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Discussion Starter · #1 ·
I recently bought a cummins. I love it so far but, a couple things are kinda funny to me. My truck is a 1991 d 250 with out an intercooler or overdrive. When i drove the thing home (about 180 miles), I only got 11 mpg. I also noticed at freeway speeds ( about 70mph) it felt like the pedal was almost to the floor.
So my question is, is this normal? Or, is something wrong with it? So far im kinda figuring its the lack of overdrive thats doing this. The guy i bought it from said it idles fast cause he turned up the pump and when you do that you cant make them idle slow. This also seems strange to me, Like he doesnt know what hes talking about.
 

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Discussion Starter · #3 ·
Thats what i was expecting, the guy i bought it from said around 20. It might be a mathmatical problem to. I will run a couple tanks threw it and see what Happens. I kinda have been heavy in the foot with it too, Im sure that doesnt help to much.
 

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The most likely reason that you maybe geeting lower mpg is the lack of overdrive, this maybe further worsened by a low axle ratio. If you have a tach, you can see where the engine is running at cruise speed.

You may also want to try draining the water separator. If theres too much water getting past the filter, you will begin to lose power.

Ed
 

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I'd check it on a whole tank, 180 miles isn't very far and you probably won't get an accurate measurement. Also, diesel's are kinda funny about filling up, the fuel tends to foam up alot which will shut the gas pump off prematurely.



 

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Discussion Starter · #9 ·
Thats a good point GlennTx. I for got about that, I will make sure it is not foaming when i fill up. If it is foaming I will note that it is not full.

RXT My axle ratio is 3.07 so its not super low or any thing. Were is the water seperator? I will do that tomorrow.
 

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peteypower said:
RXT My axle ratio is 3.07 so its not super low or any thing. Were is the water seperator? I will do that tomorrow.
On the driver's side of the engine, you'll see a small oil filter. This is your fuel filter. On the bottom of it, there is a plastic valve. Push this up to drain. Normally I use an old cup to catch the fuel. Since water is heavier than diesel, if theres water present it will drain out first. Compared to the diesel, it will look thick and have a different color.

Important: don't drain the filter while the engine is running.

Ed
 
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