I posted this on another forum but there isn't much life over there. This place seems more lively so I plan on sticking around. Anyway I've run out of ideas on chasing this knock and I'm starting to get a little bit worried. So I'm looking for what I should do next.

Here is the truck info... 2000 F250 4x4 206k. . Swamps Diesel 200/30's. Terminator HPOP. GTP38R. EBPV delete pedestal. Banks wastegate. AFE stage 2 intake. RiffRaff FRX. 4" exhaust. Hydra chip. John Wood Auto. 6.0 Trans cooler.

I have a knock sound coming from the area of #8. It is noticeably louder in that area with a stethoscope. Its not any louder anywhere else (oil pan, block, otherside of engine, or front). Truck does not smoke and runs and idles great otherwise. Was thinking possibly the cackle/fuel knock issue these trucks have but with bigger injectors and the FRX could this even still be a possibility?! Anyways here is what I've done.

Checked fuel pressure and at idle it is 61/62 with any tune. At WOT on Econ tune it goes down to ~40ish psi. With the extreme tune WOT dived down to 28/29psi. So my thinking was maybe that injector got screwed up so...

Swapped #8 injector with #2 so the front injector with the back to see if either it had some bad o rings or isolate the injector as the problem if the noise moved cylinders with the injector. While I did this I put brand new O-Rings on those two injectors and popped them in. Got it fired up and the knock is still in #8.

Unplugging the injector with the engine running the noise seems to disappear. HOWEVER, when I use the stethoscope the knocking noise still sounds like it's there but very faint. Without the stethoscope I can't hear it. Also driving the truck down the freeway and letting it coast the noise goes away when the injectors get cut off.

Recently pulled off valve cover and checked the pushrods and rockers on #8 and all looked fine.

The noise sounds just like this video.


At this point I'm thinking wrist pin, rod bearing or cracked piston??? Could it somehow still be a fuel knock? Let me know what you guys think or what I might look at next. I'm stuck. Sorry for the long post.

 

Do the hutch mod, then report back, bud

 

You sound like you know what you're doing. Have you don't any in-tank mods?

 

No in tank mods that I know of or have done to it. Even with the FRX you guys think it is a possibility air could be getting into the system and creating the knock?

 

I have tanks mods and an FRX and if I let the fuel level get too low, mine starts to knock a little bit and I can see my FP gauge flutter. The hutch mod might help with your wot pressure drop too. Dropping FP too low is begging to ruin your injectors.

 

Yeah once I found out how low the fuel pressure goes when I get on it I been easy on it. I will probably just do the hutch mod anyways. Anyone have recommendations on a kit?

 

No kit needed! Welcome to guzzle's In-tank Hutch Mod Web Page

 

Tee shirts! Get your tee shirts! No crowding needed, I got plenty of 'em. I would do the Hutch mod with all those symptoms. Oh wait.... I did. The dippy fuel pressure is a huge clue, and there is no guarantee you didn't hurt the injector. In fact, I'd say the opposite - you likely have an air-slapped injector in there. Keep track of 'em, so you know which one to send in for repair.

This got so bad with my truck that I bought a 9th injector to prevent down time. I still have one cling-on left over from the air-in-fuel days, and I'm watching it to see if things progress. They do. Once an injector has been air-slapped enough, they eventually go through many different symptoms of slap and knock, depending on EOT and stages of oil change. I am now to the point of smokey starts in just one cylinder... but my givachit is exhausted. One of these days I'll find the offending stick and swap it out... maybe.

The FRx is a great way to address the earlier fuel-in-air symptoms, but add fuel demand and more age to that poor excuse of a fuel pickup system - and the FRx is like trying to blow out trick candles. At that point, the FRx not only can't get all the air out - it also contributes to the dropping of the fuel pressure (bad juju). Even after my first few attempts at a Hutch mod, I still caught air getting into my new pre-pump strainer - so I kept at it until all air was gone for good (dropped the tank 4 or 5 times).

 

I agree with advice to do the hutch mod. This fixes a design that works fine with lift pumps in fuel tank, like many gas powered rigs. But is a lousy idea where framerail mounted pumps are creating a vacuum in that line. (What was Ford thinking?) That could solve your problem after swapping a known good injector.
That said, the odds are also strong that you have a mechanical problem as well. The good thing about the Hutch is it makes injectors live longer-they are not cheap to replace. That entrained air acts like a sand blaster to the nozzle and can destroy those heui injectors.
Larry

 

Do the hutch mod and vacume test it really good. Then let us know. I changed #8 way back and it quite it down. While you do it, send the injector back to swamps if it's under warranty,they should have it back pretty quick. But don't run your fuel pressure at 29 pounds, not good.