11 replies to this topic

[chris123]

Hi all,

I picked up a compression tester gauge while i was looking through the local auto shop the other day. I want to test it out on the gsr but need a few tips first.

1. How do i disbale fuel and spark, do i have to pull out any fuses and which ones
2. Is it best to turn the motor over a set amount of times per cylinder or until the highest value is reached
3. When I'm turning it over should the clutch be disengaged while in neutral or just keep it in neutral and thats it?
4. What values should i be looking for? whats a good, medium and bad value for the 4g93t

Cheers

[Hypo]

Hi all,

I picked up a compression tester gauge while i was looking through the local auto shop the other day. I want to test it out on the gsr but need a few tips first.

1. How do i disbale fuel and spark, do i have to pull out any fuses and which ones
2. Is it best to turn the motor over a set amount of times per cylinder or until the highest value is reached
3. When I'm turning it over should the clutch be disengaged while in neutral or just keep it in neutral and thats it?
4. What values should i be looking for? whats a good, medium and bad value for the 4g93t

Cheers

I would remove the back seat and unplug the fuel pump back there.

I would run the car till it burnt any excess fuel if any.

Remove the spark plug out of the cylinder you are testing crank the car. The pressure will be the same no matter how long you crank for.

Do it in neutral clearly.

As for values I have no idea of the factory compression of a 4g93

[chris123]

hrmm, i don't really want to remove seats, is there another way to disable the fuel?

[Hypo]

It will take 2 secs to remove the back seat.

There are two little black circlips like things. Pull them and lift the back seat up.

Not being rude but if your not confident to remove the back seat I would get someone who has some knowledge to give you some assistance with the overall process.

[chris123]

Im just assessing other options, if it's as simple as removing a fuse why bother removing the seat. thats all im saying. If there's no other way then i'll remove the seat.

[BO-00-ZT]

if its as simple as removing a fuse why bother removing the seat

dude, the seat is as easy as removing a fuse, actually probably easier as you dont need to use your brain to find out with fuse to take out!!

[Evo-00x]

As he said, sit in the back seat and look between your legs and you will find 2 plastic black/white tabs. Pull them and lift the bum section fully out of the car. Its a 5 second job. Then remove the 4 x screws on the square plate (driver's side) to gain access to the fuel pump cradle. There will be a white plug which you should disconnect to disable the fuel pump.

To disable spark just unplug both the crank angle sensor and ignitor to be double sure.

[GSR-747]

Make sure you do it with the throttle wide open, don't worry about the clutch. They are telling you to remove the seat as there is no "fuel pump" fuse, remove ALL spark plugs and crank the motor over about 4-5 revolutions.
I think about 180psi is about right, I cant remember waws ages ago when I did mine, anyway it doesnt really matter that much what the value is you are more testing for all cylinders to be all the same.

[bazeng]

Do the gsr's not have an MPI (main relay?)

If so, if you unplugged that, it should disable all power to the main electrics ie spark / fuel / ecu etc.

Also, if you disconnected the CAS, there would be no input to the ecu to fire the ignition / trigger the injectors... Wouldn't that then be ok to do the comp test?

Just make sure all values are within 4 psi.

[DOUGMO]

4psi is a pretty small difference,

would you poo poo a motor if it had 180 180 175 180 ????

[Hypo]

What is the compression meant to be on a EVO II Engine?

[DOUGMO]

az baz said mate you are after consistency over the 4 cylinders.

if you have over 140/150psi on each cylinder and they ar eclose in the readings then you should be able to eliminate low comp as an issue