Bad gas mileage.

[Red beast]

My truck has been eating gas. What used to be a 25 dollar round trip to work is now a 35-40 dollar trip. This started not too long ago and i wasnt sure if it was just me or something was up. I have owned the truck very long about 6 months or so. I swear i can smell gas under the hood like its running rich but the exhaust doesnt smell rick out of the pipe. I have looked and looked and there are no leaks that i can see. Under the hood. Everything seems to be ok. No check engine light no stalling no rough idle. So im kinda stumped. Has anyone else had this problem? What should i try? I dont want to waste money throwing parts at it that arent necessary. And there arent any decent mechanics around me. It is a 95 4x4 xlt with 4.0 and a 5 speed. Any help would be great thanks.

 

[adsm08]

Start with the small things that should always be done on a new to you used car. Plugs, wires, filters, etc. Also, check the oil, make sure it isn't overfilled and that it has no fuel in it. Fuel in the oil is a sign on a leaking injector and can cause all of your symptoms as well as severe engine damage if it hydro-locks the engine.

 

[Mark_88]

I had an 89 Ford Tempo for 14 years...when I first got it I could smell gas every time I started it...took it to the dealership to have them check it out and they could not find anything out of place that would allow gas to leak. It eventually went away or I just got used to it...not sure...but I put almost 400,000 km on that car.

Like Adsm said, go over the basic stuff first...could be something as simple as needing a new air filter...hold it up to the sun or other strong light source...if you see plenty of white then the air filter is probably still good...

Tire pressure can be a big factor as well as tire size if you recently put on bigger ones...

 

[RonD]

I would also check the Fuel Pressure Regulator(FPR), it is located on the fuel rail for the injectors.
It has a vacuum line to the intake, the FPR has a rubber diaphragm inside, this diaphragm can crack with age, so it will starting leaking fuel which is sucked into the intake.
To check it just remove that vacuum line and smell it for gas.


There is also the fuel line and the fuel return line, these can get rust holes so will leak fuel while engine is running, visual inspection is best also run fingers around tubes, especially on fuel lines in the engine compartment where you smell fuel.
Gas evaporates pretty fast when it is warm out so small leaks often don't show on the ground after parking, placing clean cardboard under specific areas can often show a drip you may not notice otherwise.

If you have access to a fuel pressure tester you can test the pressure with key off after running engine, to see if it drops steadily, this would indicate a leak in the high pressure side of the system.
Normal fuel pressure is 32-38psi
Or without a tester just cycle the key on and off 2 or 3 times then check engine compartment for fuel smell and try to track it down.
Each time key is turned to ON, fuel pump comes on for 2 seconds, then shuts off, cycling the key a few times builds up pressure to 38-40psi, so might make leak easier to find.

 

[Andy D]

I just fixed this issue on the wife's BMW. The first 2 inches of hard line was rusted and pin holed. Tip off was the long crank on cold start. and a gas smell at the RR tire. The leak was bleeding off pressure as the leak seeped through the rust Didnt drip too badly and stopped leaking after pressure was bled off. Glad I checked the main pump before I dropped the tank.

The Rat gets about 21 MPG on the highway. Its pretty much the same truck. It has stock 235 75 15s with a 3.27 diff. That is 6 mpg better than the last Waggie. If you smell gas ,you have a leak. Finding it on a fuel injected car, may take a while though. Good hunting. Definitely check the oil for gas.

If you are daily driving the truck. I would definitely tune it and check/replace stuff to keep it reliable.

 

[adsm08]

If you smell gas ,you have a leak.

Yeah, but it isn't always a liquid leak. I have a vapor leak somewhere. Sometimes I smell gas, other times I don't. I have checked and rechecked for a liquid leak, and there just isn't one.

 

[Red beast]

Where are the fuel lines that could be pin holed located exactly. It's worth checking.

 

[adsm08]

They run the whole length of the truck, from engine to fuel tank, along the driver's side inside the frame rail.

 

[RonD]

Where are the fuel lines that could be pin holed located exactly. It's worth checking.

Find the Fuel injectors in the lower intake, they are connected to the fuel rail, the fuel rail is connected to the FPR.
The FPR has two fuel connections, IN from fuel pump and OUT to send un-needed fuel back to the tank.


That's exactly where to check

 

[Red beast]

Thank you sir's. I need to go through and start changing out pieces and sensors. Not that they are bad but the truck has 250000 on it so im sure some things like egr map iac are gunked up. New plugs and wires. I did this to my jeep and it ran alot healthier. Adsm08 mine smells exactly like a vapor leak. Not exactly a full on gas smell but for sure fuel scented. Are there common culprits or is it just seek and fix?