Maddox MD39-1 Assembly instructions

Owner’s Manual & Safety Instructions
Save This Manual Keep this manual for the safety warnings and precautions, assembly,
operating, inspection, maintenance and cleaning procedures. Write the product’s serial number in the back
of the manual near the assembly diagram (or month and year of purchase if product has no number). Keep
this manual and the receipt in a safe and dry place for future reference. 21l
When unpacking, make sure that the product is intact
and undamaged. If any parts are missing or broken,
please call 1-888-866-5797 as soon as possible.
Copyright©2021 by Harbor Freight Tools®. All rights reserved.
No portion of this manual or any artwork contained herein may be reproduced in
any shape or form without the express written consent of Harbor Freight Tools.
Diagrams within this manual may not be drawn proportionally. Due to continuing
improvements, actual product may differ slightly from the product described herein.
Tools required for assembly and service may not be included.
Read this material before using this product.
Failure to do so can result in serious injury.
SAVE THIS MANUAL.
Visit our website at: http://www.harborfreight.com
Email our technical support at: [email protected] 58817

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Specifications
Pressure Scale 0 –140 PSI / 0 – 1000 kPa
Gauge Accuracy ±2%
Important Safety Information
Read all safety warnings and instructions. Failure to follow the warnings and
instructions may result in electric shock, fire and/or serious injury.
Save all warnings and instructions for future reference.
1. Stay Keep your work area clean
and well lit. Cluttered and dark
work areas invite accidents.
2. Stay alert. Watch what you are doing,
and use common sense when operating
tools and equipment. Do not assemble
or use this product while tired or under
the influence of drugs, alcohol, or
medication. A moment of inattention
while operating tools and equipment
may result in serious personal injury.
3. Wear eye protection. Wear
ANSI-approved safety impact
glasses and full face shield
when using this product.
4. Do not force the Service Kit. Use the
correct product for your application. The
correct product will do the job better and
safer at the rate for which it is designed.
5. Maintain the Service Kit with care.
Keep this product clean. Properly
maintained products are less likely
to malfunction. Do not use damaged
products. Tag damaged products
“Do not use” until repaired.
6. Check for any condition that
may negatively affect operation
of the Service Kit. If readings are
inconsistent, or if it appears that the
fuel gauge is not functioning properly,
the Service Kit should be serviced
by a qualified service technician.
Many accidents are caused by
poorly maintained products.
7. Use only accessories that are
recommended by the manufacturer
for your model. Accessories that
may be suitable for one product
may become hazardous when
used on another product.
8. Industrial applications must follow
OSHA requirements.
9. Maintain labels and nameplates
on the Service Kit. These
carry important information. If
unreadable or missing, contact
Harbor Freight Tools for a replacement.
10. Use the right product for the job.
There are certain applications for
which this product was designed.
Do not use small products to do the
work of larger industrial products. Do
not use this product for a purpose
for which it was not intended.

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11. Product service must be performed
only by qualified service
technician. Service or maintenance
performed by unqualified personnel
could result in a risk of injury.
12. When servicing the Service Kit,
use only identical replacement
parts. Follow instructions in the
“Inspection, Maintenance, And
Cleaning” section of this manual. Use
of unauthorized parts or failure to
follow maintenance instructions may
create a risk of personal injury.
13. Always make sure the area of
use for this product is clear
of any children. Do not allow
children to play with this product.
14. Do not allow the vehicle’s engine
to run while using the Service Kit.
When running, the engine of a
vehicle produces carbon monoxide,
a colorless, odorless, toxic gas
that, when inhaled, can cause
serious personal injury or death.
15. Prior to using this product, make
sure to read and understand
all instructions and safety
precautions as outlined in the
vehicle manufacturer’s manual.
16. Always keep hands and fingers
away from the moving parts
and hot parts of an engine.
17. Do not use this Service Kit
on diesel fuel systems.
18. Do not smoke while performing
any fuel injection tests or repairs.
19. Always have a dry chemical (Class B)
fire extinguisher within reach.
20. Make sure to provide a suitable
container to catch released fuel
when the system is depressurized.
21. Take extra care to prevent fuel
from contacting hot engine parts.
It is recommended that tests be
performed when the engine is cold.
22. If a drop light is used, do
not allow fuel to contact the
hot surface of the bulb.
23. Never remove any fittings
with the engine running.
24. Never loosen any fittings or attempt
to remove hoses of vehicle or
Service Kit until you have relieved
the fuel system pressure. Refer
to the vehicle manufacturer’s
service manual for specific fuel
pressure relief procedures.
25. Always check all connections for
leaks during the testing procedure.
At any sign of leaks, turn off the
engine or disable the fuel pump.
Clean up any spilled fuel and repair
all leaks before resuming test.
26. When preparing for pressure testing,
make sure the vehicle’s transmission
is placed in “PARK” or “NEUTRAL”
and the emergency brake is applied.
27. When the test is complete,
depressurize the system and remove
the Service Kit. Reassemble the
vehicle’s fuel line(s) to its original
condition. Start the engine and
check for leaks. If any leaks are
present, stop the engine, relieve
fuel pressure and repair all leaks.

