Higher amp alternator?
 

I have a 140amp right now that's pushing out 14.6 volts at the alternator terminal. After about 5 minutes the fuel pressure gauge fluctuates. And when I turn everything on, the volts drop to 11.5. The car has a FAST EFI, electric fan, electric water pump, electric fuel pump, Halo and LED lights all around (with correct conversion), a Gear Vendors OD, electric windows, and a defroster fan. Am calling Powermaster tomorrow but want to hear what ya'll are running.

Is after five minutes of running when the car really idles down? What speed is your alternator running at (pulley ratio)? More food for thought. Look into all your accesory amperage draws and add them up. It might be surprising how much power all those things need. This is where some guys are getting into pwm for fans and fuel pumps, it does cut down on power usage.

How big is your charge wire, more times than not I see too small of a charge wire that results in low voltage output to the battery.

I'm with Tim ---- might be too light of a gauge of charge wire --- BUT --- Always the big Butt!!

CHECK YOUR GROUND circuit as well!! Too light of a gauge wire -- or inadequate ground circuit will also be a problem with voltage drop and NOBODY ever thinks to check that side....


Grounded motor to chassis -- to body -- to battery....

Ok, it's reading 14.2 at the alternator and 13.9 at the battery in the trunk. I just bought another 4 gauge wire and ran it from the alt to the starter. The ground strap is a flat, metal 4 gauge with a clean ground to the frame. With the car idling at 800rpm and everything on, my laptop says 10.2 and my fuel pressure gauge is still fluctuating.
Should I get a regular 4 gauge round wire for the alt ground? Also, would it be better to run that red 4 gauge wire from the alternator straight to the battery in the trunk? Thanks again.

I've used the starter as a junction --- should be okay....


I'd check the body to chassis ground --- assuming you have an intank pump.... might be that your tank isn't making good ground

I assume this is a 1-wire Alternator? That's why I will run a 3-wire and have the sensing line read voltage right where all the accessories create the voltage drop.


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Pump is external and has a good ground.
Tried a different ground wire and different ground spot on the alternator and am getting the same readings. The guy at Powermaster said this alt was sufficient. In fact I'm spinning it a little higher bc I have a 7 1/2" crank pulley and a 2" alt pulley. Oh and this is a GM 3 wire.

GM 3-wire, the like the others said, ensure you have good grounds. Engine block to frame & engine block to body, battery to frame & battery to body.

Battery to body? Even if I have a unibody car? Also, since the alternator is working but it’s not sending the right volts to the battery, does that mean that the starter solenoid, or whatever it is, is not working?