Question On Fuel Mileage ?

[hammer]

Got a guestion for all you Deisel Heads.What would make the D/A use more fuel for the first 12-15 miles of starting out.I am in Fl.& the temp in the mournin is around 60.I could see if it was colder out but not at 60. It seems to use more fuel untill I get it up to about 180-195 in temp.After its up there in temp then it seems to go back up to were it ussually runs for fuel mileage.From 0-185 its only averaging around 12 m.p.g.at the most but when it reaches 180-195 then it jumps back up to around 17-18 m.p.g. were it should be.No codes or no indication of any thing wrong with the running ability of it.Talk to different truck drivers & they never seen a encounter like that.Checked air cleaner & its clean as a whistle.Any ideas out there on the problem? Hammer :rolleyes:

[Tim B]

Well, I would bet that there is a fuel enrichment device that operates until the water temp reaches 'normal' operating temperature. The engine probably runs 'rich' until the water temp reaches 185 (or so) irregardless of the outside air temp. This seems normal to me, except that mine doesn't take 12 miles to reach 185.

Tim B.

[hammer]

Tim B,I think ya got it right on the head.I also wondered if the fuel filter was getting dirty if that would have anything to do with it.Im gonna take it in next time I have the oil changed & have them check the thermostat out cause it dosnt want to maintain the 195 temp,most of the time it runs around 185-190. Too me this is too low for a 195 thermostat.Thanks for the comback on this issue.Hammer P.S. Unless the water temp. gauge is off. smile.gif

[mark45678]

I know the 6.5 td and the 7.3 ps use engine temp the change the fuel timeing, I would bet the 6.6 does the same thing!

[Diesel Dog]

How are you measuring your MPG? Maybe your method of measure is flawed?
Second thought. Them new trucks use a fuel cooler. Fuel expands and contracts depending on it's temperature. As the fuel tank level gets lower, the fuel temp increases. This expands the fuel. I'm poking at an idea here, not sure if it makes sense.
:confused:

[ 03-28-2002: Message edited by: Diesel Dog ]</p>

[Allison Jettester]

Hammer,
No engine runs efficiently until it reaches operating temperature and the internal parts reach their equilibrium. Added to that, the fuel control schedules fuel mixture partly based on coolent temp, so it will run rich until it gets to it's target temp of 195F. I have the same problem with all my vehicles because I only live 2 miles from work. The diesel engine is worse because it has a much more efficient cooling system and it takes much longer to reach temp.

I have gotten a low of 14.9 with a tank full of trips less than 8 miles each, and a high of 21.1 on long trips averaging 75 mph. This truck likes it hot and wants to go fast.

Joe

[ 04-02-2002: Message edited by: Allison Jettester ]</p>