How do you release fuel system pressure?

Bungee · 02-22-2005, 12:36 AM

Is there a special device needed to release pressure in the fuel system? I'll be changing the Fuel filter in my 2000 Silvy.

Thought I read in a Haynes manual some time ago you can plug some kind of purge valve gizmo into the fuel system. But the guys at Autozone have no idea what I'm asking for.

Any ideas? Is there maybe a simpler way to release fuel system pressure?
Is it even necessary?

2000CAYukon · 02-22-2005, 02:14 AM

The fuel pressure is about 60 PSI at idle and it will hold pressure for a while. If you don't relieve it you will get some fuel all over.

I release the pressure at the fuel rail using a hose from my fuel pressure gauge and catch the fuel in an old cup. There is a schrader valve on the fuel rail (passenger side).

The other trick (have not done this myself) is to remove the fuel pump fuse and let it run out of gas.

//2000CAYukon

buttnekked · 02-22-2005, 03:40 AM

the trick with the fuse works. I just pull the fuse or pump relay, which ever is easier to get to. Start the truck and let it idle til it runs out of fuel in the system.

jzurita · 02-22-2005, 08:46 AM

I think there is a fuel pressure release valve towards the front of the vehicle (depending on which motor you have). a buddy told me he released pressure with a screwdriver and rags...sorta like releasing pressure from a tire. Personally, I looked around for that pressure release mecahnism like Haynes describes-couldnt find it. I just unhooked the fuel filter with plenty of rags. Little messy, not that bad though.

bowtieguy · 02-22-2005, 09:52 AM

the shrader valve is very easy and you dont get much fuel out of it, just a good size rag or small cup to capture the amount of fuel you will get out of that valve is all you need then you can change your filter without spraying fuel all over. you will still get some fuel obviously from whats in the lines at your filter but a small container is all you will need there as well.

Bungee · 02-22-2005, 10:16 AM

Thanks for each post. Forgot to mention, the engine is 5.3. I'm assuming the shrader valve is not in the engine bay, but under the cab somewhere? (It's waaaay too wet outside right now to check).

I'm also assuming
(1) shrader valve is first choice, and to activate schrader valve, just press the valve stem just like a tire valve?
(2) second choice might be removing the fuse? Is the fuse is in the engine bay's electrical center?
(3) third choice might be to not release pressure, (because there isn't that much gas coming out anyway) but have a supply of rags handy when disconnecting fuel filter? (and not while smoking! )

Faze3 · 02-22-2005, 03:44 PM

When I changed the fuel filter on my 4.8L, I simply popped the nut, there was a little hiss, and the fuel began to drip from the line.

Much less than I expected, but nothing to worry about. I can't imagine the 5.3L would be that different. Just make sure you've got a good-sized rag on the rail below the fuel line. I had some fuel pool there.

nineball481 · 02-22-2005, 04:14 PM

The valve, at least on my car, is on the fuel rail by the injectors. I would imagine that it might be in the same area for the truck, but am not sure.

J-Ri · 02-22-2005, 04:39 PM

Pulling the fuse is a great idea... I never even thought of that. I'd say that is probably the beat way to do it. However, if you do end up using the schraeder valve, wrap a rag around a screwdriver and press the rag firmly against the valve before pressing in with the screw driver. Gas WILL shoot out a fairly long distance, someone I know got it in his eyes. That brings me to something else, wear safety glasses. even if you use a rag. I'd rather look a bit goofy wearing big goggles than to not know how I look.

silveradoking · 02-22-2005, 07:14 PM

I just took the gas cap off...and popped the nuts...on a 5.3 it's so little fuel it hardly worth mentioning....just try to make the gas tank as empty as possible...

J-Ri · 02-23-2005, 01:19 AM

I'm afraid I don't quite understand. I am a bit tired/drunk, so this may make more sense in the morning

Quote:

Originally Posted by silveradoking

(1)I just took the gas cap off...(2)and popped the nuts...(3)on a 5.3 it's so little fuel it hardly worth mentioning....(4)just try to make the gas tank as empty as possible...

1) The cap for the tank? The tank isn't pressurized.
2) The filler neck nuts? We don't need to remove that.
3) Do the 5.3s come with smaller gas tanks than other engines? Are the fuel lines smaller?
4) Are you droping the tank?

silveradoking · 02-24-2005, 09:31 PM

hey, jr....You didn't understand what I mean't... I unscrewed the cap, where you fill your gas, just in case to let the air pressure out....then under the vehicle, where the filter is unscrew the nuts to take the filter off...A little bit of gas should come out of the filter...but it is "so little that it's hardly worth mentioning,".... then just pop your new filter in, and screw back your your gas cap...turn her on...probably she won't start on the first try...but the second time you crank her...she'll be flying...I never did any type 'depressurizing' under the hood...you don't need to...I can bet that almost ever mechanic that you go to does it this way....I change my fuel filter evry 10, 000 kilometres and never had a problem... ask a couple mechanic's in your area...they don't even have that special tool...

Jake795 · 02-24-2005, 10:48 PM

I've changed many a fuel filters at the service station where i work. We drive them up on the rack and loosen the nuts on them, let the fuel come out slowly, and then proceed with removing the filter and putting in the new one. Our 5.3s are extremely easy to change the fuel filter on. Up on a rack it takes about 6-7 mins start to finish. I imagine it taking longer on the ground, but still a simple task. The schrader valve is in the engine bay. I believe it to be on the drivers side of the motor right on side of the plastic cover that say vortech on it. I never release the pressure, but it can't hurt anything to go ahead and release some.

Jake

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