Engine/Transmission (1994 - 1998) need new injectors?-- they're leaking

[d9]

Please help!! I removed and put back my stock injectors yesterday, and today about half are leaking at the injector hold-down nut washers.



I'm sure its not the high pressure line fitting nuts that are leaking, and I'm pretty sure its not the return line banjos that are leaking.



What would cause fuel to leak up through the injector hold down washers? Do I need new rubber hold down washers, new copper injector-tip washers, new injectors???



Muchas gracias

 

[thouse]

I had the same problem with a new injector in my 12 valve motorhome. I tried for two weeks to stop the leak, it turned out to be a bad injector. They can be rebuilt.

 

[bgilbert]

Did you torque the hold down nut to 44ftlbs? The rubber o-rings are to keep grit and water etc from getting in between the bore and injector body not the other way around. Normally you should replace the copper sealing washers on the injectors after removal.



Mine were doing the same thing, and upon removal and inspection they were not tight, after correct torqueing no more leaks. While I was there, I replaced all rubber o-rings, copper banjo clips on return line but did not replace the copper washers on the injector tips.

 

[d9]

yep -- all injector hold-down nuts were torqued to 44 ft/lbs.



And thanks for the clarification about the rubber seals being dust boots-- that makes sense.



I did the whole injector removal/replacement procedure one more time, with hopes that cleaning the . 5 mm copper washers at the injector tips would enable them to seat properly and stop the leaks.



They are now leaking more than the first time!!



I'm almost positive that the fuel is leaking up through the holddown nut dust seals, for I can see miniature bubbles as the fuel exits the injector bores at the seals.



So where the fuel is actually coming from still baffles me.

Is it unburned fuel that the injector tip has sprayed into the piston chamber, with compression forcing it up past the copper washers at the injector tips?



Is it fuel leaking from the injector body somewhere? (I noticed the injectors all have 2 parts threaded together midway. )

Any ideas? Thanks!

 

[bmoeller]

Are the sealing washers on the return lines leaking?

 

[d9]

return horseshoe washers

bmoeller-- Nope. The copper horseshoe washers are not leaking. I can verify this because I see fuel surrounding the injector, at the dust seals, in a ring. If it was the return banjo bolts leaking, fuel would dribble down below them onto the head towards the exhaust manifold. Instead, there is fuel at a higher point -- around the injectors closest to the valve covers, that is.



Besides, I'm seeing miniature air bubbles exiting with the fuel at the dust seals. The leaking subsides within about 30 seconds of turning the truck off. The leaking fuel seems to be under high pressure under those hold-down nuts.

 

[LHallmark]

I had two injectors do this after I had removed and tested them. They all had new sealing washers on the tips and on the return line. The two that leaked as you have described at the top of the hold down nut were removed again, put on new sealing washers on the tips and reinstalled and torqued. Vola!! No more leaks.

I suggest you replace the sealing washers on the tips and insure the bore in the head is clean prior to reinstall.

 

[bmoeller]

Yes, the fuel injection nozzle bodies are in 2 pieces. The only thing I can think of, if they are leaking there at the threads where the two parts meet, would be bad needle valves or seats to allow combustion pressure to force fuel back up and out. If that is happening, then if the copper washers that seal off the combustion chamber are scratched or other-wise compromised from the cleaning or installation/removal, then the pressure would work to push the fuel up past the hold down nut. Or it is then filling up the space between the head and nozzle (injector) and coming back out through the hold down nut.



If there is fuel that has been sprayed into the cylinder and some is not burnt, it would most lilely wind up into the crankcase oil.

 

[d9]

unburnt fuel

bmoeller, are you saying that any unburned fuel already sprayed into the combustion chamber would most likely end up in the crankcase instead of making its way upwards past the copper washers and up through the hold-down nut dust seals?



