Hi, i have a 98 blazer with the 4.3 6cyl. Running rough and whislte.
It was running just fine even with the service light is on due to the fuel tank pressure sensor.

Problem is i hit about a 4-6 inch rock in a parking lot with the rear right wheel.
Coincidence ?
Thats when it all of a sudden had a rough idle and acceloration. Cleaned the whole thing from air filter to carb.
I noticed a constant whistle sound so started crawling around and from what the closest i can tell its coming from near the top of the fuel tank.
Possibly the rough running issue.
Any suggestions or ideas. Thank you.

 

The fuel pump may have been jarred from hitting the rock. With the ignition off, apply battery voltage to the pump prime terminal, in the underhood fuse panel, and see if the noise is still there.

 

Thank you, i will try this on friday before our blizzard gets here.

 

Just letting you know i am not ignoring the suggestion. Never got to try before i got almost 2 feet of snow on blazer. Hopefully soon.

 

Ok did that and i hear the pump go but no whistle like i heard. Is there vaccum lines up around the tank ?