IIRC the new ones have smaller ports for the return? The ones from China.

I've run a few of them without issue- on a Weber 38 and a Holley 390 DP, no issues and I run my engine harder than most on the street, to include Dyno runs, never ran out of fuel.

I think I would look at something else. Are you running mechanical pump?

What type of carb? Webers had a screen filter inside the cap that get missed often. When you say new everything, like new lines, Mech pump, new gas tank?

 

My fuel system is 100% brand new and functioning fine. I've been having fuel supply issues, bad pumps, etc and have replaced them. Running an electric now, but there is a known problem with the new fuel filters in that the 1/4" outlet port for the return line is sometimes manufactured without the proper restrictive hole inside it. This causes an almost equal flow of fuel away from the carb and will cause carb starvation. What I want to know is what is the size of the hole that's supposed to be in the 1/4" return port so I can tell when looking at a new one if it's right, and secondarily if anyone has bought one recently that was correct and what make it was.

 

The "Intentional" smaller port on the original type filter is meant to be a "Regulator" of sorts. I never did any actual tests to see what the

actual Pressure reading was. I never really started getting super pressure aware until that Sorry 23/36 "W" would not do as promised in their ads.

This is where those wonderful people at the "Red" help desk told me that having the exact pressure for it was critical. (That's when I really got

more involved with checking pressures with any of my carbs) With maybe an additional $150 of "W" junk parts....still did not help.

WHEN ALL ALONG they knew that the 32/36 would never work properly on my 258.

Gotta hand it to them, they made $$$ off of me, by stringing me along.

I put my Pre-computer BBD back on and with a Pressure Gauge and regulator I could stay between 4 and 6 PSI (4 being the minimum)

Then I did the best thing ever for my Jeep, a Holley 390 on my 258!

I had to maintain 7.5 PSI fuel pressure, Other folks swore a mechanical fuel pump could not generate that pressure....Wrong!

It's all in how you restrict the flow back down the return line.

Have you seen my Post 23 in here https://www.jeepforum.com/threads/weird-engine-chug.4501540/page-2?post_id=41919881#post-41919881

----JEEPFELLER

 

The restricted return port on an old style fuel filter is not really a regulator, it is a flow restriction. Different fuel pumps

might increase or decrease the flow, and pressures could vary if the pump's output pressures vary.

Using a regulator on the return line and having a gauge right at the carb will let you know if the the pressure is

actually correct. When doing this, it will not matter which 3 port fuel filter (old or new style) you use. The regulator

will sorta be in control.

-----JEEPFELLER

 

And, this is gonna sound silly, lol, but you made sure your carbs needle is set correctly, right?

I could totally be lucky, but I've always just thrown whatever filter I got from Autozone, Amazon, etc and never an issue. But like I said, maybe blind luck.

-- watch, next time I go to start the Jeep I'll have a fuel issue. 😂

 

1/4", always position at 12o'clock.

 

MJCJ, what carb are you running, and how do you know fuel pressure is the cause of your problems?

Have you actually measured fuel pressure with the return line open and closed?

I made these 2 videos to show how the 3-port style filter regulates fuel pressure. This first video is with the return line pinched off. As you can see, the pressure is around 7 psi.

This is with the return line open, and showing the fuel pressure around 4 psi. So the return line sheds about 3psi to the carb. This is with a standard mechanical fuel pump.

Neither fuel pressure had any affect on how the engine ran. That's why I think you might be chasing the wrong tail.

 

Hi guys, I appreciate the feedback, but honestly I know this stuff already...what I'm trying to figure out is what is the size of the hole in the 1/4" return port on the filter (and before some smart-*** tells me it's 1/4 inch, we know that's not supposed to be the size of the hole in the actual filter housing). I'm 95% sure the NAPA filter I got is the "bad" kind as it looks exactly like the ones shown as examples in other threads of the "wrong" built filters. I'm going to pull it off but want to have a "good" one sourced before wasting my time. I don't want to have to guess if I can avoid it, has anyone ever cut into an old "good" filter and measured the hole? My guess is it's somewhere around 1/8" but I prefer to not guess if I can avoid it. I'm going to go get another filter, but I prefer to not throw good money after bad and buy another one that won't do the job right. Has anyone bought a new filter recently that was right? Might save me a few trips.

 

Suggest you do your own study, buy a few different brands as they are relatively inexpensive and even found at many yard sales for pennies on the dollar, to find solid information so you know.
With AI coming into play with internet searches these days, a lot of information is passed over, for a general statement about a product. You are wanting to dig deeper for actual product manufacturing data, so might need to go direct to the manufacturer to get it.
Might try over on AMC Forum too, as another resource.
Good luck with your research.

