STOW T-20H — MAINTENANCE (PUMP)
Pump Vacuum Test
CAUTION :
DO NOT attempt to start the engine unless the pump has previously been primed with water. Severe pump damage will occur if pump has not been primed.
To perform the pump vacuum test do the following:
1.Remove the pump fill cap (Figure 2), and fill the pump with water.
2.Start the engine as outlined in the initial
3.As shown in Figure 17 (next page), place a water hose inside the discharge opening of the pump, and turn on the water. This flow of water into the discharge opening will prevent the pump from running dry.
4.Place the Pump Vacuum Tester (P/N 7000030) over the pump suction (inlet) opening (Figure 17) with the vacuum gauge facing upwards. It may be necessary to apply a small amount of water around the rubber seal of the vacuum tester to make a good suction fit.
5.Check and make sure that there are no air leaks between the vacuum tester and the inlet port on the pump. If air leaks are present reseat vacuum tester.
6.Run the pump for a few minutes while monitoring the vacuum gauge. If the gauge indicates a reading between
25 in. Hg (inches of mercury)
NOTE translates into 25 feet of lift at sea level.
7.If the vacuum tester gauge indicates a reading below
6.To test the flapper valve, shut down the engine. The vacuum tester should remain attached to the pump suction inlet port by vacuum. This indicates the pump's flapper valve is seating properly to hold water in the suction hose when the engine is stopped.This prevents backflow and allows for faster priming when the engine is restarted.
Adjusting Impeller Clearance
1.If it is necessary to replace impeller or volute, be sure clearance between impeller and volute is adjusted correctly.
2.The impeller should be as close to the volute as possible without rubbing against it. Clearance is adjusted by adding or removing shims from behind the impeller.
3.Check clearance between impeller and insert by slowly pulling starter rope to turn impeller. Remove spark plug to make it easier to turn impeller.
It is important not to remove too many shims or the clearance
NOTE between the impeller and volute will become too wide and pump performance will be reduced. Remember as the impeller wear
down, additional shims may be required to maintain the clearance between the impeller and insert.
4.Check the impeller every six months for wear, and for clearance between the impeller face and the volute. Also check the shaft seal for wear, as well as the shaft sleeve.
Pump Cleaning
After pumping water containing large amounts of dirt and debris, perform the following:
1.Remove the drain plug from the pump housing (Figure 2) and drain any water left in the pump.
2.Loosen the two locking hand knobs (turn counter- clockwise) and remove
3.Clean and remove dirt, debris from pump casing. Inspect impeller and volute for wear. Replace any damaged or worn parts.
CAUTION :
The impeller may develop sharp edges. Use extreme care when cleaning around the impeller to prevent being cut.
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