Optikalillushun
Registered User
Upgraded my 7.3s fuel system from the old return line style to the new style. Wasnt hard, took maybe 2 hrs and i was ****** it. Ill have pics later on etither tonight or tomorrow.
7.3 fuel system upgrade complete
- Thread starter Optikalillushun
- Start date
Optikalillushun
Registered User
Oops forgot about this thread. Anyway, this mod (if u wanna call it that) is used on pre-89 IDIs with the 7.3 (6.9s also probably). Reason i did this was i ordered the wrong return line kit and i was looking for a way to eliminate areas of air intrustion. While walking around the junkyard one day i noticed a 92 F250 7.3, after i took what i wanted i seen the T fitting at the back was different. Intrigued i took it and when i got home i got online to search a little.
This is the part:
And this is what is replaces:
The end to the left has both banks meet up and dump fuel off from the IP via that steel line to the return line to the tank. Notice the brass nut on the end, that hides the infamous 4th olive (pic is of an olive for those who dont know):
Its an often over looked area when looking for air intrustion. I previously replaced all the olives (two at the filter head, one at the back of the IP, and that one).
Location of 4th olive on truck:
To replace that brass T, its pretty easy. After the return lines are removed remove the brass fitting that seperates the steel line from the T, then unbolt the two intake bolts that hold that line down and snake it out. For the new T, remove the other intake bolt that held the steel line at the back and put the engine hook, brass t and bolts back in and dont forget the other bolt that was removed. Torque to spec (will add later).
After that is replaced its time to move onto using the new return caps. These differ from the old style in a few ways: 1) the return line is on the side of the cap, not in the middle; 2) the return line is larger, 1/4" vs. 3/16"; and 3) the routing is slighly altered. As previously mentioned the old style took un-used fuel from both banks, merged it at the brass fitting and dumped it off to the tank. The new style runs both banks to that brass T but also uses the drivers side bank to dump excess fuel from the IP.
Old 7.3 fuel routing:
New 7.3 fuel routing:
Close up of new brass T:
Note how the two lines that merge are offset, this allows for easy hose routing under the CDR.
Also now would be a good time to replace the short 5/16" hose that runs from the brass T down to the fuel line. Mine was brittle like and crumbled like a potato chip:
Hose diameter differences (New-left; old-right):
This is the part:
You must be registered for see images attach
And this is what is replaces:
You must be registered for see images attach
The end to the left has both banks meet up and dump fuel off from the IP via that steel line to the return line to the tank. Notice the brass nut on the end, that hides the infamous 4th olive (pic is of an olive for those who dont know):
You must be registered for see images attach
Its an often over looked area when looking for air intrustion. I previously replaced all the olives (two at the filter head, one at the back of the IP, and that one).
Location of 4th olive on truck:
You must be registered for see images attach
To replace that brass T, its pretty easy. After the return lines are removed remove the brass fitting that seperates the steel line from the T, then unbolt the two intake bolts that hold that line down and snake it out. For the new T, remove the other intake bolt that held the steel line at the back and put the engine hook, brass t and bolts back in and dont forget the other bolt that was removed. Torque to spec (will add later).
After that is replaced its time to move onto using the new return caps. These differ from the old style in a few ways: 1) the return line is on the side of the cap, not in the middle; 2) the return line is larger, 1/4" vs. 3/16"; and 3) the routing is slighly altered. As previously mentioned the old style took un-used fuel from both banks, merged it at the brass fitting and dumped it off to the tank. The new style runs both banks to that brass T but also uses the drivers side bank to dump excess fuel from the IP.
Old 7.3 fuel routing:
You must be registered for see images attach
New 7.3 fuel routing:
You must be registered for see images attach
Close up of new brass T:
You must be registered for see images attach
Note how the two lines that merge are offset, this allows for easy hose routing under the CDR.
Also now would be a good time to replace the short 5/16" hose that runs from the brass T down to the fuel line. Mine was brittle like and crumbled like a potato chip:
You must be registered for see images attach
Hose diameter differences (New-left; old-right):
You must be registered for see images attach
Last edited:
boxathey
Full Access Member
Good Stuff, Great Write Up Im Getting Ready To Replace Mine As Well
gdhillon
Full Access Member
Great writeup optkcal, is the power steering pump the thing across from the alternator, or is that ac condenser?
Optikalillushun
Registered User
Thats the AC compressor. The power steering pump is below. Yours may differ slighly due to the serp belt.
gdhillon
Full Access Member
hmmm yes compressor no idea why i said condenser haha.
Optikalillushun
Registered User
Next up is going to be a carrier e-fuel pump and a fuel filter with no WIF sensor port.
gdhillon
Full Access Member
exciting! your not going to do injectors or fuel pump?
Optikalillushun
Registered User
Id like to do injectors but i just replaced these 2 1/2 yrs ago (low miles put on it) and the pump was done about 4 yrs ago by the PO.
Optikalillushun
Registered User
Bump to remind myself to add more info to this later today.
Optikalillushun
Registered User
another bump for more info and more tech!
G.W BUFFALO
Full Access Member
So do you think this fixed your starting problem's, maybe the 7.3 system is less prone to leakage?? Mine gets a tiny bit of air in it if it stits more than a week not running, so i'm looking into brass caps again but maybe i should try upgrading to the 7.3 system first.
Optikalillushun
Registered User
it seemed to fix the problem, but not by switching the brass fitting. The problem was fixed because of a good return line kit was used. I just wanted to do this so i didnt have that extra olive to deal with and make useing the wrong return line kit i ordered easier.
G.W BUFFALO
Full Access Member
Sound good, i think i'll just get the bigger 3 way fitting that uses the larger hose and have new brass caps made that use larger 1/4 hose.. i think the brass caps are going to be way worth the price, it's one and done and should be the nail in the coffin for injector return leaks..
Nice install.
Gotta question though.
Does this injection system use some back pressure to keep the injectors full? For instance, there's a return line choker in a Detroit, if it isn't installed(basically a small inner diameter washer) the returning fuel will drain the injectors and prevent them from firing. If so, where is that done? I suppose the injectors work solely off the IP pressure as a direct feed and is internally choked.
Just curious.
Gotta question though.
Does this injection system use some back pressure to keep the injectors full? For instance, there's a return line choker in a Detroit, if it isn't installed(basically a small inner diameter washer) the returning fuel will drain the injectors and prevent them from firing. If so, where is that done? I suppose the injectors work solely off the IP pressure as a direct feed and is internally choked.
Just curious.
