I've noticed a 20-50 mile drop per tank following a fuel pump replace. This has been the case for a few tanks now, with a good mix of city and highway. I manually calculate my mileage, so I've ruled out the fuel gauge.

Any ideas? I know it was a big job that took my mechanic a lot of hours to do and a lot of parts to remove and replace.

Could he have damaged the O2 sensors?

Car is a 2003 X-Type 2.5 Manual with about 70k miles.

 

dbalach, first off, welcome to the forums. I think you will find a lot of good information here. So, look around and see what you can find. We also ask that you do a formal introduction in the "New Member" area. I think you will find this a benefit.

As for your problem, I would be venturing to guess that you have a small fuel leak leading to your problem. What I would tell you to do is to tape some newspaper down on your driveway and park the car on top of the newspaper. With the car parked, start the engine and let it idle for about 15 minutes. There will be no need to reve the engine at any point during this. At the end of the time, look under the car to determine if you see any spots. If you do, look straight up as this is where your leak location is going to roughly be. You want to focus on the passenger side of the car as this is the side where the fuel lines run. Once you have a leak location, you will need to see what is in the area. If you need more help, let me know. THis is where the possibilities become too numerous to list all the fixes here.

If you don't see any leaks, I really doubt it would be an O2 sensor issue as you are not complaining about any CEL lights/codes.

 

Thermo - thank you for the response. I did get my intro up. Thank you for encouraging me.

I will try that test, though I think I would expect other indicators, like smell or maybe see the leak in other places, maybe at the gas station?

But either way, definitely worth a try.

 

Since you are only seeing a "minor" drop, you are only probably looking at something along the lines of say 5-10 drops a minute. Which, unless you idle for a long time somewhere, you are not going to smell it. If your driveway is asphault, it would be difficult to see the spot. Granted, if you look near the rear passsenger side tire and there is a spot there, I would be really looking closely for a leak.

The only way that you would probably smell the leak is if the leak was up in the engine compartment. BUt, based on the work you had done, if you are driving, all the smell is going to be behind you.

 

I replaced the fuel pump in my 2500 ram this winter, and I also noticed a difference in the amount of fuel I was using. Hopefully, I don't have any problem like this with my cat. But, I was thinking on different terms of why I'm using a different amount of fuel. I was thinking on the terms of that the fuel pump wasn't working the way it should have been so the pressure in the pump wasn't as much as it should have been. This in turn causeing the amount of fuel to be burnt, less. If your not putting your foot into it, and calling for more fuel I don't think your useing more fuel. But with the new pump and it running up to full pressure, wheather your calling for it or not it's shoveling it down the injectors. I notice more fuel, condensation, and liquid coming from the tail pipe. Not saying this is what is causeing the use of more fuel when driving, but it's a thought. I know I have no leaks, don't know what else could cause the use of more fuel, except more pressure. Any thoughts?

 

Easy. ....It's not broken.....no code, no foul.

Things are working as they should now, and you are no longer running lean. I've seen this before. Not likely a fuel leak, you'd smell it. You are now getting the mileage the car is 'supposed' to get. Remember, it's AWD and underpowered for its' 3,600lbs curb weight.

 

Hmm. Thanks for the responses. I have a hard time believing I should get 15.5 mpg on a tank that was 75% highway. I'd gotten over 30 on the way to Vegas once, which was almost 100% highway on the old pump.

I have some debugging to do this weekend!

 

15 MPG on the highway is not normal in any way shape or form. There is an issue, leak, maybe the fuel filter but do the Thermo test first since paper is free. Are you sure you're not pumping in crap gas??? Make sure you're using a reputable gas station, also it might be a good idea to run a bottle of injector cleaner in the next tank.

 

You may have a leak near where the fuel pump sits on the top of the fuel tank. You would not see an obvious leak or odor. I'd pull the rear seat and open the access panels to check it ( I have an S-type, assuming the X-type is similar.
Good luck , VMV

 

I can say definitively that every tank I've ever pumped has been Chevron Supreme with Techron.

I'll keep you all apprised through this process.

 

I didn't see any leaks in my inspection. Also had a friend look at it.

I also remembered that I got new tires about the same time I got the fuel pump so we checked the gauge and saw that they were all about 30 ... .

Anyhow, I got them all up to about 36 and I'll give it a shot. I'm sure it will make a noticeable difference and I will let you know when this tank runs out.

 

It's been a few tanks since I inflated my tires. The first few were 75% highway, so I wasn't able to compare properly to what I was seeing before.

This last tank appears to be in the range of what I was getting so I'm happy to say that this was an easy inexpensive fix.

Let's hope I didn't jinx it.

Thanks again everyone for the support and suggestions.