Owner's Problem Description
The owner reports that the 1990 Volvo 740 GLE, with 210,000 miles, won't start after a recent tune-up. They noted it started fine before the maintenance work. The owner suspects a loose wire connection due to the issues occurring after the service. Currently, the battery has been drained from repeated starting attempts, and they're charging it overnight to try again. Previous repairs included standard tune-up components like spark plugs and wires.
Professional Technical Analysis
The 1990 Volvo 740 GLE is equipped with a 4-cylinder engine, automatic transmission, and has approximately 210,000 miles on the odometer. The vehicle has recently undergone a tune-up that included spark plug and wire replacement. Following this maintenance, the owner reports that the engine fails to start, indicating potential issues related to the ignition system or fuel delivery. The sequence of events suggests either a misconnection or a failure in the ignition components, particularly since the car started without issues just prior to the tune-up. Considering the age and mileage, a thorough check of the ignition coil, spark plug wires, and battery condition is warranted. Additionally, a proper firing order of 1-3-4-2 must be verified along with secure connections at the spark plugs and distributor cap. The battery has been drained due to multiple start attempts, which adds a layer of complexity to the diagnosis. Intermittent issues like this often stem from poor electrical connections or component wear, necessitating careful inspection of the wiring harness and connectors. Tools such as a multimeter will be essential for verifying voltage and continuity in the ignition system. The immediate priority must be to ensure the battery is fully charged and then test for spark at the plugs, followed by checking the fuel system to rule out delivery issues.
Possible Causes
Most common causes (ordered by frequency):
- Loose ignition wire connections: After a tune-up, it is common for ignition wires to be improperly seated or connections to be loose, which can prevent the ignition system from functioning correctly. A check of the spark plug wires and connections to the distributor is necessary. If the wires are not firmly connected, it could lead to no spark being generated at the plugs. - Symptoms include no spark at the plugs when tested, visible loose connections at the distributor cap.
- Ignition Coil Failure: The ignition coil may have failed or developed a fault. If the coil is not supplying adequate voltage to the ignition system, it can prevent the engine from starting. Testing the ignition coil output voltage should be performed; normal output should be around 12V-15V. - No voltage present at the coil when the key is turned to the 'on' position, possible stored fault codes pointing to coil issues.
- Fuel Delivery Issue: If the vehicle is not receiving fuel, it will not start. This could be due to a faulty fuel pump, clogged fuel filter, or issues with the fuel injectors. Testing fuel pressure at the rail should show 35-45 PSI. If the pressure is low, further investigation into the fuel system is necessary. - Symptoms may include engine cranking without starting, smell of fuel, or low pressure readings.
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 - Battery Check: Start by ensuring the battery is fully charged. Given that the owner drained the battery during repeated starting attempts, connect a battery charger and let it charge overnight. Once charged, check the battery voltage; it should be around 12.6V or higher.
- STEP 2 - Spark Test: After confirming the battery is charged, perform a spark test. Remove a spark plug wire, insert a spark tester, and crank the engine. There should be a strong blue spark if the ignition system is functioning correctly. If no spark is present, check the ignition wires and coil connections.
- STEP 3 - Fuel Pressure Test: If a spark is present, the next step is to check the fuel system. Connect a fuel pressure gauge to the fuel rail and ensure it reads between 35-45 PSI. If the pressure is low, check the fuel pump and filter for any blockages or failures.
- STEP 4 - Inspect Ignition Components: Finally, inspect the ignition coil and wires. Use a multimeter to test the coil's primary and secondary resistance; primary should be around 0.5-1.5 ohms and secondary should be around 6,000-15,000 ohms. Ensure all connections are secure and free from corrosion.
