Sudden drop in mileage

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Since new in 92, my 92 F350 crew cab has gotten 22 on the highway and 18 in the city. Mileage dropped to 13 highway, 10 city so I replaced the injectors and then the injector pump when I discovered my pump was cracked. I got a slight improvement in mileage but it did not get back to normal.

The truck is all stock with 280,000 miles on it. The E40D was rebuilt a couple of years ago and it has 3.55 gears. The truck runs fine other than the bad mileage. It doesn't blow smoke and has good power. I don't smell any diesel and find no evidence of leaks anywhere. The brakes are good and no calipers or shoes are dragging.

Any ideas what would cause this kind of mileage drop?

[FordGuy100]

Was the truck properly timed when the pump was put back on?

Unfortunatly I have heard that some people do experience this. It seems some pumps just dont get as good of fuel economy as others. Kind of luck of the draw sort of deal. Although I'm not saying that is your problem, but it may be a factor.

How fast did the mileage drop?

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Thanks for the reply. Pump timing is about all I haven't worked on. I think that will have to be my next step.