Iv searched three diffrent sites and some websites but couldnt find it.Can someone give me a link to where i can find the write up to rewire the fuel pump to get 12v.

Thanks
jake

 

run a +12V wire at least 10 guage, from the battery pos. terminal to the back of the car. i go under the front carpet, under the rocker panel, beside the storage bins, under the rear carpet.
Run this wire to pin 30 on a 30A relay (available at radio shack). cut the stock wiring about 6 inches from the pump, and run the large positive wire (power side) to pin 85, the negative wire to pin 86. run the pump side of the positive wire to pin 87. also, unscrew the terminal where the ground bolts on to the top of the pump housing, clean it really good, and run a solid ground to some good point on the body, or just run a 10 or 8 guage ground all the way to the battery negative (what i do)

make sure all connections are very secure. soldering is best, crimp terminals are good too. wrapping and taping isnt.

if you cant figure this out, i or someone else can make a diagram for ya.

pat

 

Thankyou, if i could get a diagram that wiuld be better.Im better with wiring diagrams than i am with explinations

 

http://www.1300cc.com/howto/how2/rewire.htm, nzconvertable has an easy to fallow diagram on this site, just do a SEARCH and you will find it. I did this to my car and SEARCHED and found a crap load of info on this. really do a SEARCH and you will find what you need.

 

Note that the fuel pump rewire I did does not change the fact that the fuel pump sees low voltage at low load, it only eliminates most of the voltage drop caused by long, skinny wires. There's nothing wrong with the two-speed pump system, and there are no gains from removing it, only losses.

 

can you elaborate more? it looks like you did yours the same way 1300cc did thiers? Maybe I'm wrong. All I know is after doing yours I saw dramatic increases in fuel pressure.

 

Elaborate on what exactly? I followed the same procedure written by Dale Clark and posted on Scott's website. I just drew a better picture.

What exactly is a "dramatic" increase in pressure? How much? It should have been minimal, since voltage at the pump only goes up 1-2V.

 

oh ok I thought you did something differant than what is "norm" for the fuel pump rewire. Well as far as the differance before and afterwards, I was only getting about 40psi at all loads and as soon as I did the rewire I get the full fuel pressure I'm supposed to. My fuel pressure was so bad I couldn't boost and as soon as I did this I was able to boost. Pretty dramatic to me

 

I'm thinking about trying this, as soon as I can verify what pressure I'm pulling tonight.. Thanks for the links to the writeup, although I'm sure i could have searched when nessicary, It was rather convient to have a link right there

 

youre only supposed to get 40-45 psi....

 

not with boost.

 

40psi at all loads? Or 40psi at max boost? Fuel pressure is supposed to vary with load. It should peak at ~37psi + boost pressure. What boost are you running and how much fuel pressure do you see now?

 

Well basically when I would drive without the rewire I wasn't getting anything above I believe 40psi, may have been less than that however even if I was getting on it or if I was just cruising. I did the rewire and I started to boost and my fuel pressure would rise with boost.

 

Is there a simple way to tell if you should rewire, or is it just better safe then sorry?

 

Go back to the connector at the left rear strut tower (pull back the carpet). On the S4's, backprobe the BLUE wire at the HARNESS side of the connector. Make sure it's harness side, not pump side. Set the meter on volts. With the negative lead of the meter, go to chassis ground. Nice bare metal spot. With the car running, on cars WITHOUT the resistor pack, you should see at least 13v at that spot, IMO. I see about 13.4v on stock wiring with the alt running about 13.75v on mine, and that's pretty damn good with that wire run on a 12v system.

OR, leave the engine off, check the voltage at the battery terminals. Record this number. Jumper the check connector for the fuel pump. Turn the key on. Record voltage at that connector as noted above. Record that number. Voltages should be within 1v of each other between the batt and the connector (again, IMHO, there are no "rules" set in stone for this, I'm falling back on my experience with low voltage chassis-grounded systems here)...

On the S5's, I don't know what color wire may be at that connector. Maybe blue, I dunno. Check your FSM wiring manual.

And, on the cars with the resister packs, I can only guess as to what voltage you should be getting at idle (I've heard 9v, but that figure may be system voltage, before the wiring run drops it)...

 

Simple rule: If you're going to mod it, rewire it.