Best Relay Test Jumper Kits for Diesel Engines

When your diesel engine cranks but won’t start, or the fuel pump stays silent, a faulty relay is often the culprit. Testing relays without the right tools means piercing wires and juggling jumper leads—slow, risky, and frustrating.

This guide breaks down the best relay test jumper kits on the market, helping you choose the one that fits your workshop style, vehicle coverage, and budget. Whether you’re a pro mechanic or a DIYer, you’ll find the perfect tool to diagnose relay issues quickly and safely.

Lisle 56810 Relay Test Jumper Kit – Versatile Four-Jumper Set

The Lisle 56810 is a classic starter kit that includes four jumpers designed to fit the most popular relay sizes on domestic and import vehicles. You simply remove the relay, insert the correct jumper, and then plug the relay back in—no wire piercing or messy jumper connections needed. The green four-pin jumper requires careful pin alignment, but once you get the hang of it, testing becomes a breeze.

Each jumper features tabs for clamping and flat pads for placing test leads, making it easy to connect your multimeter. The blow-molded case keeps everything organized and protected. For diesel owners who work on a variety of vehicles, this kit offers solid coverage at a reasonable price.

View all product features

• Set includes four jumpers to fit the most popular size relays on domestic and import vehicles; simply remove relay to be tested, insert correct jumper and insert relay into jumper
• When using green four pin jumper be careful to align pins on jumper and relay correctly
• Jumpers have tabs for clamping and flat pads to place test leads on
• Set comes in blow-molded case for storage
• No need to pierce wires or connect multiple jumper wires

---

Lisle 60610 Relay Test Jumper Kit II – Quick Live Circuit Testing

The Lisle 60610 takes the hassle out of testing relays and live circuits. With no need to pierce wires or connect multiple jumper wires, you can quickly check relay operation directly. The jumpers come with tabs for clamping and flat pads for test leads, ensuring secure connections every time.

This kit is ideal for diesel engines where you need to verify power and ground signals without interrupting the circuit. The blow-molded case keeps the jumpers safe and easy to store. If you value speed and simplicity in your diagnostic routine, this kit delivers.

View all product features

• No need to pierce wires or connect multiple jumper wires
• Jumpers have tabs for clamping and flat pads to place test leads on
• Set makes testing relays or live circuits quick and easy
• Set comes in blow-molded case for storage

---

Lisle 69300 Master Relay and Fused Circuit Test Kit – Comprehensive Solution

For diesel mechanics who need maximum coverage, the Lisle 69300 is the ultimate kit. It includes eight jumpers to fit the most popular relays, plus a test lead kit that connects securely to your multimeter. The terminal leads with switch, fuse, and power options let you check current or voltage on many fuses and relays.

This kit also allows testing of relay configurations not covered by the eight jumpers, such as Volkswagen, BMW, and other European vehicles—a huge plus for diesel owners with imported rigs. The organized case keeps everything in place. If you want a one-stop solution for relay and fuse testing, this is it.

View all product features

• Includes 8 Jumpers to fit most popular relays
• Includes Test Lead Kit for easily and securely connecting Relay Test Jumpers to a multimeter
• Terminal Leads with switch, fuse and power options provide easy access to check current or voltage on many fuses and relays used on vehicles today
• Also allows testing of relay configurations not covered by eight Relay Test Jumpers, like Volkswagen, BMW and other European vehicles
• Relay Puller Pliers easily remove electrical relays; weorks without piercing wires

---

Sound Troubleshooting Automotive Relay Tester – Automatic Pin Detection

The Sound Troubleshooting relay tester simplifies relay diagnostics with automatic pin position detection. It checks the release time and consistency of the relay in each test phase, lighting up to indicate results. You just clip the alligator clips to your battery—black to negative, red to positive—and the red LED guides you through the process.

This tester works with most general-purpose automotive relays and requires a battery voltage between 11V and 15V, which is standard for diesel engines. Its compact design makes it easy to carry on the go. If you want a tool that does the thinking for you, this is a smart choice.

View all product features

• EASY TO USE – The tester will automatically detect the pin position, the release time of the action, and the consistency of the relay in each test phase. If the tester lights up the green LED light, the relay is normal; if the red LED light is on, the relay is abnormal. The relay puller makes it easy to remove the relays to be tested. USA Patented.
• FAST OPERATION – First, clip the alligator clip of the tester to the car battery, the black clip on the negative pole, and the red clip on the positive pole. When the red LED light is on, the tester is ready to start the test. Move the 4 Pin/5 Pin switch to match the number of pins on the relay. Select the appropriate socket according to the relay pins and configuration and insert the relay into the socket. Press the "Test" button, and the tester will automatically begin to operate the relay several times while checking all operations of the relay.
• VERSATILE FITMENT – Suitable for most general-purpose automotive relays on the market. When testing, it needs to be connected to the car's 11V-15V battery. The car battery must be a 12V battery, and the battery voltage must be between 11V-15V; 2. The applicable coil resistance is preferably above 20 ohms. *Not intended for use with all BMW relays*
• COMPACT DESIGN – Our automotive Relay tester is small and easy to carry around for on-the-go jobs or for easy storage. Its compact design allows easy use no matter where you are.
• SIMPLE AND EFFECTIVE – With our patented design this relay tester will give you the results you need quickly and easily. A red light means that the relay is bad, and a green light means the relay is good!

