Experiencing a “cranks but won’t fire” situation with your 1999 Chrysler 300M can be frustrating. This issue, where the engine turns over but fails to ignite, can stem from various underlying problems. Let’s delve into a real-world troubleshooting scenario encountered by a 1999 Chrysler 300M owner, and explore potential causes and solutions for this common automotive problem.
The Initial Cry for Help
A Chrysler 300M owner, “Basheer.D,” posted in an online forum describing a perplexing issue with his 1999 model. His car, with a relatively low mileage of 95,000 miles at the onset of the problem, would crank but not start. Having recently replaced spark plugs, he suspected a fuel pressure issue. He noted performing regular maintenance, including a new timing belt and water pump, ruling out some basic maintenance concerns. Waiting in the “on” position to build fuel pressure proved ineffective, leading him to seek advice from the online community.
Community-Driven Diagnosis and Suggestions
The forum members, a community of Chrysler 300M enthusiasts and experienced owners, quickly chimed in with suggestions. “dcsally97,” a seasoned member, proposed a simple yet often effective initial check: wiggling the cam sensor. This sensor’s malfunction can indeed prevent the engine from firing. However, this quick fix didn’t resolve Basheer.D’s starting issue.
The camshaft position sensor is a common component to check when a Chrysler 300M 1999 experiences starting problems.
Further probing by dcsally97 inquired about check engine lights. A lit check engine light would indicate stored diagnostic trouble codes (DTCs), offering valuable clues. However, Basheer.D confirmed no check engine light and no codes detected using the key trick method, complicating the diagnosis.
“FIREM,” a highly active and knowledgeable member, provided a systematic approach, emphasizing the essential trio for engine start: spark, fuel, and air. He suggested a spark test by removing a coil and checking for spark during cranking. He also pointed towards crank and cam sensors as potential culprits, even without fault codes, especially in 1999-2000 models. Disconnecting the cam sensor was recommended as a diagnostic step. For fuel, FIREM advised checking fuel pressure at the Schrader valve on the fuel rail, even using a tire gauge for a quick check. Air intake was also mentioned, suggesting a slightly opened throttle during cranking to bypass potential issues with the Idle Air Control (IAC) valve or throttle body.
Deep Dive into Potential Causes
FIREM’s methodical approach highlighted several key areas to investigate for a “1999 Chrysler 300M cranks but won’t fire” scenario:
- Spark Issues: While new spark plugs were installed recently, a spark test is crucial to confirm ignition system functionality. Coils, wiring, and the PCM (Powertrain Control Module) could be involved.
- Fuel Delivery Problems: Fuel pressure is paramount. A failing fuel pump, clogged fuel filter, faulty fuel pressure regulator, or even problematic fuel injectors could restrict fuel flow.
- Sensor Malfunctions: Camshaft and crankshaft position sensors are vital for engine timing and ignition. Their failure, even intermittent, can prevent starting.
- Air Intake Obstructions: While less common for a no-start, restrictions in air intake can disrupt the air-fuel mixture.
The Plot Thickens: Months of Intermittent Starting Issues
Months passed, and Basheer.D reported an ongoing, intermittent issue. The Chrysler 300M would often start fine in the morning but exhibit the “cranks but won’t fire” problem after being off for about an hour, occurring roughly 50% of the time. He suspected fuel injectors after finding “residual moisture” and “questionable moisture” in cylinders 1 and 2 using an endoscope. This observation led him to consider injector replacement.
Using an endoscope can help diagnose potential issues inside the cylinders of a Chrysler 300M 1999 engine.
However, FIREM cautioned against jumping to injector replacement without proper diagnosis, especially since the engine ran smoothly once started, with no misfire codes. He reiterated the importance of a fuel pressure test to rule out fuel pump or regulator issues first, before considering injectors. He stressed that fuel injectors are typically long-lasting components.
“In-trepid” further supported the sensor theory, leaning towards the cam sensor and then the crank sensor as likely culprits before injectors, suggesting that the car could even run on just three injectors, albeit poorly.
The Unexpected Twist: A Seemingly Simple Resolution
In a surprising turn of events, Basheer.D updated the forum after inspecting the cylinders and spark plugs. After reinstalling the spark plugs and ensuring proper torque and gap, the starting issue vanished completely. For over 30 days, the 1999 Chrysler 300M started flawlessly. He speculated that loose spark plugs might have been the unexpected cause.
While “LUNAT1C” noted that a loose spark plug typically causes misfires and noise rather than a no-start, the fact remains that reseating the spark plugs resolved Basheer.D’s persistent starting problem. This highlights the sometimes-unpredictable nature of automotive troubleshooting and the importance of revisiting even seemingly basic components.
Lessons Learned for 1999 Chrysler 300M Starting Problems
This forum thread offers valuable insights for anyone facing a “cranks but won’t fire” issue with a 1999 Chrysler 300M:
- Systematic Troubleshooting: Start with the basics: spark, fuel, and air.
- Fuel Pressure Test: Crucial to diagnose fuel delivery issues.
- Sensor Checks: Cam and crank sensors are common culprits, even without codes. OEM sensors are recommended for reliability.
- Don’t Overlook the Simple: Check spark plug tightness and condition.
- Community Wisdom: Online forums can be invaluable resources for shared experiences and diagnostic advice.
- Test Before Replacing Parts: “Troubleshooting is the elimination of knowns” – diagnose before throwing parts at the problem.
While the exact cause in Basheer.D’s case remains somewhat ambiguous, the troubleshooting process and community support provided a pathway to resolution. If your 1999 Chrysler 300M cranks but won’t start, following a similar systematic approach, starting with fuel pressure and sensor checks, can help you pinpoint and resolve the issue.
