need help diagnosing air leak at injector

[KLuckel]

there is air escaping in regular spurts right where the high pressure line connects to the injector. I am wondering if this can be a symptom of a bad injector, but dont want to change out the injector (which sounds tricky from some of the posts I've read) if that's not what the problem is. Any ideas?

 

[Graphic man]

Fill out your sig. so we all know what year and what mods you have done to your truck.



the only thing that should be coming out of that line is fuel.



can you give us any more details?





Scott

 

[KLuckel]

I'm still figuring out how to navigate this site. I'll try to fill out my "sig". But breifly, it's a 91 5. 9L and to tell you the truth i'm not real sure what mods have been done to it. i'd say none. the air is escaping in loud quick puffs right at the spot where the fuel line connects to the injector.

thanks! -Kasaia

 

[DVolk]

My guess the line is loose or the seal is bad or the line is cracked first try snuggying the nut up a little more

 

[Greenleaf]

... ... . so there is no fuel leaking from the injector... . just air? I didn't read anywhere about a fuel leak



You certain your not describing an exhaust system leak @ the exhaust port in the head?

 

[dpuckett]

Another possibility is a compression leak if the injectors have been recently replaced or R&Red (Removed and Reinstalled). Look at your dust cover seals on the retaining nuts. Do they look fairly new, or are they old and dry rotted?



Back to Greenleaf's post- good one about the air and fuel leak :-laf. Look for soot around the exhaust outlet around where the manifold attaches to the head. ALso, is there a chuffing sound, or a bit of a lope? If so, you may have a bad injector(s). If not, it could be an exhaust leak. Not real bad, but not real good, either. ALso, contrary to popular belief, I have never had any luck finding a bad injector by cracking the lines loose and listening to the engine for a change. By the time you get to that point, you need a new set of injectors anyway.



Welcome to the TDR. The best $35 you will spend this year. Go to user control panel in the Discusion Forums drop down menu, and when at your UCP, you will have an option to edit signature. FIll out the year, drive, transmission, miles, whatever else you think may be pertinent.



Daniel

 

[Greenleaf]

I recently recalled reading about a guy who builds Cummins engines for truck pulling. He installed a set of 7mil injectors into a 9 mil head for a TDR member. And then called it good. No adapters. Notta. Nothing. The compression was leaking out around the injector body ( leaky copper seal) and sounded like a loose spark plug. "Chuff" "chuff" chuff"



Some folks really don't deserve to own a Cummins.



I recently found that loosening the lines and the heat gun method is a big waste of time too. The last "bad injector" troubleshoot turned out to be FOUR bad injectors.



GL

 

[PToombs]

Heat gun?



Sounds like a compression leak to me too.

 

[KLuckel]

nope, no fuel comin out and the air seems to be really coming from the very spot where the high pressure line meets the injector. I've tightened it pretty good , i think. Maybe it's the seal on the high pressure line, in which case would I have to order a new line from the dealer? I'm Also wondering if this could be continued fallout from running Biodiesel once. maybe it caused some deterioration around injector body... . the "chuff chuff" noise is the one... I just didnt know how to spell it!!! kluckel

 

[PToombs]

Spray some wd-40 or something around the injector on the head, see if it blows off. I find it hard to believe that air and no fuel is leaking out of the line. My . 05. ( inflation )

 

[KLuckel]

Swear, just air. it blows the w-d40 everywhere

 

[Greenleaf]

Assuming that your engine runs, the injection pump is not pumping air. The leak, if it's around the injector body, is compression pressure inside the compression chamber leaking out around the copper seal. That is what the seal is for. Seals compression from leaking past the body of the injector.

 

[dpuckett]

Time to head to the hardware store and get an injector puller kit (bolt, couple nuts, washers, etc). Or just get a pair of vice grips.



DP

 

[Greenleaf]

Remove the line clamps to allow the line to be lifted and pulled up/away from the injector in question. Often, it's nesessary to lift a valve cover to allow the line to clear the injector. This will net you additional clearance to move the line side to side with OUT bending the line.



The biofuel didn't deteriorate the injector nor the line. There is no seal at the line. It's a compression fitting. There is a ferral pressed onto the steel line that fits to the taper machined on the injector body.

 

[KLuckel]

so maybe it's the copper washer or a part of the seal that needs to be replaced and not the entire injector? I'm going to try doing this today. I'll let you guys know what happends. Thanks for all your advice.

 

[KLuckel]

I undid all the lines and removed the nut and then I couldnt get the injector out. do you pull really hard with the vice grips or what? I ended up just cleaning it and putting it all back together and now the chuff chuff noise is gone and there is no air escaping. now I'm wondering if i might need new injectors anyway though, and how I would get them out if I needed to. also, how you know if you need new ones.

-grease monkey

 

[dpuckett]

I have had to pull pretty hard on them, rocking them back and forth a hair (emphasis on hair), while pulling up. It gets my blood flowing on a cold day, and I am fairly strong.



There is no real way to tell just by looking at them if you need new ones or not. I've seen clean looking injector tips spray very poorly, and be 1000psi low, while others with a 1/8" carbon were well within spec, and sprayed great. They need to be taken out and tested on a test stand, which any diesel pump shop should have.



But, if you no longer have the chuffing noise, I'd guess you had a compression leak that got resealed by moving stuff around. If you can live with how it drives, I'd leave it for now.



DP

 

[KLuckel]

okay, I'll leave them, and try to return the injector I bought. I'm UNfairly strong enough to embarass scrawny guys who want to arm wrestle a girl, but I didnt know if pulling as hard as I could was the thing to do. I guess it's good I wasnt able to get it out. I'm so happy to not have the chuff chuffing sound and now I can hear the faint squeaking that I originally thought was the u-joints needing to be replaced but then after I had that done I still heard it. i took it back to the shop and jr. drove around with me trying to hear the sound and couldnt, which had him concerned that his hearing was going which seemed like a reasonable concern to me, and a kind of death sentence to a mechanic who uses sound as a primary diagnostic tool, but he decided I have extra good hearing and it was a very soft squeeking that new something or others can make. take care dp! thanks alot!