What's newNew
Log in Start trial

Home › Shop skills › Pump troubleshooting

Fire pump troubleshooting - start from the symptom

Most pump trouble at a service test comes from a short list of causes, and NFPA 1910's own troubleshooting annex says to find it while the truck is still at the test site. Start from the symptom, check the cheap and common causes first, read the intake and discharge gauges together, and rule out the gauges, the supply and the engine before you condemn the pump. Where the pump makers' figures differ, this page says whose figure it is: the manual for the pump in front of you is the one that counts.

Rule out the readings before the pump

Pump speed, net pump pressure and flow always move together. If one changes and the others don't follow, NFPA 1910 says to assume a reading is wrong or something in the setup has changed.

The usual culprits are the instruments. Read the centre of a swinging gauge needle, not the top. A snubber valve closed too far, or a leak in the line to the test gauge, makes a gauge read wrong. A pitot held closer than about half the nozzle diameter reads high, and a clogged pitot reads low. A slipping revolution counter shows a drop in speed that isn't there, so check it against the apparatus tachometer.

Short on flow or pressure: power or supply?

NFPA 1910 names two possible causes for falling short on capacity or pressure: not enough power, or a restriction on the intake side. They look different on the gauges.

If the engine can't reach the speed the pumping condition needs, suspect power. If the engine is turning faster than it should for the flow and pressure you are getting, suspect the intake: a supply problem makes the pump spin harder for less. Waterous adds a third: worn impellers or wear rings also show up as more speed for the same output, so compare this year's test speeds with earlier ones.

Symptom by symptom

Won't prime, or primes slowly

Check first: Close every discharge, drain and tank valve and petcock, make sure the suction hose gaskets are in place and clean, open the intake valve, and tighten the intake caps and couplings. Prime at idle (Hale gives 1,200 rpm as the most). Waterous warns that speeds much higher than the primer maker recommends don't speed priming and can damage the primer.

  1. An air leak on the intake side, the usual reasonHow to tell: Run the dry vacuum test: cap or plug every intake, take the discharge caps off, pull at least 22 inHg, stop the primer and watch the intake gauge. A loss of 10 inHg or more in under 5 minutes means a leak in a valve, drain cock, piping, the casing or the packing. Packing that dried out while the pump sat unused leaks air too (Waterous).Fix: Listen for it with the engine stopped, wipe engine oil on suspect joints, or fill the pump and pressurize it with water and look for drips. Hale also suggests plugging the suction-side relief valve outlet and retesting. A shop method that isn't in the pump manuals: with the engine OFF and the intakes capped, put a regulated shop-air line on the master drain or a discharge bleeder at 5 to 10 psi, no more, and spray the pump body, packing and valves with soapy water. Bubbles show a leak on the intake side that won't drip under water pressure, and it's quicker and cleaner than pumping water through.
  2. A discharge or drain valve that doesn't seal, or a bypass line left openHow to tell: The vacuum test is done with the discharge caps off on purpose, so a leaking discharge valve shows up as lost vacuum: cap the discharges and repeat. Waterous lists a stuck-open check valve in the discharge-to-tank bypass (overheat) line, and drain cocks left open after the last use are a classic.Fix: Reseat or repair the leaking valve; clean or replace the bypass check valve.
  3. A worn or starved primerHow to tell: If the pump holds vacuum but the primer can't pull 22 inHg, the primer is worn (Hale). On an oiled rotary-vane primer, check there is lubricant in the tank and that it reaches the primer: a blocked tube or a check valve fitted backwards stops it (Waterous). Hale says never to put lubricant on the vanes or vane slots of its primers, because it forms a gummy residue; check the primer maker's manual before oiling any oil-free primer.Fix: Repair or replace the primer; refill or clear the lubricant feed.
  4. Too much lift, a blocked strainer, or a long or collapsed suction hoseHow to tell: Hale and Waterous say no more than 22 ft of lift, Darley 20 ft. A collapsed hose liner usually can't be seen from outside.Fix: Lower the lift, clean the strainer, try another suction hose, and tighten the connections.
  5. Primer run too long, or released too soonHow to tell: Don't release the primer before the pump is primed, and open the discharge slowly as it takes. Stop and look for a leak rather than holding the primer on: Hale says no more than 45 seconds, Waterous no more than a minute at a time with a minute off, Darley 80 to 90 seconds depending on the model.Fix: Find the leak, then prime again.

