There is no single GMAX 5900 pump. The Standard Series Hi-Boy uses 16Y706, the Standard Lo-Boy uses 16X419, the ProContractor uses 17H824, the IronMan uses 17H826, older GMAX II machines use 287513 and the TexSpray 5900 HD uses 287579. Six parts, one model name. Read the identification label before you order. And before you buy a clutch, measure it: Graco specifies 1.7 ± 0.2 ohms across the clutch field at 70°F on a 5900.
Ask a parts counter for a GMAX 5900 pump and the first question back should be which one. The name has been applied to at least five distinct configurations over the production run, and the displacement pump is different on every single one of them. This is worse than the fragmentation on the GH200 DutyMax, where there are two platforms, and worse than the 190ES split, where there are two pumps.
Most of the 5900 listings online quietly pick one pump and present it as the answer. That works for whoever happens to own that configuration and wastes money for everybody else. This page separates the series first, gives you the callout references second, and includes a measurable pass or fail test for the part most commonly replaced on guesswork.
1. Five Series, Five Pumps
All the current series share the same headline numbers: 3,300 psi, 1.6 gpm, a 0.043 inch maximum tip with one gun, and a 6.5 horsepower 200cc Honda engine. What changes underneath is the pump, the frame and the outlet.
Standard Series
17E831 Hi-Boy · 17E829 Lo-BoyEndurance Chromex piston pump, conventional retention with QuikChange field replacement.
- Hi-Boy pump 16Y706
- Lo-Boy pump 16X419
- Roughly 138 lb
- 1/4 npsm fluid outlet
ProContractor
17E832Vortex ProConnect 2 quick change pump system on a pre-packaged cart.
- Pump 17H824
- Roughly 139 lb
- Honda or Kohler engine options
- 1/4 npsm fluid outlet
IronMan Series
17E833 Hi-BoyEndurance Vortex MaxLife Extreme pump, heavier frame, flat proof tires.
- Pump 17H826
- Roughly 147 lb
- 3/8 in fluid outlet
- Built for abrasive and industrial coatings
Two more belong on the list even though they are no longer current. The older GMAX II 5900 machines run displacement pump 287513, and the TexSpray 5900 HD runs 287579 with a 3/8 inch outlet. There is also a Convertible configuration, which uses a different control letter layout covered in section seven.
The six pumps listed above are not variations of one part with different finishes. They differ in rod material, seal stack and in two cases in the mounting interface. A ProConnect 2 lower does not bolt onto a Standard Series frame, and nothing from the 287513 generation carries forward. If the identification label is gone, photograph the pump where it meets the bearing housing and send it to us before ordering. That one photograph resolves the question in most cases.
2. The Pump Table
This is the table to bookmark. It is the single most expensive decision on the machine and the one most frequently got wrong.
| Series / Machine | Model | Pump | Pump system | Outlet |
|---|---|---|---|---|
| Standard Series Hi-Boy | 17E831 | 16Y706 | Endurance Chromex, QuikChange | 1/4 npsm |
| Standard Series Lo-Boy | 17E829 | 16X419 | Endurance Chromex, QuikChange | 1/4 npsm |
| ProContractor Series | 17E832 | 17H824 | Vortex ProConnect 2 | 1/4 npsm |
| IronMan Series Hi-Boy | 17E833 | 17H826 | Endurance Vortex MaxLife Extreme | 3/8 npsm |
| GMAX II 5900 (earlier) | Various | 287513 | Conventional | 1/4 npsm |
| TexSpray 5900 HD | Various | 287579 | Heavy duty texture | 3/8 npsm |
The pump inlet thread is consistent at 1-5/16-12 UN-2A across the family, which is why suction tubes and inlet strainers interchange more freely than pumps do.
On a conventional pump you rebuild in place and the machine is down for the duration. With ProConnect 2 you keep a spare lower ready, swap it out, and rebuild the removed one when the schedule allows. If a day of downtime on a striping or production crew costs more than a spare lower, buying the second pump up front is the cheaper decision rather than the indulgent one. This is the same reasoning that applies on the Pro210ES at a smaller scale.
