2000 Chevy Malibu Fuel pump/poor fuel milage

Tiny
BMBRDFRT
  • MEMBER
  • 2000 CHEVROLET MALIBU
  • 6 CYL
  • 2WD
  • AUTOMATIC
  • 136,000 MILES
I have a 2000 Chevy malibu ls 3.1l v6 This car is currently on its 3rd fuel pump. The factory one that was in it, then one replaced by my mechanic, then one replaced by myself. All pumps that were used were ac delco brand. The moment that I changed the last fuel pump myself I was only getting around 150 miles out of a full tank of gas/ that pump was 30lbs key on fuel pressure. As soon as I put the new one in wam was getting 50lbs key on fuel pressure and 300 miles out of tank of gas. Now after about 1 year my fuel milage has dropped back to 200 miles out of tank of gas. Tested fuel pressure today key on about 45lbs one of my questions is when my buddy turned the key to the on postistion the pressure jumped up to 50lbs then held steady at 45lbs. Now chiltons manual says operating range from 41 to 47lbs key on. I had someone tell me from 52 to 55lbs I have seen some blogs say that a terminal on the connector a female one loses springing activity and could be shorting out pumps? What is making these pumps go so fast? I change fuel filter regularly What is going on?
Friday, January 16th, 2009 AT 8:08 PM

5 Replies

Tiny
RACEFAN966
  • MECHANIC
  • 5,029 POSTS
Ok first I must get some info to try to help answer your question. How low do you run your fuel tank before filling up again? How full do fill when you get gas? How old is the O2 sensor as this may have more to do with the mileage and last how often do you change you fuel filter? Get back to me and we will go from there. Thanks.
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Saturday, January 17th, 2009 AT 9:09 AM
Tiny
BMBRDFRT
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I change fuel filter about every 3 months, and rarerly ever let car drop below quarter tank before filling. When I fill up the car I stop when the click goes off at the pump at gas station. That was my next question the bank 1 oxygen sensor numbers are flicking all over the place going from.001 thru.009 and the numbers are changing so fast thats about all I could reconize, the bank 2 sensor is pretty much holding steady. I am getting no check engine light and no codes are stored. I am reading alot on malibu forums that numerous people are having trouble with these fuel pumps await your reply!
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Saturday, January 17th, 2009 AT 9:55 AM
Tiny
RACEFAN966
  • MECHANIC
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Bank 2 then is a problem I should change fast as that means it is seeing all the changes of fuel mixture to help keep a 14 to 1 air to fuel ratio. So bank 2 is what I call a lazy sensor not changing much and if it does it is slow to react.
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Monday, January 19th, 2009 AT 10:46 AM
Tiny
BMBRDFRT
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So are you saying it is the bank 2 sensor that is bad? Since numbers are holding pretty much steady with no variance? Await your reply?
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Sunday, January 25th, 2009 AT 10:48 AM
Tiny
RACEFAN966
  • MECHANIC
  • 5,029 POSTS
Yes I am saying that if the voltages to that sensor are there and all else looks good then that O2 sensor in bank 2 is bad yes. It may not fix all your problems won't know till it is replaced but it is bad none the less. Let me know how it goes and we will do more testing if needed.
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Monday, January 26th, 2009 AT 3:00 PM

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