Predator 670 Fuel Pump Upgrade: The Essential Solution for Reliable Power

Replacing the stock fuel pump on your Predator 670 engine isn't just an upgrade; it's often the critical fix for resolving persistent performance issues and unlocking reliable, long-term operation. The original equipment manufacturer (OEM) pump, while functional for basic use, frequently falls short under demanding conditions, in high-heat environments, or as the engine ages. Upgrading to a dedicated aftermarket electric fuel pump delivers consistent fuel pressure and volume, solving problems like vapor lock, stalling, power loss, and hard starting, while potentially extending your engine's overall lifespan.

Why Upgrading Your Predator 670 Fuel Pump Is Frequently Necessary

Predator 670 engines are popular for their versatility, powering everything from log splitters and pressure washers to larger go-karts, mini bikes, and custom equipment. However, the mechanical fuel pump supplied with the engine is a known weak link for several key reasons:

1. Prone to Vapor Lock: The most common and frustrating issue. Mechanical pumps operate near the hot engine block. Under demanding loads or high ambient temperatures, fuel in the pump or line can vaporize before reaching the carburetor. Since the pump relies on liquid fuel to function, vapor pockets cause an immediate loss of pressure, leading to stumbling, stalling, or a complete inability to restart until things cool down significantly.
2. Inconsistent Pressure: Mechanical pumps rely on engine rotation. At low RPMs (idle, low-speed maneuvering), they inherently produce lower pressure. At very high RPMs, their capacity can be overwhelmed, leading to pressure drops. This inconsistency can cause idle instability, hesitation on acceleration, and power loss under peak loads.
3. Susceptibility to Ethanol Fuels: Modern gasoline often contains ethanol (E10, sometimes higher blends). Ethanol can degrade rubber components inside mechanical pumps (diaphragms, gaskets) more rapidly than pure gasoline, leading to internal leaks and pressure loss over time. It also contributes to varnish buildup that can clog pump valves.
4. Reduced Flow Capacity: While sufficient under ideal conditions, the stock pump's flow rate often barely meets the 670cc engine's requirements, especially when the carburetor is modified for more performance, or if the engine operates continuously under heavy load. This limited headroom leads to leaning out and potential overheating under stress.
5. Heat Sensitivity: Its location on the engine block exposes it directly to intense heat. This exacerbates vapor lock issues and accelerates the breakdown of internal pump components.
6. Durability Concerns: Being primarily plastic/composite housing with rubber diaphragms inside, the OEM pump is vulnerable to cracking, warping due to heat, and diaphragm failure, especially under harsh conditions or improper maintenance.

These inherent limitations become increasingly apparent as your engine works harder, ages, or operates in challenging environments like summer heat. Recognizing the symptoms early is key to understanding why an upgrade is essential, not merely optional.

The Tangible Benefits of Upgrading to an Electric Fuel Pump

Replacing the problematic mechanical pump with a suitable electric pump solves the core issues and provides significant operational benefits:

1. Eliminate Vapor Lock: The defining advantage. Electric pumps are typically mounted much lower and farther from the engine block heat sources (often near or on the fuel tank). More importantly, they push fuel under pressure, significantly reducing its tendency to vaporize prematurely. This virtually eliminates vapor lock headaches, ensuring consistent fuel delivery regardless of engine temperature or ambient conditions.
2. Consistent Fuel Pressure & Flow: Electric fuel pumps deliver a near-constant pressure (regulated to your engine's specific need) throughout the entire RPM range. No more low-pressure stumbles at idle or dangerous pressure drops at wide-open throttle. This smooth, reliable delivery enhances drivability, responsiveness, and overall engine stability. Consistent fuel pressure directly translates to consistent engine performance.
3. Enhanced Reliability & Lifespan: Good quality electric fuel pumps designed for automotive use are built for longevity and harsh environments. They are less susceptible to damage from heat or ethanol exposure compared to the OEM plastic mechanical pump. Properly installed and filtered, an electric pump offers dramatically greater long-term reliability. This reliability extends the useful life and service intervals of your engine.
4. Improved Cold Starts: Electric pumps often prime the carburetor bowl with fuel before you crank the engine. This instantly supplies the carb with fuel for combustion, making cold starts significantly faster and easier – often within the first crank or two.
5. Better Performance Under Load: By ensuring the engine's fuel demand is consistently met, even at peak RPM and high load, an upgraded pump prevents the dangerous lean-out condition where the engine starves for fuel. This maintains optimal air/fuel mixture, preventing detonation and overheating, and allowing the engine to deliver its maximum designed power consistently. You get the performance you expect, when you demand it.
6. Compatibility with Modifications: If you plan on enhancing your engine performance (e.g., carburetor tuning, air filter upgrade, exhaust modifications), a higher-flow electric fuel pump provides the necessary fuel supply headroom. The stock mechanical pump is often inadequate to support even modest performance gains reliably.

