The Complete Guide to Choosing and Installing a 1967 Mustang Electric Fuel Pump: Solve Vapor Lock, Boost Performance & Reliability

Replacing or supplementing the factory mechanical fuel pump with a reliable electric fuel pump solves persistent vapor lock issues, provides consistent fuel delivery for engine upgrades, and enhances overall reliability in your 1967 Ford Mustang. While the original mechanical pump was adequate for the carbureted engines of the era under ideal conditions, modern driving demands, hotter underhood temperatures, and performance modifications often reveal its limitations. Installing an electric pump, either as a primary replacement or as a lift pump assisting the mechanical unit, offers a proven solution for smoother operation and increased horsepower potential.

Why Your 1967 Mustang Needs an Electric Fuel Pump Upgrade

The 1967 Mustang left the factory equipped solely with a mechanical fuel pump bolted directly to the engine block. This pump relies on an actuating arm pushed by an eccentric lobe on the camshaft to create suction, drawing fuel from the tank and pushing it towards the carburetor(s). While mechanically simple and cost-effective, this design has significant drawbacks in practice:

  • Vapor Lock: This is the most common and frustrating problem plaguing classic Mustangs, especially during warm weather or after the engine is hot. Gasoline in the line between the tank (located under the trunk floor) and the mechanical pump can become hot enough to vaporize. Because vapor takes up more space than liquid and lacks density, the mechanical pump struggles to pull the vapor bubbles effectively. This results in erratic fuel delivery, causing rough idle, stalling, hesitation, and difficult hot restarts. The pump is essentially trying to compress vapor instead of pumping liquid fuel.
  • Inadequate Flow for Engine Upgrades: The original pump was designed to deliver fuel within the relatively modest requirements of engines like the 200ci I6, 289ci V8, or even the stock 390ci 4V. Typical output pressures were around 4-6 psi. Modern carburetors with larger jets, high-performance camshafts (which reduce the mechanical pump's stroke effectiveness), increased engine displacements, or modifications like nitrous oxide or superchargers demand significantly higher fuel flow rates and potentially higher pressures than the stock mechanical pump can provide. Starving the engine of fuel under load leads to power loss, detonation (pinging), and potential engine damage.
  • Pressure Fluctuations: As engine RPM changes, the mechanical pump's output pressure can fluctuate. At very low idle speeds, pressure might drop momentarily. While carburetors have floats to handle some fluctuation, erratic pressure can contribute to inconsistent idle quality and transient hesitation during acceleration shifts. Electric pumps provide near-constant pressure.
  • Mounting Location Limitations: Being mounted on the engine block subjects the mechanical pump and the fuel nearby it to significant heat soak from the engine. This proximity further increases the risk of vapor forming before the fuel even reaches the carburetor.
  • Wear and Reliability: Mechanical pumps contain diaphragms and check valves subject to age, ethanol degradation, and wear. Failure can lead to leaks (both fuel and vacuum leaks if the diaphragm ruptures), low pressure, or complete loss of fuel delivery. Symptoms can mimic vapor lock initially. Replacing them often involves similar labor to installing the bulk of an electric system without the long-term benefits.

An electric fuel pump addresses these issues head-on. Mounted near the fuel tank, it pushes cool fuel from the source efficiently, avoiding the heat zones that cause vapor lock. Modern designs deliver specific, consistent pressures required by carburetors or fuel injection systems, and offer significantly higher flow rates to meet horsepower demands. Their operation is independent of engine RPM, providing fuel immediately during cranking and steady pressure at idle. For a reliable, high-performing 1967 Mustang, an electric fuel pump is a critical upgrade.

Understanding Key Electric Fuel Pump Specifications

Choosing the right electric fuel pump requires careful consideration of two critical specifications: pressure and flow rate (often listed as Gallons Per Hour or GPH). Selecting a pump that does not meet your engine's demands leads to poor performance. Conversely, an excessively powerful pump wastes money, requires more complex installation (regulators, bypass systems), generates unnecessary noise, and may overpower carburetor needles and seats.

