I have/had a leak on one of the injector return lines that I stopped by pushing the line down more securely on the plug. I do have some questions about these lines that I hope someone can answer.
Is there pressure in these lines?
Does a leak in a line affect fuel injector/engine performance/power?
Are these just shoved on or should they be clamped?
Can they be clipped to get a new piece if it begins to leak again?

The lines on my parts car seem secure but the ones on my driver came off rather easily. They are the braided lines and were installed my independent last year.

Thanks for any response.

80 300D

these lines return excess fuel to the tank so that the pump can pump the same volumn all the time. they arent under much if any pressure. they get old after 15 years or so. you can cut a little off to get a new "bite" but you need to buy new lines and replace all of them. i recommend the factory lines as they last a very long time. the leaks wont affect performance except for fuel economy but create a fire hazard, obviously.

tom w

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[SIGPIC] Diesel loving autocrossing grandpa Architect. 08 Dodge 3/4 ton with Cummins & six speed; I have had about 35 benzes. I have a 39 Studebaker Coupe Express pickup in which I have had installed a 617 turbo and a five speed manual.[SIGPIC]

..I also have a 427 Cobra replica with an aluminum chassis.

Only if the engine is running.

The fuel return hoses are made of a material used with diesel fuel.
The hose is a braided 3mm i.d. with a faint yellow line in the otherwise black braid.

I have tried to get this stuff from my warehouser with no success.
The always send totally black braid hose of 2.5 mm i.d. or the 3.2mm.

Last hose they sent was COHLINE #2122. 0207(3.2mm X 7.0mm)

Anyone got an outlet on the correct hose, as this COHLINE lasts about 15 months or less.?


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Sam

84 300SD 350K+ miles ( Blue Belle )

Excess fuel? So - more fuel is sent to the injectors than is needed so the return lines are for that "excess fuel?"

These lines were replaced because I had a leak at the same injector line that was leaking last time. Does this mean that this injector is not injecting all the fuel that it should? I have put less than 2k miles on the car since these lines were replaced.

Just trying to understand their function a little better and how/if they reflect on injector performance.

Thanks

is delivering more fuel than the injector can use unless at full throttle. the extra fuel is returned to the tank. this is more effecient than forcing the fuel pump to 'slip'.

tom w

__________________
[SIGPIC] Diesel loving autocrossing grandpa Architect. 08 Dodge 3/4 ton with Cummins & six speed; I have had about 35 benzes. I have a 39 Studebaker Coupe Express pickup in which I have had installed a 617 turbo and a five speed manual.[SIGPIC]

..I also have a 427 Cobra replica with an aluminum chassis.

I know I don't understand all things and never will. Shoot - I don't even know what I don't know.
So - the excess fuel is returned to the fuel tank that already has fuel in it so that the pump in the tank that is covered with fuel won't slip? That's number 1.
Number 2 is if a particular injector is not injecting fuel will it force fuel out of the return line?

Thanks

first there is no pump in the tank. the pump is the injector pump. it looks like a little engine with pistons and a cam that pushes them up and down. it is fiercly effecient as it needs to be to deliver 1800 psi. but it is intolerant of pumping different volumns of fuel. so it is set up to pump a specific amount all the time (this may be an oversimplification) so it pumps more than the injector can use almost all the time. so the excess is shed from the injector and it flows back to the fuel tank for re circulation through the return lines. fuel injected gas engines do this too. (they DO have a pump at the back sometimes in the tank),

tom w

__________________
[SIGPIC] Diesel loving autocrossing grandpa Architect. 08 Dodge 3/4 ton with Cummins & six speed; I have had about 35 benzes. I have a 39 Studebaker Coupe Express pickup in which I have had installed a 617 turbo and a five speed manual.[SIGPIC]

..I also have a 427 Cobra replica with an aluminum chassis.

I replaced mine with some from my local independent when I replaced the injectors. It was black with the faint yellow stripe, however several of them leaked from the start. I replaced those again, then after a 500 mile trip, one still leaks. I don't know what the size was. I am going to get the OEM from the dealer, I don't like my engine compartment all slopped up.
I did consider one thing, if you cut them too short I believe they will leak as they will have sideways tension on them, even tho the little return nipples are angled slightly.

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Brian
87 300Dturbo 180K #14 head still running R-12 SOLD 12/2017
02 F350 Powerstroke 180K
05 Chevy Express 1 ton w/Royal Utility box 120K
08 Infiniti FX-35 40K
15 Golf Sportwagen TDI 35K
10 Sprinter 3500 chassis with a Class A Winnebago on it. 56K

you cant beat the factory parts on the return lines. they are cheap enough too.

tom w

__________________
[SIGPIC] Diesel loving autocrossing grandpa Architect. 08 Dodge 3/4 ton with Cummins & six speed; I have had about 35 benzes. I have a 39 Studebaker Coupe Express pickup in which I have had installed a 617 turbo and a five speed manual.[SIGPIC]

..I also have a 427 Cobra replica with an aluminum chassis.

Thanks for the responses. Now I can see more clearly - but - how about the question about a clogged fuel injector causing the return line to leak? I ask because I notice less power.
Just trying to connect the dots before moving on to some other cause.
Thanks

a clogged injector will not make the return line leak. you could have both at the same time but it would be a coincidence.

tom w

__________________
[SIGPIC] Diesel loving autocrossing grandpa Architect. 08 Dodge 3/4 ton with Cummins & six speed; I have had about 35 benzes. I have a 39 Studebaker Coupe Express pickup in which I have had installed a 617 turbo and a five speed manual.[SIGPIC]

..I also have a 427 Cobra replica with an aluminum chassis.

the 'new' lines from the MB dealer are grey with an orange stripe. i bought some of this line and installed when/where needed. hasn't leaked since (about 2 years).
give them a generous oval shape when you install.

i also replaced the longer line leading from the secondary fuel filter
with the same good result.

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1984 300D Turbo - 231k....totalled 11/30/07 RIP

they are not clamped. if the ones your indy installed only lasted one year then they installed the wrong line. in this case clipping them to obtain further life will not work or only work temoprarily. obtain new line from an MB dealer.
btw this is a job you should do yourself, to make sure it is done right

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1984 300D Turbo - 231k....totalled 11/30/07 RIP