What the heck could be going on here? I had my fuel pump and filter changed about 3 weeks ago and have noticed that I am getting terrible gas mileage now. For example, between yesterday and today, the gauge has gone down about 1/4 tank, but I've only driven maybe 20 miles or so! I used to be able to go around 250 miles before needing to think about filling up, but I've only driven about 170 miles now and it's almost on "E". What gives???

 

I would suspect the sending unit on the pump is not functioning correctly. Fill the tank and do a manual mileage calculation to see if you have actually used as much fuel as the gauge says you have.

 

Thanks, I have a nifty app on my phone that keeps track of fill ups and gives me the mpg. I wanted to go through a couple fill up's before posting a reply.

According to the app, I was getting around 16-17MPG before, now I am getting around 14-15. Not a significant drop, and most likely because I've been auto-starting my truck to warm up in these winter months for few minutes before leaving the house.

That said, does that mean the sending unit on the new pump is bad? Or is it a separate device? I'm just wondering if I need to call the shop now if it's defective.

 

Theres an app for that!!! LOL Couldnt resist!!! But I had the same exact problem with my 96 Blazer. I have the remote start on mine as well and noticed the same things you did. I did however stop using the remote start and it did seem to get better. I was getting about 250 miles on a tank as well. I think that there is something with the blazers that burn more gas in idle than it is supposed to with the remote start. I never checked the sending unit but I will deffinately get it checked though.

 

Yeah, hey, it comes in handy! I log when I do maintenance and stuff. And it will remind me when I need to change my oil, rotate my tires, etc. It's kinda cool.

I usually only let it idle for just a minute or two though. So I think there's got to be a sending unit issue. It used to go until ~250 miles before hitting the "E", now it hits it around 200 or less!

 

The is the possiblity that the shop you went to installed the correct pump BUT the incorrect assembly, as in the current float/fuel sender unit is designed for a different sized tank.

 

whats the name of the app if you dont mind me asking

 

I am having the same issue, I used to get about 18-20 mpg and now after a new pump and sending unit I am down to about 12. Any ideas?

 

2000 4WD 4.3L 2-door Blazer
136,000 mi.

I have monitored my per tank gas mileage for about five years now. Back then I had a faulty pump problem, so I couldn't rely on the gauge. I knew then that my mileage was 270-280 per tank, so I would always reset my trip meter when I filled up. Shortly thereafter I replaced the pump and had no problems. Recently, since October 2010 or around that time, I noticed my fuel economy was significantly going down. For about two months I only got 230-240 miles to a tank. My last three fill-ups, 220 per tank.

I researched a few things and I believe the answer is not anything faulty or mechanical, but political. The problem is with ethanol blended fuel. This website (link below) is a government propaganda, saying they have changed the MPG ratings for vehicles, but the reasons stated on this page are bogus:

http://www.fueleconomy.gov/feg/calcu...umn=1&id=16315

- Driving habits
- Cold weather
- AC use

Those are factors which were already associated with fuel consumption, long before they made the changes to the MPG ratings. And, back then, I still got 270 city and 320'ish highway. The only difference in the last couple years between then and now is a wider-spread distribution of ethanol blended fuels. However, this dot gov website says nothing about e-blend and it's fuel economy. In fact, you will find out that nothing is said about it nearly anywhere. IT's been buried. Imagine what people would do/say if they were paying inflated prices for fuel, but only getting 75% of what they were paying for? **** and fan come to mind.

I've conferred with a couple different mechanics and they all agree: e-blend is the reason for the sudden and dramatic drop in MPG's. One of them suggested I install a free flowing air intake. He says it would increase both mps's and horsepower. Any thoughts? Would love to hear them. I love my Blazer. Itis in good condition and ... best of all, paid for!