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Discussion Starter · #1 ·
With normal driving the fuel pressure will stay around 10 lbs. Recently my fuel pressure gauge has started fluttering or bouncing when I accelerate or when the truck is under a load. When it bounces it will go from about 6 to 20 lbs. and fast enough that it is kind of a blur. When I let off the accelerator the gauge is rock solid again.

Things I have tried:
I have connected a test gauge to the schraeder valve on the VP44. (both gauges bounce)
New fuel filter. (no change)
Different lift pump. (no change)
Wired the lift pump directly to the battery. (no change)
Different overflow valve (the banjo bolt that fastens the return line to the VP44). (no change)

Could it be in the VP?
Any ideas or suggestions?

Bucky
 

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Discussion Starter · #3 ·
Thanks Rock.
The gauge has an isolator.
Can you think of anything else?

Bucky
 

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how is the sending unit mounted, ive heard some guys say they run a line to them and mount them on the firewall to keep vibrations down.

mines in my airdog ling about 1" from the VP (basically hard mounted to the VP, no rubber line i mean) and i have no issues.
 

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The needle bounce is caused by the feedback pulses from the VP44. You can correct it with a needle valve that will act to "snub" most of the flow. Boost gauges will also do this at times and the same cure will work. Just open the needle valve enough to get a reading..

This will do the trick..

Needle Valve 1/8 NPT
 

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Discussion Starter · #6 ·
When I installed my gauges I put a small inline shutoff in the line going to the fuel pressure gauge. I will try closing it just enough to get the needle to settle down. Thanks to all.

Bucky
 

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Discussion Starter · #7 ·
I shut the valve and then opened it just enough to make the gauge move then took a 10,000 lb trailer to NY state. No more bouncing fuel gauge. Thanks again guys.

Bucky
 
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