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Topic: Diesel fuel return line? (Read 1337 times) previous topic - next topic

Diesel fuel return line?

Why does a diesel engine have a fuel return line? Does it return the same amount no matter the load?
And you thought there were no dumb questions??! ;D
Dick
Dick, '03 U320 40' Tag, 2 slides, Coach #6075
Full Timers
2009 Honda CR-V

Re: Diesel fuel return line?

Reply #1 –
From what I understand, very little of the fuel that is pumped to the engine from the tank is used by the injectors. What is not used is returned to the tank. If I remember correctly the unused fuel is used as a coolant for the injectors?

Roland
1993 U280 4341
2010 Jeep Liberty
The Pied Pipers

Re: Diesel fuel return line?

Reply #2 –
Gas engines also have fuel return lines.

Re: Diesel fuel return line?

Reply #3 –
Diesels return fuel from both the injector pump pressure relief valve as well as the injectors. It does carry off heat from the injectors. Probably 99% returns at idle, less at full throttle. Some lift pumps are marginal so at max throttle, they may not be able to supply the proper pressure to the injection pump. Some injection pumps can be damaged by low lift pump pressure.

Gas engines with fuel injection also have return lines. Carburetor engines only have one line.

Pierce.
Pierce and Gaylie Stewart
'93 U300/36 WTBI
Detroit 6V-92TA Jake
1140 watts on the roof
SBFD (ret)

Re: Diesel fuel return line?

Reply #4 –
Carb gas engines can have fuel return lines, often from a fuel filter before carb that has a spring loaded fuel return. This is simple nice add to help eliminate fuel vapor lock and to cool fuel.

Re: Diesel fuel return line?

Reply #5 –
Quote from: Pierce & Gaylie Stewart

Carburetor engines only have one line.

Pierce.
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The way GOD intended fuel to be delivered!
1995 U320C SE 40'
Jeep 4x4 Commander - Limited - Hemi
"The Pack"  Yogi and Diesel our Airedales -  Charlie our Boxer/Akita mix. Gone but NEVER forgotten Jake our yellow Lab.
NRA Law Enforcement Firearms instructor - Handgun/shotgun
Regional Firearms instructor for national Armored Transp. Co.

Re: Diesel fuel return line?

Reply #6 –
Thanks!
Dick, '03 U320 40' Tag, 2 slides, Coach #6075
Full Timers
2009 Honda CR-V

Re: Diesel fuel return line?

Reply #7 –
There are several ways to address the water detection issue, in my world, when I need to verify water in the fuel tank, I use a paste (like tooth paste in a tube) available from commercial boiler suppliers, not from Lowes type stores. Using a stick, yard stick, what ever, smear a dab on the end up about 1-2", stick into the tank to the bottom, upon removal, any water would turn the yellowish paste red. A quick & simple test.

Re: Diesel fuel return line?

Reply #8 –
Yes, used Kolor Cut many times on fishing boats and tow boats. Positive results.
Richard & Betty Bark & Keiko our Golden Doodle
2003 U320T 3820 PBDS
Build # 6215
MC # 16926
2016 Chevrolet Colorado 4X4 diesel

Re: Diesel fuel return line?

Reply #9 –
rbark,  Thanks, could not recall the Kolor Cut name & too lazy to go to the service truck for the name.