3. The Clutch Test That Costs Nothing
The clutch is one of the most commonly replaced parts on a GMAX, and a good share of those replacements are guesses. There is no need to guess. Graco publishes a resistance specification, and a multimeter settles it in under a minute.
Clutch field resistance at 70°F
Measure across the clutch field with the machine cold and at room temperature.
GMAX II 5900 1.7 ± 0.2 Ω GMAX II 7900 1.7 ± 0.2 Ω GMAX II 3900 1.2 ± 0.2 ΩAnything outside the band for your machine means the clutch field assembly has failed and needs replacing. Anything inside it means the fault is elsewhere and a new clutch will not fix it. Note that the 3900 figure is different: do not test a 3900 against the 5900 number or you will condemn a healthy clutch.
A reading of zero or near zero indicates a shorted field. An open circuit reading indicates a broken winding or a failed connection, and it is worth checking the connector and ground wire 237686 before condemning the assembly. Temperature matters: a hot machine reads differently, so let it cool before measuring.
The clutch housing on a 5900 or 7900 is 15E277. Replacing the field assembly without inspecting the armature face is a short term fix, so look at the friction surface while the housing is open.
4. Drive Train and Pump Mounting Callouts
These are the parts between the engine and the pump. They are the ones people struggle to identify from a diagram because many of them differ between the 3900, 5900 and 7900 despite looking identical.
| Ref | Part | Number | Notes |
|---|---|---|---|
| 40 | Bearing housing | 287373 | Earlier 5900 |
| 40 | Bearing housing | 24V088 | Later 5900 |
| – | Bearing housing repair kit | 24V027 | Rebuild rather than replace |
| 43 | Connecting rod | 24V085 | |
| 29 | Pinion housing kit | 287465 | |
| 19 | Clutch housing | 15E277 | 5900 and 7900 |
| 107 | Pump pin | 15F110 | |
| 104 | Bearing housing pin | 15E625 | |
| 105 | Latch | 15E687 | Earlier machines |
| 705 | Latch | 15G890 | Later machines |
| 106 | Lock nut | 111040 | 5900 and 7900. The 3900 uses 102040 |
| 172 | Pump clamp | 16X324 | |
| 163 | Pump rod shield | 16X770 | |
| 160 | Pin | 119284 | 5900 only. 3900 and 7900 use 101579 |
| 161 | Shield | 15F386 | 5900. 3900 uses 15F384, 7900 uses 15F383 |
| 141 | Set screw | 15F503 | |
| 142 | Adjustment screw | 15F498 | |
| 79 | Spring clip | 15E975 |
References 160, 161 and 106 are all model specific inside the same diagram. The pin, the shield and the lock nut look interchangeable across the 3900, 5900 and 7900 and are not. If you run more than one GMAX size in the fleet, label the spares by machine rather than by appearance. Fitting a 3900 lock nut to a 5900 is the kind of mistake that is invisible on the bench and expensive on the job.
5. Frame, Engine and Control Box
Frame parts rarely fail on their own, but they get destroyed by handling, and a cracked leg cap or a lost wheel clip takes a machine out of service just as effectively as a worn pump.
| Ref | Part | Number | Notes |
|---|---|---|---|
| 15 | Engine, 5.5 HP Honda | 114530 | The 3900 uses the 4.0 HP 108879 |
| 1 | Frame | 287370 | |
| 3 | Wheel | 119509 | |
| 4 | Clip | 15E891 | Wheel retention |
| 2 | Washer | 156306 | |
| 14 | Leg cap | 276974 | |
| 5 | Hydraulic tube | 16C381 | |
| 11 | Ground wire | 237686 | Check before condemning a clutch |
| 130 | Control box | 16X822 | |
| 127 | Bushing | 119569 | |
| 100 | Hose guide | 278083 | |
| 99 | Screw | 113161 | |
| 162 | Torque label | 187436 | Worth replacing if unreadable |
| 115 | Identification label | 16Y782 | Record the model number before fitting |
Label 16Y782 is a legitimate replacement part, and plenty of machines need one after years outdoors. Write the full model and serial down somewhere permanent first, because once the original is off, the only way to identify the configuration is by inspecting the pump interface. Photograph it and keep the photograph with your service records.
