The 1947 - Present Chevrolet & GMC Truck Message Board Network - View Single Post - 89 S10 4.3 Need help troubleshooting TBI/IAC Idle issue

76C10Stepside · 08-24-2014, 05:50 PM

I just checked the gas can, and it had close to 1-1/2 gallons of gas in it. I removed the can, and gas started dribbling out of the hose again at a constant rate. Put a coffee can down to catch it.

I unscrewed the gas cap part way, and a lot of air rushed in. The dribble of gas stopped! For how long, I don't know.

Took a picture showing the rubber hose I'm using to divert the gas into the can where it connects to the fuel line leading to the engine/TBI, but it did not come out. But, I assure you, it's connected to the FRONT end of the fuel line (that goes to the TBI), NOT the back end that comes from the tank. The BACK end is clamped off with a c-clamp and plugged with a tapered dowel, and is not leaking at all (no sucking sounds either).

All this gas MUST be siphoning out of the tank, through the return line??? Does the Fuel Pressure Regulator permit gas to flow BACKWARDS through it from the return line if there is positive pressure? How could the gas even get from the tank to the return line, which I assume is at/near the TOP of the gas tank?

Is this truck supposed to have a VENTING gas cap, OR a NON-VENTING?

08-24-2014, 05:50 PM	#47
76C10Stepside Registered User Join Date: Feb 2012 Location: Olympia, WA Posts: 300	Re: 89 S10 4.3 Need help troubleshooting TBI/IAC Idle issue I just checked the gas can, and it had close to 1-1/2 gallons of gas in it. I removed the can, and gas started dribbling out of the hose again at a constant rate. Put a coffee can down to catch it. I unscrewed the gas cap part way, and a lot of air rushed in. The dribble of gas stopped! For how long, I don't know. Took a picture showing the rubber hose I'm using to divert the gas into the can where it connects to the fuel line leading to the engine/TBI, but it did not come out. But, I assure you, it's connected to the FRONT end of the fuel line (that goes to the TBI), NOT the back end that comes from the tank. The BACK end is clamped off with a c-clamp and plugged with a tapered dowel, and is not leaking at all (no sucking sounds either). All this gas MUST be siphoning out of the tank, through the return line??? Does the Fuel Pressure Regulator permit gas to flow BACKWARDS through it from the return line if there is positive pressure? How could the gas even get from the tank to the return line, which I assume is at/near the TOP of the gas tank? Is this truck supposed to have a VENTING gas cap, OR a NON-VENTING?