Bernard

I received my Gunson Gas tester and wanted to set my CO to 3% after installing my new headers. I pushed down on the screw all the way and turned it many times left or right with no change at all. I'm I suppose to install an allen wrench on top and then turn it?

sand_man

Yes.
Clockwise=RICH
Counter=LEAN

Bernard

Yes meaning I need to use an allen wrench? Pushing down by hand without the wrench and turning wont change the setting?

equality72521

Yes, you must use the allen wrench. No pushing down without the allen won't work. Insert the allen in the top of the plunger. DO NOT DO THIS WHILE THE CAR IS RUNNING. Turn in very small increments as it only takes a little movement to make a big change. Start the car, rev the engine a couple of times, let it settle down , and test again. Repeat as necessary.

Bernard

OK... Thanks a ton. So why did they install the spring rod? I thought it was because you wouldn't need the allen wrench just push down in turn.

Mark Houghton

When pushing down, it needs to go down far enough to engage what is essentially a threaded fitting. You should feel some slight resistance when turning, as evidence that it's pushed down far enough to engage. Very small increments of turning...we're talking less than 1/8 turn, will make considerable changes. Pretty simple once you get the feel of it.

SoCal Mike

Is it a safety reason you don't recommend adjusting while the car is running? Everyone I know, techs included, adjust while the engine is running. Just be careful of the belts/fan. I've not used the gunson tester as I have access to professional machines, but I would imagine the gunson would give the best readings if it wasn't cycled on and off.

Bernard

The allen wrench did the trick... Thanks guys I managed to get it very close to 3% at idle.

DonE

I guess its a matter of preference, but I always adjusted mine while the car was running.

kens911

when mine was adjusted it was running I havent done it myself i'll hook the lm-1 up while it's out for the newclutch.

equality72521

My factory manual says not to do it while running or you may cause damage to the metering unit.

JFairman

Gently insert your allen wrench so you aren't pushing down or altering the position of the sensor plate with the motor running till you feel it engage.
Then turn it the smallest amounts, motor running.
clockwise or, right= rich
counterclockwise or, left=lean

You won't hurt it if you don't press down on it and make it way too rich for a moment and caues a backfire or something..

It has to be a short allen wrench or heat it red hot and bend it at a 90 dgree angle to fit it under there....