Fuel economy has gone to sh*t

onetun

onetun

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Nov 22, 2007
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1999 with 220,000 miles. No performance mods, cannot say for sure if any fuel components have ever been replaced. I purchased the truck with 150,000 miles.
Anyhow I have never really calculated my economy until now, as I have definately lost some ground. I travel the hwy daily and know how many trips I can do to work and back.
Hand calulated I'm getting 15 mpg..

Truck runs the same as before, fuel filtre has been changed every 5000 miles..

Suggestions as to what may be reducing my mileage?

Thanks
 
Hey whats up........air filter's clean? Always a bit of a mileage hit when they dilute us down to the winter blend. Not that much though.
 
Have the injectors popped, alot can be lost if they are popping too early.
 
Well without a bench mark as to what it was before it's hard for us to tell how far it's really dropped. Could be a dying injection pump worst case scenario. 15mpg isn't to out of the ordinary for a VP truck.
 
Do you have a fuel pressure gauge? I think the obvious check that everyone is forgetting is if the lift pump is dying and starving the VP.
 
Joesixpack said:
Hey whats up........air filter's clean? Always a bit of a mileage hit when they dilute us down to the winter blend. Not that much though.
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Hey Chris! I'm going to have a peak at the air filter, good point.....

BgBlDodge Well without a bench mark as to what it was before it's hard for us to tell how far it's really dropped. Could be a dying injection pump worst case scenario. 15mpg isn't to out of the ordinary for a VP truck.

I know, I wished I had calculated prior, The dying pump is kinda what I wondered. I have no other signs that I'm aware of...what are the life spans of these VP pumps?


JFlagg Do you have a fuel pressure gauge? I think the obvious check that everyone is forgetting is if the lift pump is dying and starving the VP
No I do not, I suppose I could add this just to verify what it is-

Thanks all
 
onetun said:

what are the life spans of these VP pumps?
Click to expand...

1-200,000 miles LOL They last alot longer with a good fuel system. I had rebuilt some injectors in my dads VPed truck awhile back, he gained 3-4MPG. His injectors were way low on pop-off too. Id just run the valves, pop the injectors, check for boost leaks, and make sure everything is clean and getting enough fuel, see what happens.
 
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I'd hook a pressure gauge up to he schreider valve on the side of the VP and check the pressure at idle... I forget exactly what they run stock, I'm thinking between 11-15 psi? And if it is reading low, I just saw CSnyder list an Airdog 150 for sale in the want ads. If it is reading fine, I would then work your way up the fuel system then check the filter, then the injectors. Air filter wouldnt hurt to be checked too... Thats the route I would go.

Another thought... I just noticed you have an auto tranny. Does it seem to be running normal? I had a Ranger once that didnt like torque converters and when they would just barely start to slip I would lose fuel mileage since I was losing even more power through the drivetrain.
 
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sounds retarded but.... make sure your waste gate is shutting all the way. i swapped my adjustable boost elbow for an air pressure regulator from a air compressor and HOLY SH#T!!!!!!!!!! 45 PSI and spinnin the tires on the high way in fifth gear! my truck has never run like this! i drove from st.louis to charleston south carolina for my honey moon with an open gate the whole time. jesus christ!
 
Make sure your intake air temp sensor is clean and good, make sure the electrical connection is good. When one of these sensors gets dirty our out of whack it can really make MPG go south, yet not much obvious effect on drivability.
 
I'll drop 2-3mpg with winter fuel...

Find myself letting the truck idle a lot longer, too... All things considered, I'd be happy with 15mpg in the winter for combined driving. I usually get around 17-18 on the highway in the winter.

Other basic things: tire pressure. When you don't see the warm side of 20* for 2 months, it's a darn good idea to check the tire pressure.

Just a few very basic things I thought of when I read the thread.
 
If you can handle the rough ride, slightly over-inflated (5 psi) tires really helps out with fuel economy. If you're running anything bigger than a 265 on stock wheels, it's difficult to get even tire wear unless you run a little under recommended inflation so in some cases, it's not really feasible to run slightly over inflated.
 
I'd say 15mpg is good for winter time with stock intake and exhaust. Thats what I was getting all stock last winter. Added an afe intake and 4" turbo back and gained 3mpg. Check your filters and fluids and air pressure... Also as stated above, could be a dying injection pump but I highly doubt it. I think you'd notice a lot worse mileage with a dying pump
 
I would think about replacing the crank sensor. I bought my 00 with 243k and it started out ok but the mileage kept getting worse and then the computer threw a crank sensor code, changed it and wow, I was amazed I picked 3-4 mpg, paid for the senor pretty quick, just my 2:bow:
 
Thanks for the ideas and possible solutions Like I said they way the truck runs has not changed. If 15 is OK I will most likely just drive it and see if gets any worse.
For sure the mpg has decreased with the winter fuel..

Rob
 
Im gonna have my injectors popped sometime soon. My truck is down to 13.5-14 around town to where it used to be 17. I think it may be time for some bigger sticks anyways though.
 
I'd give anything to get 15mpg's again. I'm down to 11 and still dropping from 18 last spring. I can almost watch my needle move. I'm at 235,000 miles, stock vp44, new lift pump and Holley blue pump closer to the tank. Its rough, I'm not liking my truck very much these days. something big has got to change. So I'm going to rebuild the motor this spring when the money is available. Hoping to find a major problem as to why my mileage has gotten so out of whack.
 
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