Selecting the Perfect Electric Fuel Pump

Choosing the correct pump specifications is crucial for safety, performance, and longevity. Never install a high-pressure pump intended for fuel injection. Your Predator 670 requires a pump designed specifically for carbureted engines:

1. Correct Pressure Range: This is non-negotiable. Carbureted engines generally require fuel pressure between 4 PSI and 7 PSI. Exceeding this significantly (like using a 40+ PSI EFI pump) will overwhelm the carburetor’s float valve, forcing too much fuel past it and causing flooding, a rich running condition, potential fuel leakage from vents and overflow tubes, hydro-lock risks, and damage to the carburetor internals.
   • Ideal Target: Look for pumps explicitly rated for 5-7 PSI or "Low Pressure" (LP) for carburetors.
   • Regulator Importance: Even pumps advertised for carbs may sometimes run slightly over 7 PSI. For ultimate precision and future flexibility, incorporating an adjustable fuel pressure regulator in your setup is highly recommended. This allows fine-tuning pressure to your engine's optimal point (often around 5-6 PSI). Many universal electric fuel pump kits include a basic regulator.
2. Adequate Flow Rate: Flow rate is measured in Gallons Per Hour (GPH) or Liters Per Hour (LPH). The stock Predator 670 likely uses less than 25 GPH under maximum demand. However, a margin of safety is vital.
   • Recommended Range: Aim for a pump rated between 30 GPH and 50 GPH. This provides ample flow to meet the engine's maximum requirements without being oversized enough to cause unnecessary noise, heat, or excessive power draw. A 35-40 GHP pump is often an ideal balance for a stock or mildly tuned 670.
3. Solid State vs. Diaphragm: Generally, solid-state electric pumps are preferred over traditional diaphragm-style pumps for carbureted applications. Solid-state pumps (often of the roller-vane or turbine design) tend to be quieter, smoother, more efficient, and often more durable than older diaphragm styles. They are less prone to pressure pulsations.
4. Quality & Proven Reliability: Avoid the absolute cheapest no-name pumps online. Stick to reputable brands known for automotive fuel systems. Brands like Carter, Facet (Purolator), Airtex, Holley (carburetor division), Mr. Gasket, and Walbro offer reliable low-pressure pump options specifically designed for carbureted engines. Investing in a proven brand pays off in long-term reliability and avoids roadside repairs. Reading user reviews for your specific application (Predator 670 or similar large V-twins) is invaluable.
5. Safety Compliance: Ensure the pump is certified for gasoline use and has appropriate safety features inherent in its design. Check manufacturer documentation.

Recommended Specifications Table

Essential Components for Your Fuel Pump Upgrade

While the pump is the star, a safe and effective upgrade requires several key components for a robust system:

1. Electric Fuel Pump: The heart of the system. Select based on the criteria above (Low Pressure, 30-50 GPH, solid-state).
2. Fuel Pressure Regulator: Highly Recommended. While some low-pressure pumps run fine without one, an adjustable fuel pressure regulator (e.g., Holley, Mr. Gasket, Aeromotive) gives you precision control and the ability to dial in the ideal pressure (e.g., 5.5 PSI) for your specific setup. It acts as a safety net against variations in pump performance and is essential if your pump runs closer to the 7 PSI upper limit or higher. Look for one with a pressure gauge port or include an inline gauge.
3. Relay Wiring Harness Kit: Mandatory for safe operation. Do NOT power the pump directly from an ignition switch source or a simple toggle switch. Fuel pumps draw significant current. A relay kit provides the following:
   • Power: Sends high current directly from the battery (via a fuse) to the pump.
   • Control: Uses a simple ignition-switched signal (low current) to trigger the relay.
   • Safety: Protects the ignition switch from overload, prevents voltage drops to the pump (which shortens its life and reduces performance), and allows the inclusion of a safety oil pressure switch. Kits with pre-made wiring and the relay are readily available online.
4. Fuel Line and Fittings: Replace old rubber hose with fresh fuel injection (FI) rated hose (SAE J30R9), which is resistant to ethanol and high pressure. SAE J30R7 (carburetor hose) degrades quickly with ethanol fuel and can fail catastrophically under pressure. Use appropriate brass or steel barbed fittings, clamps (FI-rated smooth band "constant tension" clamps are excellent), and adapters as needed to connect pump inlet/outlet to existing lines and the carburetor. Avoid cheap plastic fittings. Use the smallest length of hose practical to reduce potential leak points.
5. Filtration:
   • Post-Pump Filter: Essential. Use a fresh fuel filter (compatible with ethanol gas) rated for your fuel pressure AFTER the pump, before the carburetor. This catches any debris generated by the pump or remaining in the lines. A common 5/16" or 3/8" inline filter works well.
   • Pre-Pump Filter/Sock (Advisable): Adding a basic inlet strainer (often called a "sock") to the inlet of the pump protects it from larger debris that could damage the pump internals, acting as a final line of defense after the tank outlet filter. Especially important if tank cleanliness is questionable.
6. Miscellaneous: Electrical connectors (crimp and heat shrink or solder), quality ring terminals, appropriately sized fuse (check pump specs, typically 10A-15A) and fuse holder for the main power lead to the relay, robust electrical wire for the battery-to-relay and relay-to-pump connections (typically 14-16 gauge). Mounting bracket or screws for the pump.

Detailed Predator 670 Fuel Pump Installation Guide

SAFETY FIRST: Work in a well-ventilated area away from sparks or flames. Disconnect the battery negative terminal BEFORE starting. Have a fire extinguisher rated for gasoline fires readily available. Wear safety glasses.

Tools Required: Basic hand wrenches/sockets (standard & metric), screwdrivers, wire strippers/crimpers/cutters, drill and bits (if making new mounting holes), utility knife or tubing cutter, measuring tape.

Installation Steps:

1. Gather & Inspect: Collect all components listed above. Verify pump ratings and fittings sizes. Plan the routing, especially for power wires and fuel lines (avoid sharp bends, heat sources, moving parts).
2. Disconnect Battery: Remove the negative battery terminal connection.
3. Relieve Fuel System Pressure (If applicable): If your old mechanical pump system was pressurized, carefully loosen the fuel line at the carburetor inlet to depressurize into a container. Wear gloves and eye protection. Cap or plug lines quickly to minimize spillage.
4. Remove Old Mechanical Pump:
   • Disconnect fuel lines from the OEM mechanical pump. Plug/cap the lines and the carb inlet immediately to prevent leaks and debris entry.
   • Unplug the pulse line (small black rubber hose) connecting the mechanical pump to the engine crankcase.
   • Unbolt the mechanical pump from the engine block. There may be a gasket.
   • Seal the Block Port: CRITICAL STEP. You must permanently seal the pulse port opening on the engine block where the mechanical pump attached. This is an open path to the engine crankcase. Options:
     • Option A: Obtain the block-off plate specific to the Predator 670. This is a small metal plate with a gasket and bolts that physically seals the hole. This is the preferred professional method.
     • Option B: Use a short bolt coated with high-heat thread sealer to block the original pulse port inlet fitting (remove the fitting, seal the block threads). This requires extreme care to avoid dropping the bolt into the crankcase. Verify a leak-proof seal. Option A is strongly recommended.
5. Choose Pump & Filter Locations:
   • Pump Mounting: Mount the electric pump as low as possible relative to the fuel tank (ideally near the tank's outlet), BELOW the level of fuel in the tank. This positioning aids gravity feed to the pump inlet, crucial for its self-priming ability. Ensure it's mounted securely using its brackets (or fabricate one) away from direct engine heat, moving parts, and sharp edges. Mount it as recommended by the manufacturer (often vertical with inlet at bottom). Avoid locations where it can accumulate water or road debris splash. Use rubber isolation mounts if possible to reduce vibration transmission. Position accessible for future inspection/replacement.
   • Filter Mounting: Mount the post-pump filter in an accessible location before the carburetor inlet. The pre-pump sock attaches directly to the pump inlet nipple.
6. Install New Fuel Lines:
   • Pump Inlet: Connect fresh FI-rated hose from the tank outlet (or existing fuel line from tank) to the inlet side of your pre-pump sock/strainer (if used), then to the pump inlet. Observe flow direction arrows on the pump body (if present).
   • Pump Outlet: Connect FI-rated hose from the pump outlet to the inlet side of your post-pump filter. Connect FI-rated hose from the outlet of the post-pump filter to the carburetor fuel inlet.
   • Ensure all connections are tight, using proper FI-rated clamps. Double-check hoses are fully seated on barbs. Keep hose runs as short and direct as possible without kinking. Use cable ties neatly for secure routing away from heat/exhaust and sharp edges. Avoid loops or dips where vapor can accumulate.
7. Install Fuel Pressure Regulator (If Used):
   • Mount the regulator in an accessible location between the post-pump filter and the carburetor inlet.
   • Plumb it inline: Pump Outlet -> Filter -> Regulator Inlet -> Regulator Outlet -> Carburetor.
   • If the regulator has a return port, you must cap it or run a return line back to the tank. Cap it for simplicity unless your engine setup demands high flow requiring a return.
   • Do not install a gauge yet unless integrated.
8. Wire the Fuel Pump Safely (USING RELAY):
   • Locate Mounting Spot: Choose a secure location near the battery for the relay.
   • Main Power: Run appropriately sized (e.g., 12-14 AWG) wire from the positive (+) battery terminal, through an appropriate fuse (mounted near battery, e.g., 10-15A based on pump specs), to terminal "30" on the relay. Secure this wire.
   • Main Ground: Run ground wire from relay terminal "86" (or specific Ground if labeled) to a clean, solid chassis ground point. Scrape paint for good contact.
   • Relay Trigger/Signal: Identify an ignition-switched +12V source (ON/RUN position only) near the relay location. This can come from a fused circuit feeding the ignition coil or any ACC/RUN fused circuit. Alternatively, tap into the wire going to the engine's low-oil shutdown switch if accessible. Run a wire from this ignition-switched source to relay terminal "85".
   • Pump Power Output: Run appropriate wire (e.g., 14-16 AWG) from relay terminal "87" directly to the positive (+) terminal of the electric fuel pump. Ensure this wire is routed safely.
   • Pump Ground: Run a ground wire from the negative (-) terminal of the fuel pump to a separate clean, solid chassis ground point.
   • Safety Switch (Optional but Recommended): An oil pressure safety switch kit can be added to prevent the pump from running if the engine loses oil pressure. These connect inline on the trigger circuit (between terminal "85" and the ignition source). The engine must be cranking/running (creating oil pressure) for the pump to run. If you include one, its install instructions will detail wiring.
   • Double-Check Wiring: Use a test light or multimeter to confirm the trigger circuit is ONLY live in the ignition ON/RUN position. Re-check all connections against the relay diagram. Secure all wiring with cable ties or loom. Apply dielectric grease to connectors to prevent corrosion.
9. Priming & Testing (Before Engine Start):
   • Important: Do not start the engine yet!
   • Temporarily connect the battery negative terminal.
   • Turn ignition switch to ON (RUN) position. You should hear the electric pump run for a few seconds to prime the system (if your relay wiring uses a momentary prime signal) or run continuously depending on the setup.
   • VERY CAREFULLY inspect every single fuel line connection you made (inlet, pump, filters, regulator, carb outlet) for leaks. Look for drips, wetness, or fuel smell. ANY LEAK MUST BE FIXED IMMEDIATELY BEFORE PROCEEDING. Tighten clamps, reseat hoses, or replace defective components. Be meticulous.
   • Checking Pressure: If you installed a gauge (temporarily or permanently), verify pressure is within the 4-7 PSI range. Adjust the regulator if equipped and necessary. If no gauge, you'll adjust via testing later.
   • Disconnect battery again after testing for leaks.
10. Finalize Installation: Tidy up all wiring and hose routing. Secure everything safely away from heat and moving parts. If using a block-off plate, ensure it's snug.
11. Startup & Carburetor Adjustment:
    • Potential Adjustment Needed: Replacing the fuel delivery system might affect your carburetor's baseline settings, especially if it was tuned to compensate for low pressure/flow from the failing mechanical pump.
    • Reconnect battery negative terminal.
    • Turn ignition ON and let the pump prime the system.
    • Start the engine as normal.
    • Observe: Does the engine run smoothly? Does it idle properly? Check for signs of richness (black smoke, excessive smell) or leanness (surging, overheating, popping). Rev the engine gently to check for hesitation.
    • Adjustments: If running rich (flooding possible), reduce fuel pressure slightly using the regulator OR adjust the carburetor float level slightly lower (if adjustable). If running lean (hesitation, surging), slightly increase fuel pressure OR adjust the float level slightly higher OR increase main jet size. Make small adjustments one at a time. Refer to your carburetor's manual. Often, simply adjusting the idle mixture screws slightly leaner helps if the engine was tuned richer to compensate for the old pump.
12. Monitor: After your first rides/work sessions, re-check for any leaks near the new components. Monitor engine performance, idling, and starting.

