Vacuum gauge tip for checking fuel pressure

[jberenyi]

I tried a little trick that we do here at work when certifying gauges and it works.  The issue some people have when using a vacuum gauge to check fuel pressure is that the needle jumps erratically because its a diaphragm fuel pump.  It did for me too just a few days ago.  However when I bled the line for the vacuum gauge to get fuel close to the connection point and started up the car...amazingly no fluttering needle.  In fact it was rock steady.  So try it, you might like it 

[Ethan1]

I tried a little trick that we do here at work when certifying gauges and it works.  The issue some people have when using a vacuum gauge to check fuel pressure is that the needle jumps erratically because its a diaphragm fuel pump.  It did for me too just a few days ago.  However when I bled the line for the vacuum gauge to get fuel close to the connection point and started up the car...amazingly no fluttering needle.  In fact it was rock steady.  So try it, you might like it 

 Interesting! Thanks for the tip!

[jamesF]

Please explain how you do this? You mean you filled the hose connected to the vacuum gauge with gas?

[jberenyi]

No problem James.  Quickest and easiest way is to just remove gauge from end of vac hose and crank the engine with the coil disconnected and allow fuel to purge the vacuum hose.  Once fuel starts to come out the end of hose, plug the end with your finger and stop cranking the engine.  Connect to the vacuum gauge and your done. 

[jamesF]

AHHHH I see I missed the part where you were using this to check fuel pressure..... I thought you were describing a bouncing Vacuum gauge...
Thanks good tip.