General Pump EZ4040G Triplex Plunger Pump Specs & Calibration Guide
Verified engineering standards for the Italian-manufactured General Pump EZ4040G (Interpump Group) commercial direct-drive triplex plunger pump. Rated at 4000 PSI and 4.0 GPM at 3400 RPM with forged brass manifold head, 15mm solid ceramic plungers, dual-stage V-packings, and external VRT3-310EZ pressure unloader tuning protocols.
General Pump EZ4040G Specifications & Rebuild Kits
Dimensions, replacement seal packages, and unloader options:
| Component / Spec | Metric Dimension | Kit / Part Number | Direct Sourcing |
|---|---|---|---|
| General Pump EZ4040G | 4000 PSI, 4.0 GPM @ 3400 RPM | EZ4040G (1" Hollow Shaft, 4-Bolt Flange) | Check Price on Amazon → |
| VRT3-310EZ Unloader | 4500 PSI Max, 10.5 GPM Flow | External Pressure-Actuated Bypass Valve | View VRT3 Unloader on Amazon → |
| Ceramic Plungers Kit | 15mm Diameter Solid Ceramic | GP Kit #69 (3 Plungers, Spacers & Copper Washers) | View Plunger Kit on Amazon → |
| High-Pressure Seal Kit | 15mm Dual V-Packing Kit | GP Kit #88 (High & Low Pressure Water Seals) | View Seal Kit on Amazon → |
How to Calibrate a VRT3 Unloader on General Pump EZ4040G
Improper unloader adjustment ruins pump seals and cracks brass manifolds. Follow this pressure gauge calibration procedure:
Loosen Black Adjustment Knob
Before starting the engine, back out the main spring tension knob on the VRT3 unloader until spring tension is completely relaxed.
Install Gauge Between Pump & Hose
Couple a liquid-filled 0–5000 PSI gauge to the unloader discharge port. Connect your 50 ft high-pressure hose and install a calibrated #4.0 spray nozzle in your spray wand.
Set Operating Pressure to 4000 PSI
Start the engine and run at 3400 RPM full throttle. Squeeze the trigger gun continuously while gradually turning the unloader knob clockwise until the pressure gauge reads 4000 PSI.
Check Pressure Spike Upon Release
Release the trigger. The pressure gauge spike should not exceed 4300–4400 PSI (maximum 10% pressure spike). Lock the locknut on the unloader shaft to secure calibration.
Technical & Field Service FAQs
Why does my General Pump leak water between the manifold and crankcase?
Water dripping from the weep holes beneath the brass head indicates worn high-pressure packing seals (Kit 88). If left unserviced, water will breach the oil seals (Kit 23) and contaminate the crankcase oil, ruining the bronze connecting rods.
Can I replace a cracked ceramic plunger on an EZ4040G?
Yes! General Pump uses solid ceramic cylinder sleeves that slide onto stainless steel plunger rods. Remove the brass manifold bolts, unscrew the plunger retainer bolt with a 10mm wrench, and install a new 15mm ceramic sleeve (Kit 69) with fresh copper crush washers.
What oil capacity does the General Pump EZ4040G crankcase hold?
The EZ4040G crankcase holds 14.0 oz (0.41 L) of non-detergent SAE 30W industrial pump oil. Change oil after the first 50 hours of break-in, and every 500 hours or annually thereafter.