Essential Troubleshooting After Upgrade

While an upgrade solves most fuel delivery issues, occasional hiccups might occur:

• Pump Doesn't Run/No Prime:
  • Check main fuse near battery.
  • Verify battery connection.
  • Check relay trigger voltage (Terminal 85) with ignition ON. Use multimeter.
  • Verify solid ground at relay and pump.
  • Check power at pump (+) terminal when ignition ON. Verify ground path from pump (-).
  • Temporarily jump pump + directly to battery + (briefly) - if it runs, the issue is upstream in wiring (relay, fuse, trigger). If it doesn't run, suspect the pump itself.
  • Check connections at the safety oil switch (if installed).
• Pump Runs but Engine Won't Start/Stalls:
  • MAJOR LEAK CHECK AGAIN: This is the first thing to suspect. Shut off immediately if leak found.
  • Verify sufficient fuel IN the tank (don't laugh, it happens!).
  • Check for kinked fuel lines restricting flow.
  • Check post-pump filter - is it clogged? Did debris from old lines plug it?
  • Verify carburetor fuel bowl is filling (look down the venturi or carefully crack bowl drain if equipped). Is the float valve stuck?
  • Check Fuel Pressure: Temporarily connect a gauge if possible. Very low or no pressure indicates pump failure, major leak upstream of gauge, or severe restriction. Pressure significantly over 7 PSI will flood carb – adjust regulator down. Pressure fluctuating wildly suggests air entering the inlet side or pump failure.
  • Listen for unusual pump noise (grinding, very loud).
• Engine Runs Rich:
  • Fuel pressure too high (adjust regulator down to target 5-6 PSI).
  • Carburetor float level set too high/float needle not sealing (inspect/clean/adjust carb).
  • Regulator malfunction or incorrectly plumbed/return port not capped.
  • Leaking fuel line between pump and carb.
• Engine Runs Lean/Hesitates:
  • Fuel pressure too low (adjust regulator up, check pump voltage/supply, ensure good tank venting).
  • Post-pump filter clogged.
  • Inlet pre-filter/sock clogged.
  • Debris in carburetor inlet/float valve sticking closed?
  • Severe kink in fuel line.
  • Weak pump, insufficient flow for demand.
  • Air leak on suction side (inlet line or connections).
• Vapor Lock Symptoms Return:
  • Rare with a good electric pump properly mounted low.
  • Check pump location – too hot? Relocate lower and farther from heat.
  • Check fuel lines – are they routed too close to exhaust/manifold? Add heat shielding or reroute.
  • Ensure pump is mounted vertically as specified.
  • Ensure no large loops/dips in fuel line where vapor can accumulate. Use "U" clips for smooth curves.

