A 2015 Jeep Grand Cherokee came into the bay with a P0440 code and an intermittent extended crank of four to five seconds. The technician wrote the symptoms down exactly as they saw them: “has extended crank at times. will take about 4 to 5 seconds to run. after initial start it will start normally without hesitation. Also has check engine light on”. This is a classic diagnostic scenario where a drivability issue and an emissions code might be directly related, or they might be completely independent failures occurring at the same time.
In the diagnostic platform we build, our engine ranks the most likely root causes by analyzing the specific fault code alongside the described symptoms. For this Jeep, the data points to a mechanical failure linking the EVAP system directly to the intake manifold.
The Purge Solenoid Valve Link
Our engine ranked a stuck-open or internally leaking EVAP purge solenoid valve as the most likely cause, at a 75% probability with medium severity. On the 3.6L Pentastar V6, this solenoid is a normally closed valve that modulates fuel vapor ingestion into the intake manifold. When it fails mechanically by sticking open, seating imperfectly, or being held open by charcoal fines, intake manifold vacuum continuously draws raw fuel vapors from the canister directly into the intake plenum while the vehicle is parked.
During a start attempt, this uncontrolled vapor flood over-enriches the combustion chambers. This results in the extended four to five second crank time before the engine clears the mixture and fires. Once started and cleared, immediate subsequent starts crank normally because the plenum is purged. Concurrently, because the valve fails to seal, the Powertrain Control Module (PCM) detects an inability to seal the evaporative system during engine-off natural vacuum tests, setting DTC P0440.
To prove this, perform a de-energized vacuum hold test on the purge solenoid port. You should also run an intake vacuum draw check at the purge valve inlet with a 0% duty cycle commanded, and monitor live scan data for Short-Term and Long-Term Fuel Trims upon a cold start.
The ESIM Switch Failure
The second ranked cause, at 65% probability with a low severity, is a faulty Evaporative System Integrity Module (ESIM) switch. The 2015 Grand Cherokee uses this module attached to the charcoal canister to monitor system integrity using natural vacuum leak detection principles. The internal microswitch is calibrated to close at approximately 0.25 kPa of vacuum as the fuel tank cools after shutdown.
High-cycle fatigue, internal contact corrosion, or sticking weighted check valves inside the ESIM prevent the electrical contacts from closing, keeping the signal circuit pulled up to 5 volts. Because the PCM expects the switch to toggle during thermal cool-down, a switch that fails to register transitions triggers DTC P0440 even when the EVAP lines and fuel tank are completely leak-free.
Diagnostic steps here include scan tool live PID monitoring of the ESIM switch state while applying calibrated light vacuum, a multimeter signal voltage backprobe test during manual ESIM switch actuation, and a physical inspection of the ESIM sealing O-ring and canister bayonet locking tabs.
Cracked or Brittle EVAP Lines
Ranked at 50% probability is a cracked or brittle EVAP purge vacuum line. On the 3.6L Pentastar engine, the rigid pre-formed nylon purge vapor line routes vapors from the purge solenoid along the passenger-side cylinder head toward the chassis hardline. Under continuous under-hood thermal cycling, this plastic line becomes brittle and develops stress fractures along its bends or at its quick-connect end fittings.
A fractured purge line allows unmetered ambient air to bypass the throttle body during cranking and idle, destabilizing manifold vacuum and contributing to delayed starting. It also directly vents the EVAP system, causing the PCM integrity monitor to fail and set P0440. Test this with a visual and tactile flex inspection along the rigid nylon line near the passenger-side valve cover, a low-pressure EVAP smoke test introduced via the under-hood service port, and a short-term fuel trim response check using intake leak detection fluid.
The Fuel Pump Module Check Valve
Finally, at a 40% probability, the engine flagged a fuel pump module internal check valve leakdown. The in-tank fuel delivery module incorporates an internal one-way check valve on the pump discharge port to retain fuel pressure in the supply line and fuel rail after engine shutoff. Check valve seat wear, spring relaxation, or foreign debris allows pressurized fuel to drain backwards into the fuel tank after shutdown.
When attempting to start after sitting, the engine requires four to five seconds of cranking while the pump purges vapor and re-pressurizes the fuel rail to operating pressure (approximately 58 psi or 400 kPa). Once running, fuel delivery is adequate, and immediate restarts succeed instantly. This mechanical check valve failure frequently occurs as an independent drivability fault alongside a separate EVAP code.
Confirm this with a mechanical fuel pressure gauge residual pressure hold test at key-off, a key-on double-prime diagnostic test prior to cranking, and fuel line flow volume and operating pressure verification.
Next Steps in the Bay
When a vehicle presents an extended crank alongside a P0440, evaluating the shared mechanical pathways saves hours of isolated testing. I would test the purge solenoid first, as it perfectly bridges both the drivability complaint and the emissions fault code. Have you seen these two symptoms present together on the Pentastar V6, and did it lead you to the purge valve?
Reference pages for the codes in this article
- P0440, what we measure for this code across real diagnostics