GMAX 5900 Parts
6. Filtration and the Fluid Outlet Trap
The GMAX filter is a 60 mesh, 250 micron reusable stainless element with Graco's Easy Out design, which means it pulls out through the top rather than requiring the manifold to be opened from below. Reusable is the operative word. These are cleaned, not consumed, and a filter that looks beyond cleaning is usually a filter that has been run past the point where it was protecting anything.
The inlet strainer 189920 is the part worth checking before anything else when output falls off. It costs very little, it is the first thing Graco's own troubleshooting sequence points at, and it accounts for a large share of calls that open with the words "I think the pump is gone."
Most GMAX 5900 configurations use a 1/4 npsm fluid outlet. The IronMan Series and the TexSpray 5900 HD use 3/8 npsm. This is the one spec difference that generates returns, because hose and whip assemblies are ordered by machine name and the thread does not match on arrival. Check the outlet on the machine, not the model name in your head, before ordering hose. Our cross-model parts reference covers hose and fitting selection across the Graco range.
On tip selection, the 0.043 inch maximum applies to single gun operation. Running two guns drops the maximum to 0.029 inch and three guns to 0.023 inch. Ignoring that is a common cause of the pressure sag that gets blamed on the pump. Orifice selection by coating and surface is covered in our spray tip size chart.
7. Control Letter Map
Graco labels the GMAX component identification diagram by letter, and this is where the Convertible configuration quietly diverges from the rest. If you are working from the manual with the wrong configuration in mind, the letters will not line up.
| Component | Standard configuration | Convertible configuration |
|---|---|---|
| Displacement pump | H | J |
| Engine controls | J | K |
| Fluid filter | L | M |
Three letters shift by one position. It reads like a trivial detail and it is the reason a technician can spend twenty minutes looking for a filter that is labelled as something else on the page in front of them. Confirm which configuration your manual is describing before you follow a lettered procedure.
Not Sure Which 5900 You Have?
Send the model number from the identification label, or a photograph of the pump mounting, and we will confirm the right pump before you order
Ask Our Parts Team Call +1 713-931-41028. Which Manual Applies to Your Machine
There are four Graco documents in circulation for this family and they do not all describe the same machine. Working from the wrong one is how the part number errors in section four happen.
| Manual | Covers | Use it for |
|---|---|---|
| 332919 / 332921 | GMAX 3400, GMAX II 3900 / 5900 / 7900, TexSpray HD | Operation, setup, troubleshooting on current machines |
| 3A6417 | Same family, parts | Callout numbers and exploded views |
| 310893 | Earlier GMAX II machines | The clutch resistance specification and the spin test |
| 3A0244 | Parts reference | Cross-checking an ambiguous callout |
Our manuals and data library lists these by name alongside the pump-specific documents for 16Y706, 16X419, 17H824 and 17H826. If your machine predates those, the 287513 manual covers references 86, 89 and 90, and the 287579 document covers reference 86 on the TexSpray HD.
9. Symptom Diagnosis
Sprayer stops, engine is still running
The engine sounds normal, the pump is not moving fluid.
Check in Graco's order: Empty paint supply → clogged inlet strainer 189920 → a severe fluid leak → failed pump. Recovery step: reduce pressure, then cycle the pump switch off and on. The first two cost nothing to check and cover most cases.
Pump does not engage at all
Engine runs, no pump movement, no clutch sound.
