as above really, what should they be roughly for a 125k engine. obviously as even as possible but just need a benchmark as going to look at a car tonight.
thanks gall
as above really, what should they be roughly for a 125k engine. obviously as even as possible but just need a benchmark as going to look at a car tonight.
thanks gall
Anythign north of 135-140 (matching) i'd be content with
thank u very much
Here's the guide for the comp test:
Nicked from DW, who nicked it from the GTROC
As a rule, most engines should have 140 to 160 lbs. of cranking compression with no more than 10% difference between any of the cylinders.
Strong compression is essential for an engine to run properly and efficiently. A noticeable loss of power or efficiency, or blue white smoke may be cause to test an engine's compression. A compression test when viewing a car to buy is always a good idea.
A compression test measures how much air an engine's pistons are compressing, which can be compared against one another, and against manufacturer standards to determine if there is a problem in this area. While a lack of compression is most common, it is also possible for compression to be too strong. Over-compression can result in a problem known as detonation, which can be very damaging to an engine's internal parts.
Low compression in one cylinder usually indicates a bad exhaust valve. Low compression in two adjacent cylinders typically means you have a bad head gasket. Low compression in all cylinders would tell you the rings and cylinders are worn and the engine needs to be overhauled.
All you need to test your engine is;
A compression testing kit. Range from £20 - £25 from any Motorstore
1/2'' inch Ratchet
A Spark Plug socket, (helps if it has a rubber grommet inside) with extension bar
A 3/8" inch Ratchet (5/16mm bit) with extension bar
Or a Possy Screwdriver. However, the ratchet and socket will work better than the screwdriver as there's a chance you will grind down your screws!!
And a wire brush if you wish to brush down your sparkplug tips.
Also make sure your battery is healthy and full of charge..
In the packet there are 2 Sparkplug sizes. The main is the one you will need.
Start your car and leave it running for 5 minutes or so to warm it. Don't leave it to long or it will be to hot to attempt to do this..
It must be warm to ensure all rings, valves and pistons are at operating temperature, doing it cold will often give lower readings.
Turn off ignition..
Now to start getting your hands dirty. Remove your coilpack cover. These bolts are normally 10mm.... Keep them safe and dont drop any in your engine bay. You may never see them again.
You will now see your coilpacks...
So the next step is to remove these. There are 2 ways of doing this.. One is to remove all bolts and remove all coilpack individually. I'm doing it the quicker way and removing them all on the plate they sit on.
The quicker way is that there are 2 different size (in length bolts). Some bolt to the head, and others to a plate that hold the coilpacks. There are usually 4 on each coilpack. 2 of which are different colours on each coillpack.
In the CA's case, the Black bolts are the ones that need to be loosened, or removed. Leave the gold ones.. You can use a screwdriver but try not to ruin the head of the bolt. It is advised to use the right socket for it. Be much easier. 5/16mm in this engines case
Once done lift them up and move them out the way....
Now you will see your spark plugs..
And begin to remove all spark plugs... The reason your remove all the spark plugs is because if you leave the plugs in, then the engine is not going to reach the desired cranking RPM, and so the readings will be lower.
Now once you have removed the spark plugs, insert your compression tester and screw so its finger tight. Don't over do it.
DO NOT START THE CAR... First you will need to either disconnect your CAS, pull out your Fuel pump fuse, or unplug ECU.. If you remove Fuel pump fuse, start the engine and allow it to idle until it runs out of fuel and stalls, repeat this three times to ensure all fuel in the system is gone.
As mine is easily accessible, I unplugged ECU....
So once done you can now try to start your car. I turned the key and ran each cylinder for the same number of revolution's, at least five to eight. That way, in each cylinder, the Piston can reach TDC (Top Dead Centre) the same amount of times to get a fair reading..
Do this and fully press in the accelerator.. Pressing the accelerator allows for maximum air intake. If you don't have the maximum available air going in, the results will be out, as its sucking against a closed throttle plate.
Then go check over your result.. And jot them down
Don't forget to release pressure by pressing the button below before you try your next cylinder.
And then repeat till your done...
So my results are....
152
151
110
120
Not the healthiest of engines, its pointing towards headgasket between 3 and 4.
The closer the numbers the better. Cylinder 1 and 2 show very good pressure, 150 is bang on.
To carry out a proper test you will need to take three or four pressure readings for each cylinder. Working on a warm engine with a fully charged battery!
If your tests turn out not to be great, then do a wet compression test..
A wet compression is carried out the same way as a normal test except that you pour 5ml of engine oil down each spark plug hole just prior to fitting the compression tester, allow about 30 seconds or so for the oil to settle around the piston rings and form a seal. Don’t forget to write down all three or four pressure readings for each cylinder. Compare the wet compression test results with the first set of test results.
An increase in pressure indicates worn piston rings and/or worn cylinder bores, as the additional oil has acted as a seal.
No increase in pressure points towards the camshaft or the valve gear and could mean any combination of: pitted or worn valve/valve seat, bent valve, worn valve guide, burnt valve or a worn camshaft lobe.
No increase in pressure may also be due to an externally cracked cylinder head or externally blown head gasket this might be obvious though, as you might be able to hear it hissing/popping or see it bubbling.
When your done re-fit all and tidy up
This needs to be stickied.
why removing the ECU? It is best to remove the fuse of fuel pump and ignition module wire same as manual says.
What he saidOriginally Posted by MerLiNz
Removing ecu is a pain and could potentially damage pins.
Yeah I'd say it was worth a mention ton th tech threads!
i understand all that apart from one bit.
do you
A - get it all set up THEN remove the fuel pump fuse and just do the test???
B - remove the fuel pump fuse and start the engine and run it till it stalls then get all set up and do the test???
remove spark plugs, remove fuel fuse, remove ignition wire, start engine (it dont start xD), and do compression test.
/\/\ won't that spray fuel all over the place and straight into the bores?
I'd pull the fuel pump fuse before doing anything else, start it as normal and then let it run till it dies which should use all the fuel in the system.
Then proceed as normal, I also wouldn't bother pulling the ECU.
Thats exactly what i thought but had to ask to be sure.
No need to remove the fuse when the engine is started. If you remove the spark plugs and pump fuse and give a few seconds start key to release the pressure injectors and fuel comes out the spark plug hole. The engine to be hot gas evaporates quickly does not remain in the cylinder.
Unplug the dropper resistor. Then the injectors have no power and won't open to release fuel.
Unplug the coils. If they are left connected they will fire and the spark has to go somewhere. If it goes though the coil winding insulation the coil is ruined as the carbon track it makes is conductive.
Or even simpler remove the brown breaker nearest the front of the engine bay fuse box. It powers the injectors, ignition and ECU.
Pete, this threads been dead for 6 years mate ! Lol
Sent from my XT1032 using Tapatalk
Yeah but.
It's the one that's linked to from the FAQ.
AhGood point.
Just thought it was a shame you were adding value to something that had died and gone to heaven...like a lot of stuff on here recently
Still, if its sticky...
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