Maintaining Your Upgraded Fuel System

Protect your investment:

1. Regular Visual Inspections: Before each use, quickly check the fuel pump area, all new fuel line connections, and filter housings for signs of leaks, abrasion, heat damage, or loose clamps. Listen for changes in pump sound.
2. Fuel Filter Changes: Change the post-pump fuel filter per manufacturer recommendation (e.g., every 50-100 hours or annually, whichever comes first). More frequently if using ethanol blends or if dirty fuel is suspected. Inspect/replace pre-pump sock annually.
3. Use Quality Fuel: Use fresh, name-brand gasoline. Add a stabilizer specifically formulated for ethanol-blended fuels during storage periods exceeding 30 days to prevent phase separation and residue buildup. Always run the carburetor dry or use stabilized fuel for storage.
4. Avoid Running Dry: Don't let your fuel tank run completely empty. This causes the pump to run dry, increasing wear and heat buildup. Keep the tank at least 1/4 full.
5. Protect Connections: Spray electrical connections with corrosion-inhibiting spray periodically.

Beyond the Upgrade: Enhanced System Integrity

For ultimate reliability and performance, consider these additions:

• Oil Pressure Safety Switch: As mentioned, this crucial device ensures the pump only runs when the engine is cranking or running by cutting power if oil pressure drops. This prevents the pump from filling a cylinder with fuel if an engine stall occurs (a major fire hazard). Install kits are available.
• Fuel Pressure Gauge: A small inline gauge mounted temporarily during tuning or permanently (in a discreet location) allows instant verification of system pressure.
• Dedicated Fuel Pump Fuse Block: Installing a small fused distribution block near the battery provides clean, fused power for high-current accessories like the fuel pump relay. Ensures proper protection and simplifies wiring.
• Full Fuel Line Replacement: If your old lines are stiff, cracked, or you suspect internal decay, replacing all lines from tank to carburetor with new FI-rated hose provides complete peace of mind.

Addressing Common Predator 670 Fuel Myths

• "I just need to shield the mechanical pump": While insulation wraps might delay vapor lock slightly on the mechanical pump, it doesn't solve the core issues of inconsistent pressure, low flow, and heat susceptibility. The upgrade addresses the root cause.
• "A bigger high-pressure pump is better": Higher PSI pumps are for fuel injection. Using one will flood your carburetor, causing severe operational problems.
• "The stock pump is fine for a stock engine": Experience overwhelmingly shows the stock mechanical pump is a frequent point of failure and performance limitation on the Predator 670, even stock, especially in heat. Many users report vapor lock on stock engines in warm weather.
• "Electric pumps are noisy and unreliable": Quality solid-state low-pressure pumps designed for carbs are remarkably quiet and offer far greater reliability than the OEM mechanical pump when properly installed. Avoid very cheap pumps.

Conclusion: The Upgrade That Delivers Real Reliability

Ignoring the Predator 670's weak OEM mechanical fuel pump often leads to frustration, downtime, and potentially costly engine damage from lean operation. The Predator 670 fuel pump upgrade, installing a purpose-built, low-pressure electric pump with associated components, is one of the single most impactful modifications for achieving consistent, reliable performance from your engine. It solves vapor lock permanently, delivers stable fuel pressure across the RPM range, improves cold starting, protects your investment from starvation-related damage, and provides headroom for future tuning. By following this guide to select the right components and install them carefully, you'll transform your engine's reliability and drivability.

Stop struggling with unpredictable performance and frustrating stalls. The solution is clear, proven, and remarkably effective. Now is the time to invest in a Predator 670 fuel pump upgrade and start enjoying the dependable power your equipment deserves.