Good idea or bad? I wanna check my injectors have a feeling I got a bad one. My plan... with engine running I wanna crack each injector lineone at a time till I find the bad one... now better to do it at each cylinder or on the rail? Cylinder prob better of the 2 no!?

I stated in a earlier post that I was experiencing a rough idle when the engine is at the high idle (1000rpm) it seems to have a "miss" at the tail pipe. Its most noticable at cooler ambient temps (-10deg C and lower) above 0deg C no miss or rough idle due to warmer ambient temps!? Had it at the stealership .... they couldn't find anything wrong (of course it was also a nice warm sunny day!![:@]) the truck didn't throw any codes so computer mechanic says all is well!! Well I'm back at work for another 2 weeks in the bush and guess what!? its below 0deg C and truck is running rough at high idle and drinking up the fuel. Truck is not smoking black/white or any other colour and I am not seeing any "extra" oil on the dipstick.
I'm hoping to do the injector check and get back to the stealer and point to the bad injector and tell the tech and his boss not to reley solely on what the diagnostic puter tells em, but to have a look and listen!!

 

On the High Pressure Common Rail engine you CAN NOT crack a line to cut out a cylinder like you could on an engine with an injection pump. Doing so will drop the fuel pressure on all cylinders, not just the single cylinder. Plus you are opening lines that have very high pressure in them, up to 20,000 plus PSI which is not good to be around since it can inject into your skin.

I am a Service Rep for Case International and we use the HPCR Cummins engines in a lot of our equipment. I will try my best to explain how the injector works on the HPCR engine. There is high fuel pressure at the tip pf the injector waiting to be injected into the cylinder, the same fuel pressure is on the top of the injector holding the injector closed. When the ECM signals the injector to "Fire" a solenoid opens a passage in the top of the injector that bleeds that high fuel pressure that was on top of the injector to the return circuit, that allows the high fuel pressure at the bottom of the injector to lift the plunger up allowing the fuel to be injected into the cylinder. When the solenoid shuts the fuel stops bleeding to the return and pushes the plunger closed stopping injection. The problem the dealer runs into is the electrical circuit is working correctly, the solenoid is opening and closing like it should and there for will not trip a code, but that plunger inside the injector could be sticking and the scan tool has no way to really detect that since the plunger is not connected to the solenoid. The plunger inside could stick causing the miss, and in our farm machines we have had the injectors stick open causing the fuel to run non stop into the cylinder and it only takes a short time of that until the cylinder burns up. In our machines when we suspect one injector sticking we replace them all since they are not really that expensive compared to wrecking an engine.

I hope this helps you out. Jeff

 

Thanks Jeff, much appreciated!

 

at idle the rail is seeing around 5K psi. . .full load you can see somewhere between 24-26,000psi

jeff is right, crack one line on a HPCR and the whole engine will die.

 

not to mention fuel squirting out at 5-25k psi would lop off a finger, also kill you. when the truck is cold, fire it off and with a temp gun watch the temps on the exhaust manifold ports. A cylinder with a bad injector will be colder than the other cylinders. To verify that it is that cylinder, swap the injector into a different hole and measure temps again.

 

Hell of an idea Jake!! I'll grab the raytech tomorrow and give it a try!! Thanks for input guys!