Post by Akµmi on Jul 24, 2006 23:45:27 GMT 7
get some info on the net.......
Rewiring the fuel pump with a larger gauge wire can help the stock pump (or any aftermarket pump) maintain higher fuel pressure/volume throughout its' entire operating range, as the stock wire is pretty small. The small wire limits the voltage to the pump, and under high boost, the lower voltage can severely affect fuel output. Some people have measured 10 volts or less at the pump under high boost with the stock wiring. Adding a larger wire and relay to feed the pump can restore the voltage to that of the battery (usually 13-14V), maximizing pump output.
So, how do you do it? It's pretty simple - just add a larger gauge wire (anywhere from 12 to 8 gauge will help, the larger the better, though 10ga seems to work fine for most people) from the battery, and run it to a relay mounted near the pump. Then cut the stock 12V wire leading to the pump, and splice the relay inline
This is a schematic of your basic relay used ( SPDT (Single Pole Double Throw) Bosch relay, others may be laid out differently, but the numbers of the terminals should match - you can buy these at any decent car stereo shop, NAPA, or even Kmart, sold as a foglight relay. Supposedly Walmart sells amplifier install kits in their car stereo section, if you find 2 kits, buy the larger one).
For reference, the terminals are:
30 - feed wire
87A - Normally Closed (NC) terminal
87 - Normally Open (NO) terminal - the wire that the relay switches to when the relay coil is energized
86 - relay coil
85 - relay coil
Note that these relays can be used in many different ways, and the terminals can be used for input or output depending on use, but I am only going to cover the way I would use them for the rewire.
My usage for the pump rewire:
30 - feed wire from battery
87A - Not used
87 - when cutting stock 12V pump wire, this is to the pump
86 - when cutting stock 12V pump wire, this is to the car
85 - ground
Note that the relay coil terminals can be switched, 86 can be ground, 85 can be power from the car.
Note that a very quick and easy anti-theft additive is to add a switch to the 85 wire (or 86 if that is what you use for ground) - with it turned off, the pump will not be powered with the ignition on, so a thief can't start the car until he finds the switch.
OK, so now you have the wire located on the car side of the fuel pump harness plug. Now what to do? Simple - cut it in half. I suggest removing the rear plastic side panel, and cutting it back behind there, so you can mount the relay behind that panel. So you now have a cut wire, what to do. Well, you wire the relay in as I said above:
30 - feed wire from battery (Large RED wire)
87A - Not used
87 - when cutting stock 12V pump wire, this is to the pump (yellow wire in my picture, not stock wire color)
86 - when cutting stock 12V pump wire, this is to the car (long green wire in my picture, not stock wire color)
85 - ground (black wire in my picture, not stock wire color)
So get the wire you cut in half, and attach the end that runs towards the pump to terminal 87, and attach the other end to 86. This causes the stock wire that normally feeds the pump to now turn on the relay. The relay gets power directly from the battery, and feeds it into the stock wire that leads to the pump. This lowers the voltage drop caused by the small gauge stock wire that runs from the front to the rear of the car, since now all that stock wire has to do is turn on a relay. Note the 2 short green wires in the photo - these are an emergency bypass. If the fuse on the feed wire blows and you have no spare, or the relay dies, reconnecting these two bypasses the relay. These are simply a jumper from 86 to 87.
Oh, this normally doesn't have to be said, but I'll say it anyways...
MAKE SURE TO FUSE YOUR LARGE GAUGE FEED WIRE AT THE BATTERY. I'd suggest using a fuse the same rating as the stock fuel pump fuse (if you can even find such a rating), or slightly higher (but use a slightly higher one at your own risk). Personally, I use a 20A fuse and have had no problems.
Rewiring the fuel pump with a larger gauge wire can help the stock pump (or any aftermarket pump) maintain higher fuel pressure/volume throughout its' entire operating range, as the stock wire is pretty small. The small wire limits the voltage to the pump, and under high boost, the lower voltage can severely affect fuel output. Some people have measured 10 volts or less at the pump under high boost with the stock wiring. Adding a larger wire and relay to feed the pump can restore the voltage to that of the battery (usually 13-14V), maximizing pump output.
So, how do you do it? It's pretty simple - just add a larger gauge wire (anywhere from 12 to 8 gauge will help, the larger the better, though 10ga seems to work fine for most people) from the battery, and run it to a relay mounted near the pump. Then cut the stock 12V wire leading to the pump, and splice the relay inline
This is a schematic of your basic relay used ( SPDT (Single Pole Double Throw) Bosch relay, others may be laid out differently, but the numbers of the terminals should match - you can buy these at any decent car stereo shop, NAPA, or even Kmart, sold as a foglight relay. Supposedly Walmart sells amplifier install kits in their car stereo section, if you find 2 kits, buy the larger one).
For reference, the terminals are:
30 - feed wire
87A - Normally Closed (NC) terminal
87 - Normally Open (NO) terminal - the wire that the relay switches to when the relay coil is energized
86 - relay coil
85 - relay coil
Note that these relays can be used in many different ways, and the terminals can be used for input or output depending on use, but I am only going to cover the way I would use them for the rewire.
My usage for the pump rewire:
30 - feed wire from battery
87A - Not used
87 - when cutting stock 12V pump wire, this is to the pump
86 - when cutting stock 12V pump wire, this is to the car
85 - ground
Note that the relay coil terminals can be switched, 86 can be ground, 85 can be power from the car.
Note that a very quick and easy anti-theft additive is to add a switch to the 85 wire (or 86 if that is what you use for ground) - with it turned off, the pump will not be powered with the ignition on, so a thief can't start the car until he finds the switch.
OK, so now you have the wire located on the car side of the fuel pump harness plug. Now what to do? Simple - cut it in half. I suggest removing the rear plastic side panel, and cutting it back behind there, so you can mount the relay behind that panel. So you now have a cut wire, what to do. Well, you wire the relay in as I said above:
30 - feed wire from battery (Large RED wire)
87A - Not used
87 - when cutting stock 12V pump wire, this is to the pump (yellow wire in my picture, not stock wire color)
86 - when cutting stock 12V pump wire, this is to the car (long green wire in my picture, not stock wire color)
85 - ground (black wire in my picture, not stock wire color)
So get the wire you cut in half, and attach the end that runs towards the pump to terminal 87, and attach the other end to 86. This causes the stock wire that normally feeds the pump to now turn on the relay. The relay gets power directly from the battery, and feeds it into the stock wire that leads to the pump. This lowers the voltage drop caused by the small gauge stock wire that runs from the front to the rear of the car, since now all that stock wire has to do is turn on a relay. Note the 2 short green wires in the photo - these are an emergency bypass. If the fuse on the feed wire blows and you have no spare, or the relay dies, reconnecting these two bypasses the relay. These are simply a jumper from 86 to 87.
Oh, this normally doesn't have to be said, but I'll say it anyways...
MAKE SURE TO FUSE YOUR LARGE GAUGE FEED WIRE AT THE BATTERY. I'd suggest using a fuse the same rating as the stock fuel pump fuse (if you can even find such a rating), or slightly higher (but use a slightly higher one at your own risk). Personally, I use a 20A fuse and have had no problems.