Check Starter Motor; Check Fuel Supply - Guardian 4700 Repair Manual

TEST 27- CHECK STARTER MOTOR
DISCUSSION:
If the engine will not crank, the Starter Motor may
have failed. This test will check that possibility.
PROCEDURE:
The battery should have been checked prior to this
test and should be fully charged.
Set a VOM to measure DC voltage (12 VDC).
Connect the meter positive (+) test lead to the cable
connection on the Starter Motor. Connect the com-
mon (-) test lead to the Starter Motor frame.
Set the Start-Stop Switch to its "START" position and
observe the meter. Meter should Indicate battery volt-
age, Starter Motor should operate and engine should
crank.
RESULTS:
1. If battery voltage is indicated on the meter but Starter Motor did
not operate, remove and bench test the Starter Motor (see fol-
lowing test).
2. If battery voltage was indicated and the starter motor tried to
engage (bendix came up), but engine did not crank, check for
mechanical binding of the engine or rotor.
If engine turns over slightly, go to Test 35 "Check Valve
Adjustment." Compression release may not be working, or
mechanical binding is occurring.
TESTING THE STARTER MOTOR
CHECKING THE PINION:
When the starter motor is activated, the pinion gear
should move and engage the flywheel ring gear. If the
pinion does not move normally, inspect the large spiral
threads of the sleeve and pinion for binding or sticking.
16 (
From Starter Contactor)
Figure 7-19. – Starter Motor
TOOLS FOR STARTER PERFORMANCE TEST:
The following equipment may be used to complete a
performance test of the starter motor:
• A digital multimeter (VOM).
• A tachometer capable of reading up to 1,500 rpm.
• A fully charged 12-volt battery.
STARTER PERFORMANCE TEST:
1. Set the meter to read DC amps.
2. Connect the starter motor, battery and VOM as shown in
Figure 7-20.
3. Insert the tachometer at end of the pinion gear and activate the
starter motor. A starter motor in good condition will be within
the following specifications:
STARTER MOTOR PERFORMANCE SPECIFICATIONS AT 12
VOLTS DC
MINIMUM MOTOR RPM = 800
MAXIMUM AMPS = 9
If the starter does not perform satisfactorily, it should
be replaced.
VOM
Black test lead
connected
to positive
battery terminal
VICE
TACHOMETER
Figure 7-20 – Starter Performance Test
TEST 28- CHECK FUEL SUPPLY
DISCUSSION:
If the engine cranks but won't start, don't overlook the
obvious. The fuel supply may be low. Many RV gen-
erator installations "share" the fuel tank with the vehi-
cle engine. When such is the case, the Installer may
have used a generator fuel pickup tube that is shorter
than the vehicle engine's pickup tube. Thus, the gen-
Section 7
DIAGNOSTIC TESTS
12 VOLT
BATTERY
Red test lead
connected to
starter terminal
Negative battery
STARTER
terminal
MOTOR suitably grounded
Page 43