I suspect I have an EFI common rail injector that fails to hold pressure and slowly leaks petrol into the manifold when the engine is shut down (and possibly while running). I am interested in why this happens and whether it is fixable.

Do injectors tend to leak because of debris buildup around the pin or mechanical wear can also make it happen? Is it something a good ultrasound clean should fix, or is replacement my only option?


Replace it, too may things can go wrong with an injector, weak spring, pitted pintle seat, shorted solenoid winding's, etc. Its not worth the time to try cleaning it.

  • Well that sucks. Definitely not shorted, just fails to hold the pressure for a long time. Are weak springs and pitted seats common? May 23 '16 at 8:43
  • Yes, I see it all the time. Also if the fuel has alcohol in it, this can definitely corrode parts in the fuel system over time.
    – Moab
    May 25 '16 at 14:32

If the engine is completely shut down, then the injector should be closed and there will not be any pressure in the system as the fuel pressure regulator and the pump would be off (although I am assuming there would be some residual pressure in the system). You can check the said injector by taking it out, putting few drops of fuel inside the injector and blowing air through it ( I just used my mouth, was very careful not to swallow the fuel and cleaned my mouth immediately after I was done). A good, working injector should not let fuel out of the nozzle. If you see fuel from the nozzle I guess your only option would be to replace it.

Experts, please correct me if I am wrong here.



  • Thank you for your answer, but there are a few problems with it. Firstly, there will be residual pressure. A whole lot of it, for hours to come. Secondly, this seems like a poor way of checking if an injector leaks, I doubt you can accumulate that much pressure with your mouth. And finally this doesn't really answer my question. I know an injector leaks and would like to know if it's something that can be fixed (i.e. it happens because of clogging and ultrasonic cleaning will save it) or it simply means the injector is worn and the only way is replacement. May 19 '16 at 10:45
  • Well the injector that I checked was stuck open and it did not require much pressure to get the fuel to leak. You are right as it might not work in your case. Also, I thought if an injector leaks, it is stuck open and even if it leaks a little bit, it is considered as damaged as default position of an injector (when not exited) is closed.
    – Vish_evo
    May 19 '16 at 10:57
  • In my case it's definitely not stuck open, but is probably unable to fully close and make a solid seal, slowly leaking pressure and causing all kinds of subtle issues. May 19 '16 at 11:03

I would start by running though a tank of injector cleaner or seafoam and see if it cleans itself out.

If that doesn't work, you can pull it out and try to clean it with carb cleaner and an air compressor. I THINK you can open an injector with a 9V battery. If not, you may need to rig up something. 12v 1A power brick with a fuse should work.

If that does not work, replace it.

  • I don't really trust any cleaner that goes straight into the tank, I've heard of it causing more harm than good. I was actually thinking about professional ultrasonic cleaning. But the question is whether it's worth doing at all. Do the injectors fail to hold pressure because of dirt or mechanical wear? May 19 '16 at 12:28
  • I'm really not sure. There could be something stuck in there holding it open, or there could be mechanical damage. Personally, I would be looking at junkyards and ebay for a new(used) injector, unless it is high performance/oversized.
    – rpmerf
    May 19 '16 at 12:45

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.