Source: NFPA 1910 (2024) 22.7.6, 22.7.7, Annex B.1, B.2.1; Hale Muscle (Q series) manual Table 6-1; Waterous F-1031 Section 1000; Darley ZSM manual

Primer won't run, or runs and won't stop

Check first: Start with the electrical side: a primer motor draws heavy current through a solenoid, a switch and a ground.

  1. No click at the switchHow to tell: Bad ground at the solenoid, low voltage, a dead switch wire or a weak battery (Hale ESP troubleshooting chart).Fix: Clean and tighten the solenoid ground, check the cables for continuity, charge the battery and check voltage with a meter.
  2. The switch chatters but the motor doesn't runHow to tell: Bad ground, a bad positive or negative cable, or a weak battery or low voltage (Hale). Waterous's test: jumper the solenoid's small terminal to its hot terminal and the motor should run; jumper hot to cold to test the solenoid; then jumper the battery straight to the motor.Fix: Repair whichever link failed the jumper test.
  3. The motor keeps running with the switch offHow to tell: A positive cable touching the switch terminal, shorted wires, or a stuck solenoid (Hale).Fix: Test and replace the solenoid, and fix the wiring.
  4. It runs but won't pull vacuumHow to tell: Waterous: an oiled primer (VPE) needs its lubricant to reach 22 inHg, while an oil-free one (VPO) does it dry. Other causes are internal corrosion, stuck or broken vanes, and walls worn by sand. Biodegradable lubricant can break down and gum the primer if it isn't run weekly. On a Darley belt-driven primer, check the electric clutch is engaging and not slipping.Fix: Clean or overhaul the primer to the maker's clearances, and run the primer weekly.

Source: Hale ESP primer manual, Figure 6-1; Waterous Priming Systems manual, Service Suggestions; Darley ZSM manual

Loses prime while pumping at draft

Check first: Watch the intake gauge and the engine. NFPA 1910 says an air leak on the intake side first shows as too much pump speed, then loss of prime and no flow at all.

  1. A high point in the suction hose, trapping airHow to tell: Hale and Waterous both list it. The hose should slope down all the way from the pump to the water.Fix: Re-lay the hose below the intake. If you can't, prime again, as many times as it takes to clear the pocket.
  2. The strainer isn't deep enough, so a whirlpool pulls air inHow to tell: A hose deep enough to prime can still pull air at high flow. Waterous says keep the hose end at least 2 ft under; Darley says at least four hose diameters.Fix: Get it deeper, move it, reduce the flow, or lay a board or sheet of metal over the strainer (Darley).
  3. An air leak at the suction side while runningHow to tell: Speed creeping up for the same output, then the prime breaks. An open or leaking suction drain or air bleeder does the same (Hale).Fix: Close every suction drain and bleeder, then find the leak with a dry vacuum test once the pump is shut down.
  4. A primer valve that lets air back inHow to tell: Waterous lists a worn or damaged priming valve, which can leak and make the pump lose prime.Fix: Repair the priming valve to the primer instructions.
  5. Taking more water than the source and lift can giveHow to tell: Discharge pressure stops following engine speed and the pump sounds like gravel: that is cavitation.Fix: Reduce the flow or improve the supply. More throttle makes it worse.

Source: NFPA 1910 (2024) Annex B.2.3, B.2.4, B.2.6; Hale Muscle manual Table 6-1 and Hale booster pump manual Table 6; Waterous F-1031; Darley ZSM manual

Can't make rated capacity, or the engine is turning too fast for the flow

Check first: Compare the engine speed to the pump test label on the truck. NFPA 1910 calls for repair if any test point needs more than 110 percent of the engine speed on the label.

