December 2004
Form No.: 433-0780
Avoid comebacks, install permeation-resistant fuel line hose
Fuel line hoses carry gasoline from the tank to the
fuel pump, to the fuel filter, and to the fuel injection
system. While much of the fuel lines are rigid tube,
sections of it are made of rubber hose, which
absorb engine and road vibrations.
There are two basic types of fuel hose: Fuel and oil
hoses that meet the SAE 30R7 standard, and fuel
injection hose that meets the requirements of SAE
30R9.
Standard fuel and oil (SAE 30R7) hose is rated for
low-pressure applications at 50 psi working
pressure up to 3/8" size, and 35 psi for sizes over
3/8". This general-purpose hose contains a light
reinforcement, and the rubber materials can be any
compound that is suitable for fuel, oil and vapors.
However, Gates Corporation engineers warn
installers that fuel formulations at many US
refineries are constantly changing as proprietary
blends are introduced according to government
mandates and seasonal influences. At times, more
aggressive fuels can extract the oils that give SAE
30R7 hose its flexibility. The result is a brittle, stiff
tube that will greatly reduce the performance and
service life of the hose.
Fuel injection (SAE 30R9) hose or MPI (multi-port
injection) hose is reinforced to handle higher
pressures up to 180 psi. It can be used on all
injection systems that use hose clamps. It is not
designed to replace coupled assemblies on fuel
injection systems.
Fuel injection hose is designed for low permeation
contact with a wide variety of alcohols, alcohol fuel
blends, and diesel fuel. It allows 15g/m2/day
permeation whereas standard SAE 30R7 hose
allows 550g/m2/day. (Gates fuel injection hose
routinely performs at 1 to 2g/m2/day of fuel loss,
well below the allowable standard.)
Gates SAE 30R9 hose uses a laminated tube of
Fluoroelastomer, as a thin wall inner layer backed
by traditional compounds. This first layer protects
the rest of the hose from attack, swelling or
permeation from aromatics, oxidized gasoline (as
can occur in fuel injection systems), ethanol or
oxygenate additives and a wide range of petroleum
based products.
The laminated tube will resist cracking caused by
"sour gas," which forms when unused gas is
returned to the fuel tank. As an added benefit, this
hose construction reduces emissions because fuel
can't evaporate through the hose walls.
SAE30R9 hose is also recommended for diesel
fuel because its fluoroelastomer tube resists
deterioration caused by some diesel fuel additives.
As refineries produce cleaner fuels and lower
allowable permeation rates during the “vehicle at
rest” condition, older hose specifications such as
SAE 30R7 are becoming less reliable. This type of
hose is no longer specified on OEM automotive
fuel applications because of stringent permeation
standards.
Therefore, Gates engineers assert that the best
choice for automotive fuel line hose applications
today is fuel injection SAE30R9 hose. For
installers, it is the best choice for reduced
comebacks and for high performance, assured
trouble free service in a changing fuel environment.
Finally, for submersible applications such as on the
in-tank fuel pump, only SAE30R10 hose should be
used, because when the hose fails, the pump will
fail. Hose construction consists of low swell
fluoroelastomer compounds in the tube and cover
that resist gasoline and diesel fuel permeation and
aging. Standard hoses have these fuel-resistant
characteristics in the tube portion only.
Contact your Gates jobber for information on Gates
MPI/fuel injection hose and submersible fuel line
hose.
Gates Corporation
PO Box 5887, Denver, Colorado 80217
