Bought a 40psi fuel pressure gauge from Genos. Installed it with the rubber hose at the injection pump. I've got good pressure all the time but shortly after the install the gauge began to bounce around at idle between 16 and 20 psi. At cruising speed is bounces around between 12 and 14 and when i get into it a little it levels out steady around 10 psi. When idling I can listen closely and hear the electrical gauge make a buzzing sound and the buzz starts and stops in relation to the gauge fluctuating. Is this normal or a problem with the electrical gauge itself? I tapped on the gauge and messed with the wires but everything seems like its got a good connection. Could it be a bad ground?

 

Very common problem.
You need to use a gauge snubber in the line before the sender.
Snubbers are available from most outfits that sell gauges or you can use a needle valve that is barely cracked open.
I prefer a needle valve because you can shut it down in the event of a leak.
This is the one I use> http://www.grainger.com/Grainger/Needle-Valve-6MN31?Pid
It's also a good idea if you want your sender to last to isolate it from engine vibration by mounting it on the firewall or fender.

 

I thought the 18" hose would do the same thing I was told. The needle valve is cheap so maybe I'll try that. I also just zip tied the sender along another line under the hood with the hose in between. This should isolate it from engine vibration, correct??

 

Its not the vibration from the engine so much as the pulsations in the fuel line from the pump. It will hammer out a gauge in a few hours.