Just got my compression tester, heated the engine up, removed the spark plugs.

none of the adaptors seem to fit together. Its an 'AM-tech' and it doesnt come with any blinking instructions!!

There is the unit itself which has a rubber tube (presumably) permanently attached. and there is a separate tube that looks identical. There are a couple of adaptors with the one I want, being the 14mm fine plug. But the booming thing wont screw onto the actual unit.

anyone know what I need to do?

now I've worked out how to put it together. However it now doesnt read anything! I guess its broken

get some pictures up mate.

If you type: 'am-tech compression' into a google images search its the first result.

I got one of those before Christmas and it did not seem to work either. After having a closer look I noticed that it had a one way valve fitted in the end of the pipe of the gauge. The purpose of this is to hold the pressure in the pipe when you crank the engine and then you can read it off the gauge after you have stopped cranking.

This valve is just a standard looking Schrader valve and it appeared that it would take quite a bit of pressure to make it open, try pressing on the pin. So I used another slightly different design of Schrader valve which I could alter by cutting the spring down a bit.

Now the engine compression easily opens this valve and just as importantly the pressure stays in when you stop cranking the engine.

Dont ask me why it was like that, but the kit was only a tenner from Ebay .

See the attached photos.

I got one of those before Christmas and it did not seem to work either. After having a closer look I noticed that it had a one way valve fitted in the end of the pipe of the gauge. The purpose of this is to hold the pressure in the pipe when you crank the engine and then you can read it off the gauge after you have stopped cranking.

This valve is just a standard looking Schrader valve and it appeared that it would take quite a bit of pressure to make it open, try pressing on the pin. So I used another slightly different design of Schrader valve which I could alter by cutting the spring down a bit.

Now the engine compression easily opens this valve and just as importantly the pressure stays in when you stop cranking the engine.

Dont ask me why it was like that, but the kit was only a tenner from Ebay .

See the attached photos.

I got one of those before Christmas and it did not seem to work either. After having a closer look I noticed that it had a one way valve fitted in the end of the pipe of the gauge. The purpose of this is to hold the pressure in the pipe when you crank the engine and then you can read it off the gauge after you have stopped cranking.

This valve is just a standard looking Schrader valve and it appeared that it would take quite a bit of pressure to make it open, try pressing on the pin. So I used another slightly different design of Schrader valve which I could alter by cutting the spring down a bit.

Now the engine compression easily opens this valve and just as importantly the pressure stays in when you stop cranking the engine.

Dont ask me why it was like that, but the kit was only a tenner from Ebay .

See the attached photos.

Thanks for the reply!

I will have a look into that. So far I have had nothing bar a little flick of the needle. So I just need to 'excersise' the valve a bit?

Is this device to be trusted at all??

Thanks Peter

If you want you can take the valve out using a standard car Schrader valve extractor. Then you can jury rig it to an airline or similar. I used one of those mini 12 volt compressors, using a rubber tap washer to seal between the pipe ends, then the compression gauge showed a similar reading to the one on the gauge on the compressor. When I put the valve back in there was no or little reading.

As far as I was concerned the engine compression could not overcome the force of the spring holding the valve shut, hence no reading on the gauge. So I used another valve with an altered weaker spring.

Then the gauge was reading pressure and holding it until I pressed the release valve on the aluminium block. (Another Schrader valve )

As far as the accuracy of the gauge itself, I have no idea. But in my case it showed one cylinder way down on compression so that was a result anyway.

Edited 12 May, 201115 yr by William24

I find it difficult to understand how something thats made to measure engine compression doesnt even open when something like 10Bar is sent trough it?!

doesnt seem fit for purpose to me! Is getting your money back an option?

get a snap-on one! amtech are crap at the best of times

I have one that is the same as this:

just got it from my local motor factors, it wasn't expensive at all and works fine

I've got a gunson. Just did a test and got good results!

on average 13 bar with a half-bar variance between the best and worst.