[Technical] 97 Civic Fuel Filter Replace (RE: Fuel Pressure)

[aznalex]

i did a little research and know how to replace the fuel filter for my car

the only concern i have is the method of relieving pressure from the fuel lines.

a youtube video told me to start the engine then remove the fuel fuse thing.

a google document told me to pull the fuel fuse first then start the engine.

both lead to the same result: engine dieing out. but which one is safer? or does less damage to the car? (if it does)

any thoughts?

[bennjamin]

Lol. Don't

Before anything - disconnect NEGATIVE from
The battery. Pop open your fuel cap and remove it ( you will hear a slight gush)
That has both made your car safe to work on and released fuel pressure.

There will be a slight leak of fuel as you undo the top or bottom nuts to the filter - just Place a rag under if you are paranoid.

[aznalex]

thanks ben!

[rotary_snail]

Ummm dude that doesn't make sense.... There is a valve in the fuel pump which is designed to maintain pressure in the fuel lines after shutdown. This is why you don't have to crank the car for extended periods to start it back up. Secondly, why disconnect the negative terminal? Fuel pumps only prime up when the ignition is on (some newer performance cars prime when the drivers door opens, but not in this case). And lastly, the fuel tank is not under pressure, although it is a sealed system.

Pull the fuel pump fuse and let it run until it dies, that will depressurize the lines.

[ECU-MAN]

Ummm dude that doesn't make sense.... There is a valve in the fuel pump which is designed to maintain pressure in the fuel lines after shutdown. This is why you don't have to crank the car for extended periods to start it back up. Secondly, why disconnect the negative terminal? Fuel pumps only prime up when the ignition is on (some newer performance cars prime when the drivers door opens, but not in this case). And lastly, the fuel tank is not under pressure, although it is a sealed system.

Pull the fuel pump fuse and let it run until it dies, that will depressurize the lines.

I agree with you about the battery terminal, however you should and still do need to releave the pressure from that tank. This is built up vapor pressure that causes fuel to rush out the fuel and return line once you have cracked
the lines open.


the initial cracking of the lines is where care needs to be taken regardless of opening the fuel tank or not.

[rotary_snail]

You don't need to open the tank, pull the fuse and let it run till the engine dies. This relieves any pressure in the lines, the feed(which on most jap cars operates at around 3 bar, if injected) and the return(around 0.5 bar), some may still leak out when you pop the line. Difference being that it will actually leak, not be a pressurised spray.

It's not a majorly important point on cars operating at only 3 bar, because it can't really hurt you, unless it gets in your eyes(but then you should wear goggles too right...). But in commonrail diesel systems where the rail pressure can exceed 200 bar, then it is alot more important.

[ECU-MAN]

your above methos is very valid however not on the older Honda's as they do not have a fues for the fuel pump on its own. the fues is intergrated with the ECU fuse so the engine wont run. thus opening the fuel cap

[rotary_snail]

Opening the fuel cap won't relieve the line pressure, refer to my first post regarding the valve in the fuelpump. In a situation like that best option would be to disconnect the pump(ie unplug it), then run the engine. Bit more difficult, but same end result.

Myself, if it wasn't as simple as pulling a fuse and i was working on a relativly low pressure system, i wouldn't bother with it. Just have a rag ready for the fuel.

[ECU-MAN]

exactly,


I just crack them open slowly and its OK, however you still have to open the fuel cap to releave the pressure to stop fuel from pooring out from the built up vapour in the tank.

its simply not worth the time and effort to disconnect the pump and run the car to relave line pressure. cracking the line slowly is good enough and as you mentioned in your prevoius post safety glasess is a must.