The 7.3 glow plug relay, situated behind the fuel filter housing on the passenger side engine valve cover, is a critical component responsible for initiating the 7.3 Powerstroke diesel engine, especially in cold weather conditions. Since this engine lacks spark plugs, the role of glow plugs becomes paramount. Unfortunately, many users have encountered issues with their 7.3 glow plug relays, but early detection of symptoms could have spared them from these problems. In this article, we’ll explore how to identify when your 7.3 glow plug relay requires immediate attention.
Contents
Recognizing the Signs of a Faulty 7.3 Glow Plug Relay
1. Loss of Power
One of the most apparent indications of a malfunctioning 7.3 glow plug relay is when your engine suddenly stalls or fails to receive proper voltage or connections. When attempting to start the 7.3 Powerstroke engine, some owners encounter difficulties, resulting in excessive white smoke and an inability to start the engine, even with the block heater on. If no power is reaching the switched terminal or large terminals, it could point to a defective relay.
2. Faulty PCM
The PCM (Powertrain Control Module) may fail to ground the relay. To diagnose this, check for power on the ground circuit directly at the PCM. If you find power there, it suggests a faulty PCM.
3. Insufficient Voltage
Proper voltage should be present at the large lugs of the relay at all times, even when the ignition key is turned off. This voltage connects to the battery on the battery-side terminal of the solenoid on the fender. If there is no voltage, there may be a blown fusible link between the solenoid and the relay.
4. Incorrect Connections
The GPR (Glow Plug Relay) wire may be connected to the wrong side of the starter solenoid. Verify the connections for the correct configuration. You can use a test light to determine if the relay is functioning correctly by attaching one test lead to each of the two large terminals. The test light should illuminate when you turn the ignition key. Connecting the battery to one of the two big terminals, and when one test lead connects to the other big terminal and the second test connects to the ground, the light should be on when you turn on the ignition. If the opposite big terminal doesn’t receive power in this scenario, it indicates a faulty relay.
These are the most commonly identified symptoms that suggest a 7.3 glow plug relay failure. If you own a vehicle equipped with a 7.3 Powerstroke engine, it’s essential to be vigilant for these signs.
What to Do When You Detect a Faulty 7.3 Glow Plug Relay
The 7.3 glow plug relay is integral to the glow plug control unit, enabling you to control the current switch. A functioning relay is essential for the heating process required to start a 7.3 Powerstroke engine in cold weather. Here’s how to respond when you suspect a faulty 7.3 glow plug relay:
- Disconnect the wires from the small posts.
- Take jumper cables and connect the positive 12V to one small post and the negative to the other small post.
- The relay should emit an audible click at this point.
- Measure 12V on the large output lug of the relay, which should remain until you disconnect one of the jumper cable feeds.
Replacing a 7.3 Glow Plug Relay
To determine if your 7.3 glow plug relay needs replacement, use a digital meter to check for any voltage difference between the posts. There should be less than 0.3 volts of difference. If replacement is necessary, follow these steps:
- Remove the wiring harness.
- Mark the position of the four wires attached to the two large and two small terminals.
- Disconnect the wires.
- Unbolt the old relay from the valve cover.
- Bolt the replacement unit in place.
- Reattach the wires to the terminals.
The cost of replacing a 7.3 glow plug relay typically ranges from $500 to $750, inclusive of parts and labor.
Final Thoughts
7.3 glow plug relays play a crucial role in facilitating higher current circulation within the circuit. They are especially suited for older glow plug systems like the 7.3 Powerstroke. Consequently, even minor issues with the relay can have a significant impact. However, with preventive measures and a keen eye on the symptoms discussed above, you can keep your relay in good health and avert more severe problems down the road.
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