Hi all... RX-7 newbie here. This is my first post, so here goes.

I recently obtained an FB with no mods and started working on the fuel system.

I purchased a Carter fuel pump to replace the stock one. Rated at 2-4 PSI. (Carter part # on the box is P60504DP, # on pump is 6G07A 504, if it helps.) Anyway, after installing it, messed around with the carb for a bit and decided to pack it in for the night. When I tried to start the car the next day, the pump was stone cold dead. Check the fuse, power, etc., all was ok. Disconnected pump and jumpered directly to a spare battery, still did not work.

Picked up a new pump (still the same model Carter) and wired it in. Was again able to start car and play with the carb. When I finished for the night, I removed the battery from the car, as I wasn't going to be working with it for a few days. Installed the battery again tonight... freaking new pump doesn't work anymore... WTF?!!!!

I've read some of the posts that recommend running a new positive wire to the fuel pump, negative to frame and using the old wires to power a relay that turns on the power. In fact the Carter installation instructions recommends doing that. Any chance NOT doing that could be to blame?

I'm at a loss here. Both pumps have less than 20 minutes running time on them. I'm using a 3A fuse (instead of the stock 10A) for the fuel pump, as recommended in instructions; it didn't blow either time. Have blown out one pump with compressed air to see if any impurities had entered it.... clean.

Anybody have any ideas about what might be causing the pumps to die? I'm stumped.

 

That is strange how the 2 pumps are acting up. And you removed the pump and hooked it up straight to the battery? What a PITA. Do you know if your car came with some aftermarket alarm system? Maybe when you disabled the battery and hooked it back up again the alarm triggered or something. Just guessing.

 

That is definately weird. I am using a carter as well and I havent had a problem with it. I have it hooked up to the stock wirig (will be upgraded in the future). I however did have a problem with the previous pump I ran (Holley red). It only lasted about 1500 miles and took a big healthy one. 20 minutes is pretty strange though. I ope you can figure it out. Could be a bad ground ad causing it to work harder than it should??? I honestly have no idea. Good luck and let us know if you happen to find out the solution to your problem.

 

I had one Carter do exactly that, sent it back to Summit who replaced it, the new one has lasted 25,000 miles so far.

OK have you checked the wires where they go through the floor, they rust and break here regularly.

Have you bench tested the pump with two containers, one with fuel, one empty, maybe you've reversed the wiring, ask me how I know that one...lol, this will make the pump push instead of pull. If it fails to run on the bench its the pump again, could you be burining thm out, check you power source with a meter.

Just a couple of ideas for you.

 

Nah, you guys are making this too complicated. If the pump fails to run, first thing to check is whether you have power going to the pump. Do this by checking the + wire right at the pump, at a time when it should be running (84 - 85 models must be cranking to run pump). If no power there, then the issue is in your wiring. If you do have good power at that point, then the issue is either your ground or your stock (or upgraded) wiring. No need to remove the pump to test it if done this way... Since you've now had two pumps die this way, I would suspect operator error. That's just way too much coincidence for me to swallow, know what I mean?

 

Kentetsu, I think I agree with you. Actually, the bad grounding sounds most likely to me.

 

Hmmmm... maybe operator error, but I don't know...

I've used the original wiring... which was good enough to keep the original pump operating. I do get power to the pump. The pump seems to die if I leave it overnight, not operating at all. It was still working before I quit working for the night in both cases. This is what blows my mind.

Voltage at the pump was between 11.6 and 12.4 volts, pump is not blowing 3A fuse and I triple checked the polarity even before turning the key.

 

Oops... didn't post quick enough.

So the grounding would completely toast the pump?

It would seem that I can't use the stock wiring. Should I just run new positive line and ground to chassis, as some of the other threads have suggested?

 

You should have purchased a better Carter. The 72gph 8psi unit available at Summit is what I installed on Saturday. I also installed a Holley fuel pressure regulator. The wiring is stock for now and it's been running fine, except blinkers cause the pump RPM the change. New wiring will be run from the battery to the pump with a relay somewhere in between.

 

Go for it.

 

Well, seems I only fried the first fuel pump. The second one I installed wasn't toast, just didn't want to go. I tried starting the car tonight... lo and behold, the pump actually came to life. I'm almost certain that when I turned the key to ON, I heard a click like a solenoid come from the engine compartment, and then the pump just decided to go again. Strange, as I spent 10-15 minutes on the pump the night before and it appeared to be non-servicable.

Geez, I finally got this my 7 started tonight, and ran it for about 10 minutes... what a lovely sound!!! Ok, it was running rough, as it had been sitting for 2.5 years when I got it, but still great to hear it run. Now to rebuild the Nikki!

 

I think there is a relay down under the dash. There are a couple of threads on it somewhere around here...

 

Is your car an '84 or '85?

 

Nope, it's an 83.

 

There is a relay directly beneath the column and above the brake pedal, it has a 6 pin plug and you can eliminate it, I did, but your pump will run whenever the ignition is on. This relay does cause this type of problem. There is a thread on it because I followed it...

 

Not on an 83 though. Only 84-85 have that relay, for the 230342930472097th time.

 

LOL! Good, I didn't have to say it! Heh heh. This second fuel pump seems to be working fine now. I believe the reason the first pump die could be attributed to something physical. Perhaps the only issue with the second pump was a poor ground, and the solenoid sound from the engine compartment was coincidental with the fuel pump working again. I think I'll replace the battery cables and check the grounds. I read that one of the grounds from the battery to the car body is in a spot where it can gather rust/get fouled. I'll be checking that baby out.

Thanks to all who provided suggestions...