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YACT: Fuel System Pressure

PricklyPete

PricklyPete

Lifer
I'm about to change the Fuel Filter in my car (99 Mazda Millenia S). The manual says that I need to relieve the fuel system pressure before disconnecting the fuel filter. To do this, the manual says I need to start the car, and while running, remove the relay to the Fuel Pump. Unfortunately it does not give the exact location of the relay and I have been totally unable to find it.

A friend told me that to relieve the fuel system pressure, I just need to remove the gas cap. Is this true? If not, are there other ways of relieving the fuel system pressure?

Thanks for any help.
 
Removing the gas cap will only relive the tank pressure not what is in the fuel line.

It is most likely located in your fuse panel under the hood (Many vehicles now have 2 panels)

Edit: I guess I should add, if you are not used to this a Relay will be in the box with the fuses you are used to seeing but they look like a 1" cube.
 
All I do is take the gas cap off, wait a coupel minuts and then take it off. Pressure for the most part in teh Filter dies down after a minute or so.
 
I just hold my finger over it and it barely sprays more than a gallon or so through the engine compartment while I change it 😀
 
Originally posted by: Skoorb
I just hold my finger over it and it barely sprays more than a gallon or so through the engine compartment while I change it 😀
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You are getting a car fire extinguisher from your secret santa 😉

 
Originally posted by: LAUST
Originally posted by: Skoorb
I just hold my finger over it and it barely sprays more than a gallon or so through the engine compartment while I change it 😀
Click to expand...
You are getting a car fire extinguisher from your secret santa 😉
Click to expand...
Skoorb has not signed up as of now, maybe he will ?

 
I've changed f/f on several types of cars. Some seem to hold more pressure and volume than others. A gas shower is not fun. If you register at AutoZone.com they have a good resource guide for auto maintenance w/lots of detail pics..................😉
 
Originally posted by: Skoorb
I just hold my finger over it and it barely sprays more than a gallon or so through the engine compartment while I change it 😀
Click to expand...

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Is that how you detail the Nissan's engine bay. Good tip..........................😀
 
Originally posted by: galvanizedyankee
Originally posted by: Skoorb
I just hold my finger over it and it barely sprays more than a gallon or so through the engine compartment while I change it 😀
Click to expand...

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Is that how you detail the Nissan's engine bay. Good tip..........................😀
Click to expand...
LOL, damn guys pulling a relay is five thousand three hundred and sixty seven times easier then getting gas all over the place. 😛

 
Originally posted by: LAUST
Removing the gas cap will only relive the tank pressure not what is in the fuel line.

It is most likely located in your fuse panel under the hood (Many vehicles now have 2 panels)

Edit: I guess I should add, if you are not used to this a Relay will be in the box with the fuses you are used to seeing but they look like a 1" cube.
Click to expand...

There are two "fuse" boxes in the trunk. One contains relays only and one contains relays and fuses. Unfortunately there is nothing labeled fuel pump. The only thing I could find that was even remotely similar was the fuel injector relay...but I believe that would have the opposite effect.

I have looked at Autozone, but they do not have maintenance guides for my car yet...and I imagine it will be a long time if ever before they do (not a very high volume car...they also seem to have mostly American cars at this point).


 
My fuel filter is underneath the back of the car right next to the tank. I just pull the hose off it and let it drip on the ground.
 
Originally posted by: Marlin1975
All I do is take the gas cap off, wait a coupel minuts and then take it off. Pressure for the most part in teh Filter dies down after a minute or so.
Click to expand...
I'm not sure what kind of car you have, but the gas cap has nothing to do with the pressure in the fuel lines...

The fuel pump produces ~40psi and has a check valve in it to keep the fuel line pressurized when the car is shut off. (If the fuel line didn't remain pressurized, the car wouldn't start immediately.)

I'm not sure that I'd recommend this to a newbie.... But what I usually did when I was a mechanic was release the pressure at the fuel rail. There's a shraeder valve on the fuel rail. Grab a rag and cover it while pushing down on the valve. If it's not covered very well, YOU WILL spray gas all over the place. I don't think I need to get into the details of how dangerous that can be.

(Actually, the above isn't really true. When I was a mechanic, I just disconnected the fuel filter and let the fuel spray. I didn't have time to be "safe." 😕 But I think the above advice is significantly better.)
 
Originally posted by: galvanizedyankee
Originally posted by: Skoorb
I just hold my finger over it and it barely sprays more than a gallon or so through the engine compartment while I change it 😀
Click to expand...

----------------------------------------------------------------------------------------------

Is that how you detail the Nissan's engine bay. Good tip..........................😀
Click to expand...

You don't need that extra horizontal line as a divider... the quote feature automatically puts a horizontal line in there for you 😀
 
Originally posted by: PricklyPete
Originally posted by: Redhotjrm
Well, I was wanting to know if the S has a 2.3L or 2.5L, but since you're LAZY I'll post the answer to both fuel pump relay locations:

2.5L Fuel Pump Relay

2.3L Fuel Pump Relay

EDIT: I'll go ahead and tell you which engine the S has too. It's the 2.3L. So disregard the 2.5L.
Click to expand...

Sorry, I was at lunch. Thanks...I should be able to find it.
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Quick Question RedHotjrm...how do you join e-toolbox. It doesn't seem to have a way to sign-up or any membership information. I know I do not need to be a member to view the pic you posted, but I was just curious about the site.
 
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