killernoodle

So I've got an accessory fuse/relay box on my turbo CTS-V that I'd like to signal with the fuel pump signal. This relay box has 5 301-1C-C-R1-U01-12VDC Automotive Relays which are draw about .1 amps on the coils a piece. If it switches all 5 of them (and the existing fuel pump relay as well), it will be a over 500mA and 6 watts being drawn from the dark green/white wire on the PCM.

Is this acceptable? Am I going to burn out anything on the PCM doing this? I'd love to do this because I've got 2 fuel pumps in the surge tank, an intercooler pump, and a oil scavenge pump all running from this relay box. I don't want them all running when the motor is cranking or when I'm just sitting in a parking lot with the key on, which is how it's hooked up now (it really kills my cranking amps)

maroonls1z

Why don't you run it through an additional relay and use the fuel pump as a switching power source so that the power goes to the fuel pump it completes a circuit between your new board and say the battery or the alternator. That way the power is not coming off the same line that feeds the fuel pump?

killernoodle

Well for one, the relay/fuse for the stock fuel pump is behind the driver's seat and under the passenger seat. The wire bundle that goes from the PCM to that fuse box passes right through where my fuse box is installed. I don't want to pull another wire through the car if I don't have to, I'd rather just make the relays all trigger from the same wire.

I guess my main question is, do you guys think it's OK to draw a little less than an amp from the PCM's fuel pump signal wire? The actual power for all the pumps is coming from the battery, I'm just talking about powering the coils on all those relays.

nuntheweiser

If you're running 5 relays and are concearned about drawing .5A from the computer to power them, maroon's solution is the best. However, another solution is to have one relay pull off the PCM signal to trip it, then run the other 4 off the switched power of the first. Draw .1A as opposed to .5A

toplessHO

iTrader: (25)

yep slave all relays off of the output of fuel pump relay
or parallel one relay with the fuel pump relay,and slave them off of it.
you can jumper the Commons to fused power and the + coil side off the other 4
fed off the NO on the first one.