Depressurising the fuel rail

[TimJM]

I finally have a fuel pressure gauge after a mix up with the order and want to test my fuel pressure at the rail and my foggers (for the NOS). I have an adapter and some hose clamps so I know how to install the gauge for the test at the various locations but I don't want to start spraying fuel around when I undo a fuel hose.

Is the best way to depresurise the fuel rail to pull the fuel pump fuse and crank the engine over? Or should I just park it up for a day and slowly unto a hose - will the petrol pressure escape naturally over time if the fuel pump/engine isn't running?

[Tanguero]

The injectors will only open at all over a certain pressure so either pulling the relay and starting it or pulling the relay while it is running (my preference) will only partially depressurise the rail. Just wrap a cloth round the joint before you crack it, its going to weep petrol regardless of whether the rail is pressurised or not.

[TimJM]

Tanguero said:

The injectors will only open at all over a certain pressure so either pulling the relay and starting it or pulling the relay while it is running (my preference) will only partially depressurise the rail. Just wrap a cloth round the joint before you crack it, its going to weep petrol regardless of whether the rail is pressurised or not.

OK, I suspect the fuel pressure may be high (if the regulator is on the way out) so I didn't want to start spraying it everywhere. I guess safety goggles and a cloth wrapped around the joint will work then. I suppose as there isn't much volume any pressure should quickly disperse.

If I would have received my test gauge before the new alarm/immobilizer went it it would have been simpler as the fuel pump was run via a hot wire so I could crank the engine without it and run the fuel pump with out starting the engine.

[Tanguero]

TimJM said:

OK, I suspect the fuel pressure may be high (if the regulator is on the way out) so I didn't want to start spraying it everywhere. I guess safety goggles and a cloth wrapped around the joint will work then. I suppose as there isn't much volume any pressure should quickly disperse.

If I would have received my test gauge before the new alarm/immobilizer went it it would have been simpler as the fuel pump was run via a hot wire so I could crank the engine without it and run the fuel pump with out starting the engine.

If in doubt just reduce the pressure as much as possible by pulling the relay while the engine is running.

[TimJM]

Tanguero said:

If in doubt just reduce the pressure as much as possible by pulling the relay while the engine is running.

Will do. Thanks for the advice. Here's hoping for 43PSI!