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PostPosted: December 4, 2007, 9:27 pm 
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I'm a little confused on how to do this in the safest, most cost effective manner possible.

I'm mocking things up on my Miata based build and I'm confused.

I understand I need to go from my fuel tank to a prefilter (one of those cheap Glass jobs to my fuel pump.
Next from the fuel pump to the factory Miata fuel filter, from there to the feul rail and then from the fuel pressure regulator back to the tank. Sounds easy right.

Here is the problem. My tank has two -8AN or 1/2" outlets in the sump. My pre-filter and my fuel pump both have -6 or 3/8" fittings. The Miata factory fuel pump and the fittings on the engine are 5/16" and the fuel return in my 8gallon Summit tank is -6 or 3/8 AN.

So in summary I need to go from -8AN or 1/2 to 3/8. (about three feet between) Then from 3/8 to 5/16". (less than a foot between) Then in 5/16 to the engine and back, Kieth's book says its about 18 feet. Once Back I need to go from 5/16 fuel line to the -6 or 3/8AN return fitting on the tank.

For the fittings on the tank, I bought a -8AN 90 degree elbow and a -8AN cap. (for the unused port) For the return I bought a 90 degree -6AN fitting.

I bought a $18 piece of 1/2" hose to run from the fuel tank to the filter. I was hoping that with a proper clamp I can secure the 1/2" hose to the 3/8" fitting. (It should be low pressure there anyway)
From the filter to the fuel pump is 3/8 to 3/8 so no worries there. Then from the fuel pump to the Miata filter is 3/8 to 5/16. I'm unsure here whether to try to stretch 5/16" line over the 3/8" nipple on the FP or clamp down 3/8" line over the 5/16" nipple on the filter. This will be under pressure so I need to be sure it won't pop loose.

From the 5/16 nipple on the Miata fuel filter Kieth just ran 5/16" flexible hose all the way to the fuel rail and back. He said he used 18 feet in his book. That stuff is $5 a foot at Advanced Auto. No freaking way I'm dropping another $100 on fuel line. :shock: The Miata runs hard steel 5/16" fuel lines back and forth from the fuel rail. I was hoping I could rebend the factory lines and put single flares on them so I wouldn't need so much hose. Below, I included a pic of the single flare I can put on the stock steel line with and without the 5/16 fuel line clamped on to help with the visual.

I feel safer with the steel lines going through the tunnel given all the vibrating and spinning bits within. The only thing I don't like is the ugly single flare I put on the lines. I think it will hold a hose well, but it isn't as pretty as the factory flare and without a doubt it concentrates more stress on the hose. I can buy 25 ft. of Aluminum 5/16 tube from Summit for under $20 and I might be able to get a double flare on that, I don't know I've never tried.


Once back to the tank I suppose I will stretch my 5/16" hose over the -6AN return fitting on the tank and clamp it.

Anyway, I was just wondering what options I'm overlooking and also what the "proper" way was to do this.


Attachments:
File comment: This is the "not for fuel injection" filter I got for $10. I think as long as I use it before the fuel pump it will be fine.
ffilter.jpg
ffilter.jpg [ 84.91 KiB | Viewed 7494 times ]
File comment: Here is the tank with one of the -8AN fittings plugged.
DSCF4457.JPG
DSCF4457.JPG [ 107 KiB | Viewed 7493 times ]
File comment: This is the stock Miata steel lined after I tried to flare it. That's some thick tough stuff. Would you trust this?
flaredline.jpg
flaredline.jpg [ 34.7 KiB | Viewed 7509 times ]
File comment: Here is my Pile O Fuel Parts. That's more $$ laying there than you would think.
fuelstuff.jpg
fuelstuff.jpg [ 120.92 KiB | Viewed 7509 times ]

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Last edited by chetcpo on December 4, 2007, 9:48 pm, edited 1 time in total.
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PostPosted: December 4, 2007, 9:43 pm 
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I just bought 2 pre-flared lengths of 3/8" (I think) steel brake hose from NAPA. I had to shorten and reflare on end on each of them, and it ws a tight fit over my hoses but looks nice and neat

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PostPosted: December 4, 2007, 9:45 pm 
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robertwa wrote:
I just bought 2 pre-flared lengths of 3/8" (I think) steel brake hose from NAPA. I had to shorten and reflare on end on each of them, and it ws a tight fit over my hoses but looks nice and neat


Were you able to put double flares on the steel line? Am I asking for trouble with the single flares?