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28. People with pacemakers should
consult their physician(s) before use.
Electromagnetic fields in close proximity
to heart pacemaker could cause
pacemaker interference or pacemaker
failure. Caution is necessary when near
coil, spark plug cables, or distributor
of running engine. Engine should be
off during distributor adjustment.
29. The warnings, cautions, and instructions
discussed in this instruction manual
cannot cover all possible conditions
and situations that may occur. It must
be understood by the operator that
common sense and caution are factors
which cannot be built into this product,
but must be supplied by the operator.
SAVE THESE INSTRUCTIONS.
Applications
# Picture Description Application
1
3.5″Pressure
Gauge with
protective boot and
hanger 0-140 psi
(0-10 BAR)
Connects to #25 for basic testing.
2Ford MPI Adapter Ford MPI.
3
7/16″x 20
GM/Chrysler
Adapter
Chrysler and Jeep MPFI, GM MPI.
4Hose Clamps &
Hose 5/16″, 3/8″Hose clamps and hose.
5M16 x 1.5 In-Line
Adapter GM TBI-used in fuel filter location.
6Seal Kit Replacements seals, o-rings, quick
couplers.
7
Double Ended
Hose Adapter:
5/16" • 3/8"
AMC and Chrysler TBI, AMC and
Chrysler MPFI, Diahatsu EFI, Subaru
Single Point, Asian AFC, European
AFC.
8
Single Ended
Hose Adapter:
5/16″,3/8″,1/4″
MPI-for fuel pump “deadhead” test
EFI and MFI.

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# Picture Description Application
9M6 x 1.0 External
O-ring Adapter Acura and Honda PGM.
10 M8 x 1.0 External
Banjo Adapter
Asian AFC, EFI, MFI, European AFC,
European CIS and CISE.
11 M10 x 1.0 External
Banjo Adapter M10 x 1.0 External Banjo Adapter.
12
M12 x 1.25
External Banjo
Adapter
Acura and Honda PGM, Asian
AFC-mostly Toyota, European AFC,
European CIS and CISE.
13 M12 x 1.5 External
Banjo Adapter
Asian AFC, EFI, MFI, European AFC,
European CIS and CISE.
14 M14 x 1.5 External
Banjo Adapter Toyota AFC.
15 M8 x 1.0 Internal
Adapter (Long) European CIS, European CISE.
16 M8 x 1.0 Internal
Adapter European CIS, European CISE.
17 M8 x 1.0 External
O-ring Adapter European CIS, European CISE.
18
M8 x 1.0 External
O-ring Adapter
(Long)
European CIS, European CISE.
19 M10 x 1.0 Internal
O-ring Adapter European CIS, European CISE.
20 M10 x 1.0 External
O-ring Adapter European CIS, European CISE.

Page 6 For technical questions, please call 1-888-866-5797. Item 58817
# Picture Description Application
21 M12 x 1.5 Internal
Swivel Adapter European CIS, European CISE.
22
M14 x 1.5 External
and Internal Swivel
Adapter
European CIS, European CISE.
23
1/4″BSPT External
and Internal Swivel
Adapter
European CIS, European CISE.
24
M16 x 1.5 External
and Internal Swivel
Adapter
European CIS, European CISE.
25
Gauge Hose
Assembly with
Relief Valve and
Drain Tube
Connects to #1 for use in pressure
release and for volume tests.
26 Ford Spring Lock
Adapter
Ford MPI-2003 and newer with return
less fuel system, 1985 and newer
with return fuel system.
27
TBI/CIS Hose
Assembly with
Shutoff Valve
Connects to #1 and #25 for pressure
tests for GM TBI-supply line, fuel
pump and return line, European
CIS-primary system.
28 5/16″Hairpin
Adapter Ford CFI, Chrysler MPFI, GM MPI.
29 3/8" Hair Pin
Adapter Chrysler MPFI, GM MPI.

