Harbor freight leak down tester

[scabber]

I've been trying to fix my 97 chevy computor says misfire #6 cylnder replaced the cap rotor wires and plugs did a leak down test with harbor freight tester set 100 lbs at compressor tester reads 18 lbs for the test cylinder tests good replaced #6 fuel injector still getting mis fire any help I'M out of ideas

 

[scabber]

Just wondering if anyone has used one and if they are worth a shit thats all

 

[grizld1]

I don't know how that reading can be in any way good. If you mean 18 lb. pressure loss out of 100 lbs input pressure, that's 8 lbs. more than the max 10% loss that's considered healthy, and quite enough to cause a stagger (and misfire code) at idle.

Don't know anything about the HF unit; I rolled my own.

 

[scabber]

The dual gages on the tester is what I was talkin about with 100 lbs from the compressor when I set the pressure regulator on the tester the gauge reads 18 lbs the other says it is ready for the test. the cylinder on the truck reads good no leaking past the valves or rings. The gauges and tester are chinese junk paper gauge material. The computor Is fucking up my head. I'm hard headed Low on funds hate to get screwed by repair shops running out of options the reason for the gage question ? The compression test read good. Getting slight flutter with a vaccume gauge.

 

[pamcopete]

I have a Harbor Freight leak down tester and I think it's a well made high quality tool.

I used it on my '81 CB750 DOHC because there are 16 valves and 4 sets of rings that could be leaking so you need to do more than just a conventional compression test.

The operation of the HF leak down tester is a little quirky and it took me a while to figure it out, but here is basically how it works.

1. With the spark plug adapter installed in the cylinder but not connected to the gage set.
2. Connect the gage set to a suitable source of compressed air. Doesn't have to be 100 PSI. Can be any pressure.
3. Adjust the gage pressure regulator for a reading of 0% leakage on the "Cylinder Leakage" gage.
4. Quickly connect the spark plug hose adapter to the gage set. This is the only part I do not like. Instead of a valve to do this part, you have to be real quick and attach the quick connect fitting from the spark plug adapter hose to the matching hose from the gage set.
5. Read the leakage as a percentage on the "Cylinder Leakage" gage.

Basically how this works is that the pressure regulator attempts to maintain the preset pressure but it can never do so because of the leakage in the cylinder, so the difference in the preset pressure and the cylinder pressure is presented as a percentage. You do not have to have a big compressor that maintains 100 PSI so you can use this tool with a smaller compressor or even a tank of compressed air from the gas station, if you're really quick connecting the hose from the spark plug hole to the gage set.

So, with the HF leakdown tester, it's not the working pressure that you are interested in. It's the percent leakage shown on the "Cylinder Leakage" gage. I think that the 18 PSI reading that scabber refers to is the preset pressure. The "Cylinder Leakage" gage reading (as a percentage) does the math for you.

On sale today for $37.99...Can't beat the price...

Note: Although you do not have to have a big compressor to use this tool, having a larger compressor and tank means that you do not have to be real quick connecting the spark plug adapter hose to the gage set because a larger compressor / tank will quickly make up for any lost pressure.

 

[scabber]

Thanks pete and griz for the reply. I'm glad the tool was good. Still have to check a few things out before I take it to a shop at least I know whats not wrong with it.