Help Needed Fuel Pressure Regulation 7.3L

[RSG]

I got a fuel gauge and the DieselOrings FPR kit, along with a fuel bowl repair kit etc, since I figured I might as well replace all the o-rings while I had the fuel bowl out...

After installing with the black "70 lb" FPR spring, I was getting 77 to 82 psi. I ran it for about 20 minutes and it reduced from the higher to the lower end of that range. So I decided maybe the spring was too strong (the new gauge is supposed to be good to 1%, I think, it's a Peformax Series digital gauge; I decided it was probably not that far out of calibration).

Putting a new spring in this kit, without removing the fuel bowl, is a royal PIA because the new FPR housing is about 3/8" thicker and that clearance is really needed to get the spring into the poppet stem, straight, and the combination of longer torx screws and thicker housing interfere with one of the two screws clearance to the fuel supply line. (the instructions do recommend removing the fuel bowl housing). I dorked around with it for another couple hours, got it back together and now it is 75-95 psi...mostly to the higher end. This probably means that the spring is not seated correctly against the housing base...or there is something else wrong with my rebuild.

I need some advice on what to do next, so I can drive again. Options:
1. pull it apart again and see if I get lucky on the spring
2. pull the bowl -- but then do I need to replace all the compression sleeves for rail lines (2) and main supply (1)?
3. disconnect the return line at a quick disconnect down by the driver front wheel to get the lateral play I need. I don't know how they come apart, or if there are other fasten points too?
4. put in the old housing to get the clearance and use the new 70 lb spring?

Suggestions please?

 

[BIG JOE]

First and FWIW Rich ?

My fuel pressure (using the Shims) will show 70-80 (mechanical gauge) psi at start up. After a minute or two it stabilizes at 70, at idle.

The key would be: the psi should Drop.. under load-acceleration.. then run about 68-70 cruising, 65 with a load/throttle demand on it.

I'm not familiar with digital gauges.. can't help you there.

Are you going to leave under the hood ?

joe

 

[RSG]

Thanks Joe. After the first install, with a "70 lb spring", the pressure would drop down to about 70 when WOT. At cruise or idle it was 77-85'ish. I was hoping it was air but it never came down below 77-78 except under large fuel flow from the accelerator, and mostly ran about 80 psi. After I put the lighter spring in, but with issues to get it in with such marginal clearance, it's higher (85-95+) and I'm guessing the new spring did not seat properly, on account of the miserable clearance.

The gauge is inside the cab, all mounted nicely and the lines routed to a "brain" up by my battery. I don't think this is a gauge problem, so I was worried about too much pressure for the fuel bowl -- even with all new o-rings, sleeves, etc 80 psi or so, seems like too much?

Speaking of which, I was surprised at how many parts are in that seemingly simple fuel bowl!

Anyway, I'm probably going to put the old housing back on, with the 65 psi spring; or pull the bowl again, if I don't need to go find new compression sleeves for the main line and the return line (got two spares for the rail lines)....?

What's the downside of over-pressure, besides possible leakage? Will it run fuel into the motor oil, for example? I'm not clear on what higher pressure does other than provide more fuel per "shot" to each injector...

<edit: 2 pictures added>

 

[BIG JOE]

Thanks Joe. After the first install, with a "70 lb spring", the pressure would drop down to about 70 when WOT. At cruise or idle it was 77-85'ish. I was hoping it was air but it never came down below 77-78 except under large fuel flow from the accelerator, and mostly ran about 80 psi. After I put the lighter spring in, but with issues to get it in with such marginal clearance, it's higher (85-95+) and I'm guessing the new spring did not seat properly, on account of the miserable clearance.

The gauge is inside the cab, all mounted nicely and the lines routed to a "brain" up by my battery. I don't think this is a gauge problem, so I was worried about too much pressure for the fuel bowl -- even with all new o-rings, sleeves, etc 80 psi or so, seems like too much?

Speaking of which, I was surprised at how many parts are in that seemingly simple fuel bowl!

Anyway, I'm probably going to put the old housing back on, with the 65 psi spring; or pull the bowl again, if I don't need to go find new compression sleeves for the main line and the return line (got two spares for the rail lines)....?

What's the downside of over-pressure, besides possible leakage? Will it run fuel into the motor oil, for example? I'm not clear on what higher pressure does other than provide more fuel per "shot" to each injector...

OTHER than leakage...I don't know the Technical side of what over-pressure would do Russ, other than what I've gleaned from several IH tech's.. that 70 PSI [Line Delivery Pressure], at static idle, is what the IH specs call for, for the IH versions of the 7.3. And 60 to 70 psi under loaded throttle demands.

I'm not so sure it's MORE Fuel per Shot.. as it is 60 to 70 psi AVAILABLE per Shot.. Is Better, or Optimum.. for the oil pressure operated injectors Used.. in the 7.3. (Where the HPOP comes into play)

(I'm in the process of R&R'ing my injectors with a slightly up-graded set. From what I'm learning.... It's All About regulated Fuel psi.. and the HPOP pressure being more Matched.. than what the stock PSD (Ford) set-up is.)

Make any Sense ? Sorry for Rambling

 

[RSG]

Makes sense -- fuel flows predictably at constant and high enough pressure. i'm just wondering whether 80'is is to high...!

 

[BIG JOE]

Makes sense -- fuel flows predictably at constant and high enough pressure. i'm just wondering whether 80'is is to high...!

PM sent.

 

[RSG]

Thanks to everybody for help and advice. I pulled the fuel bowl and sure enough the spring was cock-eyed in the housing. Trip to Intl dealer got me 2 of 3 size compression sleeves for fuel lines. Put it back in with original "70 lb" spring and pressure (w/o start) runs up to mid-70 psi.

Also decided it was time to replace the intercooler boots, a job I've been putting off since last January (!!). What a PIA.

Haven't gotten it started up again, will post a picture of the spring when I find my cell phone among all the wrenches!