Injector leak down test doesnt work.

[dhirocz]

790k miles. Ive got all the symptoms of a bad injector, so Im outside doing an injector leakdown test. I can verify that I do have a leaking injector on the front bank by cranking. After 4 or 5 seconds, Im getting bubbles. However, I cannot get any bubbles when I bar the engine over. I also notice that the engine is now much easier to bar compared to last time.

Is it fair to assume that the leakdown test requires compression to work, and given the facts that the symptoms are telling me the engine is worn out? Any other ways to know which injector is leaking? Im now at a loss here.

[hhow55]

Are you baring the engine, immediately after cranking?

[dhirocz]

Ive tried it both ways. The only way im getting bubbles is if I crank it at least 5 seconds. I get no movement whatsoever when I bar it over, no bubbles. Ive probably rolled it over 100 times or more by now.

All I can confirm is I get bubbles on both the front and rear bank. I replaced 1 and 6 last year. I could just put in the other 4, seeing that I cant verify what cylinders are leaking exactly. Im not expecting miracles in mileage though.

[Rawze]

(06-30-2019 )dhirocz Wrote:  Ive tried it both ways. The only way im getting bubbles is if I crank it at least 5 seconds. I get no movement whatsoever when I bar it over, no bubbles. Ive probably rolled it over 100 times or more by now.

All I can confirm is I get bubbles on both the front and rear bank. I replaced 1 and 6 last year. I could just put in the other 4, seeing that I cant verify what cylinders are leaking exactly. Im not expecting miracles in mileage though.

If you can't get it to leak while barring the engine right after cranking it, then don't worry about it. It is not bad enough to justify replacing injectors yet. -- Be sure also however, you have re-adjusted all the valves and injectors before performing this test. It will show leaky if the injectors are out of adjustment.

also... if your engine is easier to turn over than other people's ... don't assume its worn out. I thought that about mine, hence one of then reasons I wanted to inframe it,.. but in all reality, it was much easier than other people's because it was not carbon-packed like most people's engines are.

a carbon packed engine has a lot more resistance when turning it by hand than one that is clean on its insides. I would imagine that this would also have a large impact on overall fuel mileage as well.

[dhirocz]

Fair enough.

Im going to continue to pick up random parts (turbo oil and coolant hoses, oil pump, fuel pump, ECM, head bolts, etc) just in case. Ive already got a parts stock of ISX parts on standby. Theyll need to be used eventually anyway at my mileage. Ill also keep driving it nicely like I have been. Hoping it hangs in there until fall when its cooler out to tear it down. Ill keep in mind that its not carbon packed when I wonder why it sounds like a locomotive lol.

Wish I could buy a piston and liner kit and a head ahead of time just to have it on hand, but I know that's not necessarily the best way to go.

What bothers me is that it prefers that I drive faster, rather than slower. I did two loads this past week from savannah to Pensacola, empty one way, back at 95k the other. I got better mileage at 65 then at 58 by a noticeable margin. Normally, these iso tanks being flat faced and set back from the cab like they are, I do much better going slower because of the aerodynamic penalty, but lately, thats not the case.

I used to get 8 mpg loaded at 60 at 80k, 11-12 unloaded, 17+ bobtail. Mileage has slipped 2-3 mpg, all things being equal.

[Rawze]

(06-30-2019 )dhirocz Wrote:  ...
I got better mileage at 65 then at 58 by a noticeable margin.
...
Mileage has slipped 2-3 mpg, all things being equal.
...

Thats usually a sign that you have a fuel or air/boost leak, etc. problem somewhere.

think about it, it is a loss that is steady, (or steady above certain boost pressure, etc.) no matter the speed -- like say .. a drip, drip drip of the doser injector, independant of speed or torque,.. then say.... the faster you go,.. the less "drips" per mile, making it seem like the truck wants to go faster for better efficiency,.. believe-me,.. your loosing the game, not winning it by going faster and ignoring the problem all the time.



Otherwise, you would be breaking the laws of physics.

[dhirocz]

Ill look everything over again and see what I can find. Thanks rawze.