How long for fuel pressure to drop

[maddzz1]

I am putting in a set of precision injectors in and changing the fuel filter. How long do i need to wait for the fuel pressure to minimize after driving the MJ before releasing the remaining pressure with the schraeder valve?

 

Also, what is the part # for the o-ring kit? how many o-rings do i need in total?

[BLHTAZ]

The pressure is not that intense, so you should be able to press the schraeder valve within just a few minutes, if not immediately, after shutting the engine down. It doesn't really maintain any pressure to speak of in the line.

 

The injectors come with new o-rings, so the only ones you will need are the fuel line quick disconnect replacements. The OE part number is 83502745, but I think you can get the kits at NAPA or Autozone.

[HOrnbrod]

I am putting in a set of precision injectors in and changing the fuel filter. How long do i need to wait for the fuel pressure to minimize after driving the MJ before releasing the remaining pressure with the schraeder valve?

 

Don't know which rig you are replacing the injectors on, but my 91 typically holds 40# of fuel pressure for about 4-5 hours. I know this because of the nifty pressure gauge I have installed on the rail. :D I wouldn't press the Schraeder valve to release the pressure on a hot engine block though; wait until it cools and wrap a rag around the valve when you do it.

 

[thedave360]

take the fuse out for the fuel pump and turn the key to the on position then off. Thats how I had to get rid of the pressure in my nissan to change the fuel filter. It should work on the MJ too...right?

 

EDIT-I'm not saying nissans and MJs are the same. I'm saying it should work based on principle

[HOrnbrod]

Hmmm, that might work if turning on the ignition to ON opens an injector and lets the pressure bleed off. I'll have to try that while observing the pressure gauge. I suspect you would have to crank it over though for an injector to pulse.