7.3L Rough Idle/Knock, White Smoke when Cold, Loss of Power - Page 3 - Diesel Forum - TheDieselStop.com
'99 & up 7.3L Power Stroke Engine and Drivetrain Discussion of the '99 & up 7.3L Power Stroke diesel engine and drivetrain in the 1999-Up Super Duty trucks and Excursions. No gas engine discussion allowed except on transmissions and drivetrain that pertain to all models. Please confine discussion of topics in this forum to those items that are specific to the 7.3L Power Stroke engine.

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post #31 of 37 (permalink) Old 03-05-2014, 08:17 AM
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Yep good sign there.I thought more about it.so an engine up there putting out 300 in the clouds is going to do 350 down here.Wow I really hadn't thought that.
Still lower range numbers but will work for sure.
A leaking line will give you issues for sure as I earlier stated.I was not trying to give you a heart attack.Finding out compression is really first step after gas.Find that leak.Get a proper fuel pressure gauge fitting installed on fuel bowl.Have it tested after leak is fixed and record it for future reference.
You asked about multiple places to check for fuel pressure.If you have stock set up there are also test ports on head at opposite ends of fuel entrance.Cross over kits utilize that port.
There are check valve fuel inlet fitting with screens in them.It is possible to get debris on the screens from trash in fuel that didn't get filtered for some weird situation that arose.Sometime pieces of the vibra lock oring on the fuel supply line get on the screen from it crumbling upon the line being removed at one time.
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post #32 of 37 (permalink) Old 03-05-2014, 08:25 AM
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You think a leak down test or compression test?


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post #33 of 37 (permalink) Old 03-05-2014, 08:45 PM
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I would do a compression test for sure.A leak down will pick up a valve issue but is a little more work than just doing a running compression test with a high range high quality disel guage like a snap on,after recording cranking reading.The rocker really puts that lateral force on the valve guide.This method will show a worn guide and how the compression is lost there with it shifting while running.This condition is hard to pick up with just a crank reading or a leak down test.I have mentioned this in the past,so this time I have found a video to refer to .The guy goes by dieseltechron.
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post #34 of 37 (permalink) Old 03-06-2014, 01:22 AM Thread Starter
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Okay, so I did some looking around by the fuel bowl and I definitely have a fuel leak. I touched the back of the fuel bowl, my hand got wet and smelled like diesel. I believe it is coming from the fuel filter cap because the fuel bowl is slightly dusty on the outside, except for the entire back side, from immediately below the cap all the way down. It's clean like the fuel has been leaking from under the cap and cleaned the dust off. While the truck was running, I looked at the back of the fuel bowl and couldn't visibly see it leaking, so it must be a pretty slow leak. Every time I park somewhere, there is at least a 5" diameter spot that looks like oil below my truck. After finding this leak, I now realize that it is actually fuel that runs down the valley and picks up some old oil along the way, making it dark like oil. After consistently parking on my driveway, there is a huge spot on the concrete (about 3' x 3'), and it is much lighter in color towards the outside, like it's fuel, not oil. I don't know why I didn't think of it before.

Is it possible that such a slow leak from the fuel bowl could be creating spots like that everywhere I go, or is it more probable that I also have another fuel leak from somewhere else, also?

Also, could a leak from the fuel bowl be causing all of my issues: rough idle/knock, terrible fuel mileage, and white smoke on cold start?

Btw, thanks a lot for helping me through this!!!
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post #35 of 37 (permalink) Old 03-06-2014, 06:31 AM
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Sounds like the fuel filter gasket got installed upside down and / or it got kinked up and is causing a leak - or the cap is not tight.

(Or something cracks or the drain o-rings are leaking.....)

You can get a new filter / gasket and replace it or just inspect the one you have. You should be able to see if the gasket got bundied.

The gasket should be installed with the wide flat part down on the aluminum bowl and the tapered part against the cap. Lube the gasket with some fuel prior to setting it in the fuel bowl groove. then tighten the cap buy hand. Then I take two crescent wrenches - one I open up and put the wretch part ingot he grooves of the cap, and while pushing down on the so it doesn't jump out, I turn it with the other one. There appears to be a positive stop - just try to be smooth with it so it is all one motion. You could also just try to tighten it as it sits.

Wipe it all down and cycle the key a few times to fill the bowl.

------
If the fuel drain orings are leaking, you will need a repair kit from dieselorings.com to replace the orings. If this has never been done, it is common.


I doubt this the issue as a leak that slow will not affect the pressure enough - even if you already have other pressure issues.


But take it one step at a time.


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Last edited by Flywheel; 03-06-2014 at 06:36 AM.
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post #36 of 37 (permalink) Old 03-06-2014, 10:05 AM Thread Starter
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Okay, thanks a lot. I will try that and see what happens.
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post #37 of 37 (permalink) Old 04-09-2019, 07:03 PM
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Fixed this problem

I was having this problem with my 7.3l excursion, and I did an oil change (3k mi.). I found that I only had around half the total oil in the engine. Yikes!!!!
Not sure where it went. No detectable oil leak on the engine, no oil drips in driveway, no smoke from tail pipe (even on cold starts).
I went to Shell T6 5-40 oil. There's no noise nor loss of power at start up/cold anymore. Pretty scary. Crossing fingers that everything is okay now.
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