The vacuum pumps with 3 connectors are more common.
Plenty of 4 connector pumps are available online ,I just googled something like ,snowmobile vacuum fuel pump 4 connectors.
The 4 connections likely correspond to:
1 Fuel Inlet: From the fuel tank/on/off tap.
2 Fuel Outlet: To the carburetor bowl.
3 Primer Pump Connection: This is likely where the primer bulb draws fuel through the pump to prime the system.
4 Vacuum/Pulse Line: This line connects to the engine (often the crankcase or intake manifold) to provide the pulses that drive the pump. This is the "missing" connection on typical gravity-fed or simple electric pumps.
Pros of dismantling:
Diagnosis: You can visually inspect the diaphragm(s) for tears, cracks, or hardening. You might also find blockages in the small internal passages.
Potential Repair: If it's a simple tear in a diaphragm (which is common in these types of pumps over time), you might be able to find a suitable replacement diaphragm . Sometimes, just cleaning out debris can restore function.
Learning: You'll gain valuable insight into how this specific type of pump works, which will help in future troubleshooting.
Cost Savings: If you can fix it, it's free!
Cons/Considerations of dismantling:
Depending on the material used for the pump . Fragility: The plastic and rubber components can be brittle, especially if they're old. You risk breaking something during disassembly or reassembly.
Lack of Parts: While you might identify the issue, finding individual repair parts (like a specific diaphragm) for an obscure pump like "XINGVUZHOU PBT-GF30" can be extremely difficult or impossible.
Complexity: Reassembling vacuum pumps correctly can be tricky, ensuring all diaphragms and check valves are seated properly.
Diaphragms: These are the most common failure point. Look for tears, holes, cracks, stiffness, or warping. There might be one or more diaphragms.
Check Valves: These are small, often rubber or plastic flaps that control the direction of fuel flow. Ensure they aren't stuck open or closed, and are intact.
Debris: Look for any dirt, rust, or other foreign material obstructing passages.
Springs: Note the placement and condition of any small springs that might be involved with the diaphragms or valves.
I had a quick look and saw a new pump for $37. with free postage from china that was on eBay but I haven't checked Temu, AliExpress or Amazon.