---

RVMARINEPAT Relay Bypass Switch 9038 – Multi-Vehicle Bypass Kit

The RVMARINEPAT 9038 relay bypass switch kit is designed for seamless compatibility with Audi, BMW, Volkswagen, GM, Chrysler, and more. It lets you bypass the relay to directly control circuits like the fuel pump, saving time during electrical troubleshooting. Simply plug the tester into the relay socket and operate the switch.

Built from high-quality materials, this kit meets or exceeds OEM standards, ensuring reliable performance. The 6-pack includes multiple relay testers for versatile applications. For diesel owners who work on various brands, this kit offers excellent flexibility and durability.

View all product features

• Wide Compatibility & Effortless Control: This Relay tester kit is designed for seamless compatibility with a wide range of vehicles, including Audi, BMW, Volkswagen, GM, Chrysler, and more. Our relay bypass kit also replaces multiple relay models (9038, 9036, 9037) and provides direct control over fuel pumps, window motors, headlights, and other components
• Save Time & Diagnose Faster: This diagnostic tester is very convenient. Quickly identify electrical issues and save valuable time during repairs. Simply plug the relay tester into the fuel pump relay position to gain direct control over the circuit and pinpoint problems
• Reliable Performance & Built to Last: Crafted from high-quality materials, this relay tester is rigorously tested to meet or exceed OEM standards. Our relay bypass switch kit enjoy consistent operation with its 20 amp continuous and 30 amp surge current (12V) capacity, ensuring long-lasting performance
• Complete Kit for Versatile Applications: This 6-pack 9038 includes multiple Relay Testers, giving you ample options for a variety of repair needs and making it a valuable addition to any mechanic's tool box
• Component Included: Our product include relay bypass switch kit 9036-1(36-LRG 20AMP), 9036-2(36-MED 20AMP), 9036-3(36-SML 10AMP), 9037-1(37-LRG 20AMP), 9037-2(37-MED 20AMP), 9037-3(37-SML 10AMP)

---

Lisle 56840 Blue Relay Test Jumper – Single Jumper Convenience

The Lisle 56840 is a single blue relay test jumper that offers the same convenience as the larger kits but in a compact form. You remove the relay, insert the jumper, and then plug the relay back in—no wire piercing or multiple jumper connections needed. The tabs and flat pads make it easy to attach test leads.

This jumper is perfect for diesel owners who only need to test one specific relay size and want a simple, affordable solution. It’s also a great backup to have in your toolbox. If you’re looking for a no-frills option, this delivers.

View all product features

• Simply remove relay to be tested, insert correct jumper and insert relay into jumper
• No need to pierce wires or connect multiple jumper wires. Jumpers have tabs for clamping and flat

---

Prismora 9038A Relay Bypass Switch – Amp Loop Monitoring

The Prismora 9038A relay bypass switch gives you powerful control over the fuel pump, independent of the key on/off system. This simplifies fuel injection testing on diesel engines. The built-in amplification loop allows you to use a clip-on amplifier probe or lab oscilloscope to monitor current, giving you deeper insights into circuit behavior.

Installation is plug-and-play—just plug it into the fuel pump relay position and flip the switch to control the circuit. It handles up to 20 amps continuous and 30 amps surge at 12V, running all automotive 12V DC motors. This kit is ideal for advanced diagnostics and fuel system testing.

View all product features

• Powerful: This relay bypass switch controls the fuel pump independently of the "key on/off" system, Simplifying fuel injection testing
• With Amplification Loop: The 9038A Relay Bypass Switch can be used with a clip-on amplifier probe/lab oscilloscope to monitor current
• Plug and Play: Simple installation, can be installed vertically or horizontally, just plug in the fuel pump relay position to directly control the fuel pump circuit.
• Operating Range: Maximum 20 amps continuous, 30 amps surge (12V), runs all automotive 12V DC motors with the flip of a switch
• Wide Applications: Relay Bypass Switch Kit fits most fuel pumps, cooling fans, window motors, headlight switches, air conditioning compressors and other devices using automotive relays

---

Sound Troubleshooting Relay Tester 4 & 5 Pin – Compact Auto Tester

This Sound Troubleshooting tester is designed for 4 and 5 pin relays, automatically detecting pin position, release time, and consistency. It lights up to indicate test results, making it easy to interpret. Connect the alligator clips to your battery—black to negative, red to positive—and the red LED guides you through the process.

It’s compatible with most general-purpose automotive relays and works with 11V-15V battery systems, typical for diesel engines. The compact design makes it easy to carry for on-the-go jobs. If you need a reliable tester for standard relays, this is a solid pick.

