poor fuel milage - Ford Powerstroke Diesel Forum
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post #1 of 54 Old 08-11-2011, 01:35 PM Thread Starter
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Unhappy poor fuel milage

Well i just bought an 01 f-350 crewcab 7.3 and im only getting about 10 mpg
hand calculated... i cleaned the back pressure sensor, put tires up to factory specs, changed the oil and fuel filter... the brakes are not dragging. any ideas on why my milage sucks so bad?
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post #2 of 54 Old 08-11-2011, 09:10 PM
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Have you scanned your PCM or checked your turbo boots for any signs of a leak?

2000 PSD CCSB 4x4, Skyjacker lift on 35's, muffler delete, 6637 intake, Edge Juice w/Attitude, AIH delete plug, HPOP Crossover, Boost Tube, MAP overboost valve, '03 Side mirros, '03 headlights, Frontier Extreme front bumer, Ranch hand rear bumper, 7" K/C aux. driving lights, moderate stereo system

Next on the list: 37" tires
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post #3 of 54 Old 08-12-2011, 06:05 AM
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more boost = less mpgs. I continually debate that its a forum myth that leaky boost pipes or up pipes will decrease mileage like this. You will lose power, yes, but not mileage to 10mpg in normal unloaded driving.

Does the truck smoke at all? Have you noticed a decrease in power? Do you have more gear in the truck than normal? have you found an increase in oil consumption? Does the oil smell like diesel? Are there any drips under the truck?

First step is to get a read for any codes. Second would be a full AE test, including cyl contribution.
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post #4 of 54 Old 08-12-2011, 09:06 AM Thread Starter
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well i just bought the truck two weeks ago, i dont carry anything around except the paperwork, the truck is all stock, well i straight piped it and it has an intake on it and it doesnt blow any smoke unless i go wide open and then you can see a very very light haze, everything looks dry and everything smells as it should, i have not seen any soot on the firewall, or around the up pipe mounting flanges,
no signs of any boost leaks. and i changed the fuel filter also. and i also noticed the truck has to crank a second or two more before it fires.
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post #5 of 54 Old 08-12-2011, 12:01 PM Thread Starter
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i mean on my old late 99 f-250 i was running stage II single shots, custom tuning, exhaust, intake, and turbo but i was averaging 18mpg everywhere, and it would fire soon as you touched the switch....
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post #6 of 54 Old 08-15-2011, 11:39 AM Thread Starter
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ANY ONE?? ANY IDEAS?? COULD A WEAK FUEL PUMP CAUSE THIS?
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post #7 of 54 Old 08-15-2011, 11:42 AM
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I do not believe a weak fuel pump will cause poor mileage numbers. I'm leaning towards a leaking injector o-ring or two.

Nonconformist. Functionality over bling.

My three rules for 7.3l troubleshooting: 1) Replace CPS and keep a spare. 2) Replace FPR and know your fuel pressure. 3) Hook it to a scanner and check for codes.
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post #8 of 54 Old 08-15-2011, 11:46 AM Thread Starter
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Well the oil is not contaminated with fuel, and it doesnt blow oil burning smoke, i
do know that it does not fire right off when you hit the key, but i dont mean it takes more than 2 or 3 seconds of cranking to fire off, my old 7.3 would fire as soon as you touched the key unless it was -30 or so
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post #9 of 54 Old 08-15-2011, 11:50 AM
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Mine does the same, difficult to start, poor fuel mileage. This sounds more and more like a timing issue to me based on the CPS. Check fuel pressure to rule out pump.

I just replaced mine and noticed no change.

Nonconformist. Functionality over bling.

My three rules for 7.3l troubleshooting: 1) Replace CPS and keep a spare. 2) Replace FPR and know your fuel pressure. 3) Hook it to a scanner and check for codes.
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post #10 of 54 Old 08-15-2011, 12:29 PM Thread Starter
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SO YOUR THINKING CPS?
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