The engine is cranking over just fine and not idling abnormally rough with these leaks (I haven't dared raod test it yet). This leads me to believe that the combustion taking place is thourough, therefore there shouldn't be much fuel left to be pressurized upwards past the copper washers. Who knows!!



Thus, bad injectors would be the true source of the leaks, although my wallet just screamed at me, "NO!!!!" Everything was fine before I monkeyed with the injectors. I don't know how 4 of them could all of the sudden gone bad, but come to think of it, I did have to turn them a good deal back and forth to get them out-- Could that have loosened the threads that tie together the 2-piece injectors?



LHallmark, I'm overjoyed to hear that simply changing the copper washers fixed your leaks. Do you have a part number for those?

 

[britannic]

If the tips were gripped by carbon deposits where they enter the cylinder, it's certainly possible they might have loosened during removal as you described.

 

[bmoeller]

Re: unburnt fuel

Originally posted by d9

bmoeller, are you saying that any unburned fuel already sprayed into the combustion chamber would most likely end up in the crankcase instead of making its way upwards past the copper washers and up through the hold-down nut dust seals?

Yes, but I doubt that would be the case here, unless you are in a place that is still quite cold (<30*F). Winter is the best chance of cylinder washdown (idleing), due to incomplete fuel burn from cool cylinder temps. If that were the case you would usually see some white smoke. In that situation, you just need to drive it, or raise the idle, to warm it up.

 

[Joseph Donnelly]

They are leaking between the halves of the body, probably a bit of dirt on the steel plate inside that has to seal metal on metal. Overtorquing also causes leaks and can crack the body. 44 ft lb only.

 

[DProehl]

Sounds as if you have two problems! Small air bubbles are leaking compresion, need new copper washers, Fuel leakage is leak between tip and body, best to bring them to diesel injection shop to have them pop tested to check for leaks.

 

[LHallmark]

Sorry, no part number for the sealing washers. When I had mine pop tested, the shop had a $10 kit that contained the new sealing washers for the tips (Actually there were 3 different thicknesses of sealing washers in that kit), the new horseshoe washers for the return line, and the sealing Orings for the hold down nut, and some plastic sleeves for installing the O rings.

Check Cummins or ... ... shudder... ... the dealer. .

 

[d9]

part #'s

Called Cummins Northeast today and we figured out some part #'s. Here they are:



copper sealer washers (0. 5 mm thick): 3930324

copper horseshoe-shaped banjo bolt seals: 3903380

fuel drain manifold banjo bolts: 3905307

hold-down nut rectangular ring seal: 3909356



I can't wait to replace all of the above, and. I'll repost when all the new seals are in. If that doesn't work, its new injectors. I've been tempted many times to bomb the thing, so here would be my first window of opportunity. This might be a summer to remember!!

 

[d9]

Still Confused

Wow, Cummins delivers parts fast!! I replaced all copper washers, banjo bolts, and dust seals, to reinstall my injectors for a third time. They still leak, but not as bad. And it might not be fuel, but air that is leaking. I stll see those darn miniature air bubbles around the hold-down nut dust seals.



I think DProehl is correct-- its leaking compression. Maybe thats normal? I'm just now noticing it, because there is residual fuel all over the place from bleeding the lines. In sum, a small bit of pressure, in the form of air is leaking past the injector tip washers and up out the hold-down nuts.



I used a ratcheting torque wrench-- all hold-downs at 44ft/lbs, BUT I thought I remember that torque values change when you use an extension on your torqueing ratchet. I used a 6 inch extension, plus a 2" deep socket-- does anyone know if that would make the torque wrench ratchet over prematurely?



And one last note, to anyone ever changing injectors-- Take utmost care in reinstalling the fuel drain manifold banjo bolts. They strip so easily!!! To re-emphasize the warnings of others on this forum-- thread them in carefully by hand first-- at any signs of crossthreading, back them out and try again at another angle. Don't learn the hard way!!!

 

[thouse]

As was said the leak is from a bad injector, not the seals.