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PostPosted: December 4, 2007, 10:15 pm 
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I just used a single fare, and I remember from researching and asking people, many didn't bother with any flare to no ill effect. Once clamped it is pretty tight anyway.

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PostPosted: December 4, 2007, 10:30 pm 
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I hope these people that don't use any flare at least beaded the ends! Having 40psi fuel spraying around a hot engine compartment makes for a real bad day.

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PostPosted: December 4, 2007, 10:30 pm 
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robertwa wrote:
I just used a single fare, and I remember from researching and asking people, many didn't bother with any flare to no ill effect. Once clamped it is pretty tight anyway.


Great news. I guess I'll use the factory steel lines then and save my money for something else. :)

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PostPosted: December 5, 2007, 9:41 am 
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With your existing parts, I do not see how your going to adapt pushloc hose to your low pressure pre-filter fitting. Pushloc and low or high pressure fuel line are not interchangeable. Even if you manage to get the hose onto the fitting, pushloc is still far too rigid for hose clamps to be effective.

Making hose connections without flares is a very bad idea. Hoses will eventually creep off of the tube.

I would replace the tank fitting with a reducer. The tank may have pipe or a flared tube seat. Use an elbow with a hose fitting on one end, like an AN842. Use no more than 12 inches of low pressure fuel line to connect the pre-filter. Use a 3 inch piece to connect the pre-filter to the pump, replace the pump outlet fitting with a 5/16” hose fitting, use a short piece of high pressure fuel hose to connect the miata filter, then another short piece of high pressure hose over the end of new hard “brake” line. Carefully cut the fitting off the tube with a die grinder and no reflaring will be required. Cut the tube off the fuel rail end of the hard line also.

Two inverted flare, high pressure fuel filters for another application with inverted flare fittings on the pump would be even better, using short hard lines. A high pressure filter works fine for low pressure applications.

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PostPosted: December 5, 2007, 1:06 pm 
I originally had a low pressure filter before my pump like how your talking about. I ended up having to take it out because the fuel pump couldnt suck the gas threw it and caused a fuel starvation problem.


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PostPosted: December 5, 2007, 1:08 pm 
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I just looked at my pump on Summitand apparently the inlet is 3/8 and outlet is 5/16, so that fixes the pump to miata filter problem.


Miatav8,MstrASE,A&P,F wrote:
With your existing parts, I do not see how your going to adapt pushloc hose to your low pressure pre-filter fitting. Pushloc and low or high pressure fuel line are not interchangeable. Even if you manage to get the hose onto the fitting, pushloc is still far too rigid for hose clamps to be effective.


I looked on Jegs and Summit and couldn't find anything to do what you are describing. The bulkhead fitting in the tank is not available as a reducer.

This junction will not be under any pressure other than gravity, do you really think it will leak?

Miatav8,MstrASE,A&P,F wrote:

I would replace the tank fitting with a reducer. The tank may have pipe or a flared tube seat. Use an elbow with a hose fitting on one end, like an AN842. Use no more than 12 inches of low pressure fuel line to connect the pre-filter. Use a 3 inch piece to connect the pre-filter to the pump, replace the pump outlet fitting with a 5/16” hose fitting,


I'm not sure the pump outlet fitting is not interchangable/servicable. I also looked high and low for a 3/8" to 5/16" nipple to nipple adapter but came up empty. What now?


Miatav8,MstrASE,A&P,F wrote:
use a short piece of high pressure fuel hose to connect the miata filter, then another short piece of high pressure hose over the end of new hard “brake” line. Carefully cut the fitting off the tube with a die grinder and no reflaring will be required. Cut the tube off the fuel rail end of the hard line also.

I'm having a little trouble following you here.
Miatav8,MstrASE,A&P,F wrote:
Two inverted flare, high pressure fuel filters for another application with inverted flare fittings on the pump would be even better, using short hard lines. A high pressure filter works fine for low pressure applications.


Again, I don't think I can't change the fittings on the pump.

So you said I can't clamp the push lock hose down tightly, can I stretch 5/16" high pressure fuel line over a AN6 or 3/8" fitting?

