@davisfj62 I took your post and dropped it into a custom GPT I've been playing around with to try and make the FSM and Diagnostic Manuals more easily accessible and automated. Hope this helps!
Thanks for providing the details about your 1998 LC 100. It sounds like you've already done a lot of work on the vehicle, which helps narrow down potential issues. Here are a few potential causes and steps you can take to diagnose the problem:
### Potential Causes
1. **Fuel Delivery Issue**:
- Even though you've replaced the fuel pump and fuel lines, there could still be an issue with the fuel pressure regulator or a clogged fuel filter. If the fuel pressure drops, it could cause the engine to stall.
2. **Ignition System**:
- Although you've replaced the coil packs, there could be an issue with the ignition control module or crankshaft position sensor. These components can fail when they get hot and then work again once they've cooled down.
3. **Electrical Connections**:
- Heat can cause expansion and contraction of electrical connections, which could lead to intermittent failures. Check for any loose or corroded connections, especially around the battery, ignition system, and ground points.
4. **Vapor Lock**:
- This is less common with modern fuel-injected systems, but it's worth considering if the fuel is vaporizing in the lines due to heat.
5. **ECU (Engine Control Unit)**:
- While it's rare, the ECU itself could have an intermittent fault that doesn't throw a code.
### Diagnostic Steps
1. **Check Fuel Pressure**:
- Use a fuel pressure gauge to check the pressure at the fuel rail both when the engine is cold and after it has warmed up and started to die. Compare the readings to the specifications in the service manual.
2. **Inspect Electrical Connections**:
- Visually inspect and clean the electrical connections related to the ignition system, fuel system, and ECU. Look for any signs of corrosion or loose connections.
3. **Test Ignition Components**:
- Test the crankshaft position sensor and ignition control module with a multimeter to ensure they are operating correctly when hot.
4. **Monitor Live Data**:
- If you have access to an OBD-II scanner that can read live data, monitor the engine parameters while it's running and see if anything looks out of the ordinary when it starts to die.
5. **Vapor Lock**:
- Check the routing of the fuel lines to ensure they are not too close to heat sources like the exhaust manifold. Adding heat shields or rerouting the lines might help if vapor lock is suspected.
Resources
- Refer to the
LC100 Service Manual for specific procedures and specifications on checking fuel pressure and testing ignition components.
- For electrical connection diagrams and troubleshooting, see the section on Electrical Wiring Diagram Manual
Final Note
Don't get discouraged. Your Land Cruiser is a great vehicle, and with some thorough diagnostics, I'm confident you can pinpoint the issue. Good luck, and feel free to ask if you need further assistance!
