Probably not. The Samson meter is more accurate than the reflexes in a human hand – it divides every single quart into 310 units of individually measured teeny tiny parts – try to stop it at precisely 5.00 Quarts, and you’ll agree. So, while we advertise the meter as accurate + or – a half of a percent, it is actually measuring down to a third of a percent – about a tenth of an ounce of oil.

So why is this the most Frequently Asked Question? We’ve tracked down several answers you might consider.

The Dipstick:

The dipstick can only serve as a general guide and could have an error anywhere from 5% or so on up. If you are judging the accuracy of the meter by the dipstick you might find a meter that is likely broken and wildly out of calibration, but you certainly can’t use a dipstick evaluation to calibrate the meter.

Air bubbles:

While the meter cannot create any air bubbles in the oil, it will certainly measure them. When air is mixed in with the oil, the actual amount of oil is less that what is indicated on the meter. There is a suction leak at the pump that needs to be repaired, or possibly air was not bled out of the piping after the tank was run dry.

Comparing new/old meters:

Someone gets a new meter and discovers the amount of oil they were used to dispensing in a particular vehicle is different than the amount shown on the new meter. Maybe they overfill a crankcase by a quart or something like that. This can happen when the old meter is worn and inaccurate, and the new meter is, well – new and accurate.

Using a five quart oil jug to gauge accuracy:

This happens a lot. Someone gets a leftover five quart (or even worse, a one quart) commercially packaged oil jug with the clear stripe markings on the side. Castrol, Mobil, the brand does not matter. The issue with these jugs is that they are not accurately marked, at least not in the league of the accuracy of the gun (a tenth of an ounce of oil) but even more importantly they are too flexible to give an accurate reading. Go ahead, squeeze it and you’ll see – maybe it has a little dent in the bottom corner – maybe there’s a few ounces left over in the bottom – you get the idea.

It used to be right on, but it’s drifted out of calibration:

There is a screen inside the swivel of the gun where it attaches to the hose. If this screen gets clogged it impedes the flow of oil and can affect the accuracy.

So, you’ve eliminated all of the possibilities except that the gun is not broken and is definitely in need of calibration. First, get your Service Manual that was shipped with the gun. I’m kidding, I know you threw it away, just like I would. You can get a copy on the Samson Website. Read the instructions, it is pretty simple, since the gun does all the math for you.

What you really need is a certified one gallon measure, or even better a certified five gallon measure if you really want to take advantage of the built in accuracy of the gun, but those are really expensive. The Samson 2377 five quart jug has proven over the years to be very accurate, and it has hard sides so the volume won’t vary if you squeeze it. Before you start calibrating, go ahead and dispense five quarts into the jug and look it over. Look in the top. Are there air bubbles? Fix the pump or bleed the system if you find any air bubbles at all. Set the jug on a *perfectly* level surface. Does it show five quarts? If it is at the five quart line, or touching it above or below the line you should probably stop, you are not going to be able to manually calibrate the gun any better than it is already calibrated. If it is off and needs calibration, it will be off by more than one eighth of an inch above or below the line.

Finally, if you are convinced the gun needs calibration, go ahead.

  1. Look in your tank/drum and see if you have any oil/grease. Seriously. It happens a lot, people don’t realize the container is empty.
  2. Check the air. Look at the gauge on the air regulator at the pump, you should see somewhere between 40SPI and 100PSI on the gauge. Disconnect the quick air coupler at the pump, a whoosh of air should come out of the pump if the pump is pressurized with air. So, you’ve got air?
  3. Follow the piping, tubing or hose, whatever you have from the pump to the gun. Look for a closed valve. Open it. A ball valve is normally used, these have a handle about three or four inches long, if it is open it will be ‘in-line’ with the body of the valve, if it is closed it will be across the body of the valve. All the valves are open?
  4. Check the end of your dispense handle. Most of them have a ‘drip tip’ that can be closed to help prevent drips. Twist it and see if it opens.
  5. Still no oil? It’s probably time to call a Service Center.