  1. Pressure Requirements:

    • Carbureted Engines: The vast majority of 1967 Mustangs retain carburetors or are upgraded with performance carburetors (Holley, Edelbrock, etc.). These carburetors operate optimally with fuel pressures typically between 5.5 psi and 7.5 psi. Most aftermarket pumps designed for carburetion default to outputs around 6-7 psi. Exceeding 7.5 psi consistently risks forcing the carburetor's needle valves off their seats, causing flooding, overflow, and raw fuel leakage into the intake manifold (a dangerous fire hazard and engine damage risk). An essential component when installing an electric pump on a carbureted car is a fuel pressure regulator. This device allows you to dial the pump's output pressure down precisely to the carburetor's requirement. Never rely on the pump's inherent rating alone.
    • Fuel Injection Conversions: If you are converting your Mustang to electronic fuel injection (EFI), pressure requirements jump dramatically. Most common EFI systems (like GM TBI, Ford EEC-IV, or aftermarket systems like FiTech or Holley Sniper) demand pressures ranging from 35 psi to 65 psi, or even higher for some high-performance direct-port systems. The pump must meet or exceed the specific pressure requirement of the EFI system you choose. EFI also typically relies on a referenced pressure regulator that adjusts fuel pressure based on manifold vacuum. Pumps for EFI are inherently different (usually high-pressure turbine types) and significantly more expensive than carbureted units.

  2. Flow Rate (GPH) Requirements: Engine airflow determines fuel demand. Flow rate needs increase substantially with engine horsepower. Use these guidelines, keeping in mind crank horsepower is the relevant figure:

    • General Rule: Estimate 0.5 lbs of fuel per hour for every horsepower. Since gasoline weighs approximately 6 lbs per gallon, this translates to roughly 0.083 gallons per hour per horsepower (0.083 GPH/HP).
    • Calculation: Multiply your engine's crank horsepower by 0.083. Example: A 300 HP engine needs a pump rated for at least 300 HP x 0.083 = 24.9 GPH.
    • Safety Margin: This calculation gives a minimum requirement. Choosing a pump with 20-30% higher flow capacity than your calculated minimum is strongly advised. This margin compensates for pump aging, voltage drop, line restrictions, elevation changes, or future mild engine upgrades. For the 300 HP example, select a pump rated at approximately 30-32 GPH or higher.
    • Real-World Ratings: Be aware that advertised flow rates often represent free-flow conditions at zero pressure. Check pump specifications for flow rates at your intended operating pressure (e.g., 6 psi for carbs, 45 psi for EFI). A pump might flow 50 GPH at zero psi but only 35 GPH at 7 psi. Ensure the rated flow at pressure meets your minimum + safety margin. Reputable pump manufacturers provide flow charts.

Summary:

  • Carbureted: ~7 PSI MAX (Requires Regulator!), Flow Rate = Engine HP x 0.083 + 20-30% margin.
  • EFI: System-Specific PSI (35-65+), Flow Rate = Engine HP x 0.083 + 20-30% margin (based on pump rating at operating pressure).

Types of Electric Fuel Pumps for Your '67 Mustang

Understanding the different operating principles and mounting styles helps select the optimal pump for your needs and installation preferences.

  1. Operating Principle:

    • Roller Vane Pumps: These pumps use small rollers inside a rotating cam. As the cam spins, the rollers push fuel from the inlet to the outlet. They are common as inline external pumps and known for:
      • Moderate noise levels.
      • Good flow rates for carburetor applications.
      • Reasonable pressure capabilities (often ~7-12 psi range naturally, easily regulated down for carbs).
      • Generally good durability.
      • Require clean fuel – must have a robust pre-filter. Vane wear over time is normal.
    • Turbine Pumps: These use an impeller with curved blades spinning at high speed to push fuel. They are extremely common for both EFI (high-pressure variants) and carburetion (low-pressure variants), and as both inline and in-tank pumps.
      • Pros: Typically quieter than roller vane pumps. Can generate very high flow rates and pressures (essential for EFI). Generally offer longer service life than roller vane due to fewer wearing contact points. Tolerate low voltage slightly better.
      • Cons: Primarily, the cost is usually higher than comparable roller vane pumps. Can be slightly more sensitive to running dry, though modern designs mitigate this.
    • Gerotor Pumps: Less common for general automotive use. They use meshing gears (one internal, one external) to move fuel. Known for consistent flow but potentially noisier. Often seen as OEM pumps.

