Fuel Pressure Gauge & Shimming

[dpantazis]

So how much shimming is enough?

What yer look'n for is 68-70 psi @ idle, 65-68 running, or under load. ( IH tech sez)

What should it 'sound' like or 'behave like' when you get it 'right'?

Ok, so I am shimmed to 3 washers in. Pressure guage is not yet completed (wrong fitting). Did it while I was doing other stuff.... maybe I should have waited and only changed/modded one thing at a time.

I changed the oil out from questionable oil to Rotella T syn 5w40. No romps at least when I start up.Truck does 'seem' to run better but it should having changed out to good oil.

I will have pressure guage done in a couple of days. So I took the ole girl for a ride, about 30 miles each way to work and back. It drove well, expectedly it should.

dennis
mod party of 1

 

[CHPMustang]

One thing is for sure is to never blindly shim the FPR without a pressure gauge to test the baseline psi to calculate how many Big Joe shims you can install before it goes over 72 psi then you may accelerate roasting your stock fuel pump and/or causing leaky injector seals/o-rings

There's no perfect sound to the engine while shimming as each engine reacts differently than the next so you may be doing damage without even knowing it.

Git that gauge dun

 

[powerboatr]

ditto to bill
I found on mine, to tweak the pressure and listen to teh engine , for a subtle smoothness change like adjust fuel air on a carb engine.
this may require an external regulator to allow for your engine to be running

i ran 65-67 and over 70 was a direction in more roughness...

 

[BIG JOE]

What should it 'sound' like or 'behave like' when you get it 'right'?

Ok, so I am shimmed to 3 washers in. Pressure guage is not yet completed (wrong fitting). Did it while I was doing other stuff.... maybe I should have waited and only changed/modded one thing at a time.

I changed the oil out from questionable oil to Rotella T syn 5w40. No romps at least when I start up.Truck does 'seem' to run better but it should having changed out to good oil.

I will have pressure guage done in a couple of days. So I took the ole girl for a ride, about 30 miles each way to work and back. It drove well, expectedly it should.

dennis
mod party of 1

Hi Dennis,

What Bill & PB sez is true, fer sure. You need to get a Baseline FPR pressure. I'd Betcha you'll have between 50 & 60 psi, stock. When you hook up yer guage, start yer truck and let it idle for a minute or two, to get a stable baseline psi. Then shim from there. Youll feel better about it cuz you will have BUILT the 65-70 psi, rather than just stuck some washers in and Went fer It.

Just my observations but, Each one of these 7.3s is a bit different in basic sound, at idle and running at RPMs. What you should hear, and feel, from YOUR 7.3 after shimming the FPR is; It'll be bit quieter and smoother, at idle.... and a bit smoother acceleration with a bit more pep. The word "BIT", being the operative word. The "Pep" was always There. The lower than the, IH recommended, 65 to 70 psi fuel pressure, prevented it from being There. (Just my thoughts on it)

But what ever you hear and feel will be specific to YOUR 7'3.

JOE

 

[whatabudro]

Hey Joe, you feel like writing an article on this? The reason I ask is because you are more experienced with it, and we call it the "BIG JOE mod" out in these parts. I took lots of photos during the last mod day. We have a shimming article for the OBS in the WIKI but need one for the superduties. If you would, write up the steps, I'll copy and paste it, then put in the photos where they go. If not I'll take a stab at it.

 

[BIG JOE]

Hey Joe, you feel like writing an article on this? The reason I ask is because you are more experienced with it, and we call it the "BIG JOE mod" out in these parts. I took lots of photos during the last mod day. We have a shimming article for the OBS in the WIKI but need one for the superduties. If you would, write up the steps, I'll copy and paste it, then put in the photos where they go. If not I'll take a stab at it.

No problem Bryan. You want me to Pm it to ya or just Post it ???

JOE

 

[whatabudro]

Either way Joe.

 

[dpantazis]

So what have I learned

I picked up the last/correct fitting last night and installed my fuel pressure guage.

On startup pressure was a hair under 60 psi. Hmm, not enough i thought. No change in how the truck sounded. Shut it down, took the cap off and then I put in another washer. A hair over 60 psi. hmm. Then I began to notice how cold it felt outside. I noticed that the wind had picked up and little white things were floating around. ??? It started to flurry.

I guess I got a little greedy in my haste to finish and get to work. Took it apart, took out the washers and then stuck in a BB, ala the wiki page, put it all back together. Started the truck up, pressure on the gauge jumped up to 80 psi Now the truck idled really quite but 80 psi, ranging up to 85 psi this is too much. That or my guage is not right.

So its back to the hobby store to get some more or thicker washers. The ones I have now are brass and kinda thin. I would imagine that SS ones might be made of thicker stock? That or make aluminum buttons ala the diesel innovations kit.

I also need to find another O-ring for the fuel return pipe. The one in there is not looking too good and the last thing I want to do is spring a leak spraying diesel fuel everywhere.

so i was subtly reminded about taking my time and doing it right. in my excitment i rushed and i now have to do it all again.

dennis

 

[BIG JOE]

I'm a Fan of the Washers... There is no spec on them either but I've found > 3 < will get you 68/70 psi on >MOST< PSDs. The BB & Store bought shims... Are what They Are. With the the washers you can "Shim" to where you need to be.

Yer right (IMO) 80/85 it to much.

Also (IMO) wait a minute or two after you start it up.... to let the REAL fuel pressure reading, stabilize.

A WIKI on this is Whole shimming thing is, "In The Works"

JOE

 

[CHPMustang]

A WIKI on this is Whole simming thing is, "In The Works"

JOE

I have additional photos available for the article from several other trucks I've shimmed over the past year Joe

The washers is the way I do em!