Voltage drop on startup. PISSING ME OFF!

[2fast4y0u]

ok,
thought it could have been the battery, thought it could have been the alternator...NOPE!

so i bought a brand new Braille battery. much better then that shit hold i had before (odessy pc680). hooked it up today, and i have 13v before the fuel pump cycles, or before my altima fans turn on(which i have a DIF fant controller now).

after either of those run/cycle i have 11.2. if i start the car it goes from 13 to 11.2. then i have to rev it up to 2500-3000 to make the alternator "kick in" and get the volts up to 14.5

if i remove the fuel pump fuse, no issues. I just installed a brand new walboro 255(same as before) and it does the same thing. the old wiring for the pump on the harness was all crappy, so i used the new harness and soldered instead of using the connectors.

so, can any one think of a reason this is happening?
i have the radio turned off, no blower motor, no extra accessories running.

Jay

[NINJASPY]

grounds? voltage regulator?

[2fast4y0u]

grounds should all be good. i actually put a few more on just for good measure
voltage regulator: if u are asking about the one in the alternator then its "good". i have taken it to autozone, napa, and an alternator shop near me and that all said its good. i even bought an extra alternator to compare and same thing.

[NINJASPY]

13v(off) to 11.2 with fans on and engine off?
and 13v(off) to 11.2 with engine on?

thats a pretty big amperage draw by the fans,
whats the rating of the battery? cca?
alternator belt tight?

[2fast4y0u]

yep.
if i turn the key to acc volts read 13v...as soon as the key goes to on, volts drop. mostly from the fuel pump cycling.
the fans dont run constantly like before(had them hooked to the ac relay). so the fan issue is not a priority.

battery is 880 cca. alternator belt is tight.

[2fast4y0u]

checked the alternator ground today it is good. also checked the starter ground, it is good as well.

[2fast4y0u]

to the top.
still need help on this

[NINJASPY]

after the fuel pump primes, it should go back to 12-13v

you mention- "if i remove the fuel pumphttp://images.intellitxt.com/ast/adTypes/2.gif (http://zilvia.net/f/#) fuse, no issues" so it has no issues with fuel pump fuse removed? its at a constant 12v?

[2fast4y0u]

the volts dont return after it cycles though

correct, if i remove the fuel pump fuse from inside the car, no issue, but then i cant be 100% sure because the car wont start with out the fuel.

i talked to an alternator shop(they work/repair them) they said i might have resistance between the positive wire from the alternator and the battery that could be robbing the power the alternator is creating at an idle speed.
i dont know how accurate that info is. i was hoping to maybe get a smaller alternator pulley because that would make it "charge" at a lower rpm.

[MrChow]

Okay just checking do you have at least 4ga power wire from your
Battery Negative to Chassis
Chassis to Engine Block
Alternator Positive to Battery Positive (optional fuse)

If you still have a problem check how much your Fans are pulling.

[mxexux]

Just curious but how are you getting these voltage readings? It almost sounds like your looking at a volt gauge. Also, the voltage drop while the engine is cranking is perfectly normal as long as it doesn't drop below 7VDC. As your mechanic suggested you should be checking for voltage drop in all the battery and alternator cables with a DVM.

[2fast4y0u]

im using the oem battery cables still, so what ever size they are
i will check the fans pull today

voltage reading are coming from a volt gauge that is connected to the ecu

i guess what im concerned about is after i start the car and the volts drop, if i dont rev it up to get the alternator going the car will die from not having the power to ignite.

[Ben G]

having a little built up voltage in your battery while your car is sitting is normal it is suppose to drop when you put a load on it like turn your car on or turn on your headlights thats when your are suppose to really measure the voltage of the battery go borrow someones dmm and i think those extra ground wires are fucking you up, extra wires means extra resistances which the circuit that the alt is on is made to handle a certain amount and you are changing that with the length of wire

[mxexux]

Get yourself a good dvm and start measuring voltage drop across the battery wires as well as the alternator. If what your gauge is saying is accurate of actual battery voltage then it sounds like the wire going from your alternator to the battery may have high resistance. This is also considering that you have already tested the alternator to be good.

[ixfxi]

alternator sensing wire isnt working, there is a problem with your wiring.

[ixfxi]

and i think those extra ground wires are fucking you up, extra wires means extra resistances which the circuit that the alt is on is made to handle a certain amount and you are changing that with the length of wire

sorry


but more wire doesnt mean more resistance. more wire = more gauge = less resistance.


i dont believe in millions of ground wires, but more wires for sure cannot hurt as opposed to not having sufficient ground. its more or less redundant and therefor rather pointless, thats all.

[2fast4y0u]

alternator sensing wire isnt working, there is a problem with your wiring.

which one is this? i would like to start with that and then check everything else

[MrChow]

Have you try what I said??
Add a power wire from your Alternator Positive to Battery Positive.TRY IT.

[ixfxi]

which one is this? i would like to start with that and then check everything else

Have you try what I said??
Add a power wire from your Alternator Positive to Battery Positive.TRY IT.

its the main power wire, that goes from your alternator positive to your battery positive.


try it.

[Broadfield]

In regards to your problem of the alternator not "kicking" on until you rev it up:

What motor is this on and is it the OEM alternator?

[2fast4y0u]

its an sr redtop and it is the oem anlternator.
i will try the direct wire thing here shortly. finishing up work

[MrChow]

Also how do you know the ground is good? How did you check it? Cuz there no real way to check it.
Did you ground both Engine and the battery when you add grounds? or what?

Me personally have my engine and battery ground with 0/1ga wire and 4ga for the alt wire. I have a pretty big amp and el fan and I my volt is 14.4 at idle till I boost the vol or fan.

[Broadfield]

its an sr redtop and it is the oem anlternator.
i will try the direct wire thing here shortly. finishing up work

Is it the OEM SR alternator? Or do you not know for sure. Because at one point I used an OEM 240sx alternator on my SR. However, I had to use the SR pulley because the number of grooves is different. The SR pulley and the 240 pulleys are not exactly the same diameter. So I had to rev the engine a little before it would kick on. So I went back to an SR alternator.

[2fast4y0u]

well i guess i dont know for 100% but thats the pulley on the motorset i got and it fits the belt.

i will check tomorrow when i get to my shop