OK Seriously
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OK Seriously
I have a 1991 F250 4X4 and it gets 4 mpg it has a 351 windsor check engine light is not on and works, so whats up it does,nt matter if i'm driving 30mph or 60, there are no known fuel leaks it has dual tanks one 17 gal and one 19 gal and I only can drive 250miles before there both empty I had a tuneup done recently any idea's
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Joined: Dec 2007
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From: Lutz, FL
Edit: apparenty I misread your post. Verify that both tanks are empty when running them down, so you aren't getting the misreturn feed that many have had here.
Last edited by pc_2000; Dec 1, 2008 at 09:00 AM. Reason: Didn't read entire post, apparently. LOL
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From: Renton, WA
Wow 4, something is wrong, Does the engine seem to run well, is it crisp? How about alignment? Are your tires wearing evenly? Check the 4wd is something engadged that shouldn't? Was it this bad before the tune up and what was done?
Bad mileage is a problem of the whole truck there are so many things that can cause it, we got to eleminate them all one at a time and things will get better.
Bad mileage is a problem of the whole truck there are so many things that can cause it, we got to eleminate them all one at a time and things will get better.
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Joined: Jun 2006
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From: Ottawa, Ontario
What size tires on the truck?
What is the axle gearing?
What is the tranny?
How are you calculating milage?
Doesn't matter if the light came on or not, have you pulled the codes?.
What is the fuel pressure?
Is there any sign of fuel in the vacuum line attached to the FPR?
Is the O2 sensor attached and in good condition?
Does fuel transfer from 1 tank to the other?
What is the axle gearing?
What is the tranny?
How are you calculating milage?
Doesn't matter if the light came on or not, have you pulled the codes?.
What is the fuel pressure?
Is there any sign of fuel in the vacuum line attached to the FPR?
Is the O2 sensor attached and in good condition?
Does fuel transfer from 1 tank to the other?
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Thanks for the reply
The truck runs great only 206000kms /I always run the tanks empty/the tires are the same size as from the factory /gearing i'm not sure/ I check the mileage by how much fuel the truck eats and how far i can travel, i reset the trip meter every time I fill. this is just a truck I use for hunting and driving to the dump. I've had it for 5 years and the mileage seems to get worse all the time.I will check the codes, is it worth changing the 02 sensor just because (a mechanic from ford said not to change it if the check engine light is not on.
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From: Renton, WA
Never listen to anything that "tech" says again.
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chek the fuel pressure at rail.. and then change the 02 sensor.. i thinkits time for an replacemente..
i was getting 6 mpg.. untill i changed my fuel pressure regulator and got 10-12
i was getting 6 mpg.. untill i changed my fuel pressure regulator and got 10-12
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sorry for the bad estimate I chg tanks when she starts to sputter, I'm in canada and its all metric I get 400 km for both tanks but i'm gonna chg the 02 sensor/ DJdemon6696 how does fuel pressure have anything to do with mileage (im not being sarcastic what should the pressure be at) and where do I find the reg
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From: St Louis
Are you measuring the volume of gas in Liters or gallons, and the driven distance in km or miles. Please keep it consistant as my mind is already lost in the post. A liter is approximately 3.8 liters to one US gallon, and a 1.6 km is roughly 1 mile. So if you were estimating based on liters and km then your "mileage" will be different than the US estimation. Please confirm how you are doing it so that we can get a better understanding if you are similar to what the trucks usually average or worst. A 351 should get between 10 to 17 mpg unload but there are variances for everyone but I estimate that it is from what I have seen, so in kpl (km per liter) 4 to 7.
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no i'm measuring in mpg i got the capacity of the tanks from the manual and when I fill it it at the pump it is measured in litres like I said I can go 400kms on 36 gallons which is absolutly rediculous it should be better than that
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From: St Louis
Check for fuel leaks in the system, check to see the FPR on the fuel rail is working properly. Have you pulled the spark plugs to see their condition, i.e. carboned up black is too much fuel for the current compression state of the engine. A clean plug that looks new means that the spark isnt getting to that cylinder but you would have noticed the mis-fire state readily with lack of power and a noticeable mis in the exhaust tone.
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From: St Louis
The FPR controls the fuel pressure (fuel flow basically) at the injectors. The engine has a vacuum supply line that when full vacuum is applied (~19 ) the fuel regulator is opened to allow excess fuel to flow back to the fuel tank(s). As the engine RPM increases, the Vacuum supply decreases closing the FPR and therefore supplying more fuel to the engine.
I am not saying replace it, but make sure it is getting vacuum. That the vacuum lines are not brittle and broken as this will cause vacuum leaks. Also, make sure that fuel isnt on the vacuum side of the FPR as this means the FPR has failed by losing the seal between the vacuum and the fuel line.
What is the gear ratio of the truck, is it auto or manual, over sized tires, and etc. that you can tell us about the truck will help in judging what you need to check to make sure the truck is running optimal.
I am not saying replace it, but make sure it is getting vacuum. That the vacuum lines are not brittle and broken as this will cause vacuum leaks. Also, make sure that fuel isnt on the vacuum side of the FPR as this means the FPR has failed by losing the seal between the vacuum and the fuel line.
What is the gear ratio of the truck, is it auto or manual, over sized tires, and etc. that you can tell us about the truck will help in judging what you need to check to make sure the truck is running optimal.