That is pretty good. The biggest thing on the Carb'd Lycomings is to plumb the fuel pumps in parallel. The electric pump in the Van's kit especially is prone to clogging from small debris, and can make a really bad day if it restricts fuel flow too far. I also like that install, as it keeps everything (including the electric pump) forward of the firewall. The less fuel in the cockpit, the better in my opinion.

On an injected setup, they pumps have to be in series because of the higher pressures involved, unless you want to spend the extra money on some high quality check valves. The pressure on the outlet of the electric pump when it is turned off is enough to start fuel back-flowing through that pump and dropping the system pressure. The high pressure electric pump has a bypass built into it so fuel can be drawn through if it is plugged.

I always suggest a good quality fuel strainer such as Steve's:

http://www.stevesaircraft.com/gascolator.php

or Andair's...
 
osxuser said:
That is pretty good. The biggest thing on the Carb'd Lycomings is to plumb the fuel pumps in parallel. The electric pump in the Van's kit especially is prone to clogging from small debris, and can make a really bad day if it restricts fuel flow too far. I also like that install, as it keeps everything (including the electric pump) forward of the firewall. The less fuel in the cockpit, the better in my opinion....
Click to expand...

All