Excessive Fuel Use
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Freshman User
Joined: Apr 2014
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From: Rosedale, Md
Excessive Fuel Use
Have a 1989 F150 4WD Standard 4 speed with overdrive. Been sitting for a number of years and had to put a new fuel tank and pump on it.
Took it for a test drive and noticed the check engine light came on intermittently. Drove it 40 miles and noticed the fuel gauge seemed to start moving down pretty fast. Refilled the tank and it took 7 gallons of gas. That's 5.5 miles a gallon.
The tank nor the lines are leaking.
So what could cause this. The engine runs smoothly except when using cruise control. With cruise control it feels like it is missing slightly.
Truck has 67,000 original miles on it. I know this because it was handed down to me by my deceased Uncle.
Took it for a test drive and noticed the check engine light came on intermittently. Drove it 40 miles and noticed the fuel gauge seemed to start moving down pretty fast. Refilled the tank and it took 7 gallons of gas. That's 5.5 miles a gallon.
The tank nor the lines are leaking.
So what could cause this. The engine runs smoothly except when using cruise control. With cruise control it feels like it is missing slightly.
Truck has 67,000 original miles on it. I know this because it was handed down to me by my deceased Uncle.
Cargo Master
Joined: Jun 2010
Posts: 2,113
Likes: 4
From: Iowa
The fuel pressure regulator is a possible culprit especially with prolonged sitting, the internal diaphragm can become brittle and crack letting fuel into the vacuum system.
It's easy to check and will likely be accompanied by a rich code at low engine loads. Turn the key to run for several seconds WO starting to prime the fuel system then pull the vacuum line off of the fuel pressure regulator and it should be dry.
I don't know if this is actually your problem but it's something I have seen be a problem even on newer vehicles that sit for long periods of time.
It's easy to check and will likely be accompanied by a rich code at low engine loads. Turn the key to run for several seconds WO starting to prime the fuel system then pull the vacuum line off of the fuel pressure regulator and it should be dry.
I don't know if this is actually your problem but it's something I have seen be a problem even on newer vehicles that sit for long periods of time.
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