If the fuel gauge is way off, there’s definitely a chance there’s a problem with the pump ass’y ground connection. That would show up by probing the power connection at the pump ass’y. There should be no difference where the ground connection is probed, either at the pump itself, or the nearby chassis. It’s usually possible to hear the fuel pump running, you may need to device a stethoscope of some sort, listen to the end of a stick held against the fuel pump, use a length of discarded garden hose, etc. If you know for certain there’s a problem with the oil pressure/fuel pump switch, fix that first. The fuel pump has to be working for your truck to run properly. As mentioned above, that configuration is to protect the engine in the event the oil pressure gets too low. So first on the agenda, make sure your oil pressure is ok using a shop oil-pressure gauge.
So last week, I managed to replace the oil pressure/fuel pump switch. The space is very tight, even with the proper tool to replace the switch. When I removed the distributor cap, I noticed some oily residue and green rust, so I replaced it as well with a Delco brand. I also replaced the fuel pump relay. All this week, the truck starts easier and fast, but what I did not expect was how the truck now is driving uphills (that I always drive) much easier and in higher gear, and the engine seems way more smooth. Now that is a very pleasant surprise because my overall plan was to increase a few extra horsepower from the engine and make it more gas efficient. Id did an amp test of the pump from the fuel pump relay port, and I got 5.38 amps. Neither of my manuals, Chilton and Haynes) specifies an amp draw for the fuel pump, but the internet says that these pumps can run from 3 to 5 amps, so I was hoping I am right on target. Since my gas gauge is still way off, indicating way more gas than what I really have and never going down more than three quarters, that I would clean a new chassis spot, bolt a new ground wire, and add it to the existing fuel pump ground. The idea is to avoid dropping the gas tank. I was also thinking of replacing the gas tank cap and replacing my current paper air filter with a K&N Engine Air Filter, High Performance, Washable, Replacement Filter (just the filter, not the whole air distribution tubing since I think that would not increase anything).
What do you think? And thank you for your help!
The company I worked for tested the K & N air filter for efficiency.
When the testing was over I asked the technician who ran the test what they thought of the K & N filter.
Their response was, " If you want to keep birds and chipmunks out of your engine, that’s the filter to use."