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What cause a cylinder compression tester not to hold pressure on a weedeater 2 stroke engine?

I perchase a cylinder compression tester from ebay i use about couple of time it was working good but now the gauge drop to zero with out touching the release valve what could be the cause?

Posted by Joe Russell on


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john h

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  • Cars & Trucks Master
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Bad valve

Posted on May 07, 2019


5 Related Answers


Roberta Smith

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SOURCE: low compression in #1and #2 cylinders 1993 eclipse gs 1.8l

burned valve is likely the culprit.... or bad rings.... hook air up to that cyclinder one at a time.... and listen where the air is escaping... be aware that the motor will rotate till the piston is at the bottom of it's rotation. if it's a burned valve you will have to remove the head and replace it but somewhat easier job then replacing the rings. darn almost forgot.... it can also be a blown head gasket.... same procedure but you might need a brush and some soap water to test for an air leak at the side of the head. when you are done spray some wd 40 on it to get the water off so the spark plugs do not arc.


Posted on Sep 26, 2008


David Robinson

  • 140 Answers

SOURCE: Oil pressure suddenly dropped to zero.

Hello, let's see what you need.
Yes, the pump can go out that fast.
Do not start your engine. Go out and check the oil. If you have plenty of oil you will need to tow it to a shop. If your out of oil check the the drain plug on the oil pan and check the oil filter.

Posted on Dec 31, 2008

Richard Scordino

  • 6982 Answers

SOURCE: Fuel pressure drops immediately to zero when engine is shut off.

I am not really familiar with the setup there but I'd be looking for a second relay to kick the pump on when cranking.

Posted on Jun 05, 2009


  • 17 Answers

SOURCE: 2002 chevy trailblazer. 1.oil pressure gauge

the sensor is on the side of the engine block. there's two thing that monitors oil. a pressure switch turns you oil light on and you oil pressure sensor the operates your gauge, start with your sensor. that is near you oil filter that is where it gets it pressure reading from

Posted on Jul 24, 2009



  • 85239 Answers

SOURCE: Misfire cylinder 5 2000 dodge dakota

when u press the gas pedal to go this opens the throttle valve, the idle speed of your engine is computer controlled, this is done by the ISC (idle speed control) airbypass valve, these parts get full of gunk and then get a stalling problem at or near idle, clean them by doing the following, if u don't understand the instructions seek help from your friend.
, Get a can of intake cleaner from any local parts store, not carb spray, intake cleaner, it is made by a company called CRC, remove the air intake hose to the engine, hold the idle high so the engine won't stall, then spray the can of cleaner into the intake while keeping the engine running, use at least 1/2 the can, shut down the engine and disconnect the battery for 5 minutes, then restart and complete a number of mixed driving cycles, town, freeway, stop and go etc., after a few days the problem will go away as the system will relearn to the clean intake.

Posted on Nov 23, 2009

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2 Answers

What is a cylinder compression how much do it cost to replace it

If you have low (or no) compression in one or more cylinders, it can be due to broken/bent valves or valve seats, bad or broken piston rings, or mechanical timing way off. The cost to correct is very dependent on the specific cause. Best case is mechanical timing is way off (this will show up as low/no compression in all cylinders), assuming no other mechanical damage was done. Worst case is engine rebuild or replacement.

Aug 22, 2017 | Cars & Trucks

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On my Ryobi BC 30 I have done a compression test and the pressure will not hold.

When testing engine compression it builds up when the engine is turning over and when you stop turning it over the compression tester has a valve in it to hold the pressure reading I think your tester is defective and not holding the pressure reading

Feb 05, 2016 | Cars & Trucks

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How do you check if you have compression on a 84 porsche 944

You have to buy or borrow a compression gauge tester. It threads into the spark plug hole; so you pull all the plugs out, then check each cylinder's compression. The proper way is to first disable gas and spark, put the tester into the first cylinder, then crank the engine over a set number of times- the same amount of cranking for each cylinder, so all get a balanced test. While cranking, hold the accelerator pedal all the way to the floor-this lets the engine breathe normally, getting all the air available. then compare your compression readings: a good healthy engine will have all cylinders pretty even, in the range of somewhere between 150 psi-200 psi. Low compression readings means compression is being lost somewhere, like worn piston rings, bad head gasket seal, or valves not sealing.

Wondering if you have any compression at all? Hold your finger over a spark plug hole while someone briefly cranks the engine over. You can tell if there's any compression at all-you will feel the pressure build up under your finger. Rent or buy the gauge tester to get a true reading of your compression.

Jan 17, 2016 | Porsche Cars & Trucks

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Hi I'm getting low compression pressure on cylinder 2 on my Renault Clio 1.4 16v 2003 model 1,3&4 are OK I have changed head gasket,valves,rings but still the compression is low can anyone help please

I wonder did you check your work as you progressed?
Pressure testing the valve seats for instance or even just a paraffin test? A good valve seat is difficult to obtain with the hardened steel seats used for unleaded fuel, especially when using a coarse grade of carborundum paste.

In order to discover where the compression leak is it will be necessary to set the cylinder at the top of the compression stroke, lock the engine and then inject compressed air into the cylinder using either a propriety or home-made adapter in the spark plug hole. It will soon be obvious where the air is leaking from indicating the fault.