  1. The truck transmission in the wrong gearHow to tell: Too high a gear and the engine and pump can't reach speed at full throttle; too low and the engine runs fast. Waterous: the pump usually works best in direct drive, and an automatic must be in its pumping gear.Fix: Use the pumping gear on the pump plate, and check engine and pump speed both.
  2. A restriction on the intake sideHow to tell: Pump speed too high for the capacity and pressure you're getting. NFPA 1910's list: suction hose too small, altitude or lift too high, the wrong strainer, a clogged strainer, aerated water, water above 90 F, a collapsed or defective suction hose, or foreign material in the pump.Fix: Strainer first, then hose and lift. Waterous: clear debris from the strainer and impeller vanes by backwashing with the pump stopped.
  3. A relief valve set too lowHow to tell: It opens and bypasses water you meant to discharge (Hale).Fix: Reset the relief valve to the maker's procedure.
  4. A two-stage pump in pressure (series), or a transfer valve not fully homeHow to tell: Near-rated flow is only available in volume (parallel), and NFPA 1910 runs the 100 percent test in parallel. Hale says use volume above half of rated capacity; Waterous says above two-thirds, and check the valve travels all the way.Fix: Bring the pressure down and shift to volume (parallel).
  5. Not enough engine powerHow to tell: The engine can't reach the speed the job needs: an engine needing service, a governor set wrong, or a slipping clutch or transmission (NFPA 1910, Hale).Fix: Treat it as an engine or drivetrain problem, not a pump one.
  6. Worn wear rings or impellersHow to tell: More engine and pump speed than the acceptance test for the same output (Waterous). Compare this year's results with earlier tests: NFPA 1910 has them kept and compared year to year. Hale's overhaul figures: new clearance rings run 0.005 to 0.007 in. of radial clearance per side, and 0.015 to 0.020 in. per side is the most it accepts on a used pump; past 0.020 in., measure the impeller hub to decide between new rings and turning the impeller for undersize rings.Fix: Waterous: undersize wear rings if the clearance is within limits, otherwise new impellers and wear rings. Hale: replace the rings, or turn the impeller hub for undersize rings, by its hub-diameter limits.

Source: NFPA 1910 (2024) 22.7.8.2.3, 22.8.4, 22.8.6, Annex B.2.2, B.2.3; Hale Muscle manual Table 6-1; Waterous F-1031; Hale Muscle manual 7 (clearance rings)

Not enough discharge pressure

Check first: Close the discharges down until only a small flow is going, open the throttle until you reach the pressure you want, then open the discharges slowly, raising speed to hold pressure, until you reach the flow. That is NFPA 1910's check.

  1. Flowing more water than the pump is built for at that pressureHow to tell: Pressure comes up at a small flow and falls away as discharges open. A fire pump is rated for 70 percent of capacity at 200 psi and 50 percent at 250 psi.Fix: Match the flow to the rating. Over-speeding to chase it causes cavitation (Waterous).
  2. The water supply is used upHow to tell: On a hydrant, the intake gauge drops into vacuum before you reach the pressure you want.Fix: Reduce the flow or improve the supply. Hale says keep at least 5 psi on the intake; makers' minimums differ.
  3. A two-stage pump in volume when it needs pressure, or a stuck flap valveHow to tell: Hale: use pressure (series) above 200 psi. In series a flap valve stuck open lets the second stage leak back to the first (Waterous).Fix: Shift the transfer valve at low pressure. For a stuck flap, Waterous says switch the transfer valve back and forth quickly at 75 psi, and if that fails, free the flap with a stick or wire.
  4. The pressure control system set too low, or faultyHow to tell: A relief valve that opens early, or a governor set below what you need, caps the pressure.Fix: Reset to the maker's instructions; repair if it won't hold its setting.
  5. Only 60 to 100 psi after a rebuildHow to tell: Hale's sign of the wrong impeller, impellers reversed in a two-stage pump, or a pump built for the other rotation or mounting.Fix: Check impeller vane direction and order against the originals.

Source: NFPA 1910 (2024) 22.7.8.2.1, Annex B.2.5; Hale Muscle manual Table 6-1 and 4.3; Waterous F-1031

Transfer valve won't shift (two-stage pumps)

Check first: Bring the pressure down first. Hale says 50 to 60 psi before switching, and to warn crews on handlines; a Waterous manual valve wants 75 psi or less, and is very hard to move above about 100 psi.

  1. Trying to shift under pressureHow to tell: A manual valve that turns at idle but not while pumping.Fix: Throttle down, shift, then bring the pressure back up.
  2. A stiff remote control or a valve that's never movedHow to tell: Hale lists lack of lubrication on the remote control. Waterous says shift it back and forth monthly and grease it if it has a fitting (some ball-type valves need none).Fix: Oil the linkage and collar; exercise and grease the valve on the monthly check.
  3. It moves, but the pump doesn't changeHow to tell: Hale's test: engine off, turn the handwheel (or the power valve's indicator hex with a 3/8 in socket) through both positions. Then pump in volume at idle and switch to pressure: the reading should roughly double.Fix: If it doesn't, the valve or a flap is not seating: see the low-pressure symptom above.

