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Old 11-04-2002, 11:28 PM   #1
latinskllz
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Question how to properly do a compression test for a ej25

I bought a compression tester at Discount Auto Parts and read the instructions as well as the instructions on this thread:

I have a MY00 RS 5Speed and would like to do a compression test on it...

http://forums.nasioc.com/forums/show...eferrerid=3461

Well here's what I'm having trouble comprehending:


In the service manual Compression Test Instructions:

3) -- How do you release the fuel pressure on a EJ25?

8) -- How do you crank the engine by means of the starter motor?

Damn I sound like a noob! Anyways, I was wondering on the second page, there is a Haynes Manual Compression Test Instructions and it says that "1) You MUST disconnect the fuel pump's electrical connections (at the fuel pump). You can't have raw gas squirting around your manifold and cylinders."

I can see the necessity of this step, but is there any other source to cut fuel rather than taking apart my bench seat to do it?

Any help would be appreciated.

Thanks,
Kevin
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Old 11-05-2002, 12:40 AM   #2
ciper
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In the service manual Compression Test Instructions:

3) -- How do you release the fuel pressure on a EJ25?
Simple way? Wrap the line in a rag and unscrew the clamp.

8) -- How do you crank the engine by means of the starter motor
Hmm, have to think about this but If I remember correctly there is a fuel pump fuse right? Just remove that instead
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Old 11-05-2002, 04:18 PM   #3
SubyTechMaster
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"How do you release the fuel pressure on a EJ25?"
You could unplug the injectors or you could disconnect the Crank Sensor and Cam Sensor. This will effectively prevent the injectors from spraying fuel.


"How do you crank the engine by means of the starter motor?"
Have you considered the Ignition Switch?
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Old 11-09-2002, 11:26 AM   #4
latinskllz
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Default disconnecting the crank sensor and cam sensor

will release the fuel pressure?
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Old 11-09-2002, 07:00 PM   #5
SubyTechMaster
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No, disconnecting the Cam & Crank sensors will not relieve the fuel pressure. It will prevent the injectors from opening and spraying fuel though.

What is your objective? Do you wish to relieve fuel pressure so that you can safely open the fuel system? Or do you wish to prevent fuel from entering the cylinders while performing a Compression test? Relieving fuel pressure is one way of achieving this, so is preventing the Injectors from opening.
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Old 11-28-2004, 11:01 AM   #6
TheAntiRice
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If you let the car sit over night the fuel pressure will relieve itself. This is what I did when I changed my fuel filter and it worked quite well.
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Old 11-28-2004, 11:22 AM   #7
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Quote:
Originally Posted by TheAntiRice
If you let the car sit over night the fuel pressure will relieve itself. This is what I did when I changed my fuel filter and it worked quite well.

NO-NO-NO....

What is being achieved here is to prevent the fuel system from being able to inject fuel into the cylinders during the test....which is bad juju....and THAT is best accomplished by pulling the injector connectors, or the crank/cam angle sensor plugs, or disabeling the fuel pump relay while the car is running and letting it die from fuel starvation.

Take ya pick....don't forget to reverse whichever ya do, 'cuz it won't run if ya don't
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Old 11-28-2004, 05:50 PM   #8
Pakin
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You really don't need to relieve fuel pressure. Just that you don't want the injectors to operate while your cranking. I'd do the Crankshaft Position Sensor.

/loves remote starter switch.

-paK +2
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Old 11-29-2004, 12:36 PM   #9
rick-l
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Quote:
Originally Posted by ciper
In the service manual Compression Test Instructions:

3) -- How do you release the fuel pressure on a EJ25?
Simple way? Wrap the line in a rag and unscrew the clamp.

8) -- How do you crank the engine by means of the starter motor
Hmm, have to think about this but If I remember correctly there is a fuel pump fuse right? Just remove that instead
3) For the WRX you run the engine till it stalls after disconecting the fuel pump

4) That switch you stick a key in on the steering column
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Old 11-29-2004, 12:57 PM   #10
Jyik40
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On my 2004 RS there is a green connector that is located in the front passenger footwell. If you take of the body trim that covers the door sill, you can look under the glove box to see the connector with a round silver relay attached to it. That is the fuel pump relay. Take the plug out and try to start you car. If it starts then sputters and dies, you have relieved the fuel pressure from the rails.


Jay
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