Graco LineLazert III 3900

Questions and Answers

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robert89Dec 1, 2025
What to do if spray icon does not show on display when fluid is sprayed from Graco Paint Sprayer?
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  Gregory PopeDec 1, 2025
  To resolve the issue of the spray icon not showing on the display when fluid is sprayed from your Graco Paint Sprayer, ensure that the 5-pin connector and reed switch are properly connected. If the interrupter is improperly positioned, turn the screw counterclockwise until the spray icon synchronizes with the fluid spray. If the reed switch assembly is damaged or the magnet on the assembly is missing, replace the reed switch assembly. If a connector on the wiring harness or on the reed switch is damaged, disconnect the reed switch and 5-pin connector from the back of the control board, check continuity between pin 1 on the 2-pin connector and pin 1 on the 5-pin connector, and check continuity between pin 2 on the 2-pin connector and pin 4 on the 5-pin connector; if there is no continuity i...
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jrileyAug 25, 2025
How to fix fluid spitting from Graco Paint Sprayer gun?
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  Casey BerryAug 25, 2025
  If your Graco Paint Sprayer is spitting fluid from the gun, start by checking and tightening all fluid connections and reprime the pump. Clear the tip if it is partially clogged. Refill the fluid supply if it is low or empty, and prime the pump, checking the fluid supply often to prevent running the pump dry.
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Erica TurnerAug 25, 2025
What causes excessive paint leakage in my Graco Paint Sprayer throat packing nut?
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  bboydAug 26, 2025
  If you have excessive paint leakage into the throat packing nut of your Graco Paint Sprayer, remove the throat packing nut spacer and tighten the throat packing nut just enough to stop the leakage. If the throat packings are worn or damaged, replace them. Also, replace the displacement rod if it is worn or damaged.
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Jesse GallegosAug 28, 2025
Why is my Graco Paint Sprayer pump difficult to prime?
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  sarah28Aug 28, 2025
  If your Graco Paint Sprayer pump is difficult to prime, check and tighten all fluid connections. Reduce engine speed and cycle the pump as slowly as possible during priming. Clean the intake valve, ensuring the ball seat is not nicked or worn and that the ball seats well, then reassemble the valve. Replace the pump packings if they are worn. If the paint is too thick, thin it according to the supplier’s recommendations. Decrease the throttle setting before priming the pump if the engine speed is too high.
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Erin SmithAug 31, 2025
How to troubleshoot distance counter on Graco Paint Sprayer?
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  Bianca LeblancAug 31, 2025
  If your Graco Paint Sprayer distance counter is not operating properly, first refer to the section on "Spray icon does not show on display when fluid is sprayed" for trigger sensor setting instructions. Check the wiring connections and reconnect if necessary. Adjust the space between the distance sensor and gear to .050 --/+ .020”. Remove the tire and press in or pull out the gear to align the sensor and gear if they are not aligned. Replace the distance gear/wheel if the gear teeth are missing or damaged. Replace the sensor if the wire is cracked or broken.
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Natalie JensenSep 18, 2025
Why is the spray icon always shown on the display of my Graco LineLazert III 3900 Construction Equipment?
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  Heather FergusonSep 18, 2025
  If the spray icon is always shown on the display of your Graco Construction Equipment, here’s what you can check: * Interrupter is improperly positioned: Turn screw clockwise until spray icon is synchronized with fluid spray.
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Melanie FullerSep 15, 2025
How to adjust high engine speed at no load on Graco Construction Equipment?
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  gwareSep 15, 2025
  If your Graco Construction Equipment has a high engine speed at no load, consider these causes: * Misadjusted throttle setting: Reset the throttle to 3700 engine rpm at no load.
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Allison ThomasSep 16, 2025
What to do if the sprayer operates, but the display does not on my Graco LineLazert III 3900?
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  bcollinsSep 16, 2025
  If the sprayer operates, but the display does not on your Graco Construction Equipment, check these: * Bad connection between control board and display: Remove the display and reconnect it.
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Christina RodriguezSep 8, 2025
What to do if the engine operates, but the displacement pump does not operate on my Graco LineLazert III 3900 Construction Equipment?
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  Gary LloydSep 8, 2025
  If the engine operates but the displacement pump does not operate on your Graco Construction Equipment, check the following: * Pump switch is OFF: Turn pump switch ON. * Pressure setting is too low: Turn the pressure adjusting knob clockwise to increase pressure. * Fluid filter is dirty: Clean the filter.
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tmillerSep 5, 2025
Why won't my Graco LineLazert III 3900 engine start?
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  allensnyderSep 5, 2025
  If your Graco Construction Equipment engine won’t start, there are several potential causes: * The engine switch might be OFF: Turn the engine switch ON. * The engine might be out of gas: Refill the gas tank. * The engine oil level might be low: Replenish oil, if necessary. * The spark plug cable might be disconnected or damaged: Connect the spark plug cable or replace the spark plug. * The engine might be cold: Use the choke. * The fuel shutoff lever might be OFF: Move the lever to the ON position. * Oil might be seeping into the combustion chamber: Remove the spark plug, pull the starter 3 to 4 times, clean or replace the spark plug, and start the engine. Keep the sprayer upright to avoid oil seepage.

Graco LineLazert III 3900 Specifications

General

Model	LineLazer III 3900
Type	Airless Line Striper
Power Source	Gasoline
Spray Width	2 in to 12 in
Hose Length	50 ft (15 m)
Engine	Honda GX120
Max Working Pressure	3300 psi (22.7 MPa)