I used to monitor the fuel pressure with an Dakota Digital electric gauge.  After 8 years of service the ULSD ate the pressure sender so I replaced the gauge with an ISSPRO mechanical and isolator.  Same arrangement just different gauge.
Its been on there for about 2 years now but even though it reads quite accurately, it does something odd.  At idle the gauge needle is solid around 20 psi and when cruising along down the freeway the gauge is solid at around 18 psi.  Then all of a sudden the needle will "bob" down a couple psi and quickly return.  Its a more fluid action as this is a mechanical gauge but is also very random and kinda hard to watch for too.  But.....if I'm pulling a trailer and have reason to be hard on the throttle then the "bob" of the needle can become more regular as I'm holding steady heavy on the throttle.  Still, its only a "bob" of about 2-3 psi but its a strange action and the only way I can describe the way it moves would be like watching a fishing pole bobbin dip under water when a small fish is tasting the bait.

In saying all that, I have yet to take the tester gauge out for a drive and see if the test gauge does the same thing but I figured I'd ask around first and see if anyone has experienced the same.  My tester gauge drips and I need to fix it before I'm holding it in the cab.....

I really cant imagine why or what the bobbing action could be other than maybe the Raptor 100 (older better unit) has a regulator which has trouble regulating a smooth amount of fuel pressure when the fuel volume demand increases.

Why did you change gauges?

Why did you change gauges?

 

All right here...

http://forum.mopar1973man.com/index.php?/topic/9042-gauge-time-isspro-ev2s/

I used to monitor the fuel pressure with an Dakota Digital electric gauge.  After 8 years of service the ULSD ate the pressure sender so I replaced the gauge with an ISSPRO mechanical and isolator.  Same arrangement just different gauge.

Its been on there for about 2 years now but even though it reads quite accurately, it does something odd.  At idle the gauge needle is solid around 20 psi and when cruising along down the freeway the gauge is solid at around 18 psi.  Then all of a sudden the needle will "bob" down a couple psi and quickly return.  Its a more fluid action as this is a mechanical gauge but is also very random and kinda hard to watch for too.  But.....if I'm pulling a trailer and have reason to be hard on the throttle then the "bob" of the needle can become more regular as I'm holding steady heavy on the throttle.  Still, its only a "bob" of about 2-3 psi but its a strange action and the only way I can describe the way it moves would be like watching a fishing pole bobbin dip under water when a small fish is tasting the bait.

In saying all that, I have yet to take the tester gauge out for a drive and see if the test gauge does the same thing but I figured I'd ask around first and see if anyone has experienced the same.  My tester gauge drips and I need to fix it before I'm holding it in the cab.....

I really cant imagine why or what the bobbing action could be other than maybe the Raptor 100 (older better unit) has a regulator which has trouble regulating a smooth amount of fuel pressure when the fuel volume demand increases.

Mine does this at idle.  I hear a change in idle speed and the pressure drops from 17 to 15 and then the idle changes again and psi comes back to 17.  I know it isn't the gauge because it is brand new.  I've also had this happen maybe twice that I've seen while driving but have no clue as to the cause.

Huh? Both my DiPricol mechanical fuel pressure gauge and my ISSPro Electric gauge doesn't even vary at all. Rock solid idle pressure. Only drops 1 PSI cruising the highway.

Ok guys. I finally got around to installing my Beans diesel fuel tank sump this weekend. Low and behold, my bobbing fuel pressure gauge problems went away!! I have no idea what must have been going on in the stock fuel module but I don't have hardly any pressure drop anymore or the bobbing pressure. Before the sump, I could drag the pressure down from 20 psi to 10 psi getting on the freeway. Now it barely drops to 17 psi from 20. I don't know if you guys are running a straw of some kind but I am pretty impressed with the difference that the sump made. total installation time only took me about 20 minutes. The longest part was draining the tank.

I loved my beans sump. So simple. Did you drill directly below the stock basket?

Nope. I drilled just ahead of it. I have heard of people having issues with it interfering with the basket in there.

Ya the video i watched, they said drill right below and it was a pain to get the x piece in there.