nsantolick

Hi all;

Just wondering. I'm about to replace my ignition system. Wires, plugs, coils, cap & rotors. Was thinking maybe I should do a compression check while I've got the plugs out anyway.

Anyway, I was curious, though, how often you all typically do compression checks? Just once? More often?

I DO intend to go with a Murf Supercharge kit pretty soon, I fear, but do want to verify/renew/upgrade most everything else first.

Will my 20 year old Sears compression tool work or do these cars prefer something more snooty? lol

It WAS supposedly done by the last mechanic I had it at, and although he claimed it to be "good", I don't recall the numbers or the range, and I understand that within 10% of each other is mandated whence boosting?

Anyway, assuming it's all good, do you tend to still check regularly?









All the Best...

Nick - NE PA - '89 S4 - Significant Bank Account Modifications...

James Bailey

You need only check it if it is burning oil , running rough , not running or you intend to boost it. I do not think the very brown 1980 has had it done in 8 years....

Shark Attack

about once a week.


Whooops sorry... This is being posted about 3 hrs later than the above line. Some how I didnt post the whole answer... Sorry...

That was a joke. I only checked mine when I bought the car. I doubt I will ever check it again unless I have reason.. Maybe a starting problem... Extra use of oil issue... Loss of power.. Bad idle....

But other than that.... I will never check it again.

danglerb

Before you buy it, when you feel like it, or if a possibly compression related issue comes up. While your changing the plugs sounds dandy, but not needed. Make sure you do the thing so fuel isn't sprayed in.

Bill Ball

You should have a reason to do it. I did it once when I had a miss on idle. Compression was 190-195 on all cylinders. That was probably 80K miles ago. I haven't had any reasons to do it since.

dr bob

Nick--

If/When you do it, pull the connectors to the two brains in the passenger's footwell. That will save the ignition system and keep fuel out of the cylinders. Keep the battery charged during the tests so you have consistent engine cranking speed. Throttle propped all the way open. Engine warm if you can. WRITE THE READINGS DOWN IN YOUR LOGBOOK. Too many numbers to try and remember. At least for me. Beg/Borrow/buy a Hammer or a Spanner to get all the diagnostics out of the controllers before you pull the power from them too.

nsantolick

Why use a hammer/spanner/thingie BEFORE? Not doubting. Trying to understand. :-)





Nick - 89S4

nsantolick

Come to think of it, if I decide to just buy one of them, are they all the same? I checked a few months ago and can't remember but one used a laptop. It was the cheapest I could find. If I get one, I kind of want "the best", assuming it's not way too far off from a quite similar "cheapest by far..." lol







Nick - 89S4

IcemanG17

its one of things you do in a PPI....for example when I sold Sharky the newer owner wanted a compression check so we did it and it came back perfect...which also makes sense with the high dyno #, low oil consumption and good smog # too....all point towards a well running engine...

Once you have a baseline test...just keep the records..& years from now if you develop and engine problem you can go back to compare it...

GregBBRD

I check compression on almost every engine, whenever the sparkplugs get changed.

nsantolick

Leakdown test too?

Are 928's quite normal as far as the procedure goes? Pull the plugs in the fuse box area, etc? Do most crank with the ignition key or rig some jumper to a switch to turn over? My ancient sears set had a trigger jumper thingie. Been a while. Going to go for a compression check this week to verify that things are looking good.

I've got some vacuum issues to work through too. I'm suspecting that I've NEVER had any advance, so if it's all fixed, there might be a few more stray horses lingering in my engine. Fingers crossed...







Nick - 89S4

hacker-pschorr

At the very least, every spring along with new spark plugs.

Not saying this is necessary, just what I do.

Aspkiller

Keep in mind that you're looking for consistency between numbers for each cylinder, and then consistency from test to test, provided the testing conditions are basically the same. All gauges tend to read differently. One man's 160 might be anothers 170. Typically, the test is much easier with two people, with the person keying the starter allowing for three full compression cycles and the reader of the gauge noting the readout on the third one.

If someone else has a different take on this, I would appreciate hearing their method.