Air Leaks
Note:
Every Fuel Pro is factory tested for leaks and is iden-
tified with a traceable number prior to shipment . Most field
issues associated with leaks are related to loose fittings .
These leaks are easily eliminated by checking and torquing
the fuel fittings in the area of the leak . Some fittings may
also require the application of liquid Teflon sealer .
Note:
All suction side fuel filters experience bubbles . It
is normal to see champagne size bubbles in the Fuel Pro
cover, at the Fuel Pro outlet or at the lift pump .
IN ORDER TO RETURN A FUEL PRO FOR EVALUA-
TION, THE FOLLOWING PROCEDURES/TESTS MUST
BE COMPLETED BEFORE REQUESTING A DAVCO
RGA (RETURN GOODS AUTHORIZATION) NUMBER.
I. Air Leak:
Air bubbles will be visible in the clear cover of
the Fuel Pro if the leak originates between the fuel tank
up and the fuel filter . The following is a quick test to
isolate the air leak source .
A. Bubbles Visible:
Remove the Fuel Pro inlet hose .
i . Install a jumper hose from the Fuel Pro to
the fuel tank (through the fill cap) or to a
container of fuel .
ii . Start the engine . If this eliminates the air
bubbles, the air source is at the fuel tank
fittings or hose connections .
1 . Tighten all fittings and connectors
2 . Retest
iii . If air bubbles persist, the air source is on the
Fuel Pro side of the system:
1 . Tighten all fittings on the Fuel Pro .
2 . Hand tighten the top collar .
3 . If the drain valve is suspected, install a
plug in place of the drain valve (for test
purposes only) .
iv . If air bubbles continue to persist, test as
follows:
1 . Remove the Fuel Pro from the chassis .
2 . Plug the fuel outlet port . Do not re-
move filter, cover/collar, vent cap, drain
valve and/or check valve . If the Fuel
Pro is equipped with a pre-heater, do
not remove the pre-heater .
3 . Apply 15 PSI of air pressure at the fuel
inlet . Immerse the Fuel Pro in a tank of
water and look for air bubbles .
4 . Correct the source of the air leak and
retest .
B. Bubbles Not Visible:
If there are symptoms of
sucking air (indicated by engine loping/rough run-
ning performance/power loss, etc .) and there are
no bubbles in the clear cover, the air leak is either
at the Fuel Pro outlet fitting, vent cap o-ring, the
lift pump inlet connection, or the fuel hose/con-
nections to the lift pump . Inspect and tighten
fittings as needed .
II. Excessive Restriction:
If the fuel level is at the top
of the filter, replace the fuel filter . The Fuel Pro will not
cause excess system restriction if the fuel level is below
the top of the filter . The only exception is if the grommet
is not installed in the bottom of the filter element .
III. Loss of Prime:
When air is introduced into the fuel
system, (i .e . draining water from the Fuel Pro or when
replacing the fuel filter) a check valve is needed to keep
the fuel system primed from the Fuel Pro back to the
fuel tank . A check valve is standard with every Fuel Pro
A . To test for proper check valve operation, remove
the fuel inlet hose and open the vent cap . Fuel
should not flow out of the Fuel Pro, although a
slight seepage of fuel is normal .
B . If fuel drains back to the fuel tank, remove the
check valve assembly at the fuel inlet fitting .
Disassemble the check valve assembly . Clean
and inspect . Replace the assembly if any cuts,
grooves or nicks are evident in the ball or body
seat . Reinstall the check valve assembly .
DIAGNOSTIC PROCEDURES - AIR LEAKS
FUEL PRO
®
382
TECHNICAL MANUAL
T e c h n o l o g y , L L C
DAVCO Technology, LLC P. O. Box 487 Saline, MI 48176 Call 800-328-2611 www.davco.com F1271 REV J
October 3, 2016 11:34 AM
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