 

This, grab some, along with a bandsaw or Sawzall and some metal blades. Cut em in half and let's see.

Is this really an issue? I'll do it and film it, lol. Most are probably the same, TBH. Like Mech Pumps, I tried 3 different brands, all the same factory I think-China. The one that actually worked was one on Amazon that was made in South Korea. Just as an example.

What would be really awesome is a reusable filter. Wonder how much it would cost to make such a thing? I grow tired of parts that are so stupid, cheap and small holding back people's projects. Really feel like people would pay premium, say $50, for a good one vs 5 cheapies. Maybe I can have some machined for a test.

 

I'll ask again.

What carb are you running?

Have you actually checked fuel pressure with and without the return?

 

Perhaps cut the center seam out of top & bottom where they join, then thread both sides on outside of the casing, find a filter and O-ring to fit. To service the filter would be to simply unscrew the two halves, replace the cartridge, screw them back together..............

 

A 30 second Google search turned up this thread about this exact issue.

The alternatives to the incorrectly China-made Wix filter #33040 are AC Delco GF423 and Baldwin BF886. They both have the proper restriction in the return port.

That said, I'm going out on a limb to say I don't think the fuel filter's return orifice size is the OP's problem.

 

A 30 second Google search turned up this thread about this exact issue.

The alternatives to the incorrectly China-made Wix filter #33040 are AC Delco GF423 and Baldwin BF886. They both have the proper restriction in the return port.

That said, I'm going out on a limb to say I don't think the fuel filter's return orifice size is the OP's problem.

I've been using NAPA/Wix fuel filters for quite a while and although I had starting problems, the plumbing (restricted fuel line) and fuel pumps were to blame. Since I went to a Facet Dura Lift fuel pump, things have been working as I had expected. In his other thread, I asked the OP what Facet fuel pump he was using but I guess he forgot to indicate.

 

I have some 'experience' in this area.

First off, you NEVER EVER want to plumb a mechanical fuel line into the cab of your vehicle....NEVER. It's disaster waiting to happen.

I have TBI...so I'm using an inline pump that puts out over 100 PSI...but the regulator at the throttle body drops it down to about 13 PSI. I like to rock crawl so it's nice to know when I'm getting starved for fuel due to angles.

I have 3/8" SS hard lines up to a manifold where the pressure transducer is. The wire then goes to a gauge on my dash.

2 Answer one of your questions...gas (like water) is for the most part a non compressible medium. hence, once the lines are flooded, there is not 'flow', just pressure changes. So the size of the line does not matter.

A 2-pack of these on Amazon are likee $12

Fuel pres gauge is on the left

 

buy 4 or 6 filters and cut them up to see whats really in there. IF ya really want to know ..............J/S...

 

I'm trying to avoid that...

 

put a regulator on that has a by pass and good fuel filter before the reg and be done......

 

Those do work well, but it should be unnecessary with the correct fuel filter. The point of this post was to try to figure out what the correct fuel filter is supposed to look like...I'll figure it out.

 

What size is your return line? Smaller port/orfice in the return filter does matter but ihmo the smaller return line also makes a difference in pressure to the carb. Worked on a jeep with a low pressure electric pump mounted at the tank, then the 3 port right after the pump and short return line to the tank. No fuel to the carb, would only cycle fuel right back into the tank. Restriction due to the smaller return line is what keeps pressure at the carb.

 

Interesting, I've never even thought of that, lol. I get the idea behind it, though, to clean up the engine bay. One of those things that work in our heads or on paper, but not in real life.

Thanks for sharing, sounds like some "bright idea" I would've tried, lol.

 

The filter 3rd port/return line is a calculated leak and it sounds like your facet pump is supplying less volume than the stock mechanical pump and therefore is allowed to return a larger percentage volume of fuel supply than what would be stock and you end up with less pressure at the carb inlet. The 3 port that works fine with a mechanical pump with the 'factory' size bleed may not work for you, in your instance you may be best off to use, and it pains me to say this, jeepfellers diagram with the pressure regulator in the return line to tune in proper pressure at the carb inlet. You could also solve your problem by putting a restriction in the return line just off the filter and fine tune the orfice size until you get proper pressure at the carb inlet. with an external return restriction you won't have to worry about replacement filters in tbe future.

 

The problem is that my filter is unrestricted, so it's not regulating the fuel flow at all. Honestly, all I wanted to know is if anyone knew what the size of the restriction hole is in the filter, and it appears that they don't know either so I'm moving on. I'm trying to keep things as simple as possible if I can. Thanks for the input!