Page 7For technical questions, please call 1-888-866-5797.Item 58817
General Test
Read the ENTIRE IMPORTANT SAFETY INFORMATION section
beginning on page 2 of this manual including all text under
subheadings therein before use of this product.
For information on specific tests for a particular vehicle, refer to
the vehicle manufacturer’s service manual for specifications and
appropriate diagnostic and repair / replacement procedures.
1. Loosen vehicle’s fuel filler cap.
2. Remove fuel pump fuse from fuse box.
3. Turn ignition to START/RUN and
idle engine until fuel in fuel line is
consumed and engine stops.
4. Turn ignition to START/RUN for three
seconds and then turn to OFF.
5. Replace fuel pump fuse or
electrical connectors.
6. Connect Pressure Gauge (1) to
Gauge Hose Assembly (25).
7. If required, connect Gauge Hose
Assembly to
TBI/CIS Hose Assembly (27).
Note: For assistance, use the
Applications on page 4.
8. Connect Guage Hose Assembly or
TBI/CIS Hose Assembly to
vehicle at testing location.
Note: If using TBI/CIS Hose Assembly,
make sure shutoff valve is open.
9. Turn ignition to START/RUN and wait
1.5 to 3 seconds until fuel pump stops.
Note: Gauge pressure should stabilize.
If pressure does not stabilize or if
pump does not run properly, refer
to vehicle’s service manual.
10. Place a hose (not included) onto
end of Gauge Hose Assembly and
put end of hose into an approved
drain container (not included).
11. Press and hold open relief valve
on Gauge Hose Assembly until
fuel drains and air bubbles are
no longer visible in hose.
12. Release relief valve to close.
13. Wait 10 seconds and turn
ignition to START/RUN.
Static (Running) Fuel Pressure
Note: For all tests, refer to vehicle’s
service manual for specifications and
diagnostic/repair procedures.
1. Run engine at idle until Pressure
Gauge pressure stabilizes.
2. Compare Pressure Gauge
pressure to pressure specified
in vehicle’s service manual.
Fuel Volume
1. Place end of hose (not included) that
is connected to Gauge Hose Assembly
into approved drain container.
2. Run engine at idle.
3. Press and hold relief valve on
Gauge Hose Assembly while
keeping engine at idle.
4. Monitor fuel output for 30 seconds.

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5. Release relief valve to close. Note: Fuel pump should maintain engine
idle and output a minimum of one pint of
fuel in 30 seconds. (For CIS and CISE,
output should be one quart in 30 seconds).
Fuel Pressure Leak Down
Note: For GM low pressure TBI, test
does not work because of pressure drop
caused by pressure regulator design.
1. Run engine at idle and compare
Pressure Gauge pressure with pressure
specified in vehicle’s service manual.
2. Turn ignition to OFF and
wait 15 to 20 minutes.
3. Check gauge pressure. Pressure
should not drop more than specified
in vehicle’s service manual. If it does,
pressure may be leaking down.
Fuel Pump Output Pressure (Dead Head)
1. Turn ignition to OFF. 2. Compare Pressure Gauge
pressure with pressure specified
in vehicle’s service manual.
Cold Control Pressure (CIS)
Note: Engine must be cold for this test.
1. Run engine at idle until Pressure
Gauge pressure stabilizes.
CAUTION! Do not run engine for more than
one minute with regulator disconnected.
2. Disconnect electrical connector from
fuel control pressure regulator.
3. Turn ignition to OFF.
4. Reconnect electrical connector to
fuel control pressure regulator.
Hot Control Pressure (CIS)
1. Run engine at idle until it reaches
operating temperature.
2. Compare pressure gauge
pressure with pressure specified
in vehicle’s service manual.
Reset Pressure (CIS)
Same as Fuel pressure leak Down.
Primary System Pressure (CIS/GM TBI)
Fuel Pump Output - Dead Head
1. Run engine at idle until it reaches
operating temperature.
Note: Do not close valve for more
than 10 seconds. Closed valve
creates very high fuel pressure.
2. Close shutoff valve on
TBI/CIS Hose assembly.
3. Compare Pressure Gauge
pressure with pressure specified
in vehicle’s service manual.