  2. Mounting Location:

    • In-Tank Electric Fuel Pump: This is widely considered the preferred installation method for both safety and performance. The pump is submerged within the fuel tank.
      • Safety: Fuel surrounds the pump, acting as a coolant and lubricant. A submerged pump significantly reduces fire risk compared to an externally mounted pump in the event of a leak, as there is no air to support combustion within the liquid fuel environment. Submersion also drastically dampens operating noise.
      • Performance: Cooler intake fuel (drawn from the bottom of the tank) further minimizes vapor lock potential. Gravity feeds fuel directly to the pump inlet, enhancing priming and reducing the chance of cavitation (vapor bubbles forming within the pump). This is critical for pump longevity and consistent flow. Modern high-performance and EFI systems almost exclusively use in-tank pumps.
      • Installation: Requires modifying the factory tank by installing a fuel pump hanger assembly through a new hole cut in the top, or replacing the original tank sending unit with a combined fuel pump/sending unit assembly ("bucket" style). Sealing kits are critical. Provides a clean, protected appearance.
    • Inline Electric Fuel Pump: These pumps are mounted along the fuel line, typically underneath the vehicle near the tank or on the frame rail. They are exposed to the elements.
      • Pros: Installation is generally simpler and often less expensive initially than an in-tank solution. No permanent tank modification is required. Easier to physically access for inspection or replacement.
      • Cons: Significantly higher fire risk if leaking. Runs hotter and is usually louder. Susceptible to vapor lock at the inlet side if heat soaked (since they're not submerged). More vulnerable to damage from road debris or accidents. Gravity does not assist the inlet; they must be mounted below the tank outlet as close as possible and require careful attention to inlet path. Often need additional brackets for secure mounting. Generally less reliable and long-lived than quality in-tank pumps.

Recommendation: For a 1967 Mustang restoration or upgrade seeking maximum safety, reliability, quiet operation, and performance (especially for EFI), an in-tank electric fuel pump is the best long-term investment. Inline pumps are a viable solution for budget-focused carbureted applications, provided installation safety and proper inlet routing are meticulously followed. Popular reliable brands for classic Fords include Holley, Carter, AEM, Walbro, and Tanks Inc (often using Walbro modules).

Crucial Pre-Installation Preparation for Your '67 Mustang Fuel System

Before picking up any tools, thorough preparation is essential for a safe, functional, and reliable fuel pump installation. Rushing this stage leads to problems, leaks, pump failure, or safety hazards.

  1. Complete Fuel System Evaluation:

    • Tank Condition: This is paramount. A neglected, rusty, or contaminated original tank will destroy your new electric pump instantly. Debris clogs filters and damages pump internals. Rust creates abrasive particles. Inspect the inside thoroughly using a bright light after draining. If rust exists (visible flakes or loose sediment), sludge, or heavy varnish is present, tank cleaning or replacement is non-negotiable.
      • Cleaning: Professional fuel tank restoration shops use chemical dips and baking/steaming processes to remove internal corrosion and seal the surfaces. DIY methods (like chainsaw chain agitation with vinegar or dedicated tank cleaners) are less effective and cannot seal.
      • Replacement: Brand-new reproduction tanks (with factory-style venting) or upgraded baffled tanks (like Tanks Inc or Rick's Tanks) are excellent options. A quality new tank ensures a clean start. If installing an in-tank pump, a tank specifically designed for pump integration simplifies installation significantly.
    • Existing Fuel Lines: Inspect every inch of the steel lines from the tank to the engine compartment. Look for severe corrosion (scaling, flaking), kinks, dents, or evidence of old repairs (crimp fittings or tape). Replace compromised lines. Consider upgrading:
      • Steel: OEM replacement lines are fine. Ensure new lines follow the factory routing precisely.
      • Nickel-Copper (NiCopp): Highly recommended upgrade. Easier to bend and flare than steel, corrosion-resistant, readily available (often in 25' coils). Standard for professional shops.
      • Avoid: Plain copper or aluminum lines (too soft and fatigue-prone). Plastic lines are generally unsuitable unless explicitly rated for high-pressure EFI.
    • Venting: Verify the tank's original venting system is intact and functional (charcoal canister if present, vent lines to vapor separator, or tank vent cap). Modern gas formulations vaporize more readily, making proper venting critical. A blocked vent creates a vacuum in the tank, hindering fuel pump draw and potentially collapsing fuel lines. Consider adding a modern rollover vent valve to the vent line outlet if updating the system.
    • Existing Pump: If removing the mechanical pump, identify if it's currently connected to other systems. Some later 60s vacuum wipers used manifold vacuum tapped directly off the mechanical fuel pump body – this setup needs modification (find another vacuum source or install an electric wiper motor).

