I have been noticing a knocking kinda noise in my truck for a while now (6 mths or better) especially at higher speeds. I recently had tranny issues & was hoping the noise was tranny related. I had it rebuilt @ BTS & on the way home, I noticed the noise was still there.. I had a little over 12000 on the fuel filter so I thought I would change that out today to see if I noticed any difference. I went to the Napa near me & all they had was the Napa gold.. It was different than my usual filter, with a flat top gasket & the large o-ring also. There were no instructions, but I assume I got the ring in the right place. I cycled the fuel pump twice & fired it up & it started up fine, seemed to be idling real smooth. i went for a ride & at my first stop.. I noticed a loud knock.. I had cars behind me so i couldn't sit there so I drove a little longer. Thats when I started noticing the white smoke & it seemed to be running rougher. I went home, drained the fuel bowl & took out the filter & double checked everything, put it back together & fired it up & it started REAL rough & white smoke was coming from under the hood so I shut it down.. I checked for fuel leaks & couldn't find any, so I started it again. & it was smoking bad again. I let it run & got out.. the smoke was coming from the passengers side, near the rear.. I'm 95% sure I have a UP pipe leaking so I figured thats where its coming from. The smoke seemed to clear up some so I went for a ride to a big truck diesel shop near me to see if they could throw a meter on for me & do some checks but they were to busy. I brought it home & it seemed to run ok, maybe a little miss & was just smoking a bit. if I shut it off & restart it. I get a loud knock, white smoke & maybe 3-4 "chug chug pop pop" sounds & then it clears up.. If I hit the skinny pedal, I get a cloud of black/grey smoke..

I have a friend who is a production manager at his inlaws repair shop & they have a snap on diagnostic tool he could bring home, but I remember him telling me he really doesn't know if it can do the buzz tests, etc.. He said it most likely can.. they paid almost $2000 for it.. but then again its figuring out how to do it??? I did the 50 cent mod on the drivers side last winter & just ohmed the passengers side the other day.. IIRC, I was getting between 4.2 - 4.9 on that side.

I'm half tempted to take the new filter out & put the old one back in to see if that makes a difference.. But other than that, is there any kind of diagnostics I can do without a meter? This is making me ill.. after just spending the $$$ for a BTS & now I have a new problem..

Here's a link to my previous thread that I posted after my return from BTS.. I've just been to busy to work on my truck lately & haven't done much other then testing the UVCH & now changing the filter today..

https://www.ford-trucks.com/forums/9...ing-issue.html

 

I would tell you to check the UVCH but you already did that. Im sure he can do a buzz test with the snap-on.

 

isn't white smoke un-burnt fuel?

 

I would check your fuel pressure at the back side of the bowl. There are screens inside the tank that can get clogged. Have you done the in tank mods? The scan would be a good idea. You could also do a cylinder contribution test. Good luck! I hate it when my truck is not running right so I know how you feel.

 

The man at the Diesel shop I stopped a said maybe air in the fuel, to recheck the cap.. I did that once already & unless i'm missing something.. it seems tight.. no fuel leaking out or anything. Why would changing the fuel filter make this big change?? I haven't noticed any white smoke prior to this, but I did think the black smoke maybe had a greyish color to it.

 

How do I check the fuel pressure? I haven't done the in tank mods. I read a thread where someone said to blow air backwards thru the line from the pump to the tank to see if it ran any better.. I may try that. I hear you on the truck not running right. I have been dealing with one issue or another since my tranny started giving me fits back in August..

 

I'm wondering if some air got in the fuel sys when you changed filt. Maybe run it down the road hard enough to purge it. If you got no leaks what else could it be?

 

I'd drop the tank and do the in tank mods to eliminate that as a possibility and also check the fuel pressure. You'll need to connect a pressure gauge some where on the fuel bowl. Maybe someone can chime in and say where to plug it in.

If you lived closer I'd just drive over and we'd make a day of dropping tanks. I need to drop mine as well though haven't had time, I already have the parts.

 

I did run it pretty hard.. I'm just wondering if my knock has been something injector related & changing the filter escalated the problem? Let some dirt in or something??


I just wish I knew this was my problem.. Could low fuel pressure be causing my knocking issue all along?? It doesn't seem to be at a big loss for power really.. I just wish I had thought of the in tank mods last winter. My truck was in the body shop & they put a new bed on for me after a crash.. that would have been the perfect time.. I want to do the in tank mods.. but that would really push me over the edge if I dropped the tank & did that right now to find that I still have my knock..lol

 

You can test it at the back side of the fuel bowl. Here it is on Bob's site:
Replacement O-rings for Ford Diesel Engines.

If you blow back to the tank you probably want to drain the fuel or you'll get a diesel bath. You may want to try the old filter. I never had any problems after changing them. I usually just cycle the key 2-3 times for 20-30 seconds.

 

think td is right you will not know till you put a gauge on it. never had a problem change filt also & I got stuck with one off the napa wix before & didn't have problems. wish I wasn't so darn lazy I need to do the in tank mod also.

 

Well, I changed the filter back to my old one last evening & after about a minute.. it seemed to clear up & the smoking symptoms went away. I didn't get to drive it because we had to go out to dinner with my family. Now my problem is.. My friend never called me back about his Snap On scanner.. so odds are he didn't bring it home. If I go somewhere to get a buzz test/contribution test..it will be warm when I get there. Will that be a big issue? I know of 2 other diesel shops within 5 miles that I can go to that work on big trucks.. but don't want to waste my time if its not going to give me a good reading because its warm.

 

That's good news! The filter must of been restricting fuel. I would try to hook up with your friend and check it out.