Engine/Transmission (1998.5 - 2002) HELP! Poor Mileage w/2001 Dually

[WadePatton]

I'm pretty flexible during the week, usually tied up on Fridays. This weekend I'll won't be around.



PM sent with more info.

 

[onestackdram]

How do you test the LP. I'm having the same prob with my wifes 2500. The MPG SUCK, until I see those 20 + MPG I have to think they are a myth. I have pulled the IAT sensor (actually did it again today) and the dang thing is always SPOTLESS. I know that the 285 probably screw the overhead console up, but when you do the MPG the good ol fashioned manual way the truck still only gets 15. Thats driving it both conservatively and somewhat aggressively but not WOT. That 15 is interstate miles too, the city miles are so bad it's not even worth mentioning. So I am down to thinking maybe the LP is going bad or is bad, and if so I want to know how to check it.



TIA



Russell

 

[WadePatton]

How to test LP on 24v.

Buy a test unit from Tom (Briar Hopper) of Black Mountain Diesel. Or build your own. It is a mechanical pressure gauge on about 4 feet of hose.



On a 00-02, attach the test hose to the schraeder valve on the input to the VP44. (There is another port on the backside of the filter-which can be used to see if the filter is plugged). Now start the truck--you should get 10# or better pressure. If you get less, check the pressure at the other port. It should be a couple of pounds higher pre-filter. If the difference is much more than that, change the fuel filter.



Now, with the line attached at the VP44 port, put the gauge up on the windsheild and secure with duct tape. Visibility is enhanced if you use a folded rag or something to angle the gauge back away from the glass.



Go for a ride. Pull some WOT runs and see how low you can get the pressure. If it drops below 8psi you're out of spec. I don't worry until it drops below 5.



With injectors and/or fueling box you will be able to pull it down below 8 unless you've upgraded your banjos/lines like I have.



With stock HP, I'd replace the LP with less than 5# for a bottom number.



If you have low numbers at idle, don't even do the WOT, cause the VP is suffering when you pull the big ZERO. If you have nothing at idle, be sure that the pump is getting 12volts. Some folks have had wire corrosion problems and there is a relay involved too.



questions?

 

[onestackdram]

a pic would be great. and will my mechanical guage from my 12v work as well atleast for testing purposes?

 

[WadePatton]

Don't have one handy. Can make some if nec. There are photos of all the stuff here and there.



Your mech gauge will work fine, you just have to adapt it to the schraeder. Schraeder valve is the type used on your tires. It needs a thingy to push it open. OR unscrew the core and then you just need a female fitting. I have no idea what the thread is.

 

[onestackdram]

thank you mister wade... you better watch it with all this help you give people they might make you a moderator... LOL



thanks though



Russell

 

[JWhitcomb]

Drove 500 miles in the last few days, up and back kind of thing. With my barn door of a camper and a boat in tow (16,500 gross) I averaged 14 mpg. When I left home for the trip I decided not to excede 60 mpg and to keep the rpm's low. The same trip keeping it around 65 yields 12 mpg.