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Old 05-27-2021, 10:29 AM
campbdon campbdon is online now
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Red face Order of Devices in the Fuel Line

Hi everyone! I've been really poring over the really helpful articles and discussions on this site. Working through starting up issues at the moment.

My current setup on the fuel side is Fuel tank -> Shutoff switch -> Fuel Hose (1/4" ID) -> Facet Elect Fuel Pump -> Inline automotive filter (seems like quite coarse) -> Carb.

I am considering adding a polishing inline filter, and do understand that coarser grade filtering must precede finer, so which do you suggest as the preferred option:
a) Insert the polishing filter between the carb and current filter, or
b) Move the existing filter to before the pump and install polishing filter where original was (between pump and carb)

Seems to me (b) would help keep any larger debris from reaching the pump, etc. Should , let's say, a 5-micron coarseness be sufficient? The existing one must be well over 10. Or instead, adding a fuel/water separator (eg: Racor) but don't yet have any suspicion of water in the fuel.

Thanks for any advice,
DonC
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Old 05-27-2021, 10:41 AM
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Off the topic, but does this raise any eyebrows?
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Old 05-27-2021, 10:42 AM
Dave Neptune Dave Neptune is online now
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First welcome to the MMI Afourian Forum.

My preference is like this ~ tank ~ shut off valve ~ filter/water separator ~ fuel pump ~ polishing filter. This way the pump get clean water free fuel, this will keep the fuel pump happier and debris free.

Also while pondering future diagnosing and tuning I strongly suggest a "REMOTE START SWITCH" as it is very handy for all diagnostics.

Also keep in mind when working on the A-4 keep the water valve closed so water does not fill the exhaust and get into the engine.

Dave Neptune
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Old 05-27-2021, 10:47 AM
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Question

Bill, what do you see? I see a clamp almost off the end of the hose and the throttle arm rubs the fuel line, not real good.

Dave Neptune
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Old 05-27-2021, 11:21 AM
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Hi, Dave:

It looks to me like the hose is too big for the fitting, making up for the difference in diameters by overtightening the hose clamp (and potentially weakening the hose, especially with that bend at the end).

Bill

Last edited by W2ET; 05-28-2021 at 09:39 AM.
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Old 05-27-2021, 04:42 PM
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Hi,

I would replace all the fuel lines while I was at it. Removing the old lines from barbed fittings often tears up the inside of the line leaving little chunks of rubber that can gum up the carburetor.

Please make sure you use coast guard approved fuel lines.

New, correctly sized fuel lines ensure a nice clean supply of gas AND gives you great peace of mind that you will not be subject to fuel leaks.

Hope that helps,

Peter
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Old 05-28-2021, 09:43 AM
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Order of Devices...

Thanks all for the advice.
Mr Neptune, I especially read all your stuff! I am planning to replace all the fuel lines (the run from the tank to the pump was only 1/4" ID, not the recommended 5/16") with the USCG approved stuff. If water is not suspected as an issue, rather than adding a water/fuel separator, is there anything "wrong" with moving the coarser filter in front of the pump and adding a finer one after that (either before or after the pump)? If I decide to get the separator must it mount on a bulkhead? I don't see where on the engine block that could attach? Also intend to switch the fuel from the regular 87 to 91 to reduce the ethanol content.
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Old 05-28-2021, 10:04 AM
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I doubt the ethanol content is different. A water separator is quite necessary today due to the ethanol absorbing moisture and contaminating the fuel. Well the condensation in the tank from the warm days and cool nights also brings in moisture and the only way to get rid of it is a separator. Many aircraft have a drain at the bottom of the tank for this purpose.

Mount it on a bulkhead as near the tank as you can and be sure you can access the cartridge for easy R&R.

Do use a polishing filter and mounting a pressure gage after the polishing filter just before the carb is a great idea. A cheap one will work fine and eliminate a lot of diagnostic issues in the future.

The water separator can hold a lot of junk before loosing flow and is well worth the investment, especially when upgrading.

Also note that the 1/4" fuel lines are more than adequate for the A-4's needs.

And use the regular grade 87 or lower if you can find it. Due to the A-4's low compression and RPM's it will make more torque and run smoother on regular, premium is a waste of money.

Dave Neptune
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Old 05-28-2021, 09:00 PM
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DonC, Dave Neptune is THE man.
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Old 05-29-2021, 10:36 AM
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Is anyone else bothered by the Flame Arrestor being covered by...
...whatever that is?
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Old 05-29-2021, 10:49 AM
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Question Curious indeed

Jerry, good eye!!! Looks like a spam can covered with insulation of some sort. Possibly a "boxed isolated air intake" or an air filter.

Don can you let us know what it is?

Dave Neptune
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Old 05-29-2021, 06:28 PM
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Curious

Was curious about the box on the flame arrestor myself.
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Old 05-30-2021, 07:52 AM
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Order of Devices...

It is a box of sheet metal construction that fits snugly over the flame arrestor (a brass (I think) porous grid "filter" thingy) and (above that) a foam sponge (replacing the original which eventually disintegrated). The arrestor is at the bottom with the sponge above it so the sponge is what's visible when the whole thing is viewed from above. Everything fits tightly with no play and air can definitely pass through it all without problem. I'd have to go back to the boat to verify what makes the cover look like that, but it has been used without problems by myself and the PO (11 yrs ago). The assembly is screwed down onto the carb throat with 2 screws. Does this make sense?
Thanks
DC
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Old 05-30-2021, 08:29 AM
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Looks like foil tape to me.

