You are not looking for “a pump part.” You are looking for the pump part that fits one specific machine.
If your search history looks like atlas copco pump parts, then atlas copco spare parts catalogue - pdf, then breaker bar, then subaru truck, and finally how to test fuel pump, you are not alone. Some of those queries belong together. Some do not. The problem is knowing which one applies before you spend money.
I review parts deliveries for a heavy-equipment supplier that works on Atlas Copco equipment. Roughly 120 line items go through my station each week. In Q1 2025 I rejected about 8% of first deliveries because the invoice said one part number and the machine needed a different one. The usual reason? Someone matched a listing to a search result instead of to an application.
Here is the route I use.
Scenario 1: You already have an Atlas Copco part number
This is the easiest starting point, but do not skip one step. Part numbers change. Atlas Copco supersedes old numbers when a design changes, and some changes only apply to a serial range. A number that is correct for a 2018 machine may not fit a 2023 machine that looks identical.
If the unit is down, the cheapest option on the search page is rarely the best. From the outside, it looks like every seller is shipping the same box. The reality is that delivery certainty varies wildly. I have been burned twice by “probably on time” carriers. In March 2024 I paid extra for a priority shipment on a pump coupling rather than wait five days. It cost more. It also cost less than one day of the rental machine we would have needed.
The same logic applies to parts. Do not buy a lookalike because it is half the price and then wait two weeks for the real part when the lookalike fails. If you need certainty, buy from the source that can confirm availability before you pay.
Scenario 2: You have the old pump, but the part number is gone
Do not try to match it by eye. A customer once lifted a complete pump assembly out of an old Subaru truck and said, “I think this is the one.” The housing and bolt holes looked identical to the photo on his phone. The shaft length was not. We found the right page in the Atlas Copco spare parts catalogue - PDF and the correct part number in about 10 minutes. The photo never showed the 1.5 mm difference.
This is also where a breaker bar comes into play. A breaker bar is for loosening something that is supposed to come apart. It is not for making a part fit. When the shaft is 1.5 mm too long, more torque does not solve it; it cracks the housing. If the pump does not go together the way the old one came apart, stop and recheck the part number.
Before ordering, write down these numbers:
- Bolt hole center distance and bolt diameter
- Shaft diameter, keyway width, and shaft length from the mounting face
- Inlet and outlet size plus orientation
- Rotation direction, if it is marked on the housing
Do aftermarket Atlas Copco pump parts ever work? Sometimes. But if you replace a pump with a part that has no traceable number, you become the test lab. If it is my name on the work order, I would rather have a part with an engineering reference behind it. Genuine parts also make future warranty calls simpler.
Scenario 3: Your real search is “how to test fuel pump”
The previous scenario assumes the pump is already off. Before that point, some orders should not happen at all. A machine can lose air for reasons that have nothing to do with the Atlas Copco pump assembly. If the engine cranks but does not start, or it starts and then dies under load, check the fuel system before you disassemble anything.
How to test fuel pump, in practical terms:
- Confirm the engine has fuel supply and no shutoff valve is closed. It sounds basic, but I have seen two relays and one valve cause a “pump failure.”
- Check whether the fuel pump is receiving power during cranking. A multimeter is better than the old method of putting your hand on the pump.
- Connect a fuel pressure gauge to the service port or intake line, crank the engine, and record the reading.
- Compare that reading to the engine manufacturer’s specification, not to a guess from the internet.
Why would a Subaru truck appear in the same list of searches? Because a fuel system fault in a compressor engine can look exactly like the fault on an older truck. I once listened to a customer compare his compressor to the fuel pump in an old Subaru truck he had repaired. The test method was similar, but the pressure spec was different. If you use the fuel pump spec from the wrong engine, you will replace good parts.
Which scenario are you in?
Try the 10-minute filter before you open the checkout page:
- Does the machine crank but not run? Scenario 3. Fuel system first.
- Are you holding a pump with no readable label? Scenario 2.
- Do you have a readable Atlas Copco part number and a confirmed serial range? Scenario 1.
And one last warning. If you do not know the exact application, a breaker bar is not the next tool. The next tool is something to read the model and serial plate, plus the Atlas Copco spare parts catalogue - PDF. The few minutes you spend checking will save a return-shipping fee, an installation, and maybe a second part.
No part number, no purchase order. If you need the part today, pay for confirmed availability and shipping. In service, certainty is worth something—especially when the machine is already down.
