gobigorgohome

iTrader: (1)

had somebody tell me that all the ls wiring uses grounds to trigger relays.

i have a ls1 with a howell harnes and computer. i belive there harness is based off of stock and the computer is also stock


the question is:

what wire is used to trigger fuel pump relay?

is the wire 12v or ground?

i am running 2 walbro pumps on my off road racing car. plan is to have on and on switch switched to the remote wire to control 2 relays so i can have backup pump \\


help

Lextech

iTrader: (18)

The fuel pump output from the PCM is POS. The cooling fan output from the PCM is NEG.

Jeff

gobigorgohome

iTrader: (1)

thanks jeff, what are the wire numbers for pump and fans. is there only one wire i should use for both fans or is there two..


paul

arthropraxis

I think it is dependent on car the donor motor came out of. The GTO LS1 has one of the fan relays coming from the BCM not the PCM. What car did your motor come from?

gobigorgohome

iTrader: (1)

the harness and comp came from howell, pretty old though

engine was out of 99 camaro i believe

arthropraxis

Red connector fuel pump relay pin 9, high speed fan relay pin 33, Blue connector pin 42 low speed fan relay. If the 99 is the same as 2001.

gobigorgohome

iTrader: (1)

can i use pin 42 for one fan and pin 33 for another? what do those wires use to trigger, temp, ac switch?

arthropraxis

Right, you use red connector pin 33 for the high speed fan relay and the blue connector pin 42 for low speed fan relay. The PCM uses the temperature sensor in the drivers side head to get the info to trigger the fans. I think it turns on both fans when you trigger the A/C, not sure on that.

gobigorgohome

iTrader: (1)

so would each fan come on at different temp?

you said pin 9 but you meant 33 correct?

thanks agian

arthropraxis

My mistake, yes pin 33. I am doing this with a 3 relay setup. That is how the factory F-body fans are set up. This set up gives you dual speed fans. There are a lot of different posts about how to wire the fans. This is not the only way to do it but you still use those pins.

gobigorgohome

iTrader: (1)

ok so what i am trying to do is...(dual 12" perma cool fans btw)

i have all my own relays and circuit breakers just need to tie them into the harness...

i would like one fan to come on at a certain temp and the other later, hopefully the one fan can keep it cool and if needed the other kicks on. keeping both fans from coming on at once and drawing all those amps, sperate would be nice.

any insight on what wires and temps. this is by no means stock. off road racing truck.....

arthropraxis

Talk to Frost or one of the other tuners. The fans can be custom programed to come on at whatever temp you want. If the computer can't turn them on individually then use and independent circuit dedicated to each fan and cut the computer out all together. It may just be a matter of wiring the relays to get what you want.

bczee

iTrader: (12)

Any one have OEM Fuel pump relay diagram ? I've seen a few different ways to wire up the relay from some FAQ and threads.....

A Know a generic relay would be:
30 - 12+ power
85 - Ground
86 - Switched 12+ to activate the relay (from a switch or Key/ign)
87 - 12+ output to the device (lights, pump, etc that take a 12+volt input)

From the LS1Tech FAQ Sample #1 would seem to be backward of Sample #2 and generic wiring.
#1
LS1 FAQ
Terminal 85 connect to PCM Red 9 - Dark Green/White
Terminal 30 Connect to fuel pump 12V input
Terminal 86 Connect to Ground - black/white
Terminal 87 Connect to Switched 12V Power Supply

#2
from another thread:
Terminal 85 connect to pin D of C101
Terminal 30 Connect to Batery 12+
Terminal 86 Connect to Ground
Terminal 87 Connect to Fuel pump

Just wondering which way and if there is a Why ?

bjamick

iTrader: (31)

I believe the fuel pump is the only thing that the PCM actually sends out power to. Everything is else is done by providing a ground.

Here is a factory diagram of the fans:

bczee

iTrader: (12)

Thanks.. but I have the Fan Wiring figured out and done, have the diagram also.

I am asking for the specific OEM Wriing for the Fuel Pump setup and Relay.. wiring to which pin and color wire.

BC

Grewe02

iTrader: (4)

I'm using pin 9, dark green / white. Is there any reason why this pin would not supply 12v? I'm wiring my conversion and can't get the fuel pump to run. Relay and pump work when I use a 12v switched wire, but in trying do use the pcm wire instead.

DW SD

Normally, the computer outputs ground to trigger the switch side of the relay for the fan. Then normally, the other side of the switch, is 12V+. these are pins 85 and 86 on the relay. You could supply 12V+ switched via ignition or just 12V+ - always on. Make sure it is fused. And you probably need 30A or 40A fuse for the startup current if it is a large fan.

You could test the output from the computer with a test light with one side on the output and the other on 12V+ source.

Finally, as far as wiring, I'd wire the relay close to the fan and with heavy gauge wire for minimal voltage drop. I wired a relay box for my headlights and fan relay off of the alternator and in a water proof box. mounted on the frame rail ahead of the front suspension cross member. 6 - Gauge fed the relay box, which consumes 30A + 15A when the headlights are on and the fan is turning.

Good luck!

Doug

Grewe02

iTrader: (4)

So you're saying the fan relay needs to work in order for the fuel pump to work?

DW SD

Andy,
Yes the relay needs to be wired properly and energized first for the pump to work. Wire 12V+ dedicated to terminal 85 and fuel pump ground trigger from the PCM to 86 and it should resolve your issue.
Then 87 and 30 to 12v+ pump feed and high current 12v+ supply.

Doug

Btw - I wrote fan but meant fuel pump. They are wired and triggered in the same fashion by PCM ground trigger.

Grewe02

iTrader: (4)

I see, thank you I'll give it a try!