I finally managed to start my car after nearly 3 months of troubleshooting why it wouldn't fire up. After checking sensors, wiring, engine compression, and mechanical timing, I ended up checking the oil pressure. With a fully charged battery and a backup on hand, I cranked it over multiple times—taking care not to overheat the starter motor—until it finally fired up.
After several days of electrical testing, the hydraulic lifters bled down, which made the engine struggle to start. This led me to drop the oil pan to inspect the engine for old oil sludge and contamination. If the lifters weren't pumping up properly, it was clear that oil circulation was severely compromised.
My suspicions were spot on. Upon removing the oil pan, I found a heavy buildup of sediment and hardened oil deposits at the bottom. Although I always performed oil changes on schedule, I didn't always use top-grade oil, which undoubtedly contributed to these consequences.
In addition to this sludge, the oil pickup tube screen was severely clogged, explaining why oil wasn't reaching the top end with enough volume to properly pump up the lifters. As seen in the image, it was restricted by small particles of RTV silicone left over from a previous valve cover gasket replacement.
I usually clean engine parts with gasoline, but the fuel quality in my country has degraded so much that it no longer cuts through heavy grease effectively. So, I decided to purchase a heavy-duty degreaser called H-7. Since it's imported, it was a bit pricey, but it works exceptionally well at stripping away years of baked-on oil and sludge.
As you can see in the photos, it turned out remarkably clean. The oil pan was left completely free of debris, especially where the oil pickup tube sits, which is the most critical area. The pickup tube itself came out extremely clean; cleaning the internal passages was the hardest part, but it cleared out completely without any remaining restriction. I reinstalled everything, and the oil pressure warning light on the dash turned off—the engine is now properly lubricating the cylinder head valve train.
