So I've been trying to get my 91 gmc 1500 to idle for the past 3+ months with no luck. Im switching back from a carb to TBI and its a nightmare.

I know everything works, fuel pump works when I put power to the orange wire you use to drain your fuel tank, But wont work when I turn the truck over.

I know the throttle body is good, cause I pulled it off a running truck. I also checked to see if im getting power to my injectors and I am. I even turned the motor over to see if the plug ins to my injectors pulsed, they do.

I also have spark. and yes, there is gas in the truck.

I do have to phantom wires, BLK/WHT and a BRWN.
The Black and white one is coming off the throttle body somewhere. cant remember were off the top of my head.
The Brown one is comeing from the firewall.

The truck will run if someone keeps putting gas it. Also has great oil presure.

I've done everything I can think of and everything anyone else can think of, But the thing will not run and idle on its own.

I would love some help if anyone can give it, cause its a good looking truck. No rust and no dings. So id love to get it running instead off dumping it on craigslist.

 

Sounds like you need to check each wire in the fuel pump relay circuit. Do you have a manual to see what the "phantom wires" are for? Can you take a picture and post it here so we can see where they are exactly?

 

I think the black and white is a ground. So i think I'll try grownding it somewhere. I do have a chiltons, But I cant find the brown wire in it. I think i'll need to just bring the chiltons in the house and jusst go threw the whole book

 

If I had a throttle bodied truck I would check it for you. Do you know anyone that might let you take a peek under their hood to see whats what?

 

Well it is obvious that it is a fuel issue. Have you checked under the truck for a collapsed fuel line? Maybe an injector has seen better days. Do you have a way to check the fuel pressure on the truck?

 

I dont have a way to check for fuel pressure.

I do know the throttle body works though. I pulled it off a truck that i seen run.

 

On my 91 iacv light green blk stripe, lgt green, lght blue lght blue blk stripe.
tps drk blue, gray, black.
map. gray, lime green, purple.
Injectors. wht, blue green red.
cts. yellow, blk.
grounds brown whtstripe, brown, tan. Should have 4 ground wires.
Mine has the grommets on them. Try changing cts.