Never worked on fuel side o a car so have a few concerns:

  1. What's best way to relieve fuel pressure?
  2. After swapping o-rings, does a lubricant need to be added to the o-ring to prevent damage when installing into the fuel rail?

It's a 2003 Camry btw. Noticed a fuel leak that looks to be one of the injector o-rings

enter image description here

2 Answers 2


Fuel bleeding varies, or rather pressure relief of the lines, but some engines have Schroeder valves which could be bled.

WRT, O-ring lubrication, there would be no harm in using a drop of engine oil. Last I looked at US gasoline specs, they could be about 4% oil anyway.

In summary, a little oil would not cause any problems with all the gasoline injection systems that I am aware of. And as for bleeding, the approach will vary depending upon the injection system and fittings, and I believe there is no one universal answer.

  • Bleeding or relieving pressure? Also could I dip the o-ring in gasoline as a lubricant?
    – user140123
    Commented Sep 17, 2017 at 20:13
  • @user140123 - Gasoline should NOT be used as a lubricant. It is more suited as a cleaner. It will most likely evaporate before you ever get the o-ring in position. It provides little if any lubricating effects. Use clean engine oil as suggested by mongo. Dip the entire o-ring into oil before putting it onto the injector. This will give you enough lubrication to not only get the o-ring on the injector, but also inserted into the injector bore and/or getting the fuel rail situated on the other end. Commented Sep 17, 2017 at 22:28
  • Relieving pressure would be more accurate. I would not use gasoline as a lubricant if I had a drop of oil from a container of oil, or the dipstick available. I will spare you the story of a rag wing plane which went up in flames one cold morning...
    – mongo
    Commented Sep 17, 2017 at 22:29
  • 2
    @user140123 Pull the fuel pump relay and start the engine, let it run until it stalls. Crank it over make sure there's no residual pressure and do what you need to do.
    – Ben
    Commented Sep 17, 2017 at 23:05
  • Thanks guy. Reason I asked about using fuel on the o-rings was from a Scotty Kilmer video where he does just that. Could I use silicone grease as well? Also when the injector is placed back into the fuel rail, can it be twisted in the right position so the connector lines up or?
    – user140123
    Commented Sep 17, 2017 at 23:40

A typical fuel pressure gage will have a provision for attaching a plastic hose so you can vent the fuel into a container.

enter image description here

That may seem overkill if all you want to do is release the pressure, but my guess if you are working on the system you probably will want a gage anyway. I think you can rent one from most auto stores as well.

Not all cars have a port for attaching the gage by the way. Check on that first.

  • Sorry, but how does this answer the question?
    – Ben
    Commented Sep 17, 2017 at 23:03
  • @ben the question is "What's best way to relieve fuel pressure" what exactly is wrong with my answer? People ought to not ask multi part questions if they don't want an answer to only one part.
    – agentp
    Commented Sep 18, 2017 at 1:14
  • how do you install a gauge without relieving fuel pressure? especially on a car that doesn't use a schraeder valve? even if it did you'd still get fuel spray trying to install it.
    – Ben
    Commented Sep 18, 2017 at 2:18
  • I noted that not all cars have the port (schraeder valve). When you have it there is no issue to screw the gage on then release the fuel through the tube.
    – agentp
    Commented Sep 18, 2017 at 2:57

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