Valve clearances are important and in the case of hydraulic self-adjusting valve lifters it is possible for them to stick and hold the valve slightly open. I generally squeeze each one in a vice several times until all the oil has been evacuated.
If the valve spring is weak or the oil pressure relief valve is stuck closed tappet jacking is possible.
Good luck!

Nov 02, 2015 | Renault Cars & Trucks

1 Answer

Misfire cylinder 2 vauxhall zafira

Check for spark on cyl 2. Auto parts stores sell a spark tester. th?id=hn.608054987065067225&pid=15.1&h=205&w=160
Unplug the wire from the sparkplug, insert the tester into the wire, clamp onto metal somewhere nearby. Then, have someone crank the engine. You should see a spark. If not, then your ignition wire or coilpack is bad. If there is spark, check the fuel pressure with a tester, fuel injector by checking ohms on injector tabs, and then compression with a compression tester.

Mar 02, 2014 | Cars & Trucks

1 Answer

How to install a distributer on a 2000 mazda millenia 2.5L

You'll need to rotate the engine only in a clockwise direction, to get it to TDC on the compression stroke. When the engine is on the compression stroke, both valves to that cylinder are closed completely.

You can hold your finger over the #1plug hole with the plug removed, and as the engine is turned, you will notice pressure building, use a long rubber hose or something you won't drop into the cylinder, to put into the cylinder to feel the piston as it comes up to the very top. If you go past it, rotate the crankshaft 2 full times (almost) to get back to the TDC position.

There is also a mark on the crank pulley that will tell you when you reach TDC. Identifying the compression makes sure it's on the compression stroke, not the exhaust stroke. The engine turns 2 full turns for one turn of the camshaft.

Once you have TDC on the engine, rotate the distributor in your hand, to where the rotor will be pointing at the #1 position where it would send spark to the #1 spark plug wire & plug. Install and adjust as necessary to get the best idle, then hook up your timing light to set it to the factory specs.
Good luck!

Mar 30, 2012 | 2000 Mazda Millenia

1 Answer


The fault may very well be with the tester itself: The compression tester should have a check or "HOLD" valve which causes the needle on the gauge to REMAIN at it's highest recorded point. For example, my 1993 Isuzu Rodeo had a compression of 160 psi. The gauge "holds" the needle at the measurement UNTIL THE VALVE IS RELEASED-(mine had a button that needed to be pressed to release the pressure) then there will be a slight discharge of the pressure contained within, the needle should drop back to zero, and THEN you should be able to remove the tester. What I am getting at is if the pressure drops that fast, I think the "HOLD" valve on it may be defective, OR the tester is not properly sealing on the combustion chamber (stripped threads?). Might be worth buying another one for 20$ just to be sure.

A four cylinder engine, you say? Very rarely will you have ALL of your cylinders exhibit the same pressure loss symptoms. How did the other three cylinders test?

Here are the components required for a running engine to fire:
1-good spark (adequate voltage, good plugs/wires)
2-dedicated fuel supply (fuel pump with adequate pressure)
3-timing (slack in timing chain/belt?)

If the timing belt broke or maybe even jumped a tooth or two, it COULD cause DAMAGE to your engine-pistons hitting valves-if it IS what they call an "INTERFERENCE" engine.

Hope this helps.

Dec 31, 2009 | 2001 Hyundai Sonata

1 Answer

What order do plug wires go on distributor cap

Firing order is 1-8-4-3-6-5-7-2. Move #1 cylinder to where piston is up, and on the compression stroke (TDC). Easiest way to do this is with a compression tester on the #1 cylinder - rotor cap OFF. When you see the pressure're on the compression stroke.
The rotor cap should be at the #1 cylinder firing position...simply re-install the rotor cap at this time - noting which button is #1.
Starting at #1 install the wire for the #1 cylinder onto the rotor cap...the next button (clockwise) on the cap should correlate to #8; the third button on the rotor cap is, cylinder #4..and so on.
work your way around the rotor cap until you have all 8 cylinder wires in place...ignition coil wire in the middle button.

Engine should start and run.

Hope this helps.

Nov 21, 2009 | 1996 Buick Roadmaster

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Explain the four stroke cycleof a three cylinder

Is this a quiz? Each cylinder contains one piston that takes four strokes to coplete a a full cycle. the intake-down,compression-up, power-down, exhaust -up.
A two stroke has up and down only . Compression and power Now, I thik you really meant the firing order. I'm not sure but Would make sense 2-3-2?

Nov 18, 2009 | 1995 Isuzu Rodeo

1 Answer

How to find tdc on 95 ford escort 1.9

Using a compression tester in the cylinder all the way to the pass side, turn the engine over by hand until you see pressure rise. This gives you the start of the compression stroke. Remove the compression tester. (If you don't have one, put a finger the the spark plug hole and wait until you feel pressure. (Do not use the battery to turn it over, only do it by hand.) Once you are starting the compression stroke, put a thin but long screw driver or anything straight but easy to put in the spark plug that first cylinder.

Again, turning over by hand, turn it until the screw driver is at its highest point. You are at TDC.

Hope this helps

Oct 18, 2009 | 1995 Ford Escort

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