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Why is my fuel pressure gauge shaking??

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Hey,Before anyone ask I have a needle valve and a Autometer fuel pressure reducer which is a fitting with a small hole in the middle. That setup has worked fine for several months and was working fine after I installed the VP and injectors for about two months.Recently I noticed the fuel pressure gauge start shaking around and dropping down on pressure, a few PSI at most. I changed the fuel filter yesterday and that seemed to fix it for a few miles (5), but today after I down 2-3 miles down the road it started it again!!!!:thud:I played with the needle valve and it seemed when I closed it down more the shaking settled, however, it is still there and I bet as soon as I take it back on the road it will start again. And it's a pretty bad shaking, even worst than when I didn't have the needle valve and reducer!!:ahhh:I've looked and don't see any fuel leaks, the truck runs/ starts fine and the milage has been doing fine. I'm at a lose of what to do????? :shrug:I don't know how old the Autometer Ultra-Lite gauge is as it was in the truck when I bought it. It was shaking from water hammer when I got it, but after installing the valve and reducer that was a non-issue.Any ideas????:shrug:Thanks,Winslow

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The only thing I can think of is either a leak somewhere along the line or the needle valve is loosening up while your driving. The needle valve could also have something going on with it. Pretty fail proof but so is the fuel pressure gauge so have to think outside the box on this one. I'm betting its backing off a little while driving though.The pressure in the line behind the gauge should be rather constant, so the gauge wouldn't give those readings, the guage should either work or not work. There is just something going on with the needle valve.

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The only thing I can think of is either a leak somewhere along the line or the needle valve is loosening up while your driving. The needle valve could also have something going on with it. Pretty fail proof but so is the fuel pressure gauge so have to think outside the box on this one. I'm betting its backing off a little while driving though.

Hey, Well it's not loosening up b/c it is tight. And I've got an Autometer reducer which is an -4 AN fitting with a small hole in the middle. Pretty simple there. Is it possible for the gauge to get loose and start shaking??:shrug: Thanks, Winslow

Now I'm not sure what you mean. If the gauge fitting is loose, it should be leaking fuel.

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Now I'm not sure what you mean. If the gauge fitting is loose, it should be leaking fuel.

Hey, This is the fitting: http://www.summitracing.com/parts/ATM-3277/ The needle valve is tight. Meaning it isn't turning b/c it take quite a finger hold to move it.:thumbup2: I was wondering if you think it is possible for the gauge to go bad from the previous life??:shrug: Thanks, Winslow

It could. Everything else seems to check out fine based on what your telling me. Not sure why it would bounce around though when it should have a constant tension from the constant pressure. But it seems to be the only thing left in the solution box.. I keep thinking the needle valve could have an issue but, doesn't seem to be the case. Let me do some reading on some things.

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It could. Everything else seems to check out fine based on what your telling me. Not sure why it would bounce around though when it should have a constant tension from the constant pressure. But it seems to be the only thing left in the solution box.. I keep thinking the needle valve could have an issue but, doesn't seem to be the case. Let me do some reading on some things.

Hey, Do some reading and let me know what you find out!! Also I should add that I normally just run the needle valve 1 turn open and let the restrictor fitting so its job. I just got thinking... wonder if it could have worn open and allow more fuel in... but it still shakes some when the needle valve is just cracked open. Maybe I'll play around with when I get a chance.:thumbup2: Thanks, Winslow

Well I was just reading to see what gauges do when they die, thought they just, died. From what I can find out, this is true. They don't give erratic readings or anything. I been thinking about cavitation eating things up in there too. Is the gauge mechanical? Or does it need power to work? My EGT gauge needs power and it gives erratic readings when the power wires aren't getting a good connection, but I think yours is mechanical so this wouldn't be part of it. Let me know if it does need power though. I've never messed with a fuel pressure gauge but should the be same as oil pressure gauge, or any other gauge, but if yours needs power to move the needle, that might be it.

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Well I was just reading to see what gauges do when they die, thought they just, died. From what I can find out, this is true. They don't give erratic readings or anything. I been thinking about cavitation eating things up in there too. Is the gauge mechanical? Or does it need power to work? My EGT gauge needs power and it gives erratic readings when the power wires aren't getting a good connection, but I think yours is mechanical so this wouldn't be part of it. Let me know if it does need power though. I've never messed with a fuel pressure gauge but should the be same as oil pressure gauge, or any other gauge, but if yours needs power to move the needle, that might be it.

Hey,

No power needed as it is a full mechanical gauge. I figured they just died too, but this one has got my confused.:ahhh:

Thanks,

Winslow

---------- Post added at 03:08 PM ---------- Previous post was at 03:04 PM ----------

Hey,

Here is the gauge I have:

http://www.summitracing.com/parts/ATM-4312/

Thanks,

Winslow

If it's mechanical like that then I bet something is going on with the reducer or needle valve. I wonder if the needle valve got crap in it and isn't shutting as far as it needs to go.. Might take it and the reducer off and loosen the needle way up and shoot some brake cleaner or something in there to clean them out. Bout all I can think of. Changing the fuel filter might have pulled the fuel back and particles out of the needle valve, then when you drove it they got pushed right back into the valve. Bout all I can think of.