  2. Planning Routing and Mounting:

    • In-Tank: Measure carefully. Identify the best location on the top of the tank for the pump hanger or combined sender assembly before modifying. This is usually centered and away from seams and baffles. Ensure clearance exists above the tank for the assembly and wiring connector – check trunk floor clearance when installed. Plan wiring conduit path and location of the access hole (if needed in trunk floor).
    • Inline:
      • Location: Must be mounted as close to the fuel tank outlet as possible, below the tank level. The pump inlet must be gravity-fed. Mount securely to a structural frame rail using appropriate vibration-dampening rubber isolators and metal clamps/brackets. Never mount rigidly to the engine block. Avoid high-heat areas (exhaust) and road debris zones. Protect with skid plates if necessary. Use heat shields.
      • Orientation: Follow manufacturer instructions! Some pumps have specific inlet/outlet orientations (often labeled or specified). Mount vertically if possible. Deviating can cause pump noise or failure.
    • Pressure Regulator Location (Carbureted): Mount the regulator as close to the carburetor inlet as feasible, typically on the firewall or intake manifold. This ensures the carb sees the most consistent regulated pressure. Ensure space for inlet and outlet fittings and the vacuum reference port if applicable.
    • Filter Locations:
      • Pre-Filter: Essential to protect the pump. Install between the tank outlet and the pump inlet. Use a large canister filter (often 100-micron) rated for the pump flow rate. For in-tank pumps, this filter is often incorporated into the pump "sock" inlet, but an additional large pre-filter is still highly recommended externally.
      • Post-Filter / Inline Filter: Install after the pump and before the regulator/carb. This catches any particles generated by the pump or missed by the pre-filter. Use a 10-micron filter (30-40 micron for larger-carbed engines). For EFI, use an EFI-rated filter.

  3. Essential Component Gathering:

    • Pump (correct PSI/GPH rating).
    • Mounting brackets/clamps (if inline).
    • Fuel Pressure Regulator & Gauge (for carb).
    • Filters: Pre-Pump, Post-Pump/Inline.
    • Fuel Hose: Use ONLY SAE J30R9 (for low-pressure carb) or SAE J30R14 Submersible hose for connections within the tank. For EFI pressure hose, use J30R9 or the superior J30R14 Non-Submersible. Use EFI-rated clamps (constant tension band clamps are preferred over worm-gear clamps for high pressure). Cut hose cleanly.
    • Fuel Line: Steel or NiCopp tubing, appropriate diameter (5/16" is common factory size, OK for mild V8s; 3/8" recommended for higher performance builds).
    • Flaring Tool: Double-flaring tool mandatory for steel/NiCopp lines (ISO/Bubble flare for metric fittings, SAE 45° flare for most AN-style and brass fittings – know what fittings your pump/regulator use!).
    • Fittings: Brass or Steel unions, AN adapters, line nuts & sleeves as needed. Minimize connections – each is a potential leak point.
    • Electrical: 10-gauge or 12-gauge primary power wire (depends on pump amperage draw), same gauge ground wire, relay (usually 30-40 Amp), fuse (sized per pump specs, typically within 5-7 amps of max draw), wire connectors (crimp & solder preferred), grommets, conduit, switch wiring (if using manual prime), fuel-proof toggle switch (optional), ring terminals. Inertia safety switch (highly recommended).
    • Safety: Fire extinguisher (ABC type), safety glasses, nitrile gloves, ventilation.

  4. Depowering & Draining:

    • Disconnect the negative battery cable.
    • Relieve fuel pressure: Disconnect coil wire and crank engine briefly (for mechanical pump systems), or disconnect power from an existing electric pump. Cover distributor/coil with a rag to prevent sparks.
    • Drain Fuel Tank Completely. Siphon or drain via the outlet line into approved containers in a well-ventilated outdoor area away from ignition sources. Cap or plug tank outlet immediately.
    • Expect residual fuel in lines. Place shop towels/absorbent pads.

