How are there so many o-ring problems... I've literally tried to **** it up and it never happens.

 

That looks like the thick O-ring.

With that straight pickup tube, it needs the thin one.

The thick one probably doesn't go up into the pump body like it's supposed to, therefore might create a leak, if the pickup isn't absolutely straight up into the hole.

Not sure what the actual diameter of the 2 O-ring styles is.

As far as I'm aware it's not a year-model thing, or an engine-model. Seems to be kinda random. Although the non-straight version seems to be more common in general.

Pretty sure you can measure the bore of the pump and just get an O-ring of the appropriate thickness out of an assortment or something. You'd probably want about .010" - .015" of crush on it. Measure the hole, subtract the .875" of the tube, divide the result by 2, get an O-ring that's about .010" thicker than that. Or [gasp] [horrors] just buy the right thing, if it's available that way.

 

I got the correct oring and no more delayed pressure problem. First start in AM the gauge takes 2 or 3 seconds to register pressure but the top end noise is gone. After the first start of the day it makes pressure instantly.

 

That’s a plus. Glad to hear.

 

Had the same issue when I turned my truck back to stock. The fel pro O-ring I got from advance auto was t correct. Had to use green one from GM for my 2012

 

So I know this thread is a couple months old, but I have a 2005 6.0 that is doing this. Do you need to pull the pan to change the oring or can you just pull the front off?

 

you can do it with taking front cover off and dropping the pan down to the front crossmember but it’s a pain and you risk pinching the o ring.