Fuel Pump Issues

Recently I'm experiencing a very weird issue that I have no idea what it could be other than two bad fuel pumps. Basally the car sat for a month because of a dead battery. I just swapped that battery out for a new one and the car wont start. Before the battery went dead the car ran just fine. I noticed the fuel pumps not turning on at all, so I decided to start testing. The very first thing i noticed is my 30amp fuse to my upgraded wiring was blown, so i replaced that. Tried to start it and it was blown again. I replaced it once more but this time only turned to the on position and the fuse blew again.

I soon found out that the negative and positive wires were creating connectivity with my multimeter, so i decided to drop the tank. After investigation I found that the upgraded wiring I did was fine, but the two GT Supercar pumps still wouldn't turn on. I then used my multimeter on the pump its self and touched the negative and positive together and got connectivity ( a beeping sound on the multimeter) I then checked the other pump and the same thing happened.

I don't know how to check to see if fuel pumps are bad, but i would assume that the negative and posative terminals on the fuel pumps shouldn't be connected to each other correct? I get a beeping sound showing connectivity between both points when connected.

After all that, I decided to check the wiring after the fpdm and noticed that no voltage was showing up at the pumps with the key in the on position. I then swapped fpdm's to a known working one and the same thing happened. I figured the voltage should at least show something instead of zero.

At this point It got real late and i stopped my search. I'm completely stumped, It kinda sounds like the fpdm isn't outputting or getting power, Then the fuel pumps have connectivity which completely confuses me. If that's normal for those pumps then thats good since I'd wonder how two pumps can go bad at the same time just from not being used for a month.

All help is appreciated.

Thanks for your advice.

I'll go ahead and check the ohms of the fuel pumps later tonight. Right now its about 98 outside so I'm planning on waiting till it cools down.

I didn't think about the voltage only showing for the first few seconds on the fpdm. That makes sense.

When the pumps are disconnected the fuse does hold. It doesn't pop if i discount the pumps. During all the testing last night I actually cut the stock wiring and used my 10 gauge wiring only to test. Basically I used a 10gauge ground wire that was grounded to the chasis, then the 10gauge power wire directly from the fpdm. The fpdm got a 10guage power wire from a relay directly from the battery.

This is the diagram that I used for the wiring upgrade. Instead of tapping into the original wires I soldered new 10gauge wire directly to the pumps. I made sure that there were not any ground shorts going through the hat. I also had the stock wiring connected to the upgraded wiring.

fpdm/fuel pump wiring upgrade

I'm still confused on how this could happen from just sitting a month. I'm wondering if the bad battery caused a short or something. I checked the fuel pump cut off switch and its good. I checked the engine bay fuel pump fuse and its good. I also tried connecting the stock wiring up without my upgraded wiring and it still didnt turn on.

I'm still wondering if the pumps are bad that its creating a full circuit causing this issue. I'll check the ohms tonight.

Update, I checked each pumps resistance and it came up as 00.5 ohms on both pumps. I then tested for 12v at the inertia switch and there is 12v going to that.

I then checked for 12v at the posative of the pumps and i get zero volts, but maybe its because the voltage only stays on for a few seconds?

Also before any testing i replaced the fuse and it actually lasted the whole time without blowing turning on and off. The fuel pumps however do not come on at all.

I then checked every fuse in the hood and drivers side and every fuse is good. I tried another fpdm and still no go. I'm completely stumped, is this a bad ccrm? or something else? Or are the pumps bad?

Thanks for the input again. I actually fixed it last night at 3am, but got to tired to post up.

The first issue was the relay. The ground that i had for it worked good, but the wire came out of the butt connector. Once that was fixed the fuses stooped popping. The other issue was actually the at the inertia switch. Apparently the wire wasn't properly touching the pin or something. I pulled the pin out, re-adjusted it and put it back in and now my pumps turn on and the car runs again.

This was a very strange issue, but i guess the wire took its toll after 10 years of the cars life lol. That inertia switch area is something i never mess with. I realized it was the wiring when i realized the black/red wire should have also had power.

Thanks for all your help, you pointed me in the right direction. I'm just happy its not the pumps, i looked online and the prices of the supercar gt pumps are near $200 for 1! I bought mine when they were $90 a piece. Now I'm wishing i had bought spares.