2020 Ford Explorer Hard Start? How to Diagnose and Fix Hub Issues

The Situation

A "hard start" condition, where the engine cranks normally but is reluctant to fire and run, is a common and frustrating drivability issue. Unlike a no-crank scenario, the starter motor is functional, but the engine fails to catch promptly, often requiring extended cranking. This problem points to a deficiency in one of the three core requirements for combustion: fuel, spark, or air (compression). Based on community data, the root cause is often a failing component that provides a marginal signal or supply when cold but fails under the initial load of startup.

Owner Experiences

In the analyzed discussions, owners reported a wide spectrum of hard start behaviors, often tied to specific conditions. A frequent pattern was an overnight or cold-start issue, where the vehicle would crank for 5-10 seconds before starting, sometimes accompanied by stumbling. Many noted the problem was intermittent, making it difficult to replicate for a technician. Several DIYers successfully traced the fault to electrical connectors at sensors like the crankshaft position sensor, finding corrosion or poor pins. Others found immediate resolution by addressing fuel delivery issues, such as a weak fuel pump or a leaking check valve causing pressure bleed-down. Frustration was common when parts like camshaft position sensors were replaced without solving the problem, highlighting the need for systematic diagnosis over guesswork.

How It Manifests

Owners describe the problem through specific, observable symptoms:

• Extended Cranking: The most universal report. The starter engages and spins the engine for an abnormally long duration (often 5-15 seconds) before the engine finally fires.
• Cranking-Only When Cold: The vehicle starts perfectly when warm but exhibits hard starting after sitting for several hours or overnight. This strongly suggests fuel pressure bleed-down or a temperature-sensitive sensor failure.
• Stumbling Starts: The engine may fire briefly, stumble, and almost die before the ECU corrects and idle stabilizes.
• Intermittency: The problem may come and go without an obvious pattern, which is typical of electrical connection issues or a component on the verge of failure.
• Normal Cranking Speed: It is critical to distinguish this from a slow-crank/no-crank issue. The starter motor speed sounds normal, indicating the battery and starter are likely not the primary culprits.

Possible Causes

Based on successful repairs documented in the community data, the causes are distributed across the fuel, ignition, and sensor systems. No OBD-II codes were frequently mentioned, indicating many failures are not severe enough to trigger a check engine light.

1. Fuel System Issues (Most Common in Reports): A failing in-tank fuel pump that cannot build adequate pressure quickly, or a leaky fuel injector or check valve allowing pressure to drain back to the tank overnight ("fuel pressure bleed-down"). This leaves the fuel rails empty, requiring extended cranking to reprimed the system.
2. Ignition System Faults: Worn spark plugs, failing ignition coils, or cracked spark plug wires can provide a weak spark insufficient for reliable ignition during the cranking cycle.
3. Critical Sensor Failures: The crankshaft position sensor (CKP) is a prime suspect. A failing CKP may not provide a clean signal to the ECU during the initial low-RPM crank, preventing spark and fuel injection. Camshaft position sensor (CMP) failures were also reported but less frequently.
4. Poor Electrical Connections: Corrosion, loose pins, or damaged wiring at key sensor connectors (especially CKP and CMP) can interrupt or degrade the signal, mimicking a bad sensor. This was a frequently cited "hidden" cause.
5. Air/Compression Issues: While less common, a significant vacuum leak (e.g., from a cracked intake boot) or a failing engine coolant temperature (ECT) sensor providing an incorrect "warm" signal to a cold engine can cause a hard start by skewing the air/fuel mixture.

What Actually Works

Start diagnosis with the simplest, lowest-cost checks before replacing major components.

Step 1: Verify Fuel Pressure & Hold (Cheapest/Fastest Check) Rent a fuel pressure test kit from an auto parts store. Check key-on pressure and, more importantly, monitor the pressure hold after the engine is shut off. Pressure should remain stable (spec varies by vehicle) for many minutes. A rapid drop indicates a leaking check valve in the pump or a leaky fuel injector. This test identified the problem in numerous owner reports.

Step 2: Inspect Electrical Connections & Grounds Visually and physically inspect the connectors at the crankshaft and camshaft position sensors. Look for corrosion, bent pins, or loose fits. Clean with electrical contact cleaner and ensure a secure connection. Check the engine's main ground straps for corrosion and tightness. This no-cost fix resolved many intermittent issues.

Step 3: Scan for Pending Codes & Live Data Even without a check engine light, a professional scan tool may reveal "pending" fault codes related to crankshaft correlation or fuel trim. Observing live data for crankshaft sensor signal stability and coolant temperature sensor accuracy during a cold soak can be revealing.

Step 4: Replace the Crankshaft Position Sensor If electrical checks are good and fuel pressure is stable, a failing CKP sensor is a highly probable cause. Use an OEM or high-quality aftermarket part (e.g., Standard Motor Products, NTK). This was a confirmed fix in a significant portion of discussions. Tip: Note the orientation and air gap of the old sensor during removal.

Step 5: Test/Replace the Fuel Pump If fuel pressure is low or bleeds down quickly, the fuel pump assembly (which includes the internal check valve) is the likely culprit. Replacing the in-tank pump module restores proper pressure and hold. This is a more involved and costly repair but was a definitive solution for many.

Step 6: Evaluate Ignition Components If the above steps yield no results, perform a spark test during cranking to verify strong spark. Inspect and replace spark plugs if worn, and consider testing coil-on-plug units with a multimeter or by swapping cylinders to see if the problem follows a coil.

Budget Planning

Costs vary widely based on the root cause and whether you perform the work yourself.

• DIY Repair (Parts Only):

  • Fuel Pump Assembly: $100 - $350 (aftermarket to OEM)
  • Crankshaft Position Sensor: $30 - $150
  • Spark Plugs (set): $25 - $80
  • Ignition Coil (each): $40 - $100
  • Fuel Pressure Test Kit (rental): $0 (deposit typically refunded)
  • Professional Scan Tool Rental: $50 - $100 deposit.

• Professional Shop Repair (Parts & Labor):

  • Diagnostic Fee: $120 - $200 (often applied to repair)
  • Fuel Pump Replacement: $500 - $1,000+
  • Sensor Replacement (CKP/CMP): $200 - $400
  • Tune-up (Plugs/Coils): $250 - $600+

Recommendation: A DIYer can perform the critical fuel pressure test and sensor inspection for the cost of a tool rental deposit. Starting with these free/low-cost diagnostics can save hundreds by preventing unnecessary part replacement.

Need to Know

Q: Why does my car start fine when warm but hard when cold? A: This is a classic symptom of fuel pressure bleed-down. When the car sits, fuel drains back to the tank, so the pump must refill the lines on startup. A weak pump or leaky check valve makes this slow. It can also be a failing sensor, like the CKP, whose internal resistance changes with temperature.

Q: I replaced the camshaft sensor and it didn't fix it. What now? A: This is a common misstep. The crankshaft position sensor is more critical for establishing base engine timing during crank. Return to systematic diagnosis: check fuel pressure hold first, then inspect the CKP and its wiring.

Q: How urgent is a hard start problem? A: It is a progressive failure. A component that causes hard starting will eventually fail completely, leaving you stranded. Address it promptly. A failing fuel pump, for instance, can die entirely without further warning.

Q: Can a dirty throttle body cause a hard start? A: Yes, but it's less common as a primary cause. A severely gummed-up throttle body can disrupt the idle air control, potentially causing a start-and-stall condition. However, it rarely causes extended cranking by itself. Clean it as part of general maintenance, but look elsewhere first for a pure hard-start issue.

Source Summary: This analysis is based on 100 owner discussions from Reddit and automotive forums.