Finally got our 92 4wd CPI blazer on the road. So far we have replaced the fuel pump, fuel filter, sending unit, and the fuel line assembly. She starts up with the first turn of the key and runs great for the first few minutes. Once she starts to get warmed up she starts sputtering (starts at 35-40 mph). Usually when giving it gas, the sputtering stops but starts back when letting off the gas and we can hear whining. The whining sounds like it's coming from the back area (underneath the back seat area). All of the parts we've replaced on this old gal has been done over the past two weeks.

There's so much stuff on this forum (and a blessing it has been) but it overwhelms me trying to read through everything to find answers to my issues. What do we need to check out regarding the sputtering (not a backfire, but more like a pop-pop-pop sound as if trying to blow out a clog or something) and the whining. That sounds like it could be coming from the fuel pump, which is brand spanking new. Put just over 3 gallons of gas in it this morning and so far have possibly driven it 14 miles. (Low gas maybe causing the whining?).

 

Out of curiosity, what brand fuel pump did you install?

 

not sure what brand, just the autozone brand...pump, strainer and sending unit all in 1...it was only about 110.00. Im thinking the pump is whining because it is very low on fuel. When I replaced it and had the tank out I thoroughly dried and cleaned all of the old fuel out of the tank so it literally only has a couple of gallons in it. The sputtering seems to be associated with the air or exhaust somewhere. What would the symptoms of the map sensor, or the egr sensor be??

 

You need to check the fuel pressure and leakdown. Aftermarket pumps generally don't last long in these trucks, if they are even good off the shelf.