 

I have a Facet pump 4-7, too, but the duralift style. Here....

Facet Dura-Lift 12v Fuel Pump, 1/8 NPT, 4-7 psi, 120" lift | Pegasus Auto Racing Supplies

Facet Dura-Lift pumps are able to draw fuel from farther away than standard Facet pumps. This pump can lift up to 120 inches and can deliver up to 33 GPH.

www.pegasusautoracing.com

It is really close to the carb, so definitely working to spec. You can see the top of it on the fender.

Again, I've never had issues with any filter, large return barb years ago, smaller barb, no idea what brands, a few different types. I've used this pump on a Weber and now Holley.

Are you sure your pump is in a good spot to work?

 

I have a push style pump, it's back at the tank where it needs to be. I'm good, I'll figure out the filter thing and move on from there. Thanks!

 

Matt, the forum thread you linked to in this thread is specifically about this problem, it's a known issue...if you take your current setup and remove the restriction in the 1/4" fuel filter return your carb will likely have fueling issues.

Let me put it this way,I'll answer all your questions... I have a brand new bb2-barrel carb, brand new fuel tank, brand new sending unit, brand new fuel filler neck and vent hoses, brand new pre-formed 5/16" supply lines from the tank, brand new pre-formed 1/4" return lines, brand new hoses on the correctly repaired and functioning tank vent/charcoal canister system. New fuel pump pushing 4-7 PSI to the carb with the return line blocked off. Not blocked off, the engine will idle but run out of fuel when driving. Runs perfect with the return line blocked off. Sounds like a problem with the return line to me. It could be the carb having float issues, but more likely it's the fuel return system, which is much more easy to fix first. If you had the same situation as me, and you knew that the fuel filter didn't have a restrictor built into it, would you run down all these rabbit holes folks are suggesting, or just replace the filter with a correctly manufactured one and then take it from there?

All I asked, and it was a simple question, is what is a correct filter supposed to look like before I buy another one that's manufactured incorrectly. I'm trying to have some things set exactly right so I can eliminate certain problems from consideration when working on it. It's okay that nobody else knows either, and it appears that as long as it has some sort of restriction it should be okay. I think we get jaded to the idea that if someone is asking a question it's because they don't know what they're doing, which is sometimes the case. I do know what I'm doing here, just looking to save a little time when getting a new filter. I'm good, I'll run to a few stores to see what they have and try to find one that looks right. If I still have starvation issues with the right filter in, then I can look at the pump/floats, etc. Trying to start with the most obvious basics first then moving up from there.

I was going to put a fuel pressure gauge in the cabin of the truck so I can monitor the pressure under driving conditions, got blown up for wanting to do that in another thread where I asked a simple question about the hose tee that the sending unit is screwed into. Seems like these days some folks on this site have to have a "take" on what a guy is doing instead of focusing on what he actually asked. Then they get frustrated when I don't provide them with all kinds of information that they need to do a diagnosis I didn't ask for...things tend to go sideways.

In any case, I truly appreciate the time you put into trying to help, you're one of the "good guys" on this site and I appreciate you.

 

One more comment to annoy you... I still think that your electric pump is not supplying enough volume for the calculated leak to function correctly and no return filter, factory size bleed or not is going to give you the correct volume at the carb. With the aftermarket pump, you are going to need an aftermarket solution to get enough volume at the carb to continue to run when you put your foot into it.

 

I actually think you might be right, subject of a few other threads I've started and kind of abandoned. I just need to fix the thing that I know for 100% sure is wrong, then I'll move on to supply, etc. You're comments don't annoy me, I appreciate the help...

 

In Post 21 you say

"No judging on my part, I don't know myself. I'll just go start pulling out boxes at the parts store until I find one with a restriction in the supply line."



Either you wrote this wrong or you are looking at the wrong end of the filters! .... and in the wrong hole!

The restriction is gonna be inside the little port (the return line port of the filter) as if it were mimicking the last scenario in my diagram




IN A PERFECT WORLD (which it is not----and so the need for a gauge right at the carburetor to verify the setting)

I could turn my regulator to (edit) "WIDE OPEN" and basically it would act like it wasn't even there

I could turn my regulator to "Seven" and it partially dams up the return line and would provide "7 PSI" to everything

before the return line --- still allowing the excess to run on thru the return to the tank.

And 4, 5, 6, 7.5 (7.5 is what my Holley requires) or what ever you set it too and your gauge agrees with the setting.

