Plastic return line cap melted? How to prevent in the future.

Brian VT

Full Access Member
Joined
Oct 25, 2021
Posts
973
Reaction score
556
Location
Maine, USA
...and new copper washers. And make sure the old washer comes out. They often don't come out with the injector so you'll have to use a pick to dig it out.
 

John_piv

Registered User
Joined
Jun 12, 2022
Posts
90
Reaction score
22
Location
Florida
...and new copper washers. And make sure the old washer comes out. They often don't come out with the injector so you'll have to use a pick to dig it out.
I know you can get the o-rings at TSC. Anywhere in particular you can get the washers?
 

typ4

Supporting Member
Supporting Member
Joined
Dec 24, 2005
Posts
9,092
Reaction score
1,372
Location
Newberg,OR
Here is the facts to answer some questions.
1st- injectors are not cooled, the caps are there to capture the "leak off" fuel that gets past the pintle.
2nd- the only way that cap melts is if the injector pintle sticks open, combustion gas goes thru and melts the cap.
3rd-This can happen for many reasons, yours was the loose injector. Torque is 35ftlbs, I've been torqueing to 40ftlbs for 20 years.

I recommend a new install kit.
Your injector tip is likely stuck. You can disassemble it and see. I have some good used if you need. free if you buy the kit.

 

franklin2

Full Access Member
Joined
Feb 24, 2009
Posts
5,160
Reaction score
1,384
Location
Va
Here is the facts to answer some questions.
1st- injectors are not cooled, the caps are there to capture the "leak off" fuel that gets past the pintle.
2nd- the only way that cap melts is if the injector pintle sticks open, combustion gas goes thru and melts the cap.
3rd-This can happen for many reasons, yours was the loose injector. Torque is 35ftlbs, I've been torqueing to 40ftlbs for 20 years.

I recommend a new install kit.
Your injector tip is likely stuck. You can disassemble it and see. I have some good used if you need. free if you buy the kit.

I had a Ford engineer on another board correct me when I said the fuel leaking in the return system from the injector was to cool and lubricate the injector. He got into this long explanation which I have forgotten mostly, but what I do remember is he said a brand new injector will have little to no flow into the return system, and as something inside the injector wears, the return flow will slowly increase with the age/miles on the injector.
 

captain720

Full Access Member
Joined
Feb 20, 2022
Posts
589
Reaction score
448
Location
Washington
They’re not all the same. The 6.9 and some early 7.3 caps used 3/16 in hose, the later 7.3 caps used 1/4 in hose.
So are the injector outside dimensions the same but the hose size is the main difference? Does that mean that R and Ds return rails work for 6.9 and late 7.3s?

 

CharlesG

Registered User
Joined
Jun 3, 2015
Posts
76
Reaction score
64
Location
Escondido, CA
So are the injector outside dimensions the same but the hose size is the main difference? Does that mean that R and Ds return rails work for 6.9 and late 7.3s?


The cap ID is the same, the rubber hose between the caps is different early to late. The early caps have the hose barb centered on the cap, on the late ones they are offset.

Since the R&D rails are one piece, they will work on 6.9 and 7.3.
 
Last edited:

typ4

Supporting Member
Supporting Member
Joined
Dec 24, 2005
Posts
9,092
Reaction score
1,372
Location
Newberg,OR
I had a Ford engineer on another board correct me when I said the fuel leaking in the return system from the injector was to cool and lubricate the injector. He got into this long explanation which I have forgotten mostly, but what I do remember is he said a brand new injector will have little to no flow into the return system, and as something inside the injector wears, the return flow will slowly increase with the age/miles on the injector.
This is exactly accurate. That's why it's called leak off it's what leaks past the machine parts.
 

ROCK HARVEY

Full Access Member
Joined
Oct 3, 2021
Posts
417
Reaction score
372
Location
Dayton OH
We’ll I learn something new every day on this forum! I thought the excess fuel from the IP provided cooling to the injectors as it flowed past them, but if the experts say otherwise I 100% defer to them.
 

ROCK HARVEY

Full Access Member
Joined
Oct 3, 2021
Posts
417
Reaction score
372
Location
Dayton OH
It’s actually really good to know that the return fuel from the IP provides no benefit to the injectors, and that very little fuel flows to the tank from the injectors themselves. That means when I need to run the engine directly from a container of injector cleaner, I can route the feed line and IP return to the container under the hood, and not at the FSV or anywhere under the truck.
 

Latest posts

Forum statistics

Threads
91,217
Posts
1,128,471
Members
24,043
Latest member
tottripp
Top