Lift pump and Mileage

[DSorrells]

I have an 03 and it has 93K on it. I have always gotten 22 to 24MPG out of it. I have made no changes to it since I have been getting that kind of mileage. I am now gettign in the 14 to 16MPG range. My fuel filter only has 4or 5k miles on it. My lift pump is stock and never replaced. I have watched while all of my friends lift pumps have gone out. Could mine be dying a slow death and causing my mileage to drop? I have always had plenty of power, and I can't tell that I have lost any. My driving habits have not changed. Am I way off the mark? I am open for suggestions.

 

[ThrottleJockey]

Do a manuel MPG calculation and see if it's dropped that much. You noticing that big a change in your wallet?

 

[JLandry]

I would start by replacing the air filter, the fuel filter, and measuring the fuel pressure at the fuel inlet of the fuel injection pump. Verifying adequate fuel pressure will help you rule out any lift pump problems.



I would also replace the IAT (Intake Air Temperature) sensor. It's an inexpensive part and there have been numerous reports here on the TDR of poor fuel economy being immediately corrected by replacing the IAT sensor. The IAT sensor can fail and / or get gunked up with soot causing the ECM to command incorrect injection.



Good luck,



John L.

 

[DSorrells]

I will replace the IAT sensor. I have a new air filter in it. The MPG numbers are hand clac. Thanks again.

 

[DPKetchum]

Lift pump is measured by flow not pressure. If it fills the fuel canister up in a few seconds is ok. You can drain it,leave top of filter housing off,hit key but do not start and see if it fills up reasonably quick.

 

[CookJ]

I would start by replacing the air filter, the fuel filter, and measuring the fuel pressure at the fuel inlet of the fuel injection pump. Verifying adequate fuel pressure will help you rule out any lift pump problems.



I would also replace the IAT (Intake Air Temperature) sensor. It's an inexpensive part and there have been numerous reports here on the TDR of poor fuel economy being immediately corrected by replacing the IAT sensor. The IAT sensor can fail and / or get gunked up with soot causing the ECM to command incorrect injection.



Good luck,



John L.

Is the IAT a dealer item only? thanks

 

[JLandry]

Is the IAT a dealer item only? thanks

I'm not sure actually. I know you can order one from any of the discount Mopar part dealers online such as MoparPartsAmerica.



The part number for the combination MAP/IAT sensor in the intake manifold (the one most likely to get clogged with soot) is 5139278AA. The current cost is showing $110. 04... more expensive than I thought at about twice the cost of the IAT only sensor for the 2nd gen truck. A this cost, it might be worth trying to clean the sensor first before replacing. A local dealer would probably charge well over $150 for it.



There's another combination pressure/IAT sensor in the air filter housing, and it's part number 53032649AA. The current cost is close to $50.



Best regards,



John L.