Owner's Problem Description
The owner reports that their 1988 Ford F350 diesel truck ran out of diesel fuel and now won't start again. They mentioned previous use of starting fluid, which could have harmed the glow plugs. The glow plug relay was replaced about four months ago, but they aren't hearing the usual click from it now. The owner wishes to keep the truck running due to its unique artwork on the box.
Professional Technical Analysis
This 1988 Ford F350 diesel truck, equipped with a 7.3L IDI engine and an automatic transmission, is experiencing a no-start condition after running out of fuel. The vehicle has approximately 200,000 miles on the odometer. The owner reports that the glow plugs were recently replaced, but the glow plug relay does not seem to be functioning as expected. In diesel engines, an operational glow plug system is crucial for proper starting, especially in colder temperatures. The absence of the clicking sound from the glow plug relay indicates a potential failure, which could prevent the glow plugs from heating adequately. Additionally, if the fuel system has air in it from running out of fuel, it may require bleeding. Glow plug operation typically requires around 12V to ensure proper heating, and the relay should engage upon turning the ignition key to the 'ON' position. Testing the glow plug relay with a multimeter can confirm if it is receiving and outputting the necessary voltage. If the relay is confirmed faulty, it should be replaced with an OEM part (such as P/N F7TZ-10B198-A). Further, checking the fuel system for any leaks or blockages and ensuring the run solenoid on the injection pump is receiving 9V during cranking is essential for diagnosing the no-start condition. Overall, this case requires a thorough investigation of the glow plug system and fuel delivery to ensure reliable operation.
Possible Causes
Most common causes (ordered by frequency):
- Glow Plug Relay Failure: The glow plug relay may not be functioning properly, which is confirmed by the absence of the usual clicking sound when the ignition key is turned to the 'ON' position. The relay should output 12V to the glow plugs for proper heating during starting conditions. If the relay is defective, it should be replaced with OEM part F7TZ-10B198-A, which is common for this model. The glow plugs require around 10-14 seconds of operation for adequate pre-heating before cranking. - No click sound from the glow plug relay when the ignition is turned on, which indicates it may not be supplying power to the glow plugs.
- Fuel System Air Lock: Running out of fuel may have introduced air into the fuel system, leading to a no-start condition. The vehicle's fuel system requires bleeding to remove any trapped air. This can be confirmed by loosening the injector line and cranking the engine to check for fuel flow. If no fuel is present, air must be purged from the system. - No fuel flow from the injector line when loosened indicates the need for bleeding the fuel system.
- Faulty Glow Plugs: If the glow plugs are damaged or burnt out, they will not heat properly, leading to starting difficulties. Glow plugs typically have a resistance of 0.5-1.5 ohms when functioning correctly. A multimeter can be used to test the resistance of each glow plug individually to determine if any need replacement. - Resistance measurements of the glow plugs show values outside the normal range, indicating failure.
Diagnostic Steps
Professional Diagnosis Process
Follow these systematic steps to accurately diagnose the issue. Each step builds on the previous one to ensure accurate diagnosis.
- STEP 1 - Glow Plug Relay Testing: Start by turning the ignition key to the 'ON' position and listen for the click from the glow plug relay. If no click is heard, use a multimeter to check for voltage at the relay terminals. A reading of 12V indicates proper operation; if absent, the relay may be faulty.
- STEP 2 - Fuel System Bleeding: If the relay is functioning, the next step is to check for fuel delivery. Loosen an injector line and crank the engine to see if fuel flows. If no fuel is present, bleed the fuel system by loosening the fuel filter and allowing air to escape until a steady flow of diesel is observed.
- STEP 3 - Glow Plug Resistance Check: With the relay operational and fuel system bled, check the glow plugs' resistance using a multimeter. Each glow plug should read between 0.5-1.5 ohms. If any glow plug reads higher, it should be replaced to ensure proper starting conditions.
