Updated on 19 October, 2021
Autozone Compression Tester yesterday did the job as expected, and was really pleased with how it worked. When Autozone special compression testers first came out, well we were doing a compression testing then because this is a brand new model and all. Cylinder number 4 went okay about 185psi, Cylinder number 3 WAS okay.
But, yesterday, I noticed that the "wet floor" warning light was on when I went to do my oil change and valve changing. Was thinking about calling autozone auto parts to help but decided to try out this autozone compression tester first. Yes, it worked, even for the valves. I think next time I have to replace a valve or two, I will just use an autozone compression tester to make sure everything is ok.
About a year ago, at our local auto parts store we tried out the new autozone compression tester and it performed like a charm! We have been using it ever since and were not let down at all. The valve cover came off and the four valves came right off the cylinder head and were replaced with the new ones. My valves are not that big, but the gasket is rather large. There is nothing else to worry about.
One thing about the old Cushman "D" series of pistons, they tended to come loose and lock up over time, especially in very cold weather. A low compression cylinder head always caused issues with my engine in cold weather. That's why we always switched to the "E" series pistons. This "E" series has a "low compression" setting, as opposed to the high compression settings on the D series. So it seems to work better for us now.
With the new spark plugs, there should be no problem with the pressure passing through the cylinder at any given time. That's what I was having trouble with the D series spark plugs. However, with the Autozone Compression Tester, we will know if the pressure is too low before it gets to the piston. This is much easier than trying to diagnose a low compression problem by looking at the dipstick.
Another thing that I notice is that the Autozone compression tester is a little more robust than the regular Autozone. The other day, I took it out for a test drive and really didn't notice any degradation in power or efficiency. That just goes to show how well built these things are. The other thing I noticed, was that the replacement nozzle doesn't quite fit snuggly into the hose, but it still seems to be able to pull the charge out with minimal resistance.
Based on what I've read about the PMI (parts monitor indicator) chips inside of your engine, you can expect them to give off a false positive about something when the engine is cold. That's not necessarily good news. The PMI chips don't have a constant pressure value like the Autozone compression tester does. They also have an idle speed that is independent from the RPMs of your engine. They monitor the amount of fuel flowing though the system, and based on the readings, determine whether or not to run the engine or not.
So, since the Autozone compression tester doesn't have any built in pressure gauge, what do you do? You want to make sure that your OEM cylinder head is turned at its highest setting while your engine is running. This will get the most accurate reading that you can get. It's just a simple rule of thumb, although I'm sure there are more precise things that can be done with it.