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PostPosted: December 5, 2007, 1:18 pm 
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AlexPfeiffer wrote:
I originally had a low pressure filter before my pump like how your talking about. I ended up having to take it out because the fuel pump couldnt suck the gas threw it and caused a fuel starvation problem.


Kieth mentioned he wished he had run one since after his first tank of gas his fuel system was clogged up with fragments of the tank foam. Maybe I can take it out after I run some gas through. :?:

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PostPosted: December 5, 2007, 5:32 pm 
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When you remove the tank fitting, does it look like a an815 or an816?
http://www.skygeek.com/hardware-an-fittings.html

A an815 can be replaced with a an919 reducer.

A an816 can be replaced with a an912 reducer.

I’m saying it is easier to remove fittings by cutting them off of a tube than it is to cut steel tube and reflare.

My answer to the other questions is maybe.

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PostPosted: December 5, 2007, 6:52 pm 
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Thanks,

I'm admittedly completely lost in this realm and I think I need further clarification.

I took my tank fitting out and snapped the pic below. I checked and the "nut" screws onto either end so the thread pattern is the same on both sides. (AN-8 )

So what I need is a fitting the same size as the one pictured below on the "tank" end and with a -6AN flare fitting on the other right?

Do you know where I can get such a thing? Will the "other" parts combo I have pictured togther work, the bushing reducer with the double 3/8" piece. It would be nice to just fix it with one piece.

I included a pic of the adapter I ordered from Jegs. It would've worked if only it had enough threads on the AN-8 side.


Attachments:
Bushingreducer.jpg
Bushingreducer.jpg [ 35.56 KiB | Viewed 7408 times ]
reducer.jpg
reducer.jpg [ 60.02 KiB | Viewed 7412 times ]
tankfitting.jpg
tankfitting.jpg [ 69.01 KiB | Viewed 7395 times ]

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PostPosted: December 5, 2007, 9:02 pm 
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Bulkhead fittings are not usually found in pipe thread, only flare. The only solution for that would be to cap both -8 fittings and drill new smaller holes for the correct size bulkhead fittings away from the -8 fittings. I don’t think you’d want to, although there would nothing wrong with that. I have another idea.

If your pre filter is pipe thread where the black fittings screw into it, then a female elbow combined with a Russell straight AN male to NPT male adapter will allow the pre filter to screw directly on. You wont need to disturb that end when removing the element for cleaning. Support the pre filter within 6 inches of the tank bulkhead fitting with either a cushioned clamp on the hose or a very closely mounted pump with atleast ¼” between the filter and pump nipples.

The female elbow could be a AN939 but I’m not sure it has the internal seats for the flare to seal against. I’d make sure before ordering.

Here are few more fittings:
http://www.jegs.com/webapp/wcs/stores/s ... 3_-1_10019
http://www.bonacoinc.com/an_fittings4.htm

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PostPosted: December 5, 2007, 10:03 pm 
If I had to pay parts store prices for fuel line, I probably would have ended up with hard lines in my transmission tunnel as well :) It's a whole lot cheaper when you deal with 500' rolls of the stuff. I had 60' at home with me when I ran the lines, IIRC.

For flares on hard lines, you just need a bead of some sort. You can actually get away without them - remember, it might be 43 psi, but there are very few square inches involved so the force trying to push the line is low - but a small bead is best. I know there are some 1999-05 Miatas out there with fuel hoses simply clamped on to an un-beaded hard line.

I got lucky in my plumbing, the pump I used has a 1/2" inlet. However, it's not that difficult or expensive to drop a 1/2" hose down to 3/8" - just use hose barbs with NPT threads on them. -8AN on the tank to 1/2" hose to 1/2" hose barb to an NPT union to a 3/8" hose barb to 3/8" hose. Voila.

I run a pre-filter on my car all the time now. My pump likes it. A good pump shouldn't have any trouble sucking through a non-plugged filter, really. I've used this same style of pump to pull fuel through a dead in-tank pump, so I know it has the balls for the job!


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PostPosted: December 5, 2007, 10:19 pm 
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I got three 25' rolls of steel line, one at 3/16 for brakes, 1/4 and 5/16 for fuel. All together I think I paid a little over 50 bucks.

I thought it was a pretty good deal....

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