Harbor Freight Tools MADDOX MH-DCT19 Assembly instructions

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Email our technical support at: [email protected] 64939
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. 20h
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© 2019 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.
To ol s r eq ui r ed f o r as s em bl y a nd se rvice m ay not be in cluded.
Read this material before using this product.
Failure to do so can result in serious injury.
SAVE THIS MANUAL.

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Specifications
Pressure Gauge 0~100 PSI, 0~700 kPa
IMPORTANT SAFETY INFORMATION
1. Do not use on diesel engines.
2. Stop engine, loosen gas cap and relieve fuel
pump pressure (see service manual) before
opening fuel line. Do not change fittings with
engine running or fuel line pressurized.
3. Do not overtighten fasteners. Brass fasteners
or hollow fasteners may be easily damaged by
overtightening. Tighten enough to get a good seal.
4. Before testing fuel system, verify all
connections are tight to eliminate leaking.
5. Gasoline is highly flammable. Do not smoke, or
test near an ignition source. Do not allow gasoline
to come in contact with the hot manifolds or
other engine components. If additional lighting is
required, use only an explosion-proof drop-light.
6. Do not drive the vehicle while under test.
7. Before testing, review and follow instructions from
the vehicle manufacturer’s service manual.
8. After testing, turn engine off and depressurize
system before removing test components.
Place absorbing cloths around fittings before
disconnecting. Wipe up any spilled fuel
immediately. Place cloths in a fireproof container.
9. Clean all testing components of
residual fuel before storing.
10. Wear ANSI-approved safety goggles and
heavy-duty work gloves during setup and use.
11. This product is not a toy. Do not allow
children to play with or near this item.
12. Use as intended only.
13. Inspect before every use; do not use
if parts are loose or damaged.
14. Perform service in a well-ventilated location.
Not only are gasoline fumes flammable, but
carbon monoxide is produced by a running engine.
This is a deadly gas that you cannot see or smell.
15. Maintain product labels and nameplates.
These carry important safety information.
If unreadable or missing, contact
Harbor Freight Tools for a replacement.
16. The warnings, precautions, 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.

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Features
Gauge
Pressure
Relief Button
Relief
Hose
Test Hose
Test Fitting

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Operating Instructions
Read the ENTIRE IMPORTANT SAFETY INFORMATION section at the beginning of this document
including all text under subheadings therein before set up or use of this product.
Note: Tools referenced in these instructions are sold separately.
1. WARNING! TO PREVENT SERIOUS
INJURY: Before testing:
a. Make sure the area is well-ventilated and free
of ignition sources and flammable materials.
b. Place a dry chemical (class B)
fire extinguisher nearby.
c. Turn ignition off.
d. Inspect engine, vacuum, fuel and electrical
system for additional problems and broken or
worn components. Repair problems before
proceeding, particularly problems that may
ignite spilled fuel or allow a fuel leak.
e. Make sure fuel tank is full and
starting battery is charged.
f. If the vehicle has an fuel shutoff inertia switch,
confirm it has not been tripped.
Inertia switches are found on certain
Ford/Lincoln/Mercury vehicles.
2. Lay shop rags down to collect any spilled fuel.
A small amount of fuel will leak even during a correct
connection. Have plenty of extra shop rags available
in the event of any additional unexpected leak.
3. Find the correct connection method for your
vehicle. Refer to service instructions as needed.
A. Vehicles with a test port:
a. Remove cap from test port.
b. (Ford vehicles only) Thread Ford Test
Adapter (7) onto the end of the test
port. Finger tighten securely.
c. Connect the Test Fitting to the
test port/Adapter securely.
B. GM TBI vehicles without a test port:
a. Disable all fuel pumps and properly release
pressure from the fuel lines as needed
according to the vehicle’s service instructions.
b. Be prepared to catch any excess fuel
and disconnect the fuel line at the point
directed in the service instructions.
c. Attach the GM TBI Adapter (3) to the fuel line
and the port it was previously attached to.
d. Finger-tighten both connections securely, then
turn one-half turn farther using a wrench.
e. Attach the Test Fitting to the remaining
fitting on the GM TBI Adapter.
C. Vehicles with a banjo bolt connection:
a. Disable all fuel pumps and properly release
pressure from the fuel lines as needed
according to the vehicle’s service instructions.
b. Be prepared to catch any excess fuel and
remove banjo bolt connector at point directed
in the vehicle’s service instructions.
c. Place the stock banjo bolt and washers in a safe
location. They will be needed for reassembly.
d. Replace the stock banjo bolt with a correctly-
sized Banjo Bolt Adapter (4-6) from this kit.
Use one washer from the Banjo Bolt Adapter
above the banjo fitting, and one below it.
WARNING! TO PREVENT SERIOUS
INJURY: If none of the Banjo Bolt Adapters
in this kit fit securely, then this kit is not
compatible and should not be used.
e. Tighten Banjo Bolt Adapter finger tight,
then use a wrench to gently turn it snug.
f. Attach the Test Fitting to the remaining
fitting on the Banjo Bolt Adapter.