View all product features

• EASY TO USE: The tester will automatically detect the pin position, the release time of the action, and the consistency of the relay in each test phase. If the tester lights up the green LED light, the relay is normal; if the red LED light is on, the relay is abnormal. USA Patented
• FAST OPERATION: First, clip the alligator clip of the tester to the car battery, the black clip on the negative pole, and the red clip on the positive pole. When the red LED light is on, the tester is ready to start the test. Move the 4 Pin/5 Pin switch to match the number of pins on the relay. Select the appropriate socket according to the relay pins and configuration and insert the relay into the socket. Press the Test button, and the tester will automatically begin to operate the relay several times while checking all operations of the relay
• VERSATILE FITMENT: Suitable for most general-purpose automotive relays on the market. When testing, it needs to be connected to the car's 11V-15V battery. The car battery must be a 12V battery, and the battery voltage must be between 11V-15V. The applicable coil resistance is preferably above 20 ohms. Not intended for use with all BMW relays
• COMPACT DESIGN: Our automotive Relay tester is small and easy to carry around for on-the-go jobs or for easy storage. Its compact design allows easy use no matter where you are
• SIMPLE AND EFFECTIVE: With our patented design this relay tester will give you the results you need quickly and easily. A red light means that the relay is bad, and a green light means the relay is good
• COMPLETE TESTING KIT: Includes battery clips with alligator connectors for direct connection to your vehicle's 12V battery, making it a comprehensive diagnostic tool for electrical systems troubleshooting
• AUTOMATIC RELAY DETECTION: Features intelligent automatic detection that identifies 4-pin and 5-pin relay configurations, tests relay action timing, and verifies consistency across multiple test cycles for accurate diagnostics

---

Performance Tool 3009 Relay Tester – Self-Contained Pass/Fail

The Performance Tool 3009 lets you test relays outside the vehicle without clamping to a battery. It’s self-contained and provides instant results with a green LED for pass and red LED for fail. This makes it incredibly convenient for bench testing relays before installation.

It tests most common 12V 4 and 5 pin automotive relays found on today’s vehicles, including many diesel models. The compact design fits easily in a toolbox. If you want a no-fuss tester that gives clear answers, this is a great option.

View all product features

• QUICKLY TEST RELAYS OUTSIDE OF THE VEHICLE to check coil and switch contact function
• NO NEED TO CLAMP TO BATTERY – self-contained, accurate testing with instant results
• GREEN LED PASS & RED LED FAIL clearly indicates good or bad relay condition
• TESTS MOST COMMON 12 VOLT 4 & 5 PIN AUTOMOTIVE RELAYS found on today's vehicles
• COMPACT, ALL-IN-ONE DESIGN powered by included AA batteries

---

Lisle 56820 Relay Test Jumper, Yellow – Individual Jumper for Specific Relays

The Lisle 56820 is a yellow relay test jumper that works as part of the larger 56810 kit or as a standalone tool. It allows you to test relays or live circuits quickly and easily. Just remove the relay, insert the jumper, and plug the relay back in—no wire piercing or multiple jumper connections.

This jumper is ideal for diesel owners who need a replacement or want to test a specific relay size without buying a full kit. The tabs and flat pads ensure secure test lead connections. It’s a practical addition to any diagnostic toolkit.

View all product features

• Set of four relay test jumpers make testing relays or live circuits quick and easy
• Simply remove relay to be tested, insert correct jumper and insert relay into jumper
• No need to pierce wires or connect multiple jumper wires
• For more information check the main Lisle tool- 56810
• Replacement part for Lisle tool- 56810

---

Buyer’s Guide: What to Consider

Choosing the right relay test jumper kit depends on your vehicle type, testing habits, and budget. Here are key factors to consider before making a purchase.

• Relay Compatibility: Check the relay sizes and pin configurations (4-pin, 5-pin) your diesel engine uses. Kits like Lisle 56810 cover common sizes, while others like Sound Troubleshooting target specific pin types.
• Testing Method: Decide between jumper kits that require a multimeter and self-contained testers like Performance Tool 3009. Jumper kits offer more flexibility for live circuits, while self-contained testers are simpler for bench checks.
• Power Source: Some testers need a battery connection (11-15V), while others are battery-free. Consider your workspace and whether you often test relays outside the vehicle.
• Vehicle Coverage: If you work on multiple brands, choose a kit with wide compatibility like RVMARINEPAT or Lisle 69300, which also covers European models. Single-vehicle owners may prefer a simpler kit.
• Additional Features: Look for extras like amp loops for oscilloscope monitoring, test leads, or storage cases. These can enhance diagnostic capabilities and convenience, especially for advanced fuel system testing.

Conclusion

Relay test jumper kits are essential for diagnosing electrical issues in diesel engines. From the versatile Lisle 56810 to the advanced Prismora 9038A, there’s a tool for every need and skill level.

For most DIYers, the Lisle 56810 offers great value, while professionals may prefer the comprehensive Lisle 69300. If you want automatic testing, consider the Sound Troubleshooting tester. Choose based on your specific requirements and get back on the road faster.