Measure before you buy: clutch field resistance against the 1.7 ± 0.2 ohm specification. Inside the band means the clutch is fine and the fault is upstream in the control box 16X822 or its wiring. Check ground wire 237686 and the connector before condemning the field assembly.
Pressure sags with two or three guns
Perfectly good with one gun, falls away when the crew adds a second.
Cause, usually: tip size. The 0.043 inch maximum is a single gun figure. Two guns is 0.029 inch, three guns is 0.023 inch. Then check: fluid filter, then gun filters. This is a specification problem far more often than a mechanical one.
Fluid weeping at the pump throat
Paint appearing where the rod enters the pump.
Cause: worn throat packings. On Standard Series: rebuild with a repair kit or replace the lower. On ProContractor: swap the 17H824 lower and rebuild the removed one off the machine. Check pump rod shield 16X770 while the area is exposed.
Knocking or play in the drive
Audible knock under load, or visible movement at the connecting rod.
Inspect: connecting rod 24V085, bearing housing, and pump pin 15F110. Consider: bearing housing repair kit 24V027 rather than a complete housing. Check the lock nut torque against label 187436, and confirm you are using 111040 rather than the 3900 part.
10. Frequently Asked Questions
What pump does a Graco GMAX 5900 use?
It depends on which series you have. The Standard Series Hi-Boy uses 16Y706, the Standard Series Lo-Boy uses 16X419, the ProContractor Series uses 17H824 with Vortex ProConnect 2, and the IronMan Series uses 17H826. Older GMAX II 5900 machines use 287513 and the TexSpray 5900 HD uses 287579. Read the model number from the identification label before ordering, because these are six different parts.
How do you test a GMAX 5900 clutch?
Measure resistance across the clutch field with a multimeter at room temperature. Graco specifies 1.7 ohms plus or minus 0.2 ohms for the GMAX II 5900 and 7900 at 70 degrees Fahrenheit. A reading outside that band means the clutch field assembly has failed and needs replacing. For comparison, the GMAX II 3900 specification is 1.2 ohms plus or minus 0.2 ohms, so do not use the 5900 figure on a 3900.
What is the difference between the GMAX 5900 Standard, ProContractor and IronMan series?
All three are rated 3300 psi and 1.6 gpm with a 0.043 inch maximum tip and a 6.5 horsepower Honda engine. The differences are the pump and the frame. Standard uses a conventional Endurance Chromex pump. ProContractor uses the Vortex ProConnect 2 quick change system. IronMan uses the Endurance Vortex MaxLife Extreme pump, a 3/8 inch fluid outlet instead of 1/4 inch, flat proof tires and a heavier frame at roughly 147 pounds.
What size fluid outlet does a GMAX 5900 have?
Most GMAX 5900 configurations use a 1/4 npsm fluid outlet. The IronMan Series and the TexSpray 5900 HD use 3/8 npsm instead. This matters when ordering hose and fittings, because a 1/4 inch whip assembly will not thread onto a 3/8 inch outlet without an adapter.
Which Graco manual covers the GMAX 5900?
Manuals 332919 and 332921 cover the GMAX 3400, GMAX II 3900, 5900 and 7900, and the TexSpray HD machines. Manual 3A6417 is the parts manual for the same family. Manual 310893 covers earlier GMAX II machines and is the source of the clutch resistance specification. Manual 3A0244 is an additional parts reference. Which one applies depends on the age of your machine, so check the model number against the manual cover before working from it.
Why does my GMAX 5900 stop spraying while the engine keeps running?
Graco's troubleshooting sequence for this symptom is empty paint supply, clogged inlet strainer, a severe fluid leak, then a failed pump. The recovery step is to reduce pressure and cycle the pump switch off and on. Check the inlet strainer first, because it costs nothing to look at and it is the most common cause.
Running a Mixed GMAX Fleet?
The 3900, 5900 and 7900 share a diagram but not the parts. We can build you a spares list keyed to your actual machines
Wholesale & Fleet Pricing GMAX Manuals