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[MutantCav]

Are all compression testers pretty much the same or are some especially good (within say a £30 budget)

Is the am-tec one ok??

Also they say Checks Valves and Ring Wear, excessive carbon and late timing for petrol engines...what results show what??

And...how do you use one?? Remove the rubber from cyl 1 of the coil pack and put the compression tester in its place?

[Lazydocker]

Easiest thing is probably to unplug the crank sensor or remove the fuel pump relay.

Then remove the plug in the cylinder you wish to test (so each in turn), screw in the tester and turn the engine over. Take the reading and repeat for the other cylinders. You're looking for one that has a dramatic drop in compression compared with the others for signs of an issue. Whatever that issue is, you'll likely need to pull the head off to sort it so that's where you can look for the cause.

One way to check if the problem is rings is to put some oil into the cylinder and test again... If the compression returns to normal than it's most likely a ring fault.

Think I've got this right but it's quite hard to describe something that I used to do without thinking about it

[MutantCav]

Thanks Slapper Anyone know where the fuel relay is on a Zafira 1.6 (2002)??

[albitz]

It fits in place of the spark plug.

[Kevin Wood]

You need to crank it with the throttle wide open when testing. If it's a DBW car, make sure the throttle is opening, as sometimes this is only possible with a Tech 2. May be easier to take the throttle body off to make sure.

I tend to remove all the plugs then test each cylinder in turn, as having no compression on the rest of the cylinders gives the starter an easier life.

[MutantCav]

Thanks guys...I can use my "My Naff Code Reader" thingy to help with the compression test I think...so is a compression tester ok regardless of make?

[Lazydocker]

Thanks guys...I can use my "My Naff Code Reader" thingy to help with the compression test I think...so is a compression tester ok regardless of make?

Obviously there will be differences between makes, generally on the calibration I would think.

But, TBH, as long as you use the same tester for all cylinders then you will be OK. After all, you are comparing the readings to each other, not a calibrated value

You need to crank it with the throttle wide open when testing. If it's a DBW car, make sure the throttle is opening, as sometimes this is only possible with a Tech 2. May be easier to take the throttle body off to make sure.

I tend to remove all the plugs then test each cylinder in turn, as having no compression on the rest of the cylinders gives the starter an easier life.

I knew I'd forgotten something

[Marks DTM Calib]

Try to get a compression tester that screws in in place of the spark plug asthere a lot more convenient particularly for single person use.

[r1]

i would go for a screw in one and not a push on one

must type faster

[Auto Addict]

You can't be a good screw






































-in type

[Ken T]

There is also a leak down test http://en.wikipedia.org/wiki/Leak-down_tester which is supposed to be good at identifying cylinder faults. There is a DIY design somewhere. http://vmaxoutlaw.com/tech/leakdown_tester.htm

Ken