'00, 7.3 PSD, 275K miles, runs good but fuel economy is off... no boost leaks... ckd fuel pressure yesterday when pulling a boat... it would stay at 60psi when running steady @ 70 mph (3.5-6 lbs boost).. but would drop to 52 psi under hard acceleration (15 lbs boost).. but when I'd shut the engine off, the fuel pressure would immediately drop to -0-... and, I have never rebuilt the fuel pressure regulator, nor has the fuel pump been replaced..

Is this normal operating perameters for this engine?

 

bump, bump

 

what fuel pressure gauge are you using?? my isspro stays where it was cut off at.. the mech gauge under the hood on my RR will drop to 0 in appx 3 minutes..your pressure sounds about right for stock

 

Might want to check into this: https://www.ford-trucks.com/forums/1...nsor-pics.html

 

My Glow Shift drops as soon as I shut off. Had for a year, no issues noticed.
Fuel psi sounds in line.

 

Are you still running the stock air box ?
When's the last time you changed your air filter?
Have you checked the turbo?
What's your mpg's ?
Boost sounds a little low

 

I think boost is a little low also under hard acceleration and pulling at 70mph. Check all your clamps and tighten them up first. Then go from there and get back.

 

Fuel pressure sounds fine. Might look into tightening up some possible boost leaks..

 

It's not a mounted gauge.. Don't remember the name, but it's used for checking and setting up fuel injection systems...(it also has an attachment so I can use to check pressure under open fuel flow)

 

If your pcm is stock, ...i.e. no chip or program on it...
You are right about where you should be.

 

15psi is normal for a stock SD?

The OBS stock can do 18psi and they only have 90cc injectors compared to the 140cc a SD has

 

-Big WIX, that RiffRaff sells prefilter foam for.
-Air filter was changed last summer.
-The turbo seems fine, no movement when shaken or pulled on, spins freely, no gouge marks from turbo fin strike.
-MPG's range from 12.5-14 empty, 10-12 pulling bass boat

I used to get in the neighborhood of 16-17 empty, on a consistant basis, and around 14-15 pulling trailers.. (loaded to about 10-15K)

Been fighting this issue for some time now.. I've done the boost leak check, up pipe leak ck, ebpv clean, changed oil at 5k everytime (Rotella syn for several yrs now) 192 deg thermostat. Truck starts easily, runs great empty, however it seems to be laboring when under a modest load (boat). (even a buddy mentioned he noticed it)....

I have a couple ideas, but don't know if I'm all wet or not..
***I've seen on other engines (not PSD's, tractors, school bus engines) which held in spec fuel pressure but were unable to provide needed volume. ****In fuel tank pickup screen full of crud. ***Wonder if wastegate is hanging / blowing open *** MAP sensor being bad
Hell, I don't know,,, just tired of the slight loss of pulling power and crap fuel econ, being Diesel isnt getting any cheaper. Before anyone asks, I fuel at same place, same pump, nearly every time.. and I know how to ck my mpg with a pencil...

But, I sincerely appriciate every logical suggestion you all have... I just hate going to the dealership.. Most of them can't diagnose a briggs and stratton lawn mower engine w/o having it a week and lot of dollars thrown their way...

 

It does have a superchip tuner tune installed... the lowest setting to change the fuel timing to get rid of off idle sluggishness... and, the numbers I've listed are the same on "Stock" or "Economy" super tuner tune...

 

Here's some readings from my ScangaugeII.... I apologize because I don't remember if these were at 60 mph or 70mph... it is one or the other, just knowing the roads I drive, I believe it to be 60.
Both were on level road: #1--- 4.4 Boost, 1546 ICP, 23.1 EBP, 24 IPR #2--4.7 BST, 1537 ICP, 22.8 EBP, 25 IPR

 

Boost reading may differ with different gauges and hose lengths and stuff. After hooking up my boost gauge I was only seeing 15-16psi as well. No boost leaks, good turbo.