Order of Devices in the Fuel Line

[campbdon]

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

[W2ET]

Off the topic, but does this raise any eyebrows?

[Dave Neptune]

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

[Dave Neptune]

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

[W2ET]

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

[Peter]

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

[campbdon]

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.

[Dave Neptune]

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

[sastanley]

DonC, Dave Neptune is THE man.

[roadnsky]

Is anyone else bothered by the Flame Arrestor being covered by...
...whatever that is?

[Dave Neptune]

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

[wagner]

Curious

Was curious about the box on the flame arrestor myself.

[campbdon]

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

[Marian Claire]

Looks like foil tape to me.

Dan
S/V Marian Claire

[scratchee]

We call it the "flame arrestor" but it's also the air intake. That box to me looks like a DIY air filter.