Troubleshooting Zero Oil Pressure in Bobtail Dump Truck with Ford 385 Lima Engine

Question:

In around 1979, there was a Bobtail dump truck with a Ford "385 Lima" engine of 370 cid that I was working on. While test driving the truck after some repairs, I noticed the oil pressure reading was zero. Despite replacing the electric sending unit with a mechanical gauge, the pressure remained at zero. Upon further inspection, I discovered that no oil was coming out from the 1/4" pipe fitting. The dipstick showed the oil level as full, but upon draining the oil, around 8 quarts came out. After examining the engine, it seemed to be in good condition with no sediment or sludge in the pan. I pulled out the oil pump for a bench test and it seemed to be functioning properly. However, I am now investigating if there could be a broken tube inside the engine that is responsible for routing oil to the sending unit port. The factory manual I found for the truck mentions a different location for the sending unit, but it does not match the setup in my particular truck. I am uncertain if this is the original block/engine. The sending unit appears to be located at the upper surface of the block near the firewall, past the end of the intake manifold. I attempted to clear any obstructions in the sending unit port but did not find anything. I am now considering the possibility of a broken tube within the engine causing the issue.

Top Replies

I'm unsure, but I'll make an educated guess. It's unlikely that there is a tube inside the engine block; typically, I've only observed the port at the end of the oil gallery. However, stranger things have occurred in the past. To troubleshoot this issue, my next step would be to pressurize the oil system by reinstalling the pump and using a dummy shaft or a garden sprayer with a valve. Alternatively, compressed air could be used for a cleaner approach. One of these methods should provide a clear indication of the oil flow path.

It is unusual that if an engine doesn't have enough oil pressure, it will begin to make a loud rattling noise. Recently, we started a Ford 302 for the first time and noticed that none of the gauges were functioning properly. Despite this, the engine seemed to be running smoothly. It was then that a colleague mentioned the possibility of there being an issue with the oil pressure. I decided to check by loosening the oil filter while the engine was still running. To our relief, it was revealed that there was indeed good oil pressure. We quickly grabbed some shop rags to clean up any oil spills. It was a moment we will definitely remember and laugh about!

To rotate the oil pump, use a drill with the appropriate extension and socket on its hex shaft. What does the distributor's end appear like?

Upon reviewing the manual for oil pump inspection, a thorough investigation into the pump's operation and disassembly is necessary to determine if the bypass is malfunctioning. The search is on for the root of the issue. The distributor to oil pump drive shaft shows no signs of failure yet, but it will be the next component to be inspected. It is suspected that the oil pump or its bypass may be the culprit, and a new pump is anticipated to be the solution to the problem.

Before doing anything else, I would recommend removing the distributor first. Have you attempted to rotate the pump shaft with the oil pump taken out? The pump shaft connects to the bottom of the distributor drive gear, so it should not turn easily.

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Frequently Asked Questions (FAQ)

FAQ: 1. Why is the oil pressure reading zero in my Bobtail dump truck with a Ford 385 Lima engine?

Answer: Answer: The zero oil pressure reading could be due to issues with the oil routing system, potentially caused by a broken tube inside the engine.

FAQ: 2. How can I troubleshoot zero oil pressure despite replacing the sending unit and confirming a full oil level?

Answer: Answer: To troubleshoot zero oil pressure, consider checking for any obstructions in the sending unit port, examining the oil pump for proper function, and investigating the possibility of a broken oil routing tube within the engine.

FAQ: 3. What steps can I take if no oil is coming out from the pipe fitting despite a full oil level in my Bobtail dump truck?

Answer: Answer: If no oil is coming out from the pipe fitting, draining the oil to check the quantity, inspecting the oil pump, and investigating for any broken oil routing tubes within the engine could help identify the issue.

FAQ: 4. How can I determine if there is a broken tube inside the engine affecting oil pressure in my Ford 385 Lima engine?

Answer: Answer: To determine if there is a broken tube inside the engine affecting oil pressure, consider inspecting the oil routing system, particularly the area around the sending unit port, and compare the setup with information from the factory manual, even if it does not match exactly.

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