'00 7.3 PSD in a F250 4x4 SC, 265,000 miles, Rotella Synthetic Oil, WIX Filters, 50 cent mod, Truck runs good, easy start up, good power.... Now that winter is just a few months away, I've decided to do some maintenance on the 7.3. My main concern is MPG's suck. They are hovering in the the 13.5 highway and less in town. Last year, on one trip, I got 19.2 hwy, came home fueled at same station, 2 days later took another hwy trip, 13.8 mpg (same driving habits)... Why such a drop? I've checked the entire exhaust, no signs of soot or exhaust leaks, no signs of turbo pressure leaks around the boots or intercooler. Engine is dry on top....

The only thing I can think of is the lift pump may be getting weak and not supplying the volume or pressure needed for the injectors to operate efficiently. (is this thought process accurate?) What is the needed fuel pressure at the fuel filter bowl?

And, I haven't spent the $$ on a set of gauges either, even though I know they are a necessary expense.

Any and all suggestions appreciated.

 

Before you worried about fuel pressure issues, here is a good MPG thread with common issues like Up-pipes, EBPS cleaning, etc https://www.ford-trucks.com/forums/1...ght=MPG+thread

2 days and that much different I would think there is something else going on, hand calculated or trip computer? Did you get the same quantity of fuel in the tank, If you haven't done the Harpoon mod this can vary up to 5 gallons, making your numbers off too.

 

Old school accurate, by paper and calculator.. no lieometer here.... I try to clean the EBPS everytime I change the oil..(since it's a problem area). As far a fuel quality, who knows what we are getting in fuel.(and how would you know unless it's something obvious?)

I see no soot around the up pipes,,, I suppose if they were bleeding pressure there would be signs of it?

 

Quality can make a difference, but I said Quantity, the amount of fuel, do you fill to the same position each time, or just let it click off? If you let it click off, you would be surprised how much foaming can vary between different stations or pumps.

 

My apologies,,, I misread... I try to allow the fuel / foam to settle before I'm done fueling and fill the same point each time. What exactly is the Harpoon Mod. Just looked for it and link wouldn't work.

Everyone talks about the "up-pipes" being an issue.. If they were leaking, wouldn't I easily see signs of such (soot, minor smoke at idle). And the turbo pipe boots, what's their "signs" of leakage other than obvious oil everywhere?

 

the fuel psi can make the mpg go down when my fpr go stuck at 100psi my mpg dropped. you might look at it just to be sure, it is a free check.

 

What's correct fuel pressure at KOEO, and engine at idle?

 

around 60-67psi i have 62 psi

 

Hutch and Harpoon mods
http://www.guzzle7pt3.com/harpoon.html
Welcome to guzzle's In-tank Hutch Mod Web Page

 

Thanks izzybird, I now remember the harpoon mod...

the Hutch mod speaks of the pre-pump fuel filter, does any know the part number of that assembly or another brand that's just as good and the approx. prices of either.? Thanks,

 

You may want to find out your ICP. My truck dropped from 18 to 12 MPG. Because of very low ICP. (900 psi, 98%DC at WOT) I haven't found the cause yet, but I am down to a leak in the heads or HPOP.

 

You can use a cheap inline or a better quality spin on style, your choice. This is what I used because I already had it.

 

I like Strictly Diesels kit so I don't have to go gather up parts. They offer a spin on filter if you want it. Around $80 without filter.
Driven Diesel 7.3L Fuel Tank / Pre-Pump Kit