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System pressure (CISE)
Same as Static (Running) Fuel Pressure.
Residual pressure (CISE)
Same as Fuel Pressure Leak Down.
Maintenance
Procedures not specifically explained in this manual must be performed
only by a qualified technician.
TO PREVENT SERIOUS INJURY FROM TOOL FAILURE: Do not use damaged
equipment. If abnormal noise, vibration, or leaking air occurs, have the problem
corrected before further use.
1. BEFORE EACH USE, inspect the
general condition of the tool. Check for:
• loose hardware
• cracked, worn, or damaged Adapters
• damaged Pressure Gauge and Hose
• any other condition that may
affect its safe operation.
If a problem occurs, have the problem
corrected before further use.
Do not use damaged equipment.
2. AFTER EACH USE, wipe external
surfaces of the tool with clean cloth.
3. Periodically check the
threads for damage.
4. Keep clean and free from dirt,
grease and grit.
5. Store tool in its Carrying
Case when not in use.
PLEASE READ THE FOLLOWING CAREFULLY
THE MANUFACTURER AND/OR DISTRIBUTOR HAS PROVIDED THE PARTS
LIST AND ASSEMBLY DIAGRAM IN THIS DOCUMENT AS A REFERENCE
TOOL ONLY. NEITHER THE MANUFACTURER OR DISTRIBUTOR MAKES ANY
REPRESENTATION OR WARRANTY OF ANY KIND TO THE BUYER THAT HE
OR SHE IS QUALIFIED TO MAKE ANY REPAIRS TO THE PRODUCT, OR THAT
HE OR SHE IS QUALIFIED TO REPLACE ANY PARTS OF THE PRODUCT. IN
FACT, THE MANUFACTURER AND/OR DISTRIBUTOR EXPRESSLY STATES THAT
ALL REPAIRS AND PARTS REPLACEMENTS SHOULD BE UNDERTAKEN BY
CERTIFIED AND LICENSED TECHNICIANS, AND NOT BY THE BUYER. THE BUYER
ASSUMES ALL RISK AND LIABILITY ARISING OUT OF HIS OR HER REPAIRS TO
THE ORIGINAL PRODUCT OR REPLACEMENT PARTS THERETO, OR ARISING
OUT OF HIS OR HER INSTALLATION OF REPLACEMENT PARTS THERETO.

Page 10 For technical questions, please call 1-888-866-5797. Item 58817
Parts List and Diagram
Parts List
Part Description Qty
1
3.5" Pressure Gauge with
protective boot and hanger 0-140
psi (0-10 BAR)
1
2 Ford MPI Adapter 1
3 7/16" x 20 GM/Chrysler Adapter 1
4 Hose Clamps & Hose 5/16", 3/8" 2
5 M16 X 1.5 In-Line Adapter 1
6 Seal Kit 1
7Double Ended Hose Adapter;
5/16", 3/8" 1
8Single Ended Hose Adapter:
5/16",3/8",1/4" 1
9 M6 X 1.0 External O-ring Adapter 1
10 M8 X 1.0 External Banjo Adapter 1
11 M10 X 1.0 External Banjo Adapter 1
12 M12 X 1.25 External Banjo Adapter 1
13 M12 X 1.5 External Banjo Adapter 1
14 M14 X 1.5 External Banjo Adapter 1
15 M8 X 1.0 Internal Adapter (long) 1
Part Description Qty
16 M8 X 1.0 Internal Adapter 1
17 M8 X 1.0 External O-ring Adapter 2
18 M8 X 1.0 External O-ring Adapter
(long) 1
19 M10 X 1.0 Internal Adapter 1
20 M10 X 1.0 External O-ring Adapter 1
21 M12 X 1.5 Internal Swivel Adapter 2
22 M14 X 1.5 External and Internal
Swivel Adapter 1
23 1/4" BSPT External and Internal
Swivel Adapter 1
24 M16 X 1.5 External and Internal
Swivel Adapter 1
25 Gauge Hose Assembly with relief
valve and drain tube 1
26 Ford Spring Lock Adapter 1
27 TBI/CIS Hose Assembly with
shutoff valve 1
28 5/16" Hairpin Adapter 1
29 3/8" Hairpin Adapter 1
Record Serial Number Here:
Note: If product has no serial number, record month and year of purchase instead.
Note: Some parts are listed and shown for illustration purposes only, and are not available
individually as replacement parts. Specify UPC 193175447159 when ordering parts.

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Diagram

Limited Lifetime Warranty
Harbor Freight Tools Co. makes every effort to assure that its products meet high quality
and durability standards, and warrants to the original purchaser that this product is free from
defects in materials and workmanship for the period of 90 days from the date of purchase.
This warranty does not apply to damage due directly or indirectly, to misuse, abuse, negligence
or accidents, repairs or alterations outside our facilities, criminal activity, improper installation,
normal wear and tear, or to lack of maintenance. We shall in no event be liable for death,
injuries to persons or property, or for incidental, contingent, special or consequential damages
arising from the use of our product. Some states do not allow the exclusion or limitation of
incidental or consequential damages, so the above limitation of exclusion may not apply to you.
THIS WARRANTY IS EXPRESSLY IN LIEU OF ALL OTHER WARRANTIES, EXPRESS OR
IMPLIED, INCLUDING THE WARRANTIES OF MERCHANTABILITY AND FITNESS.
To take advantage of this warranty, the product or part must be returned to us with transportation
charges prepaid. Proof of purchase date and an explanation of the complaint must accompany
the merchandise. If our inspection verifies the defect, we will either repair or replace
the product at our election or we may elect to refund the purchase price if we cannot readily
and quickly provide you with a replacement. We will return repaired products at our expense,
but if we determine there is no defect, or that the defect resulted from causes not within
the scope of our warranty, then you must bear the cost of returning the product.
This warranty gives you specific legal rights and you may also
have other rights which vary from state to state.
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