Experiencing a no-start condition in your 1999 Lincoln Town Car can be incredibly frustrating, especially when accompanied by a lack of communication with your diagnostic scanner. This combination of issues can leave you stranded and scratching your head, wondering where to even begin troubleshooting. You’re not alone. Many owners of this classic model face similar challenges, and understanding the potential causes is the first step towards getting your Town Car back on the road. This guide will walk you through the common culprits behind a 1999 Lincoln Town Car that cranks but refuses to start and won’t communicate with a scan tool, providing you with actionable steps to diagnose and potentially fix the problem.
Understanding the Problem: No Start and No Scanner Communication
When your 1999 Lincoln Town Car cranks but doesn’t start, and simultaneously, your OBD-II scanner fails to connect or communicate with the car’s computer system (PCM – Powertrain Control Module), it indicates a deeper issue than just a simple fuel or spark problem. The “no communication” aspect is crucial. It suggests a potential breakdown in the electrical system that is preventing the PCM from operating correctly and also hindering diagnostic tools from accessing the car’s data. This symptom often points towards problems affecting the power supply, ground connections, or the PCM itself.
Potential Causes of a No-Start Condition
Before diving into the communication issue, let’s briefly cover the fundamental reasons why a car engine might crank but not start. These usually fall into three main categories: fuel, spark, and compression. However, given the “no communication” symptom, we’ll focus on areas that could affect both starting and PCM function.
Fuel System Issues
Lack of fuel delivery is a common cause of a no-start. While you might hear the engine cranking, without fuel reaching the combustion chamber, ignition is impossible. Potential culprits in a 1999 Lincoln Town Car’s fuel system include:
- Faulty Fuel Pump: The fuel pump is responsible for delivering fuel from the tank to the engine. A failing or failed fuel pump will prevent fuel from reaching the engine.
- Clogged Fuel Filter: A severely clogged fuel filter can restrict fuel flow, starving the engine.
- Fuel Pump Relay or Fuse: Like any electrical component, the fuel pump relies on a relay and fuse. A blown fuse or faulty relay can cut power to the fuel pump.
- Inertia Switch: This safety switch, often located in the trunk area, is designed to cut off fuel supply in the event of a collision. It can sometimes be tripped accidentally.
Ignition System Issues
For an engine to start, a spark is needed to ignite the air-fuel mixture. Problems in the ignition system can prevent this:
- Faulty Crankshaft Position Sensor (CKP): This sensor is vital for telling the PCM the crankshaft’s position and speed. Without a signal from the CKP sensor, the PCM won’t trigger spark or fuel injection.
- Faulty Camshaft Position Sensor (CMP): While less critical for starting than the CKP, a failing CMP sensor can sometimes contribute to no-start conditions, especially in sequential fuel injection systems, as it helps the PCM synchronize injector firing.
- Ignition Coils: The 1999 Town Car uses coil-on-plug ignition. A faulty coil (or multiple coils) can prevent spark at one or more cylinders.
- Spark Plugs: While less likely to cause a sudden no-start, old or fouled spark plugs can contribute to hard starting and misfires.
Security System Issues
The 1999 Lincoln Town Car might be equipped with a security system (SecuriLock). If the system malfunctions or isn’t properly disarmed, it can prevent the engine from starting.
- Anti-theft System Malfunction: A problem with the security system could be inhibiting the fuel or ignition systems. Look for a rapidly blinking security light on the dashboard, which can indicate a security system issue.
Addressing the “No Communication to Scanner” Issue
This is where the diagnosis becomes more focused and potentially points to electrical or PCM-related problems. The inability to communicate with a scanner is a strong indicator that the PCM is either not powered up, malfunctioning, or there’s a break in the communication lines.
Blown Fuses and Relays (PCM Power and Communication)
The first and simplest check is to inspect all relevant fuses and relays. Specifically, look for fuses related to the PCM, ignition system, and data link connector (DLC) – the OBD-II port where you plug in your scanner. Refer to your owner’s manual or a wiring diagram for fuse box locations and identification. A blown fuse can cut power to the PCM or the DLC, preventing communication and potentially causing a no-start.
Wiring Problems (DLC, PCM Connections, Grounds)
Electrical wiring issues are common culprits in no-communication scenarios. This includes:
- Data Link Connector (DLC) Wiring: The DLC needs power and ground to function. Check for power at pin 16 and ground at pins 4 and 5 of the DLC. Wiring diagrams like the one below can be invaluable in pinpointing the correct pins.
DLC Connector Diagram
- PCM Power and Ground: The PCM requires both power and ground to operate. Check the PCM connectors for proper voltage and ground. Pinout diagrams like the following are essential for this step.
Alt Text: Diagram of a 1999 Lincoln Town Car PCM connector illustrating pin locations for power and ground checks.
- CAN Bus or Communication Lines: Modern vehicles use communication networks like CAN bus. Problems with these wires (shorts, opens) can disrupt communication between modules, including the PCM and the scanner.
PCM Failure
While less common than wiring or fuse issues, PCM failure is a possibility, especially in older vehicles. If all power and ground checks are good, and communication is still absent, a faulty PCM may be the cause. Replacing the PCM is a more complex task and may require programming.
Diagnostic Steps for a 1999 Town Car No Start and No Communication
Here’s a step-by-step approach to diagnosing your 1999 Lincoln Town Car’s no-start and no-communication problem, drawing from the experiences shared in online forums:
- Check Battery Voltage: Ensure the battery is properly charged and terminals are clean and tight. Low voltage can cause all sorts of electrical issues.
- Inspect Fuses and Relays: Thoroughly check all fuses and relays related to the PCM, ignition, fuel pump, and DLC. Replace any blown fuses.
- Test for Fuel Pressure: Use a fuel pressure gauge to check if fuel is reaching the fuel rail. If there’s no pressure, investigate the fuel pump, filter, relay, and inertia switch.
- Check for Spark: Use a spark tester to confirm if spark is present at the spark plugs. If no spark, investigate the crankshaft position sensor, camshaft position sensor, and ignition coils.
- Verify DLC Power and Ground: Use a multimeter to check for 12V power at pin 16 and ground at pins 4 and 5 of the DLC.
- Check PCM Power and Ground: Using wiring diagrams, identify the power and ground pins on the PCM connectors and verify they are receiving proper voltage and ground.
- Inspect Wiring Harnesses: Carefully inspect wiring harnesses, especially in areas that may have been disturbed recently (like around the driver’s door if work was done there, as mentioned in the original forum post). Look for damaged, corroded, or shorted wires.
- Consider Security System: If you suspect a security system issue, try any disarming procedures outlined in your owner’s manual.
- PCM as Last Resort: If all basic checks are exhausted and communication is still absent, PCM failure becomes a more likely possibility. Consider professional diagnosis or PCM replacement and programming.
Conclusion
Diagnosing a 1999 Lincoln Town Car with a no-start condition and no scanner communication requires a systematic approach. Start with the basics – fuel, spark, fuses, and relays – and then delve into the electrical system, focusing on power and ground to the PCM and DLC. The “no communication” symptom is a crucial clue pointing towards electrical or PCM-related issues. By following these diagnostic steps and using wiring diagrams, you can methodically narrow down the problem and hopefully get your Town Car starting and communicating again. If you’re uncomfortable with electrical troubleshooting, seeking professional help from a qualified mechanic is always a wise decision.