Source: Hale Muscle manual Section 2, 5.4 and Table 6-1; Waterous CM manual, F-2013, F-1031

Pressure surges, or the relief valve or governor won't hold

Check first: Know which system the truck has, because they work completely differently: an electronic pressure governor holds pressure by changing engine speed, a relief valve by bypassing water. Check the one fitted. Either way it has to pass the same test: pumping rated capacity at 150 psi net, close all discharges over 3 to 10 seconds, and the pressure may rise no more than 30 psi. A pressure control system that doesn't work takes the pumping system out of service.

  1. Electronic governor: a fouled transducer or bad engine dataHow to tell: Check these before suspecting anything mechanical. A clogged discharge-pressure transducer port (some have a small snubber or screen) gives the governor a false or slow reading, so it hunts or won't regulate. Compare the governor's pressure display with a calibrated test gauge. The governor also commands the engine over the J1939 data link, so a data-link fault stops it changing engine speed.Fix: Clean or replace the transducer and its port screen, repair its wiring, and check the J1939 connection to the engine. For the governor unit itself, Hale sends you to the governor maker's manual.
  2. Electronic governor: running in RPM mode instead of pressure modeHow to tell: In RPM mode engine speed is held, so shutting one line raises pressure on the others.Fix: Run handlines in pressure mode, where the governor cuts engine speed to hold the set pressure.
  3. Relief valve: won't open, or won't return to its settingHow to tell: Hale: the control was set wrong or the valve is stuck; a dirty valve or a blocked bleed orifice keeps it from returning. Waterous: a sticky pilot valve or plugged tube lines.Fix: Repeat the setting procedure; take the valve and pilot apart, clean them and replace worn parts; clean the bleed orifice.
  4. Relief valve: hunts, or is slow to respondHow to tell: A blocked strainer in the line from the pump discharge to the control valve, dirty tubing or a dirty control valve (Hale, Waterous). Relief and pilot drains tied into the master drain cause trouble too (Waterous).Fix: Clean the strainer and flush the lines. Waterous suggests exercising the relief valve monthly: at 150 psi, cycle the pilot and confirm it opens and recloses.
  5. Relief valve: pressure surging back and forthHow to tell: Waterous: the springiness of the intake and discharge lines can fall into step with how fast the relief valve reacts.Fix: Change one of those factors - hose lay, flow or setting - enough to break the timing.
  6. A supply problem the pressure control can't fixHow to tell: If the intake can't keep up, discharge pressure swings no matter what the governor or relief valve does.Fix: Fix the supply first, then judge the pressure control. After drafting salt or dirty water, flush the pump, piping and pressure controls with fresh water: NFPA 1910 says so for salt water, and Hale for salt or contaminated water.

Source: NFPA 1910 (2024) 6.9.1, 22.7.9.2.1, A.22.3.1; Hale Muscle manual Table 6-1 and Section 5; Waterous F-1031 and relief valve care notes; transducer and J1939 checks: shop practice

Won't shift into pump, or the pump lights don't come on

Check first: A pump that won't engage, or pump shift indicators in the cab or on the panel that don't work, takes the pumping system out of service under NFPA 1910. Don't leave the cab or advance the throttle until all the green pump lights are on (Hale, Waterous).

