Addressing the Engine Start Issue: Can a Bad Oil Pump Be the Culprit?

When your engine needs a rebuild, ensuring that all components are functioning optimally is crucial. One common concern that arises is whether a bad oil pump can prevent an engine from starting. In this article, we will explore the relationship between a faulty oil pump and engine starting issues, along with tips to ensure a smooth start after a rebuild.

Understanding the Role of the Oil Pump

The oil pump is a vital component in any engine. Its primary function is to distribute lubricating oil to various moving parts, ensuring they receive the necessary lubrication to function correctly. Without a properly functioning oil pump, the engine cannot operate safely and efficiently. A faulty oil pump may lead to low oil pressure, which can cause severe damage to the engine if left unchecked.

During an engine rebuild, it's critical to install a new oil pump. If you have fitted a new oil pump but are still experiencing starting issues, it might be due to a lack of proper priming or other related issues. However, a genuinely 'bad' oil pump typically won't present a starting issue directly but can lead to stalling or other operational problems once the engine is running.

Common Causes Leading to a Rebuild

Many factors can necessitate an engine rebuild. Low oil pressure is a common culprit, often caused by a faulty oil pump. This can lead to a variety of issues, including noisy lifters and even a shutdown of the fuel system if a low oil pressure switch is installed.

Rotating the distributor is essential to assess the health of the oil pump during a rebuild. If you notice that the distributor does not rotate when you crank the engine, there might be a failure in the drive mechanism. In such cases, the oil pump would not function, leading to a failed start.

Priming the Oil System

Priming the oil system correctly is crucial for a successful engine start, especially after a rebuild. Here are some steps to follow:

Prelube with Lubricant: Use prelubrication with oil assembly lubricant or gasoline, as in the case of my 3.8-liter Buick L36 V6 engine. This can help displace any air from the oil pump and ensure proper lubrication. Check for Air Locks: Ensure there are no air locks inside the cylinder that could hinder oil circulation. Use a pressure gauge during this process to determine if the issue is resolved. Use Proper Pre-Lubricants: For more modern engines, use specialized lubricants like molybdenum disulfide grease, as demonstrated when I replaced the hydraulic lifters in my 5.7-liter Chevrolet LS1 V8 engine. Open Oil Gallery Plug: This allows you to fill the oil pump with oil before starting the engine, especially if the pump has been removed during the rebuild. Cold Cranking: Give the engine a few cranks to prime the system with oil before starting it.

Other Common Start Issues

While a bad oil pump is not typically the direct cause of starting issues, other factors can contribute. For instance, leaving a connector disconnected can result in a no-spark issue, as I discovered when I connected a previously disconnected ignition connector and the engine started running.

Always double-check all electrical connections and fuel lines to ensure they are properly connected and operational. Additionally, make sure the ignition system is functioning correctly.

Conclusion

A bad oil pump can indeed contribute to starting issues in a rebuilt engine, but it is more likely to cause problems while the engine is running, such as low oil pressure and related malfunctions. To avoid these issues, ensure you have a properly functioning oil pump and follow the steps to prime the oil system correctly. Regular maintenance and attention to detail can help prevent many of the common issues that arise after an engine rebuild.