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2006 cm870 air in injector leakdown test - CTTOWING - 04-03-2026
The original engine had oil in the coolant and right before we pulled it off the road it was overheated due to a blown coolant hose and we found coolant in the oil. Still was running decent otherwise. I already know, I should have purchased a cummings drop in and all cummings parts, lesson learned. I purchased an engine from a remanufacturer out of Colorado that had good reviews. I purchased injectors, turbo, manifold, and oil cooler from {big name trash tuning company}. When we went to start it, the engine barely ran, it was surging erratically and puffing black smoke like over fueling in one or more cylinders. Short version of the story is we had the 6 injectors warrantied with {big name trash tuning company} ones. We replaced the 4 fuel actuators, fuel shut off solenoid, and low pressure fuel pump with cummings parts and repaired harness from a previous repair. At this point truck runs good going down the road except has trouble finding idle and long crank time when starting. We had bubbles in injector leak test on three cylinders. We purchased 3 cummings injectors. Right now they are all in the front bank. Still have air bubbles from cylinder 1. Have checked cam timing and have adjusted the overhead multiple times. I think the issues we have are caused by air intrusion. What else can cause air in injector leak test, Can cracked head, injector cups? Is there a way to diagnose and the isolate problem?
RE: 2006 cm870 air in injector leakdown test - Rawze - 04-03-2026
Someone was drinking the cool-aide on that one big time ... Must have been the chicks in bikinis and all the chrome polish fumes at the truck show that got you in a state of sheer glee and awe at how badly an engine can be tortured and abused.. and so you bought into it hook, line, and sinker.
== There is only one solution at this point, as it will never be right. - it is a trash-can after-garbage parts engine put together by trash-can companies, and was shoved into it, nothing but complete engine destroying garbage.
Every single bit of what was done is beyond complete trash. - Now you have a trash engine ... What did you expect?.
No one here can help you with it.. it will never be right, and would be far cheaper at this point to replace it with a certified OEM reman long block from the red engine maker.
Donate that engine to a corral reef somewhere or third world country.. go buy an OEM certified reman and call it a day.
- One day,.. after wasting a whole lot more moneys... maybe... just maybe.. you will realize that all the things I say on this forum ... actually matter.
It also sounds to me like someone has been guessing a lot that does not know so well how to perform proper procedures towards troubleshooting.. and then replacing parts blindly.
== You also would have been far better off re-using the old engine, replacing the oil cooler (oil in coolant)... and inframing what you had (if needed) with all OEM certified parts.. building it back stronger than OEM while doing so ...
ref: https://rawze.com/forums/showthread.php?tid=8105&pid=70606#pid70606
and getting rid of the most likely engine killing bad tuning programming in the ecm while you were at it.
... and if you were really h#ell bent on doing mods and upgrades to the engine... putting a CM871 ecm and electronic VGT turbo on it + having it all programmed PROPERLY, and calling it a day.
RE: 2006 cm870 air in injector leakdown test - CTTOWING - 04-03-2026
I understand your opinion and agree with a most of what you said. I donated $100 to your website this morning because it said the purpose of the website is to help others with there trucks. I accept the roasting because of my poor judgement, but hopefully you have some constructive information about the specific problem. Do you have any knowledge or have experienced anything other than an injector causing air in a leak test on an ISX.
RE: 2006 cm870 air in injector leakdown test - Rawze - 04-03-2026
(04-03-2026 )CTTOWING Wrote: I understand your opinion and agree with a most of what you said. I donated $100 to your website this morning because it said the purpose of the website is to help others with there trucks. I accept the roasting because of my poor judgement, but hopefully you have some constructive information about the specific problem. Do you have any knowledge or have experienced anything other than an injector causing air in a leak test on an ISX.
How are you doing the leak test?. Just like this video???>
info: https://rawze.com/forums/showthread.php?tid=7747&pid=67948#pid67948
Also ensure the overhead cams have not slipped.. pin the crank and check it.
if so,.. then no.. the only thing that would make bubbles is a leaky injector(s) due to issues with them, or the overhead valves for injectors not set properly.
isx overhead video with a lot of useful info in it: https://youtu.be/gQprOKCVln8?si=ERJCR2bo5MdjyT3X
What cylinder is the bubbles coming up for when turning it by hand?.
RE: 2006 cm870 air in injector leakdown test - CTTOWING - 04-03-2026
First crank with the starter and getting bubbles out of the hose going to the front actuator location. I crank it by hand and get a bubble just before it gets to C on the crank pulley. Between B and C is cylinder 1. Was getting air out this same cylinder when it had aftermarket injectors in it, but now has cummings injectors in the front bank. I think I still have air in the rear bank, focusing now on the front bank because that is where the cummings injectors are.
RE: 2006 cm870 air in injector leakdown test - Rawze - 04-03-2026
(04-03-2026 )CTTOWING Wrote: First crank with the starter and getting bubbles out of the hose going to the front actuator location. I crank it by hand and get a bubble just before it gets to C on the crank pulley. Between B and C is cylinder 1. Was getting air out this same cylinder when it had aftermarket injectors in it, but now has cummings injectors in the front bank. I think I still have air in the rear bank, focusing now on the front bank because that is where the cummings injectors are.
injector cam set to 8 nm with a precision dial type torque wrench and not a clicker?.
I mention this in detail at 20:25 in the video I mentioned above.
New OEM injector(s)? ... So move cyl #3 injector to hole #1, and injector #1 to to cylinder #3 and do the check again?. - Make sure it follows the injector.
It could be something wrong with the head itself?.
... and is it hard to get it to bubble when turning by hand?... or is it bubble very easily?.
RE: 2006 cm870 air in injector leakdown test - CTTOWING - 04-03-2026
I will try moving injectors now. Number 1 has always made bubbles easy when hand cranking. When had bubbles in other cylinders were barely moving the air bubble.
RE: 2006 cm870 air in injector leakdown test - Rawze - 04-03-2026
just my own personal experience ...
I have never (so far) had a certified OEM new or reman injector for CM870/CM871 leaky form the box... but that is not to say it cannot happen.
I have heard of other ppl having it happen, but it was usually an injector that ended up being on a recall list somewhere.
info: https://rawze.com/forums/showthread.php?tid=692&pid=2508#pid2508
... yet another reason never to buy non-OE injectors, or any internal parts whatsoever from a non certified OE stealeers%it, .. as there are literally thousands of recall and chineesuim parts in the wild out there that are sold as reman/rebuilt, or used... some still looking new in the box.
RE: 2006 cm870 air in injector leakdown test - Rawze - 04-03-2026
At this point, is it impossible to simply put the engine back together with the parts it came with and ask for all your moneys back from the place you purchased it from?. Does it not have some kind of warranty?. - just a thought.