190E Fuel Pump Relay Location: Find It Fast and Fix Starting Issues

The fuel pump relay on your Mercedes-Benz 190E is located inside the main engine compartment fuse/relay box, typically mounted near the driver's side strut tower or close to the windshield/firewall. Finding this relay is crucial when troubleshooting hard starts, engine stalling, or a silent fuel pump when you turn the ignition key. Accessing it usually requires removing the black plastic cover of this box and identifying the specific relay using the diagram printed on the cover or in your owner's manual. For most W201 190E models, it's one of the several colored relays grouped together inside this central box.

Understanding its exact spot saves time and frustration when diagnosing fuel delivery problems. Let's break down the specifics step-by-step.

Why the Fuel Pump Relay Matters

The fuel pump relay acts like an automatic electrical switch. Its primary job is controlling power delivery to the electric fuel pump located inside the fuel tank. When you turn the ignition key to the "On" position, the engine control unit sends a signal to activate this relay. This closes internal contacts, sending battery voltage directly to the fuel pump, which pressurizes the fuel lines and enables the engine to start. A faulty relay interrupts this process. Symptoms mimic a dead fuel pump: cranking without starting, engine stalling shortly after startup, or a complete lack of pump priming noise. Knowing its location is the first step in confirming or ruling out this critical component.

Detailed Step-by-Step Location Guide

  1. Locate the Engine Compartment Fuse/Relay Box: Open the hood. Stand facing the windshield. Look for a prominent, rectangular black plastic box. It is mounted near the driver's side (left side for North American LHD vehicles, right side for RHD vehicles) either:
    • On the upper fender ledge next to the windshield washer reservoir and driver's side strut mount, or
    • Along the firewall/bulkhead behind the engine bay.
  2. Remove the Cover: This box has a removable cover secured by plastic clips, sometimes with additional screws. Carefully unclip or unscrew and lift the cover straight off. Set it aside safely.
  3. Identify the Fuel Pump Relay: Inside the box, you'll find an array of fuses and several colored plastic cube-shaped relays (often blue, yellow, white, black, or green). The fuel pump relay is one of these cube relays. Your primary identification tools are:
    • Cover Diagram: The underside of the cover you just removed has a printed diagram or chart. This map shows the position and function of every fuse and relay inside the box. Find "Fuel Pump" or "Kraftstoffpumpe" (German) on this diagram – note its position number or physical location relative to others.
    • Relay Label: In later models, the relay itself might have small printed text like "FP" (Fuel Pump), "F/P", "87", or "K." on its top or side. Compare this to others.
    • Color/Location Clues (Use with Diagram): While not universal, the fuel pump relay in many 190Es is a green relay, sometimes positioned near the center or top of the relay section within the main box. Never rely solely on color! Always cross-reference with the diagram. Typical position numbers vary but are often in the range of positions 1-10 for the relays.
  4. Note Position and Removal: Before removing the suspected relay, note its exact position and orientation (how the pins face). Relays plug in firmly but are removable by hand. Grasp it firmly and pull straight out. If stuck, gently wiggle while pulling.

Tools Needed (Minimal)

Accessing the fuel pump relay requires no special tools. Simply have:

  • Your hands (to unclip the box cover and pull the relay)
  • A flashlight (for better visibility inside the box, especially in dim conditions)
  • A small flat-head screwdriver may be helpful if a cover clip is stubborn, but use gentle prying to avoid breaking plastic.

Symptoms Indicating a Possible Faulty Relay

Suspect the fuel pump relay if you experience:

  • No Start, Engine Cranks: Engine turns over but doesn't fire up. No buzzing or humming sound heard from near the rear wheels/tank area for 2-3 seconds when turning the key to "On".
  • Engine Stalls After Starting: Starts briefly, then dies a few seconds later. The relay contacts might be failing.
  • Intermittent Starting Issues: Sometimes starts fine, other times exhibits no-start symptoms. Heat can worsen intermittent relay failures.
  • Silent Fuel Pump: Confirmed absence of the fuel pump priming noise at key-on. (Important: Also check relevant fuses before condemning the relay).

