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Injector knock

 
  #1  
Old 12-20-2014, 11:40 PM
Rigormortise
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Injector knock

minor injector knock got worse. I now have hard start, louder knocking and loss of power. Here is what I've done so far...
Rebuilt fuel bowl / new filter
Isolated knock to #2 cyl
- stethoscope on top of injectors
- unplug injectors one at a time w/engine running
- measured temperature at each port on exhaust manifold
All point to the #2 cyl
Replaced injector with reman
Still knocking....
Returned injector and got a new one
Still knocking....(power does seam much better)
Did a fuel pressure test (at idle) and getting 55 psi (I checked out at fuel pressure test kit at the parts store and the bypass valve was leaking on the gauge so I did not test it under load, but I am getting 55 with the leak).
Removed UVC harness and did a visual check and an ohm test
All good...
Did another ohm test with UVC harness installed from com pin to each positive injector pin.
All good...
Still knocking...
The only odd thing I have found is a lack of oil coming out of #2 injector at idle, all other injectors looked normal, I'm not sure what happens at higher RPMs.

So that about sums it up, it's still knocking. Any ideas?
Sincerely,
Injection Dejection
 
  #2  
Old 12-21-2014, 05:26 AM
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{cracking knuckles}

While many may have chased this beast, I lived in a high-hide and documented it's behavior patterns - National Geographic style.

You may already know some of this - but I have to walk through all of it to make sure nothing is skipped over:

I don't know how many miles you put on the truck between disruptions of the injector. I can tell you air in fuel or oil will make the injector knock as it passes through the guts, with #2 and #7 getting first dibs on the air in fuel. I have read many things on #8 knock being attributed to air in fuel - but #8 has a different form of the air-in-fuel problem (momentary pressure drop because of firing order). #1 and #2 don't like air in oil, they are the highest point on the dead-head ICP oil line.

Saying all of that, you need at least 50 miles on the truck after pulling the injector - just to get all the air out. I've had situations where I had a cling-on in the engine for over 75 miles. I've learned going out on the highway and bringing the throttle to the ground Fred Flintstone style abbreviates the air purging process.

Air in fuel can have many sources, but a proper and thorough Hutch mod typically puts all the usual suspect in the big-house. Here's the question that may raise an eyebrow: Have you ever noticed if it seems to get better right after a fill-up? A higher fuel elevation in the tank puts more pressure on the fuel pick-up, so it is less inclined to suck air.

55 PSI fuel pressure at idle is good, but the real questions is... what happens at WOT? If you can't monitor the FP while driving, then you can't conduct an air-in-fuel test the easy way. A big drop in fuel pressure at WOT is strobe lights, a trumpet riff, and the Rockettes high-stepping across the gauge - trying to raise the alert that you have air in fuel, a clogged fuel system, or both. I have bigger-than-stock injectors, and my FP never dips more than 5 PSI at WOT. When I had issues with the fuel line before the pump, I'd loose as much as 20 PSI at WOT because of a poor hose fitting, and as much as 40 PSI because of fuel restriction.

Air in oil is a more dastardly creature, I would avoid going near its lair until you're assured it's not air in fuel that climbs into the upstairs room to get your sticks knocked up.
 
  #3  
Old 12-21-2014, 05:42 AM
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I had pretty much the same symptoms on an engine, but it was cylinder 8. The noise went away completely with the injector disabled. What I was convinced was injector knock turned out to be a bent crankshaft. Just sayin' . . .
 
  #4  
Old 12-21-2014, 09:40 AM
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Total disaster cannot be ruled out yet, but I've found many of my woes in the past have been things other than parts in the short-block. I've had a knock in #7 since I bought the truck - 80,000 miles ago.
 
  #5  
Old 12-22-2014, 02:22 PM
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The only odd thing I have found is a lack of oil coming out of #2 injector at idle, all other injectors looked normal, I'm not sure what happens at higher RPMs.
You see the lack of oil from #2 with the old injector AND the new one? I don't want to send you on a wild goose chase but could there be an issue with the IDM not firing #2 properly? The solenoid can be ruled out but maybe a weak signal?