Step-by-Step Installation Guide for a 1967 Mustang Electric Fuel Pump

Proceed methodically, following all safety precautions. Never skip pressure testing before connecting to the carb/engine.

  1. Remove Old Components:

    • Disconnect fuel lines at tank outlet and at the fuel pump/carb end. Plug/cap lines immediately.
    • Remove the factory mechanical fuel pump (if replacing it entirely – see the "Assist" section below for hybrid setups):
      • Disconnect inlet and outlet fuel lines.
      • Remove the two mounting bolts.
      • Remove pump. Inspect the eccentric arm hole for debris. Clean the mounting surface. Determine if a block-off plate is needed (common to prevent oil leaks and maintain cleanliness). Install plate with appropriate gasket/sealant.
    • Tank Removal: This is necessary for safe in-tank pump installation or serious tank cleaning/replacement.
      • Support car securely on jack stands.
      • Disconnect and cap fuel fill hose and vent hoses at the tank.
      • Support tank (floor jack with wood plank).
      • Remove retaining strap bolts.
      • Carefully lower tank. Be aware of sharp edges and weight.

  2. Install New Fuel Tank or Modify Existing Tank:

    • New Tank (Recommended): Install baffled tank or factory replacement.
    • Existing Tank Cleaning: Send for professional cleaning/sealing if contaminated.
    • Modify for In-Tank Pump:
      • Identify exact location – center, away from baffles/weld seams. Measure meticulously relative to original sender location and tank features.
      • Carefully cut hole per pump hanger specifications using hole saw and cutting fluid. DEBURR the hole thoroughly inside and out!
      • Test fit the hanger/sender assembly without seal. Ensure it sits flat and doesn't interfere with baffles or tank bottom when fully inserted. Mark hole orientation if necessary.
      • Assemble pump, hanger, and tank seal/gasket exactly as per instructions. Apply sealant if specified (usually around the seal). Tighten lock ring evenly, ensuring the seal is uniformly compressed. Do not overtighten.
      • Connect the submersible fuel hose between the pump outlet and the hanger outlet fitting. Use submersible hose clamps.
      • Reinstall the tank carefully, connecting the new pump outlet tube to the fuel line, and reconnecting fill/vent hoses. Reinstall straps securely. Fill tank with at least 5 gallons of clean fuel ASAP to prevent pump dry running. Never run the pump until fuel is present.

  3. Install Inline Fuel Pump (If Chosen):

    • Mount pump securely below tank level, near tank outlet, using isolators and sturdy brackets. Follow inlet/outlet orientation! Maintain inlet path clarity and direct gravity feed. Orient vertically if possible.
    • Cut the original metal line between the tank and where the mechanical pump was. Install a robust pre-filter (100-micron) immediately after the tank outlet. Use appropriate tubing adapters.
    • Connect pre-filter outlet to the pump inlet using short sections of new fuel hose (J30R9/R14) and proper clamps.
    • Connect pump outlet to the metal fuel line running toward the engine using new fuel hose and clamps (again, maintain as straight a path as possible).

  4. Install Post-Pump Filter & Pressure Regulator (Carbureted):

    • Install a 10-40 micron inline filter in the supply line after the pump (and before the pressure regulator).
    • Mount the fuel pressure regulator securely near the carburetor. Connect the inlet of the regulator to the fuel line coming from the pump/filter. Connect the regulator outlet to the carburetor inlet. Connect the reference vacuum port (if present) to a ported or manifold vacuum source on the carburetor/intake using vacuum hose. Install a fuel pressure gauge temporarily on the test port (if available) or use a T-fitting between the regulator and carb. Cap unused ports tightly.

  5. Install New Fuel Lines (If Needed): Where replacing or running new lines:

    • Use NiCopp tubing or steel.
    • Plan route carefully, avoiding moving parts, heat, sharp edges. Secure lines every 12-18 inches with appropriate clamps (not steel on steel).
    • Use flaring tool to create precise double flares at ends. Attach flare nuts and sleeves before flaring! Deburr ends. Connect to fittings securely.

