gump

Hello, I want to check the compression on my GSL-SE and I am unsure of how to do it. I have a Mazda shop manual in front of me and it lists Mazda part numbers for their tester, and to make sure I use that, not a conventional one. What do I need to do the test? What kind of compression tester? I've never tested compression before on any engine so I'm sorta looking for the idiots guide on testing compression, and where to get the parts? Thanks

P.O.S. Racing

Sit down, and take a deep breath, then read on…

Mazdatrix offers a Digital Compression Tester gives a compression reading for each chamber of each rotor. No conventional compression gauge will allow the separation of rotor chambers. A graph is supplied to show minimum PSI for any given cranking RPM. P/N 49-F018-9A0B. It sells for $1640.00.

I'm GREATLY interested to know if there are any other, more cost effective alternatives.

speckamp

You can usually take it to a Mazda dealership and have them test it for you.

They'll charge ya a little bit, but it's cheaper than a 1500$ tester that you'll prolly only use a few times in your life.

Almost cheaper to buy a new engine as opposed to a tester

--matt

rx-7pr

if they tell you its low then your done for i had to put a new engine in mine it sucked. there is a way to get some compression but mine was low and well it just stoped working.
but now after the new engine is it runs great.

Turbo FB.

You can use a conventional type compression tester.
just take off the pressure relief valve so it wont hold at peak pressure. Then all you have to do is watch the needle bounces.
Simple & cheap.
Oh and it helps to have some one crank the motor for you.

RXcetera

And if you're really cheap, you can simply use your ears. Do one rotor at a time, and check that all 3 pulses sound the same. If it sounds like PSHH, PSHH, pshh, then you've probably got a side seal poblem. If its PSHH , pshh, pshh, that's probably an apex seal problem. Not an exact science in any way, but it'll give you a general idea of the condition of your engine.

Turbo FB.

Hows this one, If you dont want to defile you comp. tester
how about taping a whistle to the hose that goes in the plug socket. Even though it may be loud as hell.

Carefull we dont want any boot camp flashbacks.

ON YOUR FEET SOLDIER !!!

gump

thanks for the ideas guys, i think i might go out and get me a conventional compression tester and try that method. I'm doing it to help me diagnose if my engine is in bad shape or not. I'm having so much trouble with the engine just running normally that I'm not able to concentrate on getting the rest of the car up to par. o well, such is life with a 16 year old car.

Josepi

Modified thought on this. Instead of tape, get cork (cork or rubber, cork would be easier) take a dremel and make a round hold engine side, slot for whistle on the other side. Hold by engine pull all fuel and spark. Crank. Listen to whistle. Or get a standard compression gauge and remove the schrader valve at the end where you put into spark plug hole. Its hard to watch it when it bounces, but you should get even sequential bounces.

Hope that helps. Do a search, in the old 1st gen archives I had a write up like 12 steps on how to do it detailing painfully everything. But I can't get to the archives...sucks.

Joe

P.O.S. Racing

Gump did you run Rxcetera’s Pshh, Pshh, Pshh test? How did it do?

What exactly is the car doing that has you wanting to check compression? You mentioned you are having trouble with the engine just running normally. Fill us in, what all is it doing, maybe one of use has had a similar problem with ours and we can help direct you to a solution!

gump

No, I have not run the Pshh pshh pshh test yet. I have done it before once when I had to unflood it. Is a difference in Pshh's really that noticible to the ear?!? I wanted to check compression because my car goes through a quart of oil every 300 miles, but the engine sounds normal, runs normal, feels strong. I do however believe i have a malfunctioning oil metering pump which may play a roll in that? So I thought I'd check compression and if it's not good, I know not to waste any more money buying different parts trying to fix it. However, if it turned out good, that would lead me to keep trying different things (like the oil metering pump) to try fixing.

Other than using a lot of oil, it's got a wierd idle problem that has steadily increased in how often it occurs over the past few weeks. At any given time, my car will decide to idle at 2000 rpm with the clutch pedal in, and bounce up and down between 1000-1500 when i have the clutch pushed in. Now, when this happens and the idle hits 2000rpm, it is not the same as when i rev the car to 2000rpm, it's a nasty 2000rpm's, makes the car vibrate and it just doesnt sound right, like it 's missing. It will go away all by itself sometimes, or I may have to shut the car off and let it sit for 30 mins or so before it goes back to normal. Some days it won't do at all, other days, i can't get the car to idle normally because of this problem. I'm beyond frustration with this one. So there it is, I've gone through the Solving GSL-SE Idle problem document many times. I need to find someone in my area that can fix my car for good. I'm officially throwing up the white flag on this one, i surrender, my car has defeated me.

RXcetera

Sorry to hear about your idle gremlins. I wish I had an answer for you, but it seems like everyone has had this problem and solved it differently. Short of taking everything apart and readjusting everything to spec, you might be trouble shooting for awhile.

As far as the Pshh pshh pshh test (lol), its pretty acurate at gauging variances in compression within your engine. You'll notice if there is a difference between pulses. The thing you dont want to hear is a rythm... it should be P,P,P,P,P,P... not P,P,p,P,P,p or P,p,p,P,p,p.