Measuring dwell, Fig. 15 – Actron AutoTroubleShooter CP7677 User Manual

Page 12

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connect RED test lead to negative
side of primary ignition coil. (refer
to vehicle service manual for loca-
tion of ignition coil)

4. Connect BLACK test lead to a good

vehicle ground.

5. Turn multimeter rotary switch to

correct CYLINDER selection.

6. Measure engine RPM while engine

is cranking or running.

7. View reading on display.

• Remember to multiply display read-

ing by 10 to get actual RPM.

If display reads 200, then actual en-
gine RPM is 10 times 200 or 2000
RPM.

Measuring Dwell

Dwell measuring was extremely impor-
tant on breaker point ignition systems of
the past. It referred to the length of time,
in degrees, that the breaker points re-
mained closed, while the camshaft was
rotating. Today’s vehicles use electronic
ignition and dwell is no longer adjust-
able. Another application for dwell is in
testing the mixture control solenoid on
GM feedback carburetors.

To measure Dwell (see Fig. 15):

Ground

Black

Red

Fig. 15

Typical

Ignition

Coil

1. Insert BLACK test lead into COM

test lead jack.

2. I n s e r t R E D t e s t l e a d i n t o

test lead jack.

3. Connect RED test lead to DWELL

signal wire.

• If measuring DWELL on breaker

point ignition systems, connect
RED test lead to negative side of
primary ignition coil. (refer to ve-
hicle service manual for location of
ignition coil)

• If measuring DWELL on GM mix-

ture control solenoids, connect
RED test lead to ground side or
computer driven side of solenoid.
(refer to vehicle service manual for
solenoid location)

• If measuring DWELL on any arbi-

trary ON/OFF device, connect RED
test lead to side of device that is
being switched ON/OFF.

4. Connect BLACK test lead to a good

vehicle ground.

5. Turn multimeter rotary switch to

correct DWELL CYLINDER posi-
tion.

6. View reading on display.

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