Electrical issue?!

[HisandHerTurbo]

K, a lot of you will be seeing this as a repeat. BUT, I still think there is an electrical issue with my car and the reason my fuel pressure drops under WOT.

Once the car fully warms up there is around 13.0-13.3 volts showing in DSMLink. There is about a .3 volt drop from the alternator to everything else, which I guess is "OK", but who knows, so MAX of 13.6 at the alternator, but usually lower, expecially if the fans kick on.

Some will say this is fine voltage, then why under WOT due I drop to 12.0-12.2 (only after 1 1/2 gear pull, starting about 20mph and almost finishing second).

I have tried 4 different NEW alternators and currently have another brand new battery installed (700CCA).

What I have noticed electricly that isn't correct. The 2 factory white wires that connect to the alternator were "burnt" (about 6") so I cut off the bad and rewired it. Also the wire that feeds my fuel pump had a very small sign of burnt on the end that connects to the relay. I tried another relay, new fuel pump. IF the car ISN'T running I see the same votage everywhere on the car. Also tried stock ignition/MSD, stock coils/COP.

There is just something wierd in the electrical part........... where/how do I start? I have tried to see if any of my wires going from the alternator to battery were shorted, and nothing, besides, you would "Think" if there was a short some fuse would blow.

TY
JOE

[Spooled50trim]

Have you tried checking or possibly replacing ground wires? I had bad/low voltage when my ground wire to my tranny was loose.

[HisandHerTurbo]

Yeah, I have checked it, jerked it, re-connected it. I even added another 4ga wire going from the back (where the battery has been) up to the front where the stock wire is that connects to the tranny. What's also wierd is with the key off, or even on voltage everywhere in the car is the same. BUT, when I start the car I have about a .3v drop from the alternator to the battery.

[Cloud]

So you have your battery in the trunk? Is it possible your power wire is crimped somewhere or something similar? Generally the modifications you do are the first things to look at when something goes wrong. The reason you would see more voltage drop when you run the car is because you are drawing more current through the same resistance.

In a system that is properly wired you 'shouldn't' see noticable voltage drop but for instance my friend left off an engine ground strap and the car started VERY slowly if at all trying to ground through auxilliary components. There was nearly 6v of drop when the starter cranked at that point. Is .3v enough to worry about? Maybe at the full current draw of WOT it turns into 2v of drop and one of your relocation wires is corroded/crimped or something.

[XakEp]

If it really is a short, the only way to prove it dirty is to get the multimeter out and have fun going through yards of wire. Personally I dont think its a short - I think its the stock alternator utterly blows when trying to handle any kind of load. Brian has a good pont - check your wiring for the pump both visually and with a multimeter.

[drcustom]

In audio a trick to reduce the effects of voltage drop was to upgrade some wiring. It's called the "magic 3" or the "big 3".

Battery negative to Chassis
Chassis to Engine
Alt to battery positive

Wiring is only as good as the weakest connection in the circuit. You can run 00 gauge from your alt to your battery, but if you've got 10 gauge from your battery to chassis, or chassis to engine, then current is basically bottlenecked by the 10 gauge. Also check your connections - rust, corrosion, or a loose connection at any point (including your terminals) can cause similar issues.


PS - "you would "Think" if there was a short some fuse would blow."
You still might want to check your fuses to be sure the last owner didn't short one or use a rating that was way high.

[Wazzelby]

You can also run a ground from the alternator to the frame. Adding grounds from electrical components is a pretty easy (and cheap) test.

[HisandHerTurbo]

The battery's always been in the trunk. The only difference is 2 added wires and where my MSD and Fuel pump get their power. Added the 4GA extra gound (just for good measure) and also added a 0/1ga wire from the battery.

I don't thnk that .3 is really enough to worry about, just wierd that it's different, when running and with the key on.

I checked the fuel pump wiring, even tried a "live" wire straight from the battery.

I have visually checked and with a multimeter checked every inch of the (2) 2ga wires and also the new 0ga wire going from the front to the back.

I am the only onwer and also did check all fuses and all are good and the proper amp rating.

I think I am going to start dis-connecting stock sections of wiring and just run jumper cables to see if something changes as far as the .3v drop. I just think with NO drop with just the battery and then .3 at ONLY idle when the alt actually tries to put put power there is a bigger drop.

[HisandHerTurbo]

Like for example, what I just tried........
I have 1 2ga wire that connects to the 2 factory alternator white wires (through a circuit breaker) around where the battery used to sit. That runs to the back to another CB then into the battery, then from the battery to my kill switch............. I OPENED both of them circuit breaker and disconnected the B+ off of the alt. Then using jumper cables ran a connection from the B+ back to the battery........... still a .7v loss. 14.2v at the alt and 13.5 everywhere else........... that was after the car warmed up a lil it was 14.5 and 13.8 at the beginning. I even added the open circuit wires BACK to the equation (more wire, carries more power) volts didn't change. I also used the other side of the jumper cables to add another ground this whole time.

It really sounds like either something is shorting out or causing excessive drain AFTER the alt and battery. Like in the car wriing itself. And I don't really know how/where to begin checking that.

Aside from the ignition/injectors/fuel pump, what is actually "working" when the car is running vs. just the key "ON". I have tried to dis-connect one injector at a time to see if there was a wierd draw there, but nothing.