Testing the Relay (Basic Method)

While specialized testing with a multimeter is most accurate, a simple swap test is effective:

  1. Find a known working relay of the same part number/type within the same fuse/relay box. Common candidates often include identical-looking relays for lights (Headlight/Hi-Beam) or the purge valve (ATX). Ensure the substitute relay matches the pin configuration and rating.
  2. Swap the suspected fuel pump relay with this known good relay.
  3. Turn the ignition key to "On" and listen for the fuel pump priming sound.
  4. Try starting the engine.
  5. Result: If the car starts normally after the swap (and the component controlled by the borrowed relay still functions), the original fuel pump relay is likely faulty. If the problem persists, the relay may be okay, and further diagnosis is needed (fuses, pump, wiring, ECU signal).

Replacing the Faulty Relay

  1. Confirm Failure: Use the swap test above or multimeter testing to be reasonably sure the relay is bad.
  2. Source Replacement: Get an exact match:
    • Part Numbers: Common OEM Bosch numbers include 0 332 014 137 (older style), 0 332 014 135 (green), or 0332014019 (blue). Check the number printed directly on your old relay.
    • Purchase: Buy from Mercedes-Benz dealers, reputable auto parts stores (ensure Mercedes application), or specialized online retailers. Using a quality OEM (Bosch, Hella) or OEM-equivalent relay is recommended over cheap generics for reliability.
  3. Install: With ignition OFF, insert the new relay into the exact socket in the correct orientation (match the pin layout to the socket). Push firmly until seated.
  4. Test: Turn key to "On," listen for pump prime, then attempt to start.

Troubleshooting If Problems Persist

If replacing the relay doesn't fix the issue:

  1. Recheck Fuses: Inspect all relevant fuses in the engine compartment box and the interior fuse box (often near driver's knees) – especially any marked "Fuel Pump," "Injection," "DME," or similar. Replace blown fuses, but investigate why it blew.
  2. Fuel Pump Circuit: Problems can lie in the fuel pump itself, wiring from the relay to the pump (check for corrosion/breaks), ground connections, or the fuel pump power connector at the tank/pump hanger.
  3. ECU Signal: The ECU must send the activation signal to the relay coil. This requires good power/ground to the ECU, functioning crank/cam sensors providing signal for engine start detection, and intact wiring to the relay's control terminal. Diagnostic scan tools or specialized wiring checks are needed here.
  4. Ignition Switch: Worn contacts in the ignition switch can prevent the initial signal needed for relay activation when turning the key.
  5. Fuel Pump: The pump itself could be seized or burnt out. Confirm if it gets power at its connector during key-on (requires testing at the rear) to isolate the issue.

Model Year Considerations

While the fundamental location (main engine compartment fuse/relay box) is consistent across the W201 190E production (1983-1993), be aware:

  • Exact Box Position: Its mounting spot might shift slightly depending on the year and engine (e.g., 190E 2.6 vs 2.3 vs 2.5) but remains on the driver's side near the strut tower/firewall.
  • Relay Position/Color: The specific slot number or color of the fuel pump relay within the box can vary. Always prioritize the diagram under the cover or in the manual over generic descriptions. Later models might use slightly updated relay designs.
  • Early Models: Pre-facelift cars might have minor relay layout differences, reinforcing the need to use the diagram.

Final Tips

  • Manual is Key: If possible, consult your specific year's Mercedes-Benz 190E Owner's Manual or Workshop Manual for the definitive relay position diagram. Online sources like enthusiast forums can also have specific photos.
  • Photo Before Removal: Use your phone to take a picture of the relay box interior before removing any relays. This provides a quick reference for positioning.
  • Safety First: Always disconnect the negative battery terminal before extensive wiring checks to prevent shorts. Handle relays with clean, dry hands. Ensure ignition is OFF before relay removal/installation.
  • Quality Parts: Invest in a high-quality replacement relay to ensure longevity and reliability. Cheap relays fail prematurely.

Knowing the 190E fuel pump relay location within the engine compartment fuse box is essential DIY knowledge. This information empowers you to quickly diagnose no-start issues, test the component efficiently, and perform a relatively simple and inexpensive fix. By following the precise location steps and using the provided troubleshooting guidance, you can effectively resolve one of the most common fuel system problems on your classic Mercedes-Benz 190E.

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