-----JEEPFELLER

 

Yeah, I typed it wrong, I was talking about the return line. I can use a regulator, I have another thread where I was talking about doing that with a more powerful pump. First, though, I need to get the right filter which I'll do first. I'm trying to just set it up the way it came from the factory and worked fine for 40 years. Hopefully I don't need all the other stuff, though I might need a pump that puts out more volume. Honestly I'm not sure it's a pressure issue as much as a volume one. There are pumps that put out 5 psi at 20 GPH and others that put out 5 PSI at 70 GPH. I think I just need a little more capacity, but I don't want to go overboard because I have a 1/4" "leak" in my filter. I'll get it set up, thanks for the help.

 

Interesting conversation for me for sure. It sounds like many of you are already aware of the restriction that the OP is referring to. I know you’ve all said you haven’t pulled one apart, but have you ever looked into the port and seen an actual orifice?
It was always my understanding, correct or not, that the whole purpose of using a smaller return port, was to BE the restriction. In theory at least.
No need for an orifice when the return line was already smaller.
Unless a specific application, such as the CJ with this engine, needed it to be restricted even further? Never heard of it, but that certainly doesn’t mean it didn’t happen.
So if there was, I’m learning something new today. Which I like.

And what we’re probably seeing with the inconsistently manufactured units, is that somewhere, someone decided it would be cheaper not to build it that way and should work just fine.
Or the original designs called for a smaller opening that the hose barb was attached to. Later manufacturing methods had the hole as the same size as the hose fitting. Perhaps?
We see these kinds of changes all the time in replacement and reproduction parts.
Can’t wait until someone chimes in and says they have an old original that they never threw away. Would love to see what’s on the inside of a factory original filter.

Even the return-type filter on the old 60s Corvair turbo models with 5/16 input and 1/4 return, didn’t have an actual restriction/orifice that I’m aware of.
I should go pull one apart to find out. Got plenty of old ones, but finding them in stacks and boxes won’t be fun.
And I don’t think that one of those would be in the decent price range for just buying one as an experiment. Probably cost five times what a Jeep filter costs. Hmm, now I’m going to have to look into that as well. 🙄

Good luck MJCJ. hope you’re able to find one in the modern supply chain that has the specified orifice and are able to measure it.

 

Interesting conversation for me for sure. It sounds like many of you are already aware of the restriction that the OP is referring to. I know you’ve all said you haven’t pulled one apart, but have you ever looked into the port and seen an actual orifice?
It was always my understanding, correct or not, that the whole purpose of using a smaller return port, was to BE the restriction. In theory at least.
No need for an orifice when the return line was already smaller.
Unless a specific application, such as the CJ with this engine, needed it to be restricted even further? Never heard of it, but that certainly doesn’t mean it didn’t happen.
So if there was, I’m learning something new today. Which I like.

And what we’re probably seeing with the inconsistently manufactured units, is that somewhere, someone decided it would be cheaper not to build it that way and should work just fine.
Or the original designs called for a smaller opening that the hose barb was attached to. Later manufacturing methods had the hole as the same size as the hose fitting. Perhaps?
We see these kinds of changes all the time in replacement and reproduction parts.
Can’t wait until someone chimes in and says they have an old original that they never threw away. Would love to see what’s on the inside of a factory original filter.

Even the return-type filter on the old 60s Corvair turbo models with 5/16 input and 1/4 return, didn’t have an actual restriction/orifice that I’m aware of.
I should go pull one apart to find out. Got plenty of old ones, but finding them in stacks and boxes won’t be fun.
And I don’t think that one of those would be in the decent price range for just buying one as an experiment. Probably cost five times what a Jeep filter costs. Hmm, now I’m going to have to look into that as well. 🙄

Good luck MJCJ. hope you’re able to find one in the modern supply chain that has the specified orifice and are able to measure it.

i expect those old filters had a restriction in them too. 1/4" isn't that much smaller than 5/16", at the low pressures we're talking about for a carburetor I don't think the difference in size would provide much resistance. Well, from experience, actually I can tell you it doesn't. I think the hole is probably around 1/8" or so. This simple question kind of stirred up a lot!

 

I have an extra Chinese made Wix filter #33040. The orifice in the 1/4" return tube will accept a #50 wire gauge drill (.070) but will not accept a #49 (.073) FWIW. .

 

Now there you go! Some nice hard, Data.
I was thinking a drill bit might do the job of measuring, if someone had the right type of filter.

Hopefully that’s just what MJ was looking for.
Well, I suppose that, even more than the actual data, you were looking for a filter that would actually work!

Still wishing good luck on that!😉

 

I'M STRESSED!