  6. Wire the Electric Fuel Pump Safely (MANDATORY): Electrical wiring demands precision and safety features to prevent fires and ensure reliable operation. Never power the pump directly from the ignition switch.

    1. Fuse: Install an appropriately sized fuse (check pump specs – e.g., 20A for many carb pumps) in an inline holder within 6-12 inches of the power source (usually starter solenoid or battery junction box).
    2. Relay: Essential for handling the pump's current draw.
      • Terminal 30: Connect to battery positive (via the fuse!). Use 10-12 AWG wire.
      • Terminal 85: Ground (to body or chassis) – use 16-18 AWG wire. Ground this securely to clean bare metal.
      • Terminal 86: Connect to a switched ignition source that is ONLY hot during "Run" and "Start" (cranking). Sources vary:
        • Common: Use the ignition "I" (Run) terminal on the factory ignition switch harness.
        • Safe Alternative: Connect to the coil positive terminal circuit (ensure it's powered during cranking on your specific car).
        • OEM Safety: Use the existing wire that powered the later-model resistor wire to the coil (often Orange/Blue or Pink/Black) before the resistor wire section.
      • Terminal 87: Connect to the positive terminal of the fuel pump (10-12 AWG wire).
    3. Pump Ground: Run a dedicated ground wire (same gauge as positive feed) directly from the negative terminal of the fuel pump to a clean, bare metal chassis point. Do not rely on pump mounting for ground.
    4. Inertia Safety Switch (HIGHLY Recommended): Wire this safety device in series between the relay output (Terminal 87) and the fuel pump positive. Mount it securely on a vertical body panel (like the passenger kick panel near the glovebox or trunk divider) as per manufacturer instructions. This switch automatically cuts power to the pump in the event of a significant collision. Test its operation after installation.
    5. Manual Prime Switch (Optional but Useful): Wire a momentary SPST (on)-off switch in parallel with the relay's switched ignition source (Terminal 86). Mount this switch on the dash. Briefly pressing it triggers the relay and runs the pump independent of ignition position – handy for filling carb bowls after long storage or testing.

  7. Pressure Test the System: DO NOT START THE ENGINE YET!

    • Reconnect battery negative.
    • Temporarily install a fuel pressure gauge at the regulator test port or carb inlet.
    • Connect the fuel line to the carb inlet except for the pressure test setup.
    • For Carbureted:
      • Ensure the regulator is set to its highest pressure setting initially.
      • Turn ignition to "Run" (do not crank) or press the prime switch. Pump should run briefly. Check for leaks everywhere – fittings, hoses, pump, tank seams. Use flashlight and mirror. Fix any leaks immediately.
      • Observe pressure gauge. If regulator is adjustable (most are), gradually turn the adjustment screw counter-clockwise to decrease pressure to the target 5.5 - 7.0 psi. Check for leaks again after adjustment. Let system sit pressurized for 10-15 minutes; pressure should hold relatively steady. If it bleeds down significantly, find the leak.
    • For EFI: Follow EFI system prime/test procedures. Verify pressure meets the system specification.

Hybrid Setup: Using an Electric Pump as a Lift Pump with the Mechanical Pump

Some owners want to retain the original mechanical pump for authenticity but eliminate vapor lock. An electric pump mounted near the tank acting as a "lift" or "helper" pump can achieve this.

  • How it Works: The electric pump pushes cool fuel from the tank to the inlet of the mechanical pump. This ensures the mechanical pump always receives liquid fuel under positive pressure, eliminating its suction pull which causes vapor lock. The mechanical pump then feeds the carburetor normally.
  • Pump Selection: Choose a low-pressure (1.5 – 4 psi) electric pump designed specifically for lift pump purposes (e.g., Facet Cylindrical, Carter P4070 or P60504). Avoid using a standard 6-7 psi electric pump for lift duty.
  • Installation:
    • Mount inline pump near tank, fed by pre-filter.
    • Connect pump outlet to the inlet side of the original mechanical pump using new fuel hose.
    • Crucial: Install a check valve in the line between the lift pump and the mechanical pump. This prevents the mechanical pump from trying to force fuel backwards through the lift pump when it's off. Mount check valve vertically if possible.
    • Electrical: Wire identically to a primary electric pump (relay, switched ignition source, inertia switch, fuse). Its purpose is primarily for priming and hot starting prevention, so continuous running at speed isn't always necessary, though it provides constant vapor lock protection. It can run whenever the ignition is in Run/Start.
  • Pros: Retains stock appearance of mechanical pump. Provides strong vapor lock solution. Simple electrical demands.
  • Cons: Two potential points of failure. Still relies on aging mechanical pump components. Requires precise pump choice (low pressure). Check valve adds restriction.

