but every wire was still intact, so I just used some waterproof electrical tape to fix it.
Both power and ground wires lead straight back into the stock wiring harness, and I cleaned the ground the other day in the trunk (or what I believed was the fuel pump ground wire) just to make sure the pump wasn’t affected by that.
It doesn’t appear to be rewired. I was in there a while back taping up the wire because the outer rubber casing was chewed away but every wire was still intact, so I just used some waterproof electrical tape to fix it.
Both power and ground wires lead straight back into the stock wiring harness, and I cleaned the ground the other day in the trunk (or what I believed was the fuel pump ground wire) just to make sure the pump wasn’t affected by that.
In the bin area, unplug the fuel pump connector and check for 12V across the body side connectors.
In the bin area, unplug the fuel pump connector and check for 12V across the body side connectors.
Sorry, I’ve been sick, and was also waiting for the solder seal connectors to arrive.
I fixed that alternator wire, and I also swapped out the current regulator with my spare one, as I was reading another thread on the forum where a guy was having similar issues and thought I might try that. I believe both regulators are fine as there’s no difference between their performances.
Hooked up the battery and the pump still runs and won’t stop, which is still the case when the key is in and in the “on” position.
I can hear just a little fuel gurgling in there, probably left over in the fuel pump because I pumped everything else out and cleaned the tank.
Also, when the regulator is plugged in and no key in the ignition, several things happen:
The “Gen” and “Add Oil” lights come on
The tach is going crazy w/ no key and w/ key in “on” position
When I turn on turn signals and hazards, they flash at rapid speeds (But I just found they do that even when the regulator is unplugged, probably need to change some bulbs?)
When I first plug the regulator in, there’s this ticking noise in the carb area
When I unplug the regulator all of that stops (except the blinkers) and then when I turn the key to “on”, only the seatbelt light comes on, and then the fuel pump comes on, but runs continuously as before when the regulator was plugged in, but that’s only in the “on” position; otherwise the pump is off.
Hope that all made sense lol, and hopefully the video also helps that I attached; it shows everything happening when the regulator’s plugged in.
This sure sounds like a bad voltage regulator or even the alternator.
Ah, okay. What would you recommend replacing first?
I was thinking maybe the alternator would be the best bet, as I used that spare regulator from my parts car, and still had those same issues, so either both of my regulators are bad, or else maybe it is the alternator.
One thing I'll mention is that, when I first got the car, I wanted to try hooking the battery up, but when I did, it sparked and smoked a little, and I didn't know what I was doing lol, I was just hoping for something cool, but it turned out that that had killed the battery, and then fast-forward months later, I was searching for any wiring issues and found the biggest issue you could have lol 🤦♂️:
The alternator and voltage regulator are close in cost. I'd go through that wiring first and fix that.
I had fixed that wire probably a month ago. Every other wire in the car is solid and uncut. I’ve been behind the dash and used my spare dash harness because the old one was spliced apart for a new radio that was never installed. I’ve also replaced all fuses, and the battery has been just fine every time I’ve hooked it up, so I believe everything else is good.
I guess I’ll get the alternator first? I would be surprised if I had two faulty regulators lol, so I’ll just start with the alternator and see what happens
Or should I just get mine rebuilt if I can find someone to do that?
Someone used a weird replacement kit for the battery cables and then made that bad connection to connect the two, so I just used the universal terminal clamp replacements:
I just used that spare power wire from my parts car, the wire that runs to the fusible links, to fully replace the cut one.
Other then replacing the brushes, a rebuild will cost just as much as a buying a rebuilt one off RockAuto. The brushes are easy to replace and only cost like $10. Brushes may not be the issue though. Have you done a charging test across the battery? I've never seen that style of voltage regulator on an RX-7.
Another thing I wanted to mention is that the connector for the alternator on a '79 has that 4-slot connector with 3 prongs inside, connector A-08 in the diagram above. My alternator doesn't have that; it has two wires in a two-prong connector, which you can kind of see in this picture:
I haven't checked, but I was wondering if that's an FB connector, which would mean the alternator is also from an FB? My connector is missing that white wire, so I was wondering if I'm having issues because of that?
Also, I did notice that weird difference between my voltage regulator and the spare one I have. The spare has the Mitsubishi logo on the front, just like all the others I've seen online, but even though I swapped that spare one into my car, I'm still having those same issues, so I haven't seen a difference between how the two regulators work to determine whether one is bad or not (or if they're both bad....) My parts car was sitting for years outside before I got it, so the regulator's back side is rusty, but I opened up the inside of it, and that rubber seal did it's job because everything looks brand new, so I would assume it would still work just fine despite being rusty on the outside?
I also haven't done a charging test on my battery, and the car doesn't run yet, so I could wait to start it up to see if the alternator is charging the battery, but I know I'm also trying to fix the fuel pump issue so I can start it up....
Is there a way to test whether the alternator is operating correctly without starting the car? And is there a way to test whether the voltage regulator is working? It would be ideal if I could test both but I'm just not sure if I can.
Hope you can follow all of that, sorry there's so much info and so many questions there 😅
05-15-24, 09:45 PM
