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DISCLAIMER: This is **NOT** a COMPRESSION TESTER, if you do not know what a leakdown tester is, please do not post, you will just confuse people. I bought this leak down (leakdown) tester from Harbor Freight this weekend to test a motor that hasn't run in a long time. I am testing a cold motor. No, I can't start the motor to warm it up, I realize the readings won't be 100% accurate, please get past that. Leakdown Tester 
94190 Product Manual I understand how a leakdown tester "should" work, but several things about this unit don't add up. First, the instructions don't seem to make sense. On page 6 of the user's manual, steps 7 and 8 don't make sense. In step 7, in reference to the Regulator Knob, "its" gauge should be the left gauge, marked in psi. There is no "yellow band" on it, as step 7 describes, and the gauge with yellow on it is on the right, not the left. Step 8 called the Leakage Gauge the one with the percentage scale on it; which is obviously the gauge on the right. So, those steps seem to be at odds with each other regarding information. Next, I left the female quick disconnect off so there was no air escape path from the tool. The air compressor regulator was set at 100psi. When you adjust the regulator on the leakdown tester off of the closed position, the right gauge needle swings up to full scale (yellow band on right of gauge, 0% leakage) when the left gauge only reads 20 psi or so. This doesn't make sense to me, as the two gauges "should" be indentical with respect to full scale, with only the faceplate being changed on the right one. It acts like the right gauge is a 0-20 psi gauge. I.E., if both gauges were 100 psi gauges, and you had the tool air outlet (going to the cylinder) blocked off, both gauges should always read the same pressure, as you are measuring the pressure of a common volume. When there is no flow through the tool, there is no pressure drop across the orifice to be read. If you now hook the above tool up to a cylinder, you will get a leakage out of the cylinder, and will register a pressure drop on the tool. If the right gauge reads 100 psi and the left reads 95 psi, you should have 5% leakage. Here are some more instructions for other leakdown testers, and they work they way that makes "sense" to me, i.e. it would seem they have two identical gauges: Leakdown tester 1 DIY leakdown tester Leakdown tester 2
Pics of leakdown gauge faces, note they are the same full scale reading So, I guess I'm looking for someone that has used this Harbor Freight leak down tester and can tell me how you operated it. Or, if someone can decipher what the instructions were trying to say, that would work also. Thanks,
Mike ------------------------------------------------------
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Anyone used Harbor Freight Leak Down Tester model 94190? - 