  1. The shift sequence wasn't followed (split-shaft, automatic transmission)How to tell: Shift only with the driveline stopped: transmission in neutral, speedometer at zero, engine at idle (Hale, Darley). After the shift to PUMP, the transmission goes into pump gear (usually direct drive) and the speedometer should then show a reading. NFPA 1910's table: "Pump Engaged" with the shift made, and "OK to Pump" only once the transmission is in pump gear with the parking brake on.Fix: Go back to neutral and repeat the shift in order, checking each light.
  2. Butt-tooth: the gear teeth meet end to endHow to tell: The control is in PUMP but Pump Engaged stays dark (Waterous, Darley).Fix: Put the chassis transmission in a forward gear for a moment (Drive on an automatic) so the gear turns into mesh. If it still won't go with the transmission in Drive, Waterous says shift to Reverse for a moment, then Neutral, then Drive, to relieve driveline torque.
  3. Not enough air for an air-shift unit, or an air leakHow to tell: External leaks are usually audible; internal ones mean taking the unit apart (Hale, Waterous).Fix: Let air pressure build and fix the leaks. In an emergency there is a manual override, used only with the engine OFF (Hale).
  4. A multiplex node that isn't firing the shift (multiplexed trucks)How to tell: On many late-model apparatus the pump shift switch, the interlock inputs and the pump lights run through multiplex nodes (Weldon's V-MUX, for example, or a builder's own CAN modules) instead of straight wires. If air pressure is up and the switch is being thrown, open the multiplex diagnostic screen: see whether the node sees the switch input change, and whether it is commanding the shift output. Low chassis battery voltage, for example during cranking, or a loose data-bus connector can keep the output from firing even with the dash switch on.Fix: Input not seen: the switch or its wiring to the node. Input seen but no output: the node's output circuit, the shift solenoid wiring, or an interlock condition the program is still waiting for. Fix battery voltage and data-bus connections before replacing a node.
  5. An indicator or interlock fault rather than the pumpHow to tell: Pump Engaged on but Throttle Ready won't light: check pump gear, the parking brake, and the lockup and interlock wiring with the apparatus builder (Waterous). Lights that stay on in ROAD mean a shift-indicating switch stuck closed (Waterous). NFPA 1910 tests the shift indicators (22.7.4) and the throttle interlock (22.7.5) as two separate tests.Fix: Repair the switch, wiring or interlock. A dead panel light still takes the pump out of service even if the cab light works.
  6. A PTO pump that won't engage on the moveHow to tell: Most PTOs must be engaged with the apparatus stopped; only a hot-shift PTO engages while rolling (Hale).Fix: Stop, engage at idle, then roll.

Source: NFPA 1910 (2024) 6.9.1, 22.7.4, 22.7.5, Table 22.7.5.1; Hale Muscle manual 4.3, 4.7 and Table 6-1; Waterous C20 transmission manual; Darley ZSM and TSM manuals; multiplex check: shop practice

Pump water overheats at low or no flow

Check first: With no water leaving, the impeller churns the same water and turns engine power into heat - fast. Waterous says a closed single-stage pump with no cooling line can heat 35 F a minute or more. Get some water moving.

  1. No flow, and the cooling path closedHow to tell: Discharges shut with the tank fill, the bypass and the cooler valve closed.Fix: Keep one discharge slightly open, crack the tank fill or open the auxiliary cooling valve (Hale, Waterous).
  2. A thermal relief valve that doesn't openHow to tell: Know its setting: Hale's TRV-120 opens above 120 F (a TRV-170 is also made); Waterous's thermal valve opens at 140 F on CM and CS pumps and 120 F on others, with the alarm at 180 F. A Hale TRV only flows 1 to 2 gpm. If the pump gets hotter than the setting with no water from the valve, it has failed or is full of sediment.Fix: Clean or replace the valve. Hale has the TRV tested every 12 months against its maximum closed-discharge run times.
  3. The engine or pump transmission running hot during the testHow to tell: NFPA 1910 requires that the engine, pump and transmission not overheat during the whole test.Fix: Treat it as a cooling-system or transmission problem, and use the auxiliary cooler where fitted.

Source: NFPA 1910 (2024) 22.8.1; Hale Muscle manual 3.3, 4.3 and Table 5-2; Waterous OPM manual and F-1031

Packing leaks too much, or a mechanical seal drips

Check first: Know which you have. Packing is meant to drip while pumping, to cool and lubricate the shaft. A mechanical seal is meant to run without dripping.

  1. Packing gland too looseHow to tell: More than the maker's drip rate at 150 psi, and the makers differ: Hale's midship manual says 8 to 10 drops a minute, Waterous 10 to 120, Darley 5 to 60 for its plastic packing. Use the figure for the pump in front of you.Fix: Always with the engine shut down: Hale, one slot of the packing nut at a time; Waterous, tighten the nuts evenly half to one flat at a time, run 10 to 15 minutes at 150 psi and recheck, then the pump must still pass a vacuum test.
  2. Packing too tight, or no drip at allHow to tell: No drip means no cooling: the packing runs hot and scores the shaft sleeve. Braided graphite packing is the exception: Waterous says it can run at or near zero, and up to 300 F while new packing runs in.Fix: Back it off to the maker's rate. Replace packing that won't respond, or graphite packing that runs over 300 F. Hale suggests new packing every two to three years.
  3. A worn or damaged mechanical sealHow to tell: Water from the drain hole in the pump head (Hale). Seals are damaged by running dry.Fix: Replace it: a mechanical seal can't be adjusted like packing.
  4. Water getting into the pump gearboxHow to tell: Milky gear oil at the drain plug. Hale lists leaking oil seals or pump seals among the causes, and a missing slinger ring lets water run along the shaft into the bearing and gears.Fix: Find and fix the source, then replace the oil.

