Diagram How To Jump Ignition Relay On Chevy Truck

Alright, let's dive into jumping the ignition relay on a Chevy truck. This is a technique that can be incredibly useful for troubleshooting starting issues, diagnosing electrical problems, or even temporarily bypassing a faulty relay. While it's not a permanent fix, understanding this process can significantly enhance your diagnostic skills and get you out of a bind. We're going to focus on a typical, relatively modern (late 90s to early 2000s) Chevy truck setup, but the principles are broadly applicable across different years and models. However, always consult your specific vehicle's wiring diagram for the most accurate information. And by the way, we have a downloadable, detailed wiring diagram available for you, just keep reading!

Purpose of Understanding the Ignition Relay Jump

Why bother learning this? There are several reasons:

Troubleshooting Starting Problems: If your truck cranks but doesn't start, a faulty ignition relay could be the culprit. Jumping the relay allows you to bypass it and see if that resolves the issue.
Diagnosis of Electrical Issues: If other systems relying on the ignition circuit are malfunctioning, bypassing the relay can help isolate whether the relay itself is the problem or if the issue lies elsewhere.
Emergency Start: In a pinch, if your ignition relay fails completely and you're stranded, jumping the relay *might* get you going, although this should only be a temporary measure.
Understanding Automotive Electrical Systems: This is a great learning experience. By tracing the circuit and understanding the function of each component, you gain a deeper understanding of how your truck's electrical system operates.

Key Specs and Main Parts

Before we get into the diagram, let's review the key components and their specifications:

Ignition Relay: A small, electromechanical switch that controls power to the ignition system. Typically rated for 12V DC and a specific amperage (e.g., 20A or 30A). Located in the under-hood fuse box or relay center.
Fuse Box/Relay Center: Houses the ignition relay and other relays and fuses. Provides a central point for electrical connections and protection.
Battery: Provides the 12V DC power source for the entire electrical system.
Ignition Switch: The switch you turn with your key to start the truck. Sends a signal to the ignition relay to energize the ignition system.
Starter Solenoid: Receives power from the ignition relay (sometimes directly, sometimes through other components) and engages the starter motor to crank the engine.
ECM (Engine Control Module): The "brain" of the engine. Receives signals from various sensors and controls engine functions, including fuel injection and ignition timing.
Coil(s): Step-up voltage (thousands of volts) to the spark plugs to ignite the air/fuel mixture.

Diagram Symbols: Understanding the Language of Electricity

A wiring diagram is like a map for electrons. Understanding the symbols is crucial. Here are some common ones:

Solid Lines: Represent wires or conductors carrying electrical current. Thicker lines often indicate higher current capacity.
Dashed Lines: Usually represent wires or conductors carrying signal or control voltage.
Colors: Wires are color-coded to help identify their function. Common colors include red (power), black (ground), and various other colors for specific circuits. Refer to your specific wiring diagram for the color codes used in your truck.
Relay Symbol: A rectangle with a coil symbol inside and a switch symbol next to it. The coil represents the electromagnet that activates the switch.
Fuse Symbol: A wavy line inside a rectangle. Indicates a fuse that protects the circuit from overcurrent.
Ground Symbol: Usually three horizontal lines, decreasing in size. Indicates a connection to the vehicle's chassis ground.
Battery Symbol: Series of alternating long and short parallel lines, indicating positive and negative terminals.
Switch Symbol: A line pivoting to connect or disconnect from another line. Represents a mechanical switch.

The Specifics of the Ignition Relay Circuit

In a typical Chevy truck ignition relay circuit, you'll find the following:

Battery (+) → Fuse → Ignition Switch → Ignition Relay Coil
Ignition Relay Coil (other side) → Ground
Battery (+) → Fuse → Ignition Relay Switch (one side)
Ignition Relay Switch (other side) → Starter Solenoid and/or ECM Power and Coil(s)

Remember: this is a simplified representation. Consult your specific vehicle's wiring diagram for the complete circuit.

