Actron Fuel Pressure Tester Kit CP7818 User Manual download pdf (Page 3)

Fuel Tank: A large container that holds your

vehicles supply of fuel.

Fuel Pump Filter: A filter that is usually

located in the fuel tank. Its function is to

prevent foreign particles from reaching the

fuel pump. A clogged or restricted fuel pump

filter can cause low fuel pressure readings.

When replacing a fuel pump it is a good idea

to clean or replace the fuel pump filter.

Fuel Pump: An electric motor that pumps

fuel into the fuel system at a constant pres-

sure. It is mounted in the fuel tank or on the

frame. Some vehicles have more than one

fuel pump.

Return Line: Path way for excess fuel to

return to the fuel tank.

Pressure Line: A pressurized fuel line that

carries fuel from the fuel tank to the fuel

injectors.

Fuel Filter: A filter that is located in-line with

the pressure line. Its function is to prevent

foreign particles from reaching the fuel injec-

tors. A clogged or restricted fuel filter can

also cause low fuel pressure readings. This

is the only fuel system component that re-

quires periodic replacement. Refer to vehicle

owners manual for replacement interval.

Fuel Rail Test Port: A schrader valve lo-

cated on the fuel rail (Fig. 4) that allows easy

connection of a fuel pressure gauge to mea-

sure fuel pressure. Do not confuse this valve

with the schrader valves that are used for

recharging air conditioning systems.

Fuel Pressure Regulator: The fuel pres-

sure regulator (Fig. 5) is connected across

the pressure line and return line. It contains

a spring loaded valve assembly that opens

to allow fuel to move into the return line,

when the pressure line fuel pressure is ex-

ceeded. It is used to keep a constant fuel

pressure drop across the fuel injectors. Some

fuel pressure regulators have a vacuum port

so fuel pressure can be adjusted based on

engine load. These are commonly called

vacuum actuated (compensated) fuel pres-

sure regulators. A leaking fuel pressure regu-

lator can cause low fuel pressure readings

and hard starting problems.

Fuel Rail: The fuel rail assembly is bolted to

the intake manifold. Its purpose is to hold the

fuel injectors in place and to deliver pressur-

ized fuel to the fuel injectors.

Fuel Injectors: A precision valve that is

controlled by a solenoid. Fuel injection is

controlled by the amount of fuel pressure,

and the size and duration of the valve open-

ing. Fuel injectors contain a filter used to

prevent very small particles from clogging

the valve. Leaking fuel injectors will cause

fuel pressure to slowly decrease when the

ignition key is on and engine is off.

Pre-Testing Checks

1. Read Safety Precautions.

2. Do a thorough visual and “hands-on” in-

spection of the engine and fuel system.

Look for loose or cracked electrical wir-

ing, battery cables, ignition wires, and

fuel or vacuum lines.

3. Verify that the battery is fully charged and

fuel tank has an adequate supply of fuel.

4. Verify that the inertia switch on certain

Ford/Lincoln/Mercury vehicles has not

been tripped. (The inertia switch is usu-

ally located in the trunk.)

5. Verify that all fuel system fuses are good.

6. Verify fuel vapor recovery system and

gas cap are in good condition.

7. Verify that manifold vacuum is within

manufacturers specification which is typi-

cally 18-20 in. at idle.

8. Look for fuel leaks and wipe up any spilled

fuel immediately.

Fig. 4

FUEL

RAIL

PROTECTIVE

CAP

FUEL RAIL TEST PORT

Typical

GM Multi-Port Fuel Injection System

Fig. 5

VACUUM PORT

RETURN

LINE

PRESSURE

LINE

Vacuum Actuated (Compensated)

Fuel Pressure Regulator

Fig. 6

100

200

300

500

400

600

700

10 0

psi

kPa

FUEL RAIL

TEST PORT

SHOP

RAG

END OF

BLEED-OFF

HOSE MUST

BE PLACED IN

APPROVED

FUEL

CONTAINER

9. If engine will not

start, check igni-

tion system for

spark. If no ignition

spark is present,

refer to vehicle ser-

vice manual for No

Start Diagnostics.

Fuel Pressure

Testing

Procedures

This test procedure

explains how to make

fuel pressure mea-

surements on vehicles

while the ignition key

is on and while the engine is at idle. The

procedure also explains the safest way to

connect and disconnect the fuel pressure

tester kit from vehicles equipped with

schrader valves as their fuel rail test ports. If

the fuel pressure readings measured in this

test procedure are not within your vehicles

manufacturing specification, then you must

use your vehicle service manual along with

the fuel pressure tester kit to service the

problem. This test procedure does not con-

tain any vehicle specific diagnostics.

1. Read all SAFETY PRECAUTIONS and

PRE-TESTING CHECKS.

2. Apply a lightweight household oil to

the rubber “O” rings inside both test

port adapters.

3. Turn Ignition Key OFF.

4. Locate fuel rail test port and remove

protective cap. (See Fig. 4.)

For Ford/Lincoln/Mercury Vehicles...

• Screw Ford test port adapter to fuel rail

test port until finger tight.

• Screw GM/Chrysler test port adapter to

the Ford test port adapter until finger

tight.

For GM/Chrysler Vehicles...

• Screw GM/Chrysler test port adapter to

fuel rail test port until finger tight.

Note: Always wrap a shop rag around

fuel rail test port when attaching test port

adapters. This is a precaution in case a

small amount of fuel leaks out while at-

taching adapters.

5. Place end of 6 ft. bleed-off hose in an

approved container for fuel.

Bleed-off hose must remain in container

until testing is complete.

6. Turn all accessories OFF. (i.e. Radio,

A/C, Blower Fan, Headlights, Wind-

shield Wipers...)

7. Turn ignition key ON.

Do the following checks...

• Listen for fuel pump. Pump should run

for approximately 2 seconds.

• Check fuel system for leaks. If leaks

found, turn ignition key OFF and wipe

up fuel immediately!

• Read fuel pressure from dial face. Pres-

sure should rise to manufacturers speci-

fication and hold steady even after fuel

pump stops running. Refer to vehicle

service manual for fuel pressure speci-

fications.

• If fuel pressure is not within manufac-

turers specification, than service ve-

hicle according to vehicle service

manual.

• When repair is completed and key-on-

engine-off fuel pressure is now within

manufacturers specification, then pro-

ceed to Step 8.

• For instructions on how to safely dis-

connect the Fuel Pressure Tester Kit

from the fuel rail test port, proceed to

Step 9.

8. Start engine – Let idle.

• If your vehicles fuel system uses a

vacuum actuated (compensated) fuel

pressure regulator then fuel pressure

should drop approximately 3-10 psi, de-

pending on manifold vacuum.

1 2 3 4

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Actron Fuel Pressure Tester Kit CP7818 User Manual Page 3

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