tman94

i have a 1990 Chevy C1500 with a 350 V8 in it. im like 99% sure its not the original engine that was in the truck. the guy i bought it from said that they replaced the engine, ecm, and the wiring harness. the truck will start, but will not idle. it starts fine sometimes and other times you have to push the pedal in just a hair to get it to start. once its started, it will run fine as long as you give it gas. if you let the truck go to an idle, it will idle anywhere from 1-30 seconds then sputter and die. it doesnt backfire or anything, just does. the injectors are spraying fluid just fine, and i just recently today, took out all 8 plugs, cleaned them with a wire brush and re-gapped them. it starts better now but still does not want to idle.
any help would be much appreciated.
oh and my other question is, i need to bleed the brakes but i know some vehicles, it needs to be running in order to bleed the brakes correctly so i was wondering with this vehicle, does it need to be running to bleed the brakes?
thanks alot everyone for your help in advance.

samsaridinc1500

I'd give the throttle body a good look over, for starters. A lot of people don't even think of it, I didn't either until my '96 did the same thing and somebody mentioned it to me. I just pulled off the intake and opened the butterfly to see that the inside had a bunch of crap just dried up and gross from the last 17 years in there. If that's your problem just pull the throttle body off, cover the electric plugs and clean it with a toothbrush and a liberal amount of carb/throttle body cleaner. Also spray some on a rag and clean what you can around where the throttle body actually mounts.
One other thing I'd check is the throttle position sensor. Also pretty easy, just need a multimeter. I don't remember the exact steps but it's pretty easy to find online. After that I'd look into fuel delivery. Good luck

tman94

okay so i havent done anything to it yet. i actually just checked this today but thanks for the help. as soon as i can, ill take the throttle body off and clean it. in regards to the fuel delivery, i was talking to my buddy and he said his truck requires 45-60 psi fuel pressure to run properly and i googled the fuel pressure and everywhere i look, its says only 10-15psi. now i dont know if my buddys truck has any aftermarket parts and i dont know if that would even affect the fuel issue.

Camaro 69

Your truck has/had a TBI unit, which is a throttle body that resembles a carburetor. You want 12 psi, (+/- 1) with the engine running.
Your buddy most likely has a newer truck with multi port injection (individual fuel injectors), which explains his higher fuel pressure requirement.
Here's a TBI troubleshooting guide

tman94

well i found out that they had the wrong serpentine belt so i got a new one and got the belt routed right and put more gas in it just too make sure i wasnt low on gas and i noticed while looking at the tbi that theres 2 gas lines that run into the back of the tbi but there isnt any schrader valves so how would i go about to check fuel pressure? also, on the ignition coil, theres 4 wires that come off from it in sets of 2. 2 go off and connect to something then the other one goes off and connects to something off whilst the 4th one just goes off like 4 inches then has a connecter on the end of it and isnt connected to anything, could that be something that affects the starting of the truck?

marinetech

i have a 1990 chevy 1500 w/ 350. this is one of those things that you don't listen for until you have to listen for it. My fuel pump has a very intermittent cycle when i key on. lets say i cycle the key 10 times in a row, the pump may cycle twice. is there a built in pressure regulator of some sort or do i have a weak fuel pump? it wouldn't start this morning, so this afternoon i introduced it to carb spray. needless to stay, i had air, i had fire, i just needed the fuel. once i introduced carb spray into the tbi unit, it started. i ran it around the block and it ran good. i then shut if off and tried to restart it and it had a very hard start and the fuel pump continues to be intermittent. so, back to my original question, should my fuel pump cycle every time i key on?