wierd knocking sound

early99powerstroke · Feb 13, 2012

got an early 99 7.3 powerstroke 178k miles. started it up one day and after it started to warm up it started making a LOUD knocking sound. I installed a riffraff diesel FPRX fuel crossover and it quieted down alot, but the sound is still slightly there if I listen carefully. I also have small amount of blue smoke under heavy acceleration with my chip turned up. This is really worrying me.... I haven't done a compression check yet(but will be soon, kinda scared...) I did a contribution test and it passed (don't know how reliable a contribution test is). Any ideas to what is causing this? worn Injector O-rings, bad injector, worn piston rings, scarred cylinder wall? All ideas and theories are welcomed. I just want to track down this problem....

BigAlsPSD · Feb 13, 2012

If you flip the oil fill cap over upside down and set it on the oil fill will it sit there? Or will it blow off with pressure behind it?

early99powerstroke · Feb 14, 2012

When I flipped the oil cap upside down itll just on the oil fill tube until the vibration from the motor causes it to slowly vibrate off which I don't believe the pressure from the blow by caused cuz there really doesn't seem to be any pressure. My truck does seem to have some blow by out of the oil fill tube. Is that normal for 7.3 powerstrokes?

Dmstrucks02 · Feb 14, 2012

There will be some vapor coming out

BigAlsPSD · Feb 14, 2012

Sounds like quick check blow by is fine.

hawgdoctor · Feb 14, 2012

How do the injectors sound on a buzz test? Are they all pretty equal? What does your fuel pressre look like? How old is the filter? How about shaft play in the turbo?

early99powerstroke · Feb 16, 2012

changed fuel filter a few days ago cuz it was extremely black, don't know what my fuel pressure is, buzz test sounded equal on all injectors, passed contribution test. What is wierd is that after changing my fuel filter the knock got really loud after starting the truck up but quieted down after a few mins (maybe the air bleed out due to my riffraff fprx). Hopin my compression is fine...

Curtis@Vision Diesel · Feb 16, 2012

Just throwing this out, I know awhile ago working on a guys truck he brought to a buddy and myself saying he could hear a slight knock to it. When we go the truck we could barley hear it as well. We traced it down to an injector then pulled that injector moved it with one that was not giving a little knock and the knock followed the injector. Have you pulled your valve covers at all? Or is the knock not even coming from there? Like you said injectors can loose o rings ect, Or internaly wich I know nothing about. Good luck man

BigAlsPSD · Feb 16, 2012

If your filter was really black that is usually a sign of bad injector orings, which could very well be your issue.

moose99psd · Feb 19, 2012

ive never heard a "knocking" from bad injector orings, or read about it. and i had all 8 bad orings when i changed mine. sounds like you have an injector issue. if it quieted down after making mods to the fuel side, try adding a fuel addative like schaeffers and see what happens.

early99powerstroke · Feb 20, 2012

Ok update. I pulled injectors 4,6, and 8. I replaced all the O rings and copper washers on them. I didn't pull injector 2 because its brand new and was replaced about half a year ago. I wanted to pull the passenger side but didn't have time. After replacing the injector O rings I put the injectors back in a different order to see if it made a difference and it did but not in a good way.... The knock got slightly louder...and the blue smoke is still emitting from my tail pipe... Was it possible that I didn't get the injectors to seat all the way in? I'm gonna do the passenger side and see if it makes a difference. Anyone got an idea of what this means? Also is it possible to have a bad injector that the buzz test and contribution test wouldn't be able to pick up?

Curtis@Vision Diesel · Feb 21, 2012

early99powerstroke said:
Ok update. I pulled injectors 4,6, and 8. I replaced all the O rings and copper washers on them. I didn't pull injector 2 because its brand new and was replaced about half a year ago. I wanted to pull the passenger side but didn't have time. After replacing the injector O rings I put the injectors back in a different order to see if it made a difference and it did but not in a good way.... The knock got slightly louder...and the blue smoke is still emitting from my tail pipe... Was it possible that I didn't get the injectors to seat all the way in? I'm gonna do the passenger side and see if it makes a difference. Anyone got an idea of what this means? Also is it possible to have a bad injector that the buzz test and contribution test wouldn't be able to pick up?

Sounds like you got a bad if not a few injectors. Where did you have your last injectors done buy? When re installing ur injectors, while seating them, did each one feel like it bottomed out eventually? They should and the heads of the injectors should damn near be flush with you rocker arms.
As far as a buzz test. They do nothing but tell you if the injector is firing. Does not tell you what's going on internally and what the injector itself is flowing and so on.
You got a bad injector somewhere. Have you tried unplugging each injector individually with the valve covers off and listen to how the truck runs and idles through each injector.
Good luck keep us posted and if you got any other questions.

early99powerstroke · Feb 21, 2012

Well I've decided to do a compression test on my motor. Can anyone give me an idea of what my specs should be such as an acceptable range? I also remember someone saying that my elevation will have an effect on my compression readings? Also how many times do I crank the motor over? Is there any fuses I should pull out before doing so? Thanks.

Curtis@Vision Diesel · Feb 23, 2012

I know everyone has different opinions on what a good to not so good compression reading is.
Just make sure that you dont have 1 cylinder 10psi off from the rest or Huston....we have a problem.

neverkickn · Feb 23, 2012

97pwrstroke said:
I know everyone has different opinions on what a good to not so good compression reading is.
Just make sure that you dont have 1 cylinder 10psi off from the rest or Huston....we have a problem.

I wouldn't be that concerned with a 10 psi difference, it is a percent variation that you look for. A common acceptable max percent difference that I have read is 15%. Understand that that is ideal but your engine may fire and run fine with a percent difference even higher than that.

You know you had oil in the fuel so you know that you have an oring or internal injector failure so why not just change all of the injectors out as a set and be done with it, assuming you have decent compression.

As far as the smoke, it will do that for a few miles if you managed to get oil/fuel into the exhaust manifolds during the injector swap.

Curtis@Vision Diesel · Feb 23, 2012

neverkickn said:
I wouldn't be that concerned with a 10 psi difference, it is a percent variation that you look for. A common acceptable max percent difference that I have read is 15%. Understand that that is ideal but your engine may fire and run fine with a percent difference even higher than that.

You know you had oil in the fuel so you know that you have an oring or internal injector failure so why not just change all of the injectors out as a set and be done with it, assuming you have decent compression.

As far as the smoke, it will do that for a few miles if you managed to get oil/fuel into the exhaust manifolds during the injector swap.

Really? They way I took it was if all your cylinders checked out good, but you had that one cylinder 10psi lower then the rest, would be a sign of bad motor compression. As Im still new to this in depth on these motors. Just stating as what I have been told.
I 100% agree with you on the injectors. I also like to tell friends and people after driving with new sticks, to change your oil sooner than later from fuel being where it shouldnt and what not.