Actron CP7665 Operations Instructions download pdf (Page 25)

Fuel System Testing

The requirements for lower vehicle emissions has increased the need for

more precise engine fuel control. Auto manufacturers began using elec-

tronically controlled carburetors in 1980 to meet emission requirements.

Today’s modern vehicles use electronic fuel injection to precisely control

fuel and further lower emissions. The digital multimeter can be used to

measure fuel injector resistance.

Measuring Fuel Injector Resistance

Fuel injectors are similar to sole-

noids. They contain a coil that is

switched ON and OFF by the ve-

hicle computer. This test measures

the resistance of this coil to make

sure it is not an open circuit. Shorted

coils can also be detected if the

specific manufacturer resistance of

the fuel injector is known.

Test Procedure (see Fig. 26):

Fig. 26

Typical

Fuel Injector

Black

Red

1. Insert BLACK test lead into

COM test lead jack.

2. Insert RED test lead into

test lead jack.

3. Turn multimeter rotary switch

to 200

Ω range.

Touch RED and BLACK multim-

eter leads together and view

reading on display.

Display should read typically 0.2 -

1.5Ω.

If display reading was greater

than 1.5Ω, check both ends of

test leads for bad connections. If

bad connections are found, re-

place test leads.

4. Disconnect wiring harness

from fuel injector - Refer to

vehicle service manual for pro-

cedure.

5. Connect RED and BLACK

test leads across fuel in-

jector pins.

Make sure you connect test

leads across fuel injector

and not the wiring harness.

6. Turn multimeter rotary

switch to desired OHM

range.

If the approximate resis-

tance is unknown, start at

the largest OHM range and

decrease to the appropri-

ate range as required. (see Set-

ting the Range on page 6)

7. View reading on display - Note

range setting for correct units.

• If display reading is 10Ω or

less, subtract test lead resis-

tance found in Step 3 from

above reading.

• Compare reading to manufac-

turers specifications for fuel in-

jector coil resistance.

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Actron CP7665 Operations Instructions Page 25

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