compression testing?

[fiznat]

As some of you may know from my other thread, I'm gonna be checking out a car tomorrow (Wed) that I might buy. I really would like to test the compression of each cyl before I buy it, but I'm not too sure on one of the procedures.

1. I understand from the 240sx.org faq that I need to release fuel pressure. How do I do this? After I do that, how do I restore pressure once I'm done testing?

2. What do the plugs look like on the twin cam KA? Are they recessed deep within the valve cover like they are in Saturns? I'm only asking to find out if I'm gonna need an extra deep socket to get it out or what? Hopefully someone can point me in the right direction here... what other tools do I need? (I have a compression tester already- but its not the screw in kind, you just press it on and it'll read- like a little rubber cone keeps the seal) I imagine just the socket set and the tester (and whatever it takes to release fuel pressure?) will be fine?

3. Anything else I should know about this? I know all about the numbers and comparing them and all that, I'm just talking about technical step by step procedures to get it done...

Anyways please if you know how to do this, let me know right away- I'm leaving to check out the car at 12pm on Wed.... HELP!!

[JJ240]

to release fuel pressure you can pull the fuel pump fuse but i dont know which that is so im a whole lot of help :-). You will need an extension and the spark plug socket with a rubber grommet inside to pull the plug out because it is deep inside. then just hold the tester down in and crank it. I believe 170-190 is good, but that could be wrong im just going by memory.

[JJ240]

forgot...even if they are low as long as they are all close its not so bad. to an extent. if they are all 150 then its not so great, but not as bad as all 170 except one that is 140.

[fiznat]

hmmm ok I think I have an extension that's long enough, but what about that grommet? can I find it quickly at NAPA or something? does it have a specific name?

thanks for the help!

[DAEDALUS]

The reason for doing anything with the fuel is so there's no fuel spraying into the cylinders while you do the test. It would wash off lubrication and give a lower reading than normal. There's usually fuel in the rail even after pulling the pump fuse, so it's a good idea to pull the injector fuse too to prevent the injectors from firing at all. Do the test with the engine warm--long sleeves and gloves to ward off burns. Remove all plugs before doing the test and hold the throttle wide open while cranking so the engine can breathe right. Try to read the pressure after the very first pump. It should be about 1/2 the final pressure.

[DAEDALUS]

You can probably use a magnetic pick-up tool to get the plugs out too. Forgot to mention, before pulling the plugs, make sure the wells are clean so nothing falls into the cylinders.

[JJ240]

The grommet actually comes in most spark plug sockets. I only mention it because mine fell out somehow and I had to cobble stuff up to get the plugs out. Magnet doesnt work either the plug tops are non-ferrous (idk what material they are made of) or there just isnt enough metal for the magnet to grab. I used some of the foam on one side sticky on the other insulation in the socket to grip the plugs and pull them out. Some really skinny needle nose pliers would probably get them out too.

[fiznat]

cool cool... so how should I be able to ID which fuse is for what? Is there a chart under the fusebox cover, or do I need the manual to figure it out? If he doesnt have a manual, how else can I find out which fuses to pull on it (it's a 91- LE I think)?

[Cyberkreig]

Fiz, the Fuel Pump fuse is in the passengerside fusebox up by the battery. It is labled on the cover of that box.

As for the injectors not firing, you can just pull the connectors off the individual injectors... works for me.