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Fuel Pressure spread

notlimah
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notlimah

notlimah

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Haha thanks Mike! I appreciate the talk, gave me the 'warm and fuzzy' to make the drive. Made it down to Seattle with no problems (other then the hood not latching and flying open at 45mph!) ugh! Perfect way to top off an already crappy day!

But..

My pressure was fairly steady the whole way. Cruising at 65mph around 18-1900 rpm was seeing 18.5psi and by the end of the trip was up to 19.5 and held steady. Hoping things stay the same for a while!

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notlimah

notlimah

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Alright guys I got another update...

 

I'm in the process now of jotting down my psi numbers on every drive so I can track what it's actually doing. Just from taking a quick look at my numbers so far it seems I'm slowly declining. :(

 

Fast forward to today on the drive into work. Fired her up, psi was right under 15. After getting her warmed up, it got to a solid 15psi, but even under 3/4-WOT I was getting what looked like zero movement. Once I got to work I popped the hood to check for leaks, couldn't find or see any. Next I noticed that I had some air bubbles in my line from my isolator to the gauge. Would that be enough to give me erroneous psi readings on the gauge?

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Ilikeoldfords

Ilikeoldfords

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Isolators are notorious for showing false gauge readings. I would definitely be looking to bleed the air out the that line if it were me. The air can compress in the line where the fuel wont. Most people I have seen start out with an isolator end up taking it off and running the fuel direct to the gauge or through a snubber. I am doing it the "Mike" way and just using a needle valve and airbrake tubing running the fuel directly into the gauge in the cab. If you do this, just double check that the airbrake tubing is fuel/oil rated. I have come across a few brands that are not. Wouldn't want the tubing to come apart on you later down the road.

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notlimah

notlimah

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Yea, I'm starting to see why! I can't stand the inconsistency of it and I haven't even had it on for that long! I might just give the isolator the boot and go with the straight forward setup. My only question is I'm currently using the setup from Vulcan so I'm not sure how or where I could plug in the needle valve. I'll run out to my truck and snap a pic real quick to help with the visualization.

 

Ok so here's my thought process, please tell me if it sounds crazy!

 

somzcx.jpg

 

1. Red Arrow/Oval will be capped off due to that leading to the isolator.

2. Obviously that will get rid of the hosing and isolator. I'll re-use the push fitting that the hose connects to on the other side of the isolator.

3. Yellow Arrow/Oval will be spliced into and will add the following...

    Push lock tee

    Snubber

    Needle Valve

    Then the push lock fitting for the hose, then hose to the gauge

 

Does that seem right?

   

 

Edited by notlimah
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Ilikeoldfords

Ilikeoldfords

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Sounds pretty good to me. If it were mine, I wouldnt worry about getting a snubber AND a needle valve. It is a little redundant in my opinion. Just go with a needle valve and barely crack it open. That will deaden the waterhammer from the VP and also give you a good valve that you can shut off in the case of a leak in the future.

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notlimah

notlimah

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Gotcha! I wasn't sure if they were both needed or not but I figured it couldn't hurt! I'll probably just order up the push lock and needle valve.

Now since I'm using the same tubing to the gauge that had antifreeze in it prior, if I just drain it as best I can and then hook it up it should be fine right? I just want to avoid pulling it back through the firewall just to clean it then reinstalling it haha

In the meantime I'm going to bleed the isolator and line and see it that fixes it for now.

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notlimah

notlimah

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Mike do you have part numbers for all of the pieces on the mechanical gauge setup?

 

Also, once I get the gauge running without the isolator, how do you bleed the line? I saw your video where after the truck is running you slowly crack open the needle valve but what about all the air in the line?

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Mopar1973Man

Mopar1973Man

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I typically just left the fitting on the gauge loose and bled it out and tighten the fitting up. But after awhile I gave up bleeding the air out.

 

All the brass is found typically in a NAPA store. The tubing is 1/8 air brake line (rated burst strength of ~600-800 PSI). Tapped banjo is normal found at Geno's Garage or Vulcan Performance.

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notlimah

notlimah

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Ok dumb question I know, but I'm not entirely sure what all those brass fittings are!

I assume that you loosen the fitting on the gauge when the truck was running right? I'm just wondering how the fuel pressure reading isn't affected by air in the line like it is with the isolator?

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Mopar1973Man

Mopar1973Man

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rs7k21.jpg

 

Tapped Banjo Bolt -> Needle Valve (WH6820) -> Male 1/8 NPT to Compression 1/8" tubing -> 5 feet of Air Brake Line -> Female 1/8 NPT to Compression 1/8" tubing -> Gauge

 

Because the air isn't trapped in the fuel system. As pressure goes up and down the air is replaced with fuel automatically. But on a isolator system the air is trapped in the coolant side and never get out. Not to mention thee isolator typically takes on water hammer damage eventually.

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notlimah

notlimah

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How do I set the delay? Is that just cracking it open just enough to get pressure?

I need to get this done! Even after bleading the lines a couple times and making sure the isolator bladder was pushed all the way back I'm getting a huge psi spread. I just want solid pressure!

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notlimah

notlimah

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Yea, I'm still on the FRRP. It has less then 500 miles on it, and I've shown pretty steady pressure before I tried re-bleeding my anti-freeze line so for now I'm still leaning towards air in the line/running an isolator as the problem. I'm going to stop by NAPA on the way home and get some parts to replace the isolator. I figure it's the easier way to go right now and I'll see if that clears the issue up. If not then it's probably the damn raptor!  :mad:

 

Still not sure how to set needle valve to delay the needle rise   :shrug:

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