Compression is testing 145 across the board

[toki]

ok, so I decided I would do a comp test because I am thinking about going KA-T, so i went out and bought the meter and some rathces and got to it, and I was disapointed to see 145 on 1 2 and 3, didn't bother testing 4. I just got the car 2 weaks ago so I dont know what oil it is running to add some to see if it's just the piston rings, but I emailed the guy so I should know by tomorow. If it goes up a good amount like 20+psi should I just get my rings replaced, and if doesn't go up does that just mean I need a rebuild?

[:: orion ::]

Low number across the board are sometimes user error - Did you:

1) Test while the engine was warm?

2) Hold the throttle Wide open?

If so, then try the oil trick...

Otherwise, warm that sucker up, hold the pedal down while you crank it, and let us know the results then...

Later - Brian

[toki]

being warmed up really doesnt matter, my friend got a clip that had been sitting for 4 months to test 200+ on every cyl with just oil. Let me tell you it was not warmed up (NO GAS keke) but engines are never really cold per say in an arizona summer..and the first round i didn't have my cool helper (mom) hold down the throttle, went back and did it again with WOT, same numbers...

[:: orion ::]

Warm does help - The one isolated incident that your friend had with good numbers does not mean that a warm test is not the right way to do it.

My old KA motor read 150 cold, 180 warm...here in hot, sunny Florida.

Try it again, warm, and let us know. Or, disregard my advice and rebuild/replace it when you may not have to. It's your dime...

Later - Brian

[Toahk]

Also be sure all spark plugs are out, fuel pump fuse is pulled and pressure is out of the tank, and you start the car up untill it dies after pulling fuse/letting out pressure in tank. As stated be sure you hold it Wide Open Throttle and crank it 5-7 times, and be consistent of the cranks on every cylinder.

[toki]

so the idea is this: take everything out, take test, put everything back, go drive it, come back, take everything out again, and do it again?

[:: orion ::]

I'd just drive it until warm, pull all the plugs and fuel pump fuse, unscrew gas cap, hold at WOT, and see what she says...

A cold test is inaccurate and useless...skip it.

Let us know - Brian

[toki]

fuel pump hose? I am still new with under the hood, where would I find this.

[:: orion ::]

fuel pump hose?

...and fuel pump fuse

Hehe...fuse. So the pump doesn't turn on and spray fuel, which will wash the cylinder walls and cause bad readings.

It's in the fuse box inside the car.

Later - Brian

[toki]

hah yeah i'm all about reading what people type..haha.

[red240ne]

Also be sure all spark plugs are out, fuel pump fuse is pulled and pressure is out of the tank, and you start the car up untill it dies after pulling fuse/letting out pressure in tank. As stated be sure you hold it Wide Open Throttle and crank it 5-7 times, and be consistent of the cranks on every cylinder.

don't take ALL the plugs out at once. take them out one at a time, or else the numbers won't be as accurate.

[toki]

that makes no sense.

[red240ne]

yea it doesn't, ok

take one plug out, do the test. then put that plug back in.

take the next plug out, do the test, then put it back in.

and so on..

so all the holes are always filled.

[Toahk]

No, the correct way is to take all the plugs out. Read it in the instruction manual that comes with compression testers, your FSM, 240sx.org FAQ.

[Toahk]

Also remember to always disconnect the center cable on the distributor.

[toki]

yeah i keep getting people telling me different **** to do. I dont see why I need to disconnect the center cable as all the spark plugs are out, but I will anyways. Better safe than sorry. Tomorow I am going to go back to the house and get the plugs back in, get a funnel that will allow me to get oil in through the plug holes, and retest. I just am worried about driving it to warm it up, or will sitting at idle be good enough? I dont really want to drive it as the clutch is slipping and could go at any moment. Remind me not to buy cars from southwest autoworks when they tell me the clutch is good, because apperntly good means goes to hell a week later. Oh well that is another issue and we are in the midst of working out a resolution.

[:: orion ::]

Yeah - Proper way to test is with all plugs out, fully charged battery, engine warm, 300rpm from the starter IIRC...

And warm is warm, whether you drive it or not. If it idles for 5 minutes and the dash gauge shows warm...you're set.

Later - Brian

[toki]

it ran 2-3psi higher warmed up, and went to 170 on 1 and 2 after i added oil. I didn't do 3 and 4 because frankly it's 130 in my garage. I was satisfied enough though. Just need new rings probably. I will have them look at it when I go to get my 3angle done. I also did release the fuel pressure, and I had the center distributor cable disconnected on one end, it was shooting sparks out the tip, did it the other way, it was shooting sparks out of the power thing onto some random piece of metal. I just left it all plugged in as it was fine before and i didn't feel like having a spark jump to something flammable and dieing. But thanks for all your help and input guys, I will keep you all updated.

[Toahk]

Yeah watch out if your the person holding the compression tester too close to the distributor like I did, haha gives you quite a jolt of electricity. Zzapp .. F**K S**T A** GoD D*mnit (re-enactment)

[leper421]

You are supposed disconnect the center wire from the distributor and ground it. No sparks.

[red240ne]

Yeah - Proper way to test is with all plugs out, fully charged battery, engine warm, 300rpm from the starter IIRC...

hmm...i was just taught otherwise, but ok i guess. and let's see, it said it in the ASE book as well.