Source: NFPA 1910 (2024) 10.2.2; Hale Muscle manual Section 5 and Table 6-1; Waterous CS manual and packing notes; Darley ZSM manual

Gravel noise, and pressure that won't follow the throttle

Check first: Back off the throttle. This is cavitation: the pump is asking for more water than the intake can give. Hale says the most reliable sign is engine speed rising without pressure rising, because the compound gauge isn't accurate near zero.

  1. Flow higher than the supply or lift can feedHow to tell: The gravel sound, and discharge pressure that doesn't rise with engine speed.Fix: Lower the speed or gate the discharges; add more or bigger intake lines; shorten the lift or move closer.
  2. A restricted intake or an air leakHow to tell: Clogged strainer, collapsed suction hose, a partly closed intake valve, or an open air bleeder on the suction tube (Hale).Fix: Clear the restriction and close the bleeder before pumping harder.
  3. Warm waterHow to tell: NFPA 1910 counts water above 90 F as an intake restriction, and tests between 35 and 90 F.Fix: Find cooler water or lower the speed.
  4. Running far below capacity at high speedHow to tell: Waterous: low-flow running at high speed causes noise, vibration and impeller erosion.Fix: On a two-stage pump, the pressure (series) position reduces it.

Source: NFPA 1910 (2024) 22.4, Annex B.2.3; Hale Muscle manual Appendix G and Table 6-1; Waterous F-1031 and pump selection notes

How to test it

  1. Rule out the readingsCheck the gauges, pitot and tachometer before believing a bad number.
  2. Read intake and discharge togetherBoth falling points to the supply; discharge alone points to the pump, the power or the pressure control.
  3. Vacuum test before priming workProve the pump holds 22 inHg before you work on the primer.
  4. Compare with the test labelMore than 110 percent of the label's engine speed at any test point means repair.
  5. Fix it at the test site and write it downRecord the results and compare them with earlier years: a slow climb in engine speed is the pump wearing.

Numbers to work to

ItemStandard / specReference / notes
Dry vacuum test22 inHg, lose 10 inHg or less in 5 minNFPA 1910 22.7.7; 1 inHg less per 1000 ft above 2000 ft
Priming time30 s up to 1250 gpm; 45 s 1500 to 2999; 90 s 3000+22.7.6; +15 s with a 4 in. or larger auxiliary intake of 1 cu ft or more
Pressure controlrise 30 psi or lessall discharges closed in 3 to 10 s at 150 psi net (22.7.9.2.1)
Engine speedwithin 50 rpm of governed; repair over 110% of label22.7.3.2 and 22.8.4
Readings that varymore than 5%find and correct the cause (22.7.8.5)
Gauges and flowmetersoff by 10 psi / 10%recalibrate, repair or replace (22.7.11.2, 22.7.12.2)
Test water temperature35 to 90 F22.4; warmer water restricts the intake
Maximum lift22 ft (Hale, Waterous); 20 ft (Darley)less at altitude
Packing drip at 150 psiHale 8-10; Waterous 10-120; Darley 5-60 per minuse the maker's figure for the pump
Clearance (wear) ringsHale: new 0.005-0.007 in./side; used max 0.015-0.020 in./sideradial clearance, Hale Muscle manual; use your pump's manual

Common mistakes

  • Working on the primer before running a dry vacuum test.
  • Revving the engine to prime faster.
  • Reading the top of a bouncing gauge needle instead of the middle.
  • Adding throttle to a pump that is cavitating.
  • Shifting the transfer valve at high pressure.
  • Leaving the cab before both green pump lights are on.
  • Tightening packing until it stops dripping, or adjusting it with the engine running.
  • Oiling a primer's vanes without checking the maker's manual - Hale says never on its primers.
  • Trying to tighten a leaking mechanical seal - it has to be replaced.

Practice tests that cover this

EVT F3 Fire Pumps & AccessoriesEVT F1 Maintenance, Inspection & Testing

Drill this until it's automatic

Overhaul Prep has 19,209 practice questions across ASE, EVT, EPA 609 and engine certifications — every answer explained, with the questions covering this skill filterable by topic inside the app.

Start free Try a sample quiz 🖨 Printable card
Fire pumpPriming & cavitationKinds of fire pumps