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Replacing Fuel Filter

 
Old 05-12-2019, 02:24 PM
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Joe K
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Default Replacing Fuel Filter

I'm going to be replacing the fuel filter in my 85 Z51 in the next few days. I'm getting a pressure gauge from autozone. Want to check pressure before and after. Not sure if it will allow me to relieve pressure with it. Is there an alternative way? Car has an adjustable regulator. Should the pressure reading be the Factory specification? Don't want to adjust anything I don't need to. TIA

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Old 05-12-2019, 02:47 PM
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Originally Posted by Joe K View Post
I'm going to be replacing the fuel filter in my 85 Z51 in the next few days. I'm getting a pressure gauge from autozone. Want to check pressure before and after. Not sure if it will allow me to relieve pressure with it. Is there an alternative way? Car has an adjustable regulator. Should the pressure reading be the Factory specification? Don't want to adjust anything I don't need to. TIA

Joe K
I forget if the l98 uses vacuum reference for fuel pressure or not. At any rate, the easiest way to relieve fuel pressure is to pull the fuel pump relay while it's running and just let the car stall. Crank it for a few seconds after and then you should be left with little to no residual line pressure.

As to the vacuum reference, it should read the factory spec while running and then higher or lower... I forget... with just a key on while priming.

Edit: just realized you said it has an aftermarket regulator? All bets are off if the car has some work as to what the pressure is set it... if it runs well, don't mess with it.

Last edited by 84 4+3; 05-12-2019 at 02:48 PM.
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Old 05-13-2019, 09:24 AM
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85WHITEZ51
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Relieving pressure is best done as suggested above. Also, remove the pressure cap from the gas tank. It helps with the siphoning effect but still be prepared that fuel will continually come out of the line while you work on the filter so wear some good rubber gloves and have several rags with you that you can throw away.

If you don't have them already get some flare nut wrenches. I don't recall the sizes off hand needed but it's this type of wrench -
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You ABSOLUTELY do not want to strip one of those bolts as it's a major PITA at that point. Ask me how I know ;-) If it's the first time it's been changed in a long time it very likely could be harder to remove than you would think. As such I would spray with some penetrating oil as well.

Also, be sure to have a wrench on the filter and the fuel line. Overall it's not hard but it can be messy.

To answer your other question. A fuel pressure gauge should allow you to relieve pressure as well as it should have a bypass hose that would go to a bucket. You want to check fuel pressure with the vacuum line off and the car at idle. Should be around 35 PSI for an 85 but could be different based off what the car has done.
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Old 05-13-2019, 09:32 AM
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Picked up the gauge and it does have the pressure relief hose too. Filter arriving later today. Thanks for the help everyone.
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