* Faulty Injector: The most likely culprit. Even with good spark and reasonable compression, if the injector isn't delivering fuel, you won't get combustion. Test the injector's spray pattern and flow using a fuel pressure gauge and a suitable injector tester (or have a mechanic do it). A simple resistance check with a multimeter might also reveal a faulty injector, but it's less definitive.
* Valve Issue (though less likely given the compression): While 150psi isn't terrible, a slightly bent or burnt valve could still restrict airflow enough to cause a dead cylinder, especially if it's only slightly off. A leak-down test would be crucial here to determine if there's any significant air escaping past the valves in #1 cylinder. Low compression *could* also indicate worn valve seals, although 150 psi isn't dramatically low.
* Blocked Intake Manifold or Runner: A blockage in the intake manifold, specifically the runner leading to cylinder #1, would starve that cylinder of air. Inspect the intake manifold for any debris or restrictions.
* Clogged Fuel Filter: A severely clogged fuel filter would restrict fuel flow, potentially impacting injector performance.
* Wiring Issue (Less likely): Double-check all the wiring related to cylinder #1: injector wiring, spark plug wire, and any related sensors. Look for breaks, corrosion, or loose connections.
Troubleshooting Steps:
1. Fuel Injector Test: This is the most important step. Test the #1 injector as described above.
2. Leak-Down Test: This is the best way to diagnose valve issues or piston ring problems. This test is best left to a mechanic unless you're experienced in engine repair.
3. Visual Inspection: Thoroughly inspect the intake manifold runners and the area around the #1 cylinder's intake port for any obstructions.
4. Compression Test (Again, More Precisely): While you've already done a compression test, re-run it to ensure accuracy. Ideally, you should have a consistent reading across all cylinders within a small margin. A significant difference between #1 and other cylinders confirms a problem in #1.
5. Fuel Pressure Test: Measure fuel pressure at the fuel rail. Low fuel pressure can also cause a cylinder to misfire.
Important Note: 150 psi is relatively low compression for a normally aspirated engine, even an older one. While it *might* not be the direct cause of the dead cylinder, it does suggest that other issues might be present or developing in the engine. You should address the lower compression regardless.
If you're not comfortable performing these tests yourself, take your Geo Storm to a qualified mechanic. They have the tools and experience to diagnose the problem accurately and efficiently. Describing the symptoms clearly (dead cylinder, 150psi compression, good spark and timing) will help them pinpoint the issue quickly.
