Replaceing injector O-rings on cat 3126???

Just got a FL-70 with 3126, has 298k miles. Runs good. Noticed on start up when cold smokes a lot. (25 degrees) Takes about 10 min to warm up, before smoke clears up. Smoke is not white, more like grey-black. When you listen to exhaust pipe, sounds like a small miss, when you open hood and listen to engine it sounds ok, doesn't seem to shake like a miss. Seems to have to crank more than what I think is normal when starting, even after warmed up. It will still smoke a small amount for 30 seconds when restarting. I changed oil, no antifreeze in oil that I could find, drained fuel tanks and no antifreeze in fuel, drained fuel filter, no anti freeze in it, looked in radiator reserve bottle no oil or diesel smell. I am thinking a injector O-ring may be leaking. If so, is there any to test the injectors while out (can a diesel shop test them)? And when I have them out should injector cups be replaced? From what I have read cups don't seem to be leaking. I am just basing my diagnosis on another truck I have with a 3116 cat 328K miles. Starts up cold, smokes for about 2 minutes, clears up, starts right up when warm, no excessive cranking, sounds smooth at tail pipe. I know the 3126 has a different fuel delivery system and is different from a 3116.

Hi John. Before you jump on the injector band wagon you should check the air intake heater. It is a grid style heater mounted in the engine intake. The ECM controls a relay which in turn operates the heater. The ECM will cycle the heater for starting as well as after the engine is running to help reduce smoking. The 3126 injector sleeves are stainless steel vs the copper sleeves in a 3116. The stainless sleeves don't cause as much trouble. The 3116 sleeves work well if the forcing tool is used but that is another story for another thread. Typically the HEUI injectors are tested in the engine using Cat ET.

I will certainly check the intake heater before tearing into the injectors. I just went through that with my 3116. For a couple of years it has been hard to start when cold and smoked. I keep it inside a unheated building and when much lower than 30 degrees, I would just plug the block heater in a hour or so before taking the truck out. It was one of those problems that was annoying but because of trying to drain the swamp from all the other alligators, just never had time to tackle running it down, so a few weeks ago checked the intake heater relay and replaced it and now starts like a new truck. Do you happen to know where the relay is located on the 3126? Must be in a different place that the 3116. I thought I had located it but when checking it out found that it was a relay that some how would cause my engine to crank over when jumping across it. It looked almost the same as the 3116 relay. If some one hooked a Cat scanner would it tell if a cylinder was weak or not firing right? If one of the O-rings was leaking what would be the sympthom? Like I said if you go back to the tail pipe it sort of sounds like a cylinder is weak, compared to my 3116. Maybe that is just the way it is supposed to sound. Though the engine feels smooth and seems to have plenty of power going down the road.

I'm not sure where that relay is. The OEM often supplies that relay, so it may be a Freightshaker part. It is possible that you have an injector O ring leaking or a leaky injector. ET may or may not show a bad injector. It is a shot in the dark with those systems. If you have ET hooked when you start it cold you could cut out cylinders quickly before it warms up and see which hole is the problem. At that point you still don't know if the problem is injector or O ring. If you want to chase the problem you could swap the injector from the bad hole with another one and see if the problem follows the injector.

That boat anchor Cat calls a 3126 will do a lot of things from a bad inector seal. It can and will fill the cooling system with fuel and push coolant/fuel out the overflow tank. Check your fuel tanks and see if the fuel is a black color from high pressure oil going to fuel return to the tank. If you don`t already use Cat oil and fuel filters, do it as soon as you can. You will lose way to many valves on the HUEI pump than it`s worth. The one you may want to look into for your problem and I don`t remember twhat they call it is the top left rear of the HUEI pump, horizontal in line withthe engine,when it gets dirt in it, it will cause an engine miss.

If not done, replace the fuel pressure regulator/check valve on the outlet from the head, there are a new version without that crappy oring seal avaliable.

Eriksson: Where is this valve located at and what does it look like? (is it the same one GregD1 is talking about?)

Scratch that, I was thinking of never engines than yours is.
But do put a fuel gauge on it and check during starts cold and warm, could also put a pice of clear hose on the return and check for air bubbles.
And as mentioned before, make sure inlet heater is working.

3116 engine cat 938F

I find fuel in my radiator was advice to change the o-ring for the injector and also the sleeves which do u think anyone can advice me here i am first time owner ... thank you