FASS + Mechanical fuel psi gauge = CHATTER!!!
 

I have a FASS and an Isspro mechanical fuel pressure gauge on my steering column. Normally the FASS pumps a steady 15 psi, but sometimes (more than not lately) I'm getting a lot of chatter. The needle is fluctuating 5 or so psi, but more irritating is the rattling noise. I just came off of a 2600 mile vacation pulling my trailer and the chattering noise liked to drove me crazy.

I seem to remember someone telling me, or reading something on here about installing a "snubber" in the line to eliminate the chatter at the gauge. I have checked a couple of shops and an on-line store and no one seems to know anything about a "snubber". Does anyone have any recommendations on something I can install to stop the chatter at the gauge?

Thanks!

Get a needle valve and mount it inline to the gauge. Then reduce the flow to the gauge to almost nothing. Also works well as a shut off...if ever needed.
If you don't do something right away...you can kill the gauge.
Just too much steady pressure for the closed system on your gauge!

Mine chattered for 4 months. Needle valve saved having to replace it and gauge has lasted 4 more yrs.

RJ

I have a needle valve on my fuel line to the gauge that I barely crack open and it relieves most of the chatter but I know I'm going to have to install a snubber. Google McMaster-Carr...that's where I got mine for my boost gauge.

Thanks guys! I'll look for a needle valve.

Dracula:

I had the same problem as you on my 1996 Dodge CTD 12 valve. As the Members said, installing a needle valve will stop that "chatter." FWIW, "Auto Meter" also makes a "snubber" to stop it too.

The part number for theirs is Auto Meter #3279. RJ is right about
that "chatter" killing the gauge. I had used the "DiPricol Mechanical FP Gauge" with the Isolator and anti-freeze before going full mechanical and I "killed" three (3) of those Isolators before I figured out what was going on.[duhhh][laugh]

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John_P

Ouch!! I opted not to go with the isolator because of price and install headaches. I wouldn't want to kill too many of them!!!:( I keep a plug and wrenches in the truck in case of a leak at the gauge. I figure I can get pulled over and cap it off at the IP before I get too much diesel dripping down my leg! [yuk][duhhh]:o[laugh]

Thanks for the info. :cool:

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Dracula:

You are very welcome Sir!;) One thing in your favor though over my 96' Dodge CTD 12 valve, is that you are probably not running as much fuel pressure as I am with your trucks. I have about 40-45lbs at the inlet to the P-7100 fuel pump and those P-Pumps have alot of internal "vibrations" etc. over the pumps in the 24 valve trucks or the CR CP-3's. Just a thought........

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John_P

Sort of surprising but with a needle valve cracked open only enough to work the gauge the full flow of fuel with the gauge disconnected is nothing more than a slow drip.

COOL! Maybe it won't be enough diesel to run Mamma out of the cab![laugh]

will the valve stop the guage from dancing. id be nice to get a steady reading on the guage

Yes it will! Dancing is Stage 1. When dancing gets bad enough it will start 'talking' to you.
Actually slapping the stops, I believe; hence the chatter. All caused by too much pressure to a sensitive instrument and a close ended system.
As mentioned above, the smallest opening in the needle valve is all it takes to read accurate pressure.

RJ

i was talking about a boost guage. will it still work and it delay the guage reading?

A gauge is a gauge. Just a needle valve should stop the pulsations.

stuckey:

Infidel is right,....the needle valve will work on any type gauge.

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John_P

Snubber
 

Hey Guys, I looked on McMaster-Carr, at the snubbers. To order, I must specify the orifice size. The options are 0.004, 0.008, and 0.015. Which is the best, or does it matter?