How It Works: Jumping the Ignition Relay

Jumping the ignition relay involves bypassing the relay switch contacts to directly supply power to the circuits that the relay normally controls. This should only be done for diagnostic purposes or as a temporary emergency measure.

Here's the basic process:

Identify the Ignition Relay: Locate the ignition relay in the under-hood fuse box or relay center. Your owner's manual or a wiring diagram will show its location.
Remove the Relay: Carefully remove the ignition relay from its socket.
Identify the Relay Terminals: Look at the bottom of the relay. You'll see a number of terminals. The diagram on the relay body *usually* indicates which terminals are the coil terminals and which are the switch terminals. The common labels are: 85, 86, 30, and 87. 85 and 86 are the control coil (low current side) and 30 and 87 are the switched high-current side.
Use a Jumper Wire: Using a fused jumper wire (a wire with an inline fuse – very important!), connect the 30 terminal to the 87 terminal on the relay socket. This bypasses the relay switch. Ensure the jumper wire is rated for the amperage of the circuit. Using too small of a gauge wire could cause it to overheat and melt, potentially creating a fire hazard.
Observe the Result: If the truck starts when you jump the relay, it strongly suggests that the ignition relay is faulty and needs to be replaced. If it still doesn't start, the problem lies elsewhere in the ignition system.

Real-World Use: Basic Troubleshooting Tips

Here are some troubleshooting tips when dealing with the ignition relay:

Check the Fuse: Before jumping the relay, always check the fuse associated with the ignition relay. A blown fuse is a common cause of ignition relay failure.
Listen for the Click: When you turn the ignition key, you should hear a "click" from the ignition relay. This indicates that the relay coil is being energized. If you don't hear a click, the relay coil may be faulty, or there may be a problem with the ignition switch or the wiring to the relay coil.
Relay Swap: If you have another relay in the fuse box that is the same type as the ignition relay (e.g., the horn relay or the accessory relay), you can try swapping them to see if that resolves the starting issue.
Visual Inspection: Check the relay for any signs of damage, such as cracks, burns, or corrosion.
Multimeter Testing: A multimeter can be used to test the continuity of the relay coil and the switch contacts. You can also use it to check for voltage at the relay coil terminals when the ignition key is turned.

Safety: Handling Risky Components

Working with electrical systems can be dangerous. Here are some safety precautions to keep in mind:

Disconnect the Battery: Whenever possible, disconnect the negative battery terminal before working on the electrical system. This will prevent accidental short circuits.
Use a Fused Jumper Wire: Always use a fused jumper wire when jumping the ignition relay. This will protect the circuit from overcurrent in case of a short circuit.
Wear Safety Glasses: Protect your eyes from sparks and debris.
Don't Work in Wet Conditions: Water and electricity don't mix. Avoid working on the electrical system in wet or damp conditions.
Consult a Professional: If you're not comfortable working on the electrical system, consult a qualified mechanic.
Be aware that jumping the relay bypasses safety features, like the neutral safety switch. Make sure the truck is in Park (or Neutral for manual transmissions) before jumping the relay.
The fuel pump will probably run continuously when you jump the ignition relay, so don't leave it like this longer than needed for testing.

Understanding how to jump the ignition relay on your Chevy truck is a valuable skill for any DIY mechanic. It allows you to diagnose starting problems, troubleshoot electrical issues, and even get yourself out of a bind in an emergency. However, it's important to remember that this is a diagnostic procedure and not a permanent fix. If you find that the ignition relay is faulty, replace it with a new one as soon as possible.

As promised, we have a detailed wiring diagram for a typical late-90s/early-2000s Chevy truck ignition system. While we can't embed it directly here for technical reasons, just contact us through the contact form on our website (link here: [insert fictitious link here]) and mention "Chevy Truck Ignition Relay Diagram" in your message. We'll email you a PDF copy free of charge! Good luck, and be safe out there!