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If it's mechanical like that then I bet something is going on with the reducer or needle valve. I wonder if the needle valve got crap in it and isn't shutting as far as it needs to go.. Might take it and the reducer off and loosen the needle way up and shoot some break cleaner or anything in there to clean them out. Bout all I can think of. Changing the fuel filter might have pulled the fuel back and particles out of the needle valve, then when you drove it they got pushed right back into the valve. Bout all I can think of.

Hey, I might try that. Wouldn't hurt anything except for a little time and trouble!!:thumbup2: Thanks, Winslow

It really has to be that or just cavitation keep the valve from doing its job. Not sure how much fuel actually cavitates the valves though. Definitely some water hammer going on but, never read into it. Let me know if it works!

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This is the fitting I use, and it works well http://www.summitracing.com/parts/ATM-3279/

Hey, That's basicly the same fitting just with female threads!:thumbup2: I'll see what the gauge does this morning on my drive to school. I might take my camera with me and shoot a little video for you guys!:thumbup2: Thanks, Winslow

Hey, That's basicly the same fitting just with female threads!:thumbup2: I'll see what the gauge does this morning on my drive to school. I might take my camera with me and shoot a little video for you guys!:thumbup2: Thanks, Winslow

No, it actually has sintered metal in it like a restricted filter and is Dodge Cummins specific, and yours has a small orifice hole?
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No, it actually has sintered metal in it like a restricted filter and is Dodge Cummins specific, and yours has a small orifice hole?

Hey,

Oh I figured it was the same thing!!!!:surrender:

Mine has a small orifice hole in it. It has worked for about 5- 6 months, but I'm kinda wondering if maybe the hole has worn out and is allowing too much fuel to hit the gauge?!?!?!?!:shrug:

This morning it didn't shake around like it was doing. Of course I played with the needle valve a little yesterday, closing it, then cracking it open. I'll see how it does and if it starts shaking I'll take a video of it. I might even pull the needle valve and restrictor off and have a look see!:thumbup2:

Thanks,

Winslow

---------- Post added at 10:07 AM ---------- Previous post was at 07:58 AM ----------

Hey,

Here is a couple of videos:

Those are minor compared to what it was doing the other day.

Thanks,

Winslow

Hey,

Oh I figured it was the same thing!!!!:surrender:

Mine has a small orifice hole in it. It has worked for about 5- 6 months, but I'm kinda wondering if maybe the hole has worn out and is allowing too much fuel to hit the gauge?!?!?!?!:shrug:

This morning it didn't shake around like it was doing. Of course I played with the needle valve a little yesterday, closing it, then cracking it open. I'll see how it does and if it starts shaking I'll take a video of it. I might even pull the needle valve and restrictor off and have a look see!:thumbup2:

Thanks,

Winslow

---------- Post added at 10:07 AM ---------- Previous post was at 07:58 AM ----------

Hey,

Here is a couple of videos:

Those are minor compared to what it was doing the other day.

Thanks,

Winslow

i know for a fact the you want a gauge that where the psi should be running should be in the range of 2/3rds of the sweep..hay..i like them gauges tho...and also..if i am not mistaken the needle valves i have ever worked with..the seats are ceramic..easy to overtighten and break..i work as a pipefitter in the coffeyville ks refinery and have to replace them all of the time because the operators really crank down on them and it is not needed.if you overtighten the sending unit for fuel psi..prolly goes for all sending units..overtightening them will crush the insides and cause an INACCRUATE READING.hope some of this helps ya!!
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i know for a fact the you want a gauge that where the psi should be running should be in the range of 2/3rds of the sweep..hay..i like them gauges tho...and also..if i am not mistaken the needle valves i have ever worked with..the seats are ceramic..easy to overtighten and break..i work as a pipefitter in the coffeyville ks refinery and have to replace them all of the time because the operators really crank down on them and it is not needed.if you overtighten the sending unit for fuel psi..prolly goes for all sending units..overtightening them will crush the insides and cause an INACCRUATE READING.hope some of this helps ya!!

Hey, Autometer doesn't make a 0-30 psi gauge unless you go electric for $200+!!!!!:banghead: I've never tightened it down, it normally just runs 1 turn open as I have the restricter fitting in there; But thanks for the info!!!!:thumbup2: I tighten the needle valve down a little more and on my way just class the second time it isn't shaking at all. I'll see if it stays that way!!!!!:pray: Thanks, Winslow

I keep my needle valve cracked just enough to pressurize the gauge, it is only 1/6th of a turn open.

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I keep my needle valve cracked just enough to pressurize the gauge, it is only 1/6th of a turn open.

Hey, I tried that and so far so good!!! I hope it stays that way. I wonder why it started acting up... I'm thinking that orifice hole enlarged itself!!:shrug: Thanks, Winslow
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