Post-Installation Testing, Break-in, and Troubleshooting

Once installed and leak-free, it's time to start the engine and verify operation.

  1. Initial Start-Up:

    • Ensure carburetor bowls are dry or mostly dry to prevent flooding during prime.
    • Turn ignition to "Run" (or press prime switch) for 5-10 seconds. Listen for pump sound. Watch pressure gauge. Fuel pressure should build quickly and stabilize (carb). For EFI, this primes the rail.
    • Attempt to start normally. Expect a slightly longer crank as fuel fills lines from the rear. The engine should start more readily, especially if vapor lock was a chronic issue.
    • Listen for abnormal sounds: Air bubbles whistling (indicating an inlet leak before the pump), excessive pump whine (strain, wrong pressure), or fuel leaks.

  2. Break-In & Operation Checks:

    • Check Idle Fuel Pressure: Ensure it's stable at the carb's required setting (or matches EFI specs).
    • Drive Test: Check engine responsiveness under moderate acceleration. Perform a simulated vapor lock test: Drive until fully warm, shut off for 10-15 minutes in a hot environment, then restart. Should start easily. If hesitation exists under hard acceleration at high RPM, verify flow rate adequacy (pressure shouldn't drop significantly under load).
    • Monitor for Leaks: Check all connections carefully after the first drive cycle and during routine checks in the following weeks.

  3. Common Troubleshooting Issues:

    • Pump Doesn't Run:
      • Check main fuse.
      • Verify battery voltage at pump positive terminal (with relay triggered). Test by bypassing relay temporarily.
      • Check ground connection on pump body.
      • Verify power reaches terminal 86 on relay (proves switched source works).
      • Check inertia switch is reset. Verify any manual prime switch operation.
      • Check pump connector is secure. Caution: Never jumper voltage directly to a pump without checking resistance first.
    • Pump Runs but No/Low Fuel Pressure:
      • Severe inlet restriction: Clogged pickup sock or pre-filter, pinched inlet line, collapsed hose. Fuel tank vent blockage causing vacuum (listen for sucking sound when opening gas cap).
      • Air leak before the pump (inlet side). Pump draws air instead of fuel. Check all pre-pump hose clamps and fittings. Submerge connections to test for bubbles.
      • Worn pump (if used).
      • Incorrect regulator setting (carb), or stuck-open regulator.
    • Excessive Pump Noise:
      • Pump running dry or low on fuel (keep tank at least 1/4 full!).
      • Cavitation due to inlet restriction (see above).
      • Air in the inlet line.
      • Incorrect pump mounting orientation.
      • Mounting too rigid (isolate with rubber).
      • Normal turbine whine vs. abnormal grinding.
    • Fuel Pressure Too High (Carbureted): Adjust regulator downwards. If pressure won't decrease, regulator is faulty or incompatible.
    • Carburetor Flooding: Pressure exceeds carb bowl needle valve rating. Adjust regulator pressure down. Verify pump isn't producing >7.5 psi and regulator is functioning.
    • Loss of Pressure After Engine Off: Minor bleed-down is normal over minutes. Rapid loss indicates a leak or bypassing regulator/pump.

Maintenance for a Reliable Electric Fuel Pump System

Protect your investment with routine checks:

  1. Filter Replacement: Change the pre-pump filter every 6-12 months or per mfgr interval. Replace the inline filter annually or if fuel flow seems restricted. Filters are cheap insurance. When changing, note debris found in the filter.
  2. Visual Inspection: Annually, inspect:
    • All rubber hoses for cracks, swelling, or brittleness. Replace every 5 years regardless.
    • All fittings, flare nuts, and clamps for tightness and leaks. Clean fittings yearly.
    • Metal lines for corrosion or damage.
    • Pump mount security (if inline).
    • Wire connections, especially grounds.
    • Operation of inertia switch.
  3. Fuel Quality: Avoid letting the car sit for months with modern ethanol gasoline. Use fuel stabilizer (marine grade) or ethanol-free fuel if storing. Keep tank as full as possible during storage to minimize condensation.
  4. Listen: Pay attention to pump sound changes (increased noise often signals impending failure or an issue).