Page 5For technical questions, please call 1-888-866-5797.Item 64939
D. Vehicles with rubber hose connections:
a. Disable all fuel pumps and properly release
pressure from the fuel lines as needed
according to the vehicle’s service instructions.
b. Be prepared to catch any excess fuel and
disconnect fuel hose at point directed
in the vehicle’s service instructions.
c. Determine size of fuel hose, either 1/4″ or 3/8″
inner diameter. Connect the appropriate
Hose (8,9) from the kit to one of the aluminum
fittings on the Hose Manifold (2). If using
the 3/8″ Hose, slide it all the way onto the
inner part of the Hose Manifold. Secure the
Hose using a Hose Clamp (10).
d. Slide a Hose Clamp over the end of the
vehicle’s fuel hose. Connect the vehicle’s
fuel hose to the other aluminum fitting on
the Hose Manifold. If it is a 3/8″ hose,
slide it all the way onto the inner part of the
Hose Manifold. Secure it using a Hose Clamp.
e. Slide a Hose Clamp over the end of the
Hose that is attached to the Hose Manifold.
Connect this Hose to the vehicle’s fuel
connector where the fuel hose used to be
connected. Secure it using a Hose Clamp.
f. Tighten all Hose Clamps securely
using a screwdriver.
g. Attach the Test Fitting to the remaining
fitting on the Hose Manifold.
WARNING! TO PREVENT SERIOUS INJURY
AND DEATH FROM FIRE, do not proceed
with testing unless all connections are
the correct size and seal completely.
4. Secure end of clear relief hose inside an appropriate
fuel collection container in a safe place that will
not be damaged, heated, or knocked over.
5. If fuel pumps were disabled for
connecting the kit, re-enable them.
Note: This is a generic procedure. Follow vehicle
service instructions for correct test procedure.
6. Turn ignition to on position.
7. Turn off all accessories, such as
radio, air conditioning, etc.
8. Listen that fuel pump starts briefly.
9. Check for leaks. If a leak is found, turn ignition off,
then clean up and fix any leaks before proceeding.
10. Turn ignition off, then back on to cycle fuel pump
again. Continue cycling fuel pump to ensure
pressure builds to manufacturer’s specification.
11. Again check for leaks. If a leak is found,
turn ignition off, then clean up and
fix any leaks before proceeding.
12. Perform any additional idle or
other test measurements as directed
in vehicle’s service instructions.
13. Turn ignition off.
14. Make sure end of clear relief hose is still secured
inside an appropriate fuel collection container.
Then press and hold the pressure relief button
until the pressure gauge reads 0.
15. Allow remaining fuel to drain out of relief hose,
then remove it from the fuel collection
container and seal that container.
16. Use shop rags to catch any spilled fuel while
disconnecting the kit from the fuel system. If a banjo
bolt connection was used, put the stock banjo
bolt and washers back in place exactly as they
were before the test. Tighten all connections
according to manufacturer specifications.
WARNING! TO PREVENT SERIOUS INJURY
AND DEATH FROM FIRE, place all shop rags
and other materials that contain fuel or fuel
vapor into an approved, ignition-resistant safety
oily waste can or dispose of them properly.
17. Allow kit to dry completely in an area
away from ignition sources and other
flammable materials before storing it.

Page 6 For technical questions, please call 1-888-866-5797. Item 64939
User-Maintenance Instructions
Procedures not specifically explained in this manual
must be performed only by a qualified technician.
TO PREVENT SERIOUS INJURY AND DEATH FROM FIRE:
Do not use damaged equipment. If any damage or wear is found,
have the problem corrected before further use.
Cleaning, Maintenance, and Lubrication
1. BEFORE EACH USE, inspect the general
condition of the tool. Check for:
• loose hardware or housing,
• misalignment or binding of moving parts,
• worn or cracked hoses,
• deformed fittings,
• cracked or broken parts, and
• any other condition that may
affect its safe operation.
2. Before storage, make sure all fuel has been
drained from all hoses and fittings and all fuel
vapors have dissipated. Keep all flammable
materials and ignition sources away from this kit.

Page 7For technical questions, please call 1-888-866-5797.Item 64939
Parts List and Diagram
Part Description Qty
1 Pressure Gauge Assembly 1
2 Hose Manifold 1
3 GM TBI Adapter 1
4 Banjo Bolt Adapter M12*1.5 1
5 Banjo Bolt Adapter M12*1.25 1
6 Banjo Bolt Adapter M8*1.0 1
7 Ford Test Adapter 1
85/16″ Hose 1
91/4″ Hose 1
10 Hose Clamp 4
11 Repair Kit 1
Record Product’s 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.
1
2
3
4
5
6
7
89
10
11

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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.
Limited 90 Day 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.