Ever since I had the fuel pump changed on my 1998 Chevy Blazer, the gas mileage has gotten worse.?

Fuel pumps working as designed . I don't know about any check engine light problems you may

have had but oxygen sensors can take away gas mileage, The pump installers may have left line

loose but you should smell fresh gas if this were true. There are fuel pump regulators that can cause

these problems. You sound too me like if the gas mileage is that bad it should be checked out at

a place that has proper scan tools and resources.

I have a 98 blazer that the fuel pump went out on it the same day i bought it. There is a test wire you can hook up to your battery somewhere under the hood that's supposed to kick on the fuel pump if it's good, (i couldn't find it, but the repair manual says there's one). Dump alittle bit of gas down the throttle body, if it starts up and dies, then it's either your fuel pump, fuel filter, fuel pump relay, or your just plain out of gas. Hope this helps you

The reality is the fuel pump doesn't really control the mileage. That is a function of how efficient your vehicle is burning fuel. New plugs and wires are a must. However, you may want to check all of your fuel line connections and ensure that they are not leaking. Though not directly a function of the pump, if you are squirting gas out of fittings, you aren't burning it!!

no..either the pump is pumping enough to run or not,,,tune it will yuh