FAQs: 1967 Mustang Electric Fuel Pump Installation

  1. Do I need an electric fuel pump for my stock 289? Answer: While not strictly necessary for operation, an electric pump significantly reduces or eliminates vapor lock, ensures quicker starts (especially hot), and improves idle quality consistency. It's a major reliability upgrade even for stock engines.
  2. Can I just "T" into the existing fuel line for an inline pump? Answer: No. Never simply tee into a line. You are replacing the source of pressure. The pump must be installed in series, replacing the suction line between the tank and the mechanical pump (if used as lift) or the entire supply line function (if replacing the mechanical pump). The path must be continuous from tank to pump inlet, to pump outlet, to carb/filter/regulator.
  3. Why is my fuel pump so loud? Answer: Common causes: 1) Low fuel level (keep tank >1/4 full), 2) Pre-filter clogged causing starvation/cavitation, 3) Air leak before the pump, 4) Poor mounting allowing vibration, 5) Generic inline roller vane pump (often louder), 6) Normal turbine sound mistaken for problem. Diagnose using the steps in troubleshooting.
  4. Can I use a fuel injection pump on my carbureted Mustang? Answer: Technically yes, but it requires specific setup to avoid catastrophic consequences. EFI pumps generate high pressure (40-100+ PSI). You must install a return-style fuel pressure regulator with a dedicated return line back to the tank. Without this, pressure will skyrocket, blow out carburetor gaskets, flood the engine, and create a severe fire hazard. It's generally unnecessary and complex for carb applications – choose a low-pressure carb-specific pump instead.
  5. Is an inertia switch really necessary? Answer: YES. It's a critical safety device. In an accident, fuel spray from a ruptured line onto hot components or sparks is a huge fire hazard. An inertia switch instantly kills the pump during impact, significantly reducing this risk. It's highly recommended and inexpensive insurance. Mount it securely on a vertical surface per instructions.
  6. What size fuse do I need? Answer: Check the specific pump manufacturer's specifications. This is crucial. The fuse protects the wiring circuit from overload. Typical carburetor pumps may need 15-25 amps; confirm using pump datasheet max amperage draw value. Choose a fuse rating slightly above this (e.g., pump max 9A, use 10A or 15A fuse). Never oversize excessively.
  7. My car has factory Air Conditioning - does that change routing? Answer: Possibly. The AC evaporator box occupies space on the passenger side inner fender where fuel lines may have run or where you might mount a regulator. Plan routing (often along the firewall or inside frame rails) carefully to avoid interference with AC lines, drain tubes, or the box itself. Firewall clearance can be tight. Mock-up with hose before bending hard lines.
  8. Can I keep my vacuum wipers if I remove the mechanical pump? Answer: Maybe not directly. If your original wipers were powered by manifold vacuum taken off the fuel pump body, you lose that source when removing the mechanical pump. Solutions: 1) Relocate the vacuum tap to the intake manifold using a plugged port (check for an unused manifold port like the brake booster source on some V8s - Y-fitting needed), 2) Install a small vacuum reservoir tank to store vacuum, or 3) Convert to electric windshield wipers for better performance and simplicity (recommended).

Conclusion:

Installing a modern electric fuel pump is one of the most beneficial upgrades for a 1967 Mustang. Whether battling vapor lock, seeking reliable hot starts, supporting a high-performance engine build, or converting to fuel injection, the correct electric pump provides a consistent flow of cool fuel that the original mechanical pump simply cannot match. Carefully selecting the pump type and rating based on your engine's needs, performing a meticulous installation with robust electrical safety measures, and adhering to routine maintenance transforms your classic Mustang into a dependable cruiser eager for the next road trip. Enjoy the newfound reliability at the heart of your Mustang’s performance.

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