Experiencing difficulty starting your 1999 Mercedes C280 when the engine is warm? You’re not alone, and there’s a common culprit that might be causing your frustration. If your 99 Mercedes C280 cranks normally but refuses to start once it’s reached operating temperature, the Crank Position Sensor (CPS) is a prime suspect, just as it was in my case. This guide will walk you through understanding, diagnosing, and potentially resolving this issue yourself.
For owners of a 1999 C280, it’s important to note that this model does not have an Over Voltage Protection Relay, so we can rule that out as a cause. Instead, let’s focus on the Crank Position Sensor, a critical component in your engine’s operation.
Understanding the Crank Position Sensor in Your 99 Mercedes C280
The Crank Position Sensor plays a vital role in your 1999 Mercedes C280‘s engine management system. It monitors the position and rotational speed of the crankshaft. This information is essential for the engine control unit (ECU) to accurately time fuel injection and ignition. When the CPS malfunctions, especially when heated, it can send incorrect or no signals to the ECU, leading to starting problems, particularly when the engine is warm.
Locating the Crank Position Sensor on a 1999 Mercedes C280
The Crank Position Sensor on a 99 Mercedes C280 is located at the rear of the engine, on the driver’s side. Imagine it positioned like a spoke on a bicycle wheel, pointing downwards towards the crankshaft. Specifically, it’s situated just in front of the transmission bellhousing. Access can be a bit tight, but with a few simple steps, you can gain better visibility and access.
Step-by-Step Guide to Access and Remove the CPS on Your 1999 C280
To effectively access and remove the Crank Position Sensor on your 1999 Mercedes C280, follow these steps:
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Remove the Plastic Intake: The first and most helpful step is to remove the plastic intake duct that connects at the back of the engine. This component, while seemingly minor, significantly obstructs your view and access to the CPS. Removing it will dramatically improve your workspace.
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Disconnect the Electrical Plug: Once the intake is out of the way, you’ll clearly see the electrical plug connected to the Crank Position Sensor. Carefully disconnect this plug. Take your time and ensure you don’t damage the connector.
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Remove the Mounting Bolt: The Crank Position Sensor on the 99 Mercedes C280 is typically held in place by a single 8mm (E8) star pattern bolt. An E8 star socket is required to remove this bolt. A set of these sockets is readily available and affordable at most auto parts stores, including Harbor Freight. Remove the bolt completely.
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Slide Out the Old CPS: With the bolt removed, the Crank Position Sensor should slide straight out. It’s usually a snug fit, but it should come out relatively easily.
Ensuring You Order the Correct Replacement CPS for Your 99 Mercedes C280
Before ordering a replacement Crank Position Sensor for your 99 Mercedes C280, carefully examine the electrical connector on your old sensor. There are typically two connector types for this model:
- Two-Prong Connector: This type has two prongs positioned on opposite sides of the CPS connector (left and right).
- Single-Prong Connector: This type features a single prong located at the bottom of the CPS connector.
It’s crucial to order the replacement CPS with the correct electrical connector to ensure a proper fit and function. Many online retailers, like eBay, provide detailed pictures of the sensors, making it easier to identify the correct type for your 1999 C280. A Bosch CPS is a reliable replacement option.
Installing the New CPS and Getting Back on the Road
Installation is the reverse of removal. Slide the new Crank Position Sensor into place and secure it with the E8 bolt. Reconnect the electrical plug, ensuring it snaps in firmly. Finally, reinstall the plastic intake duct.
With the new CPS installed, your 99 Mercedes C280 should hopefully be free from the warm start issue. This relatively straightforward DIY repair can save you significant money compared to dealership or mechanic costs.
The wealth of information available online from fellow Mercedes enthusiasts is invaluable. Sharing experiences and solutions like this helps keep these cars running smoothly for years to come. Thanks to everyone who contributes to these online communities!
