Experiencing a no-start issue with your 1999 Chrysler 300M can be frustrating. If your engine cranks but fails to fire up, you’re likely facing a problem with one of the essential components required for ignition. This guide, based on real-world troubleshooting advice from experienced Chrysler 300M owners, will walk you through potential causes and diagnostic steps to get your classic sedan back on the road.
One owner of a 1999 Chrysler 300M, let’s call him Bash, encountered this exact issue. After recently replacing his spark plugs and performing routine maintenance like timing belt and water pump replacement, his 300M began to crank but not start. He suspected a fuel pressure problem initially, but the issue persisted despite attempts to prime the fuel system by waiting with the key in the ‘on’ position.
The troubleshooting process, as suggested by the online community, began with checking basic sensors and systems.
One of the first suggestions was to check the camshaft position sensor. A faulty cam sensor can prevent the engine from starting by disrupting the timing of fuel injection and spark. Wiggling the cam sensor connector was proposed as a quick check to see if a loose connection was the culprit. Unfortunately for Bash, this didn’t resolve the no-start condition.
An engine bay similar to a 1999 Chrysler 300M, highlighting the complexity of modern automotive systems that require precise sensor readings for proper function.
The next step in diagnosing a “cranks but won’t fire” scenario is to consider the fundamental requirements for an engine to start: spark, fuel, and air.
Spark: To check for spark, a simple method is to remove a spark plug coil, insert a spark plug, ground the plug’s threads against the engine block, and have someone crank the engine. Observing for a spark across the plug gap will confirm if the ignition system is delivering spark. Both the crankshaft and camshaft position sensors play a crucial role in signaling when to spark and inject fuel. It was noted that sometimes a failing crankshaft sensor might not throw a code, yet still cause a no-start condition. A specific tip for 1999-2000 models was to try disconnecting the cam sensor to see if the car would start.
Fuel: Fuel delivery is another critical area. The system should maintain adequate fuel pressure for the engine to start and run. A Schrader valve located near cylinder #4 on the fuel rail allows for a quick pressure check, even with a tire pressure gauge in a pinch. Proper fuel pressure for a Chrysler 300M should be around 58 psi ± 5 psi, and it should hold at least 30 psi for 5 minutes after the fuel pump is turned off. Low fuel pressure can point to a failing fuel pump, fuel filter blockage, or a faulty fuel pressure regulator.
Air: While less common in modern fuel-injected vehicles, air intake can sometimes be a factor. A simple check is to slightly open the throttle while cranking the engine. If the engine starts, it might indicate an issue with the Idle Air Control (IAC) valve or a dirty throttle body requiring cleaning.
Despite these initial checks and suggestions, Bash’s 1999 Chrysler 300M issue was intermittent. It would often start fine in the morning but struggle to restart after sitting for about an hour. This pointed away from a complete failure of a sensor and more towards a potential pressure leak or sensor malfunction that was temperature or time-dependent.
After several months of this intermittent starting problem, and after trying fuel injector cleaner and waiting for pressure to build up, Bash decided to investigate further by removing the spark plugs again. Using an endoscope, he inspected the cylinders and found residual moisture in cylinder 1 and possibly cylinder 2. This led him to suspect leaking fuel injectors, which could flood the cylinders and cause hard starting.
An example of an endoscope being used for cylinder inspection, similar to how the Chrysler 300M owner visually checked for fuel leaks.
However, experienced forum members cautioned against jumping to injector replacement without proper diagnosis. Fuel injectors are generally robust and long-lasting. The advice was to first perform a fuel pressure test to rule out fuel pump or pressure regulation issues before considering injector replacement. It was also suggested that a leaking injector would likely cause misfire codes and rough running, which was not the case in Bash’s situation, as there were no engine codes or misfires reported.
Interestingly, after re-installing the spark plugs and adjusting the gaps, Bash reported that the starting issue mysteriously disappeared for over a month. He speculated that perhaps loose spark plugs were the initial problem. While a loose spark plug can cause misfires and noise, it’s less likely to cause a complete no-start condition. The act of removing and reinstalling the plugs, however, could have inadvertently improved a connection or resolved a minor issue elsewhere in the ignition system.
In conclusion, troubleshooting a “cranks but won’t fire” condition in a 1999 Chrysler 300M requires a systematic approach. Start with the basics: spark, fuel, and air. Check sensors like the cam and crank position sensors, perform a fuel pressure test, and inspect the ignition system. While intermittent issues can be more challenging to diagnose, methodical testing and community advice, as seen in this real-world case, can guide you towards identifying and resolving the problem, even if sometimes the solution appears unexpectedly after basic maintenance checks. Remember to always prioritize testing and eliminating known possibilities before replacing parts blindly.
