gastank wiring HELP!!!!!!!

**89 406 6speed** · 06-09-2007, 01:45 PM

installing 2000 ls1 gastank in 1989 iroc need to know the wiring of the ls1four wire plug there A B C D letters on it. please can anyone help.

pulled out sending unit there are two purple wires to the sending unit and a black and gray wires to the fuel pump.

also this unit all stock.

thanks raleigh

**0rion** · 06-09-2007, 02:49 PM

the black is ground, grey is hot, the 2 purple wires are to the sending unit and I don't think it matters which way those 2 go on there. As for how it wires up to that plug I can't help you. Since you're putting it in a 3rd gen then you have no way of testing the car side of the connector but can't you test your existing wiring for the hot and ground?

**89 406 6speed** · 06-09-2007, 04:57 PM

The car only has one wire for the sending unit, red so i assume its hot, i havent tested it. the tank grounds to the body on the 3rd gen but the ls1 doesnt seem to have a ground for the sending unit, only the two purple wires and thats where it gets confusing as to getting the gauge to work.
i thought the black was ground and the gray was hot but wanted to double check.
im afraid to hook up the two purple wires wrong and mess something up. im hoping someone can tell me for sure how to hook them up.
thanks raleigh

**0rion** · 06-09-2007, 10:02 PM

I know the ohms are different between the 2 so your gauge won't work. I can't say for certain yours is definitely different but I know gm's old standard was 0-90 ohms and my 98 is 40-259ohms. Back at one time I looked around for an aftermarket fuel gauge and although I found 1 or 2 there wasn't a ton of gauges out there for the 40-259ohm senders. There might be now. Check the ohms on the purple wires to be certain but I'm betting it's 40-259 ohms. If I remember correcly 40 is empty and 259 is full. Just put a meter on it and manually swing the sender. Now, how do you wire that up to even work with an aftermarket gauge?? Beats me.

**89 406 6speed** · 06-10-2007, 05:43 AM

thank you for the help. ill check ohms. and ill also look into autometer gauges although i wanted to use the factory ones. thats the way customizing goes though its never easy!!!!!

**sleeper** · 06-10-2007, 09:58 AM

A= 5V source PCM
B= fuel pump relay
c= Ground
D= PCM low reference

A=PCM low reference
B=fuel tank pressure sensor signal ground PCM
C=5V source PCM

**89 406 6speed** · 06-11-2007, 04:36 PM

does anyone know of a fuel gauge that will wire up to the factory sending unit directly???? not through the pcm

**0rion** · 06-15-2007, 08:49 PM

did you ohm out that sender to verify the ohms? If so just contact someone from autometer or your preferred gauge company. Back when I was looking for one I did find one that worked with 40-259ohms but don't remember who made it or where I found it. If I stumble onto it again I'll post it up for you.