How Do Oil Pressure Gauges Work?
Mechanical oil pressure gauges work almost like the pressure gauge on your air compressor in your garage. The plastic, copper, or braided Teflon oil pressure line connects between the oil gallery port on your engine and the back of the gauge, which uses a spring or a coiled tube with the display needle attached. The pressure within the line moves the oil pressure gauge needle. Whenever there’s a lack of oil pressure, due to either a pressure line issue, or an actual lack of engine oil pressure, the spring or coiled tube isn’t seeing any pressure and reflects that fact on the gauge face via the needle location. Electric oil pressure gauges use a sender that reads the pressure as a resistance value and sends that number to the gauge. With electric oil pressure gauges, if the gauge doesn’t reflect any oil pressure, it could be the sender, the wiring, or the gauge itself besides of course the possible unfortunate lack of oil pressure in your engine.
Do Oil Pressure Gauges Go Bad?
A gearhead’s worst nightmare is an oil pressure gauge sitting at zero. A flat oil pressure gauge doesn’t always mean the engine needs a rebuild, though. With both mechanical oil pressure gauges and electric oil pressure gauges, there are instances where the engine is perfectly healthy, so oil pressure gauges can and do stop working on their own. With both style of oil pressure gauges, you need to make sure the gauge isn’t at fault. That means checking the sender, wiring and gauge function of an electronic oil pressure gauge. With mechanical oil pressure gauges, checking the oil feed line and fittings at both the engine and the back of the gauge will help determine the cause of the issue. Regardless, if the oil pressure gauge goes to zero, immediately shut off the engine. Doing so, and figuring out why the gauge is at zero, whether it’s an internal engine issue or a defective oil pressure gauge kit, will go a long way in minimizing damage and repair costs.
How Do You Test Oil Pressure Gauges?
When your oil pressure gauge kit reads zero, the first thing to do is figure out if it’s the gauge or an actual engine issue. Testing electric oil pressure gauges is a matter of checking for ground, confirming a signal from the sending unit, and then checking for that signal at the gauge. If all the above are good, if it were us, we would even try another known good gauge just to make sure.
To check mechanical oil pressure gauges, first, use a drill and an oil pump attachment to confirm engine oil pressure. With the valve covers off, running the drill, and priming the oil pump, once you see oil come up through the valvetrain, you have oil pressure. However, with mechanical oil pressure gauges, you can also see the amount of oil pressure on the gauge using a drill. A mechanical oil pressure gauge kit consists of a fluid line from the engine to the gauge, and some use a 12-volt switched power and ground arrangement (usually though just for illumination or a warning light). Therefore, check to make sure there aren’t any leaks with the line and that you have power to the gauge. If you have confirmed oil pressure with a drill, the line is free of leaks and you have power to the gauge, the gauge itself could be bad. Try a known good gauge to double check for oil pressure. With any oil pressure gauge, try a gauge you know is good before going any further, and that includes a basic test gauge you would attach directly to your engine’s oil gallery port.
What Causes Oil Pressure Gauges to Fluctuate?
With all oil pressure gauges, even digital oil pressure gauges, if oil pressure fluctuates, there are things to look for if this happens. A fluctuating oil pressure gauge reading could be the result of a low oil level, too many miles between an oil change, a clogged oil filter, using the wrong weight oil, or a blocked oil passage. With the above issues, change to the right oil and add a new oil filter to see if this fixes the problem. Lastly, worn engine bearings or a bad oil pump can also cause an erratic oil pressure reading as well, but most often when an oil pump fails you will not have oil pressure at all.
What Are the Differences Between Electric and Mechanical Oil Pressure Gauges?
Mechanical oil pressure gauges use either a clear plastic, braided Teflon, or copper hard line running from the gauge to an oil gallery port on the engine. Most factory engines have a fitting on the engine for factory mechanical oil pressure gauges or electric oil pressure gauges. An electric oil pressure gauge kit uses an electrical sending unit with wiring ran to the gauge.
Shortfalls include a mechanical oil pressure gauge kit’s standard plastic line from the engine to the gauge. If that plastic gets damaged from heat or chafing, that means the line will eventually start leaking your engine’s oil, making a mess, and possibly causing a fire, so keep the line away from heat sources like headers or exhaust components and make sure to route the line in a way that it doesn’t get cut on the firewall or any sharp edges. Better yet, upgrade the original plastic line in your mechanical oil pressure gauge kit with a braided Teflon line for safety.
Electric oil pressure gauges can suffer a similar fate with its wiring being damaged by heat or chafing as well. While this will not create an oil leak or loss of oil pressure to your engine, it will render the gauge inoperable and not allow you to monitor your oil pressure easily. Furthermore, electric oil pressure gauges use a larger electric sending unit versus the mechanical gauge’s oil line fitting. Sometimes this larger sending unit can create fitment issues depending on where your oil gallery port is located and an adapter fitting or even off-engine mounting of the sending unit with a length of braided Teflon line might be necessary.