Injector replacement can of worms

[jonny d]

So here it is. Crossover tubes. Now for the long answer.

I called Todd at TC diesel. I described my symptoms:
With the engine cold, a light smoke, almost like a light haze at idle. But the truck ran ok.
When the engine reached about 150 degrees, I started getting noticeable black smoke, even at idle. Also, there was a large loss of power, to the point of not being able to reach 55mph. No check engine light at any point. Engine would die when I engaged clutch to shift gears if I let the rpms drop below 1,000.

When installing the injectors I was meticulous about cleanliness and the installation procedure. Everything was torqued to spec. I checked everything twice, and then a third time to make sure I didn't miss anything.

Todd's first thought was the crossover tubes but the smoke wasn't a usual symptom of that. ( if I am not remembering that right Todd, feel free to correct me)

I decided to take Todd's advice and check the crossover tubes. Before I pulled them I took a torque wrench to each one to verify they were torqued properly. I set the torque wrench at 34 ft lbs and checked each bolt, increasing the torque by .5 ft lbs each pass. 3 did not budge up to the 37 ft lbs. 2 moved at 36 ft lbs, and one moved at 35 ft lbs. How critical is 2 ft lbs you may wonder? I decided to find out and put the truck back together.

All symptoms resolved.

Without spending a million dollars on a torque wrench how accurate do you get? My 3/8 proto is advertised at +/- 3%, the equivalent snap on claims +/- 2%. So the margin of error at 37 ft lbs would be +/- 1.11 ft lbs and .74 ft lbs. So even at the outer limits of my torque wrenches accuracy, it has been within 1 ft lb in the mid range when calibrated, it doesn't explain the crossover tube the was 2 ft lbs under torqued, the other two were within the margin of my torque wrench.

So now I have to wonder, what caused that one to be loose? I can without a doubt say that I torqued them all the same. Heat made the problems worse, so maybe that had something to do with it?

Well there you have it. I hope that isn't too much incoherent rambling, I just typed all that on my phone and it is after midnight.

 

[Wayne M.]

I’m glad that’s all it was, however labor intensive it was.

 

[TCDiesel]

This is why we recommend 42FT, If everything is seated perfectly with virgin Mating surfaces 37FT works, 42TF is more forgivable TQ.

 

[seafish]

I am very glad that you and TC got it figured out without too much head scratching and having to replace the actual injectors!!! Like I said, his HPCR diagnostic skills are impeccable.

In terms of torque variation in general, I have noticed that how quickly and how evenly I apply pressure to the wrench handle directly affects final torque even when leaving the wrench at the same setting between bolts. For example, after rotating tires, when I torque the lug nuts on my truck back to 135 fp, like many if us, I approach the final value on each wheel in 3 rounds (85,105,135). But I have always noticed that ANY lug nut will turn farther then another (in other words, will be tighter at a final higher torque) if I turn the wrench more quickly ar apply more pressure to the wrench while turning it. SO all that being said I am guessing that that might well be the source of your SLIGHT variations in final torque,

Of course, I am NOT at all saying that you don't know how to use a TW...obviously you do, but only that light discrepancies are built in to the use of the wrench, as well as the accuracy of the wrench as you noted. AT 135 pounds, I am not worried at all about a slight variation, but at the lighter 37 fp for the XO tubes, there is obviously a concern.

I LIKE Todd's idea of lightly increasing final torque on the XO tubes to overcome that problem!!!

 

[steelhead01]

Always pays to go back in and do a retorque after at least 1 heat cycle.
Too many contact/tension points on the injectors/tubes. Tube threads, tube contact>injector, injector seat, injector bolt threads.
RPs vibrations help to vibrate and settle every contact point in or loosen them if under torqued.

 

[sag2]

I'm glad that fixed it. Although nothing wrong with 42, I have never seen one that was a couple lbs loose cause a problem like you had. they are generally around 1/8 of a turn loose when they have trouble