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Old 05-30-2021, 09:10 AM
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We call it the "flame arrestor" but it's also the air intake. That box to me looks like a DIY air filter.
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Old 05-30-2021, 09:41 AM
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Cool

Quote:
Originally Posted by campbdon View Post
It is a box of sheet metal construction that fits snugly over the flame arrestor (a brass (I think) porous grid "filter" thingy) and (above that) a foam sponge (replacing the original which eventually disintegrated).
Don-
That is most certainly not a "stock" setup and I'm not even sure if it'd pass the Coast Guard spec.
"Arrestor should be kept clean to prevent contamination from propagating a flame."
Just the fact it is a sponge would be a concern for me.
At the least, I would think it is affecting your fuel mix.

You may want to add it to the list to "upgrade" that setup while you're going through your fuel system end-to-end.
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Old 05-31-2021, 01:26 PM
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Order of Devices...

Spoke with the PO, who says it was his attempt at adding an air cleaning function in front of the arrestor. I plan to replace it with the properly sized housing for arrestor only, or at the very least remove the sponge.
Thanks guys!
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Old 05-31-2021, 05:45 PM
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Quote:
Originally Posted by roadnsky View Post
Don-

"Arrestor should be kept clean to prevent contamination from propagating a flame.".
Removing the element from the back flame arrestor and cleaning it in solvent was a yearly matience procedure for me. The element is a good air filter by itself and does not need a "booster" filter.

ex TRUE GRIT

Edit: Sharp eye Jerry.
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Old 05-31-2021, 07:27 PM
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Carb looks clean.
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Old 06-01-2021, 09:38 AM
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Quote:
Originally Posted by campbdon View Post
I am planning to replace all the fuel lines (the run from the tank to the pump was only 1/4" ID, not the recommended 5/16") with the USCG approved stuff. If water is not suspected as an issue, rather than adding a water/fuel separator, is there anything "wrong" with moving the coarser filter in front of the pump and adding a finer one after that (either before or after the pump)? If I decide to get the separator must it mount on a bulkhead? I don't see where on the engine block that could attach?
Don-
I think we got a bit off-course (but for a valid reason) and I want to make sure you got the answers to your main questions...

Quote:
"If water is not suspected as an issue, rather than adding a water/fuel separator, is there anything "wrong" with moving the coarser filter in front of the pump and adding a finer one after that (either before or after the pump)?"
No. In fact that is preferred to your current setup.

Quote:
"If I decide to get the separator must it mount on a bulkhead? I don't see where on the engine block that could attach?"
Yes, that is the typical setup and adding the Racor would be an improvement to your current system IMHO.
While you're at it, maybe add a fuel pressure gauge too as Dave mentioned?
(Attached is a pic of my setup. Although my Facet is also on the bulkhead for other reasons)
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Old 06-02-2021, 02:36 PM
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Seems to me adding a sponge on top of the flame arrestor is a bad idea for three reasons:
1. It restricts airflow, performing the function of a choke to some extent.
2. If the engine does backfire, and a flame tries to emit the air intake, it could catch the foam sponge on fire. Or partially melt it, causing more air restriction.
3. cleaning the flame arrestor is easier than cleaning a foam sponge. The foam may absorb water in the air, further choking the engine.

You might experiment with removing the sponge while it is running to see what difference it makes. If you have a vacuum gauge, check that at the same time to see how much it may be restricting airflow. Let us know what you find. Then leave the sponge box off. I think the flame arrestor is all the air filter an A4 needs. The PO was being too clever, though well-meaning. Let the engine breathe.
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Old 06-03-2021, 10:35 AM
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Order of Devices...

I have already removed the sponge and reverted to original arrestor and it's housing. The modified version was indeed a homemade sheet metal enclosure in which the original arrestor+sponge+housing was nested. Now I'm back to discover what's actually preventing my engine from starting. I think I'll open a new thread under Troubleshooting for that.
Thank you all for your helpful suggestions. My engine environment is steadily improving.
DonC
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Old 06-04-2021, 10:02 PM
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Sorry if I missed it, but what sort of starting issues are you having? What are the symptoms? Last year I did some similar work to what you are doing, including adding a water separator and polishing filter, due to extremely long cranking required to start and sometimes no start at all. After all is said and done, I'm pretty sure the problem was an air leak at one of my fuel lines, specifically at the squeeze-bulb primer that I removed from the system. I now have a very reliable start.
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Old 06-26-2021, 10:08 AM
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May I ask one more related question? I'd like to add a second fuel shutoff to the chain. Already one at the tank, so I thought one near the carb?
If the secondary shutoff became closed would the backpressure faced by the pump be harmful?

Tank -->FS1 --> H20/filter -->F1 -->Pump-->F2 -->FS2 -->FPG --> Carb

FS1 = fuel shutoff primary
F1 = Filter1 (coarse)
F2 = Filter 2 (polishing)
FS2 = Fuel shutoff secondary (to be added on bulkhead)
FPG = Fuel pressure gauge (to be added on bulkhead)

Also, how about some sort of manual drain petcock to mostly drain fuel from the lines before disconnecting hoses? Or would that be another point of failure?
Thanks
DonC
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Old 06-26-2021, 02:52 PM
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I have a manual shut off valve immediately ahead of the carb in addition to the USCG required valve on the tank that's near impossible to reach or at least it's a PIA. A benefit you didn't mention is with the valve next to the carb always closed when the boat is unoccupied it's a safeguard against an uninterrupted fuel leak if the carb's float valve is stuck open. That was my experience and why I added the valve.

As for concerns over dead heading the pump with the valve closed, it's no different than the carburetor float valve closing so in my opinion, a non-issue.
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