Surging Run Condition; Engine Speed Does Not Change - Ariens Sno-Thro Deluxe Series Service Manual

If no voltage is present at the ECU, replace ECU. If voltage
is present at the ECU, check wires for kinks or damage. If
damage is present repair wires if possible, or replace
throttle body. See Figure 166.

Surging Run Condition

1. Check wire harness connection to the ECU.
a. With the ignition key in the off position, check the
wire harness connections to the ECU. If
connections are secure, disconnect the 12-pin
and 14-pin connections to the ECU and inspect
connectors for bad connections or burn marks.
b. Check that all wire terminals are snug in their
connectors. If connections appear to be good,
reconnect wire harness and start engine to check
if issue is still present. If bad connection is
present, replace wire harness.
c. If issue is still present, advance to next step.
2. Check the ECU.
a. Disconnect wire harness from ECU and test with a
new ECU to verify the original ECU is not cause
for malfunction. If malfunction is not resolved with
a new ECU, reconnect wire harness to original
ECU and continue diagnostics.
If the AC output wire from the engine charging system is
damaged, it may cause an intermittent short. This will result
in erratic running such as the engine over revving or
"popping" through the exhaust.
3. Check the engine wiring and wiring under the
handlebar to verify that it is not damaged.
Figure 166
4. With an inline spark tester, check ignition for
intermittent spark.
5. Check fuel pump output.
a. Remove the heater box.
b. Check voltage at fuel pump. See Code 27: Low
Fuel Pressure on page 66 for voltage readings.
c. Remove fuel hose from fuel pump outlet and
attach a suitable length of fuel hose to the fuel
pump outlet that can safely reach a clearly marked
fuel container.
d. With battery voltage between 7.2 V DC – 8.4 V
DC, turn the key to the ON position for 10 seconds
to pump fuel into the container. Fuel should
measure approximately 160 mL (5 oz.).
If fuel amount measures less than 160 mL, remove the fuel
pump and check the pre-filter for blockage. If filter is clean,
replace fuel pump. See Figure 162. If fuel pump output is to
specification, replace the ignition coil.

Engine Speed Does Not Change

If engine speed does not change when using the
potentiometer (throttle control), check the following:
1. Set a multi-meter to ohms (Ω) and measure the
potentiometer resistance. See Figure 167 and
Figure 168.
a. Unplug the 14-pin connector from the ECU.
b. Position the red probe on the terminal of the red
wire at the potentiometer (Pin 5 in Figure 167) and
the black probe on the terminal of the
green / white wire.
The potentiometer output should measure approximately
0 Ω – 5000 Ω.
If ohm reading measures close to 0 Ω at full throttle and
close to 5000 Ω at low-idle, potentiometer is operating
normally. If ohm reading stays constant at either position,
replace potentiometer.
2. With a multi-meter, measure the V DC of the red wire.
a. With engine off, reconnect the 14-pin connector to
the ECU.
b. Position the red probe on the terminal of the red
wire at the potentiometer (Pin 5 in Figure 167).
EN – 71
Figure 167