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Bad gas mileage.

 
  #16  
Old 12-30-2015, 11:40 PM
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Originally Posted by Gunnerboy View Post
Well i recognize those gauges.. I think my father has some .. ill have to go find out and see if i can figure this out... And im on the WA coast so its just rainy and wet 24/7 340 days a year ..
What part of the Washington Coast, I am on the North Oregon Coast and may be able to help.
 
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Old 12-31-2015, 08:49 AM
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It's 8%diameter difference, it should be about 4.2 mph off. But none the less. You should pull the codes. We have pretty much the same truck and setup and I get between 15-18 dependent on my driving
 
  #18  
Old 12-31-2015, 09:19 AM
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What part of the Washington Coast, I am on the North Oregon Coast and may be able to help.
Well everywhere from Naselle to longview depending on the time of year
 
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Old 12-31-2015, 09:56 AM
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So im looking at the spark plugs and they are all bosch platinums...Should i put autolite #25s back in? I remember that being correct for the 90 f150 i fixed 7yrs ago
 
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Old 12-31-2015, 12:34 PM
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Originally Posted by Gunnerboy View Post
So im looking at the spark plugs and they are all bosch platinums...Should i put autolite #25s back in? I remember that being correct for the 90 f150 i fixed 7yrs ago
Just the generic Autolite copper cores in mine gapped at a little over recommended with a MSD cap and rotor (brass terminals) and timing set at 14* BTDC. Big thing is making sure timing is right. You said in a previous post the timing chain has been changed I'd double check that the timing is at least where its supposed to be
 
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Old 12-31-2015, 07:21 PM
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So how do you de presureize the fuel line to change the filter?
 
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Old 12-31-2015, 07:24 PM
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With the truck running unplug the relay for the fuel pump and that should do the trick. Can't tell you where that relay is though. So maybe not that much help haha
 
  #23  
Old 12-31-2015, 08:17 PM
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There might be a Schrader valve (aka tire air valve) on the fuel rail on top of the engine where you can release the pressure.

This change in mileage, was it all of a sudden directly after a change you had made (e.g. new exhaust)?
 
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Old 12-31-2015, 08:34 PM
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Ok cool a valve should be easy enough to find!..And not sure about mileage i just bought the truck Sunday.. It was a older gentleman that took real good care of it he just didnt use it anymore so sold it.
 
  #25  
Old 01-01-2016, 12:02 AM
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Originally Posted by Gunnerboy View Post
Well everywhere from Naselle to longview depending on the time of year
I work across the river. If you need a hand holler.
 
  #26  
Old 01-01-2016, 11:22 AM
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New plugs, wires, cap and rotor and fuel filter...Time for a test drive go see how she does...If no change then onto timing and compression?
 
  #27  
Old 01-01-2016, 11:33 AM
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Ignition timing is computer-controlled; ask the PO what gas mileage he was getting.

I would be interested in a tailpipe sniff test to see what is coming out the back.

Have you ruled out a fuel leak?
 
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Old 01-01-2016, 11:48 AM
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It might sound stupid but how did you determine it was getting 8mpg? Hopefully it had nothing to do with anything indicated by the fuel gauge because these things are notoriously inaccurate, the only way to measure it is miles driven as indicated on the ODO divided by gallons needed to refill the tank and averaged over as many refills as you can come up with.
 
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Old 01-01-2016, 04:29 PM
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^ Did the math off of 1 fill up it was 8mpg...Now today went and did some highway and logging road cruising after the tune up and its 14.8mpg according to the gas i put in an mileage driven. Called my grandpa turns out he still has compression and timing tools so i can head over there and check that all out. Im assuming being it takes 10 miles of driving to get to temp that i probably need a thermostat also haha And yes i crawled all over looking for a fuel leak and couldnt find one.
 
  #30  
Old 01-01-2016, 08:06 PM
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Originally Posted by ctubutis View Post
Ignition timing is computer-controlled; ....
The "vacuum advance" and "centrifugal advance" are computer controlled, but that all goes off the base timing that's set by turning and locking down the distributor, just like in the old days

But that makes me think. If the SPOUT connector was left out you wouldn't get any spark advance and mileage would suck. Might be worth a look.

Originally Posted by Gunnerboy View Post
^ Did the math off of 1 fill up it was 8mpg...Now today went and did some highway and logging road cruising after the tune up and its 14.8mpg according to the gas i put in an mileage driven. ...
Two tanks isn't really enough to know that you've got a real problem, but it's better than 1. So now you're averaging somewhere around 12 mpg between the two tanks. Was the speedo corrected for the larger tires? If not you're actually going 8% farther than your odometer shows and your mileage is 8% better. That would put your 14.8 at about 16, which is pretty good, but your 8 mpg becomes 8.6 (which still sucks) and the ~12 average is ~13.
 

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