Mechanics

GMC SONOMA FUEL TANK PROBLEM

2000 GMC Sonoma • 180 miles

Replaced the fuel pump module inside the fuel tank today. Motor started right up. However we have a fuel leak from a small black box located under the center of the pickup bed near the fuel tank. What is this device. Why is it leaking now after the pump replacement when it hadn't been leaking before. What's the fix on this type of leak. Thanks. Paulle.
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Guest
December 15, 2012.



Can you show us a picture of the part you are refering to? If it is after the fuel tank, I believe that is the EVAP Canister Control valve. Open the fuel filler cap to release the pressure in fuel tank.
Remove the canister control valve and check the hoses/lines for presence of fuel. Check the valve for damage.
When replacing the fuel pump, was any hoses wrongly connected?

KHLow2008
Dec 15, 2012.
Thanks. There is definetly fuel in the hose going to this device. It is rectangular in shape about 4x2 inches mounted above the drive shaft to the underside of the truck bed. The hose to it is large diameter (like a heater hose and unlike those smaller lines coming off the pump) about one inch diameter. There's fuel in the hose. Is this device designed to handle fuel vapor or liquid fuel. There were three fuel lines coming off the fuel pump. Two were of the same diameter. Looking at them head on in the direction where they coupled with the fuel lines, the two to the left were the same diameter, the one on the right was larger diameter obviously the engine feed. Of those two smaller ones I connected the one on the far left (aft) to a fuel line that ran aft to the rear of the truck. Probably going to this evap valve which is now leaking. The center fuel line ran forward to the front of the truck. Were they switched on the assembly. Thanks for responding. Paulle

Tiny
Paullefebure
Dec 15, 2012.
. The leak stops when the gas tank cap is opened and pressure is released.I think the fuel lines to the pump are ok. The engine starts and runs good.I now see the larger recovery cannister which receives fuel lines from forward end of the truck. The large hose that goes to the leaking device originates there. The faulty condition seems to be excess pressure in the fuel tank forcing fuel out to this smaller control valve. Is there supposed to be fuel at the control valve lor just fuel vapor? Paulle

Tiny
Paullefebure
Dec 15, 2012.
Is the Check engine Light indicating?
When there is a failure in the EVAP system, it would normally trigger trouble codes.

The component is for fuel vapor venting purpose and there should be no fuel in it, at leas not too much.

There is a possibility the hoses were switched when installing. One line is for the fuel return from engine fuel rail and would have liquid fuel in it.

The other is connected to the EVAP canister. Disconnect both hoses and put a container to collect any fuel coming out. Turn ignition on and note which hose has fuel returning, which should be connected to the fuel tank and not the valve.

KHLow2008
Dec 15, 2012.