Not sure about the mileage on your rig but these beasts require attention to the fuel delivery at some point. As mentioned, Hutch Mod and I'll throw in the RiffRaff FPx regulated return with CVD (check valve delete) fittings.
 
  #6  
Old 12-22-2014, 04:19 PM
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That's some quality troubleshooting guys. Subscribed.
 
  #7  
Old 12-23-2014, 06:02 AM
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I haven't brought this up, assuming you are torqueing the injector bolts properly. I shouldn't assume, so here it comes: You cannot elbow-torque an injector. Drifting from the torque spec will certainly cause the symptoms you are describing. I paid dearly for that little lesson.


Have you tried the UVCH link in my signature? It's a bit more thorough with the wiring to the injectors.
 
  #8  
Old 12-23-2014, 10:35 AM
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have you compression tested the cylinders?
 
  #9  
Old 01-05-2015, 06:05 PM
Rigormortise
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It's been a couple of weeks off from head-butting my injector knock. But my excuses have grown old. Here is where I am.

I have been using Torque App w/ford enhanced, but get no codes.

I downloaded car gauge pro, performed a buzz test (sounded good) and received a P1272 high side to low side open

I ohm tested from the IDM connector, according to to this link GB Remanufacturing - Tech Bulletin #103
All tests were within specs (Performed all three tests).

I have put on over 200 miles since I changed or removed the injector.

I haven't done a compression test so I'll need to find an adaptor for that, I don't think the rental kits at the auto parts stores are set up for the 7.3's.

On the fuel pressure at WOT, I agree I need to check that, but if the knock is present at idle and my idle pressure is good, then my brain (or lack of) tells me that isn't the issue.

Oh yeah, I did torque the injector bolts to 120 in. pounds.

I did the hutch & harpoon mod a couple of years ago.

What am I missing?
 
  #10  
Old 01-06-2015, 07:52 AM
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Fuel pressure: While I'm sure you were diligent with your Hutch mod, it is still best to conduct some tests to be sure no air is in the fuel. You can have a ton of air in the fuel and good FP at idle. It's WOT that really tests the fuel pump and the integrity of the fuel lines. I had perfect fuel pressure at idle... but not so much at WOT - I had to double-clamp the fuel line out of the tank.

Have you seen the Torque Pro PID thread on the forum? Are you monitoring ICP/IPR/FIPW?

Did you spin the pushrods to make sure none were bent?

Are there running issues with the truck, or is it just knock?

Smoke at startup? Did you flip the oil filler cap over the snout to do the hover test?

#1 and #2 frequently don't have oil coming out of them immediately after draining the oil rails. It takes time to get the air out of the system and for oil to shoot out of either of those. If you covered the VCs before the air was purged, you wouldn't see if #2 has oil shooting out now.

When did the knock start? Did something change or did you do any work on the truck at that time?
 
  #11  
Old 01-06-2015, 08:37 AM
liquidlounge
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Tug- I have wondered how this product would do on a diesel. One of its claims is reduced air. Maybe a buckzooka reload will be in order. Haven't found out if its diesel rated yet. http://youtu.be/4rG97UuVgmQ
 
  #12  
Old 01-07-2015, 12:07 AM
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Just what wanted to hear, if I don't figure something else out I will drop the tank (after I burn off 30 gallons of fuel).
 
  #13  
Old 01-07-2015, 06:39 AM
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Originally Posted by liquidlounge View Post
Tug- I have wondered how this product would do on a diesel. One of its claims is reduced air. Maybe a buckzooka reload will be in order. Haven't found out if its diesel rated yet.
Diesel rating is one question, the other is "wouldn't that behave like a filter?" While ingenious, it is a media that can load up over time. It's perfect for a rock crawler that works a few weekends a year - but a road machine that uses the quantity of fuel we do? I don't know how long it would last before the need to drop the tank to swap it out.

Originally Posted by Rigormortise View Post
Just what wanted to hear, if I don't figure something else out I will drop the tank (after I burn off 30 gallons of fuel).
The fuel pressure gauge really paid off for me. Not only did it point out the problem, it also pointed out I didn't get it fixed the first time. I don't know what your budget is, but the fuel pressure gauge rates right up there with EGTs. My analog gauges are dual EGTs and fuel pressure. The rest is OBDII.
 
 
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