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New Isspro R5604R Mechanical FP Gauge/R7798 Snubber- Slow Response

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Replaced 5YO Isspro Gauge due to it reading 3.5 PSI higher - when compared to VPMAX liquid filled gauge from Vulcan. Both readings were taken at top of OEM Fuel Filter housing.   

I have a direct custom made 1000# tested line with JIC fittings between Cab Gauge and OEM Fuel Filter housing via a New Isspro R7798 Snubber connected to Needle Valve,  going into Fuel Filter housing.  No Isolator.

Only thing different in new arrangement is the new Isspro R7798 Snubber - with pistons. (Correct Diesel Piston is installed) Previous Set up had the simple brass small hole Snubber and Needle valve, needle valve set so gauge responded exactly like Moparmans video. 

New setup works, but Gauge is “very” slow to respond.  I switched back to old gauge, same slow response.

Anyone using this Isspro R7798 Snubber with similar experience?






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When my was new I could slow it to a crawl and worked fine. It is a bit older now and a little harder to do that now. Sounds like the snubber is the cause since both gauges react the same way. Not sure I would worry about it. What is your concern?

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Yep. Needle valve is wide open. Pretty certain you could put on a pot of coffee on after start/up and it would be ready before gauge was at full swing.


I guess plus of this is there is no danger of damage to internal gears of gauge.  😏


Talked with ISSPRO today and was told I might need to change out the Snubber piston to the one for Oil (#02) since it’s less restrictive than the Diesel  #2 piston that gauge comes installed with. 


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Thanks for all the Feedback.



Changed the piston in Isspro R7798 Snubber to the #02 (for Oil) and gauge now responds really good. 
Believe the Standard #2 piston (that comes installed with Snubber)would have worked fine, however I have Needle Valve/Snubber combo which put addition restriction on flow to Snubber on to the gauge.   But I have to have a shut off valve just in case. I DO think the R7798 is a very good Snubber.   


Just curious if anyone has checked the accuracy of the permanent Cab gauge with a portable Diesel Fuel Pressure tester. 
If so, was there any disparity in the readings.  I have found 1.5-2.1 deviations.  Readings taken from top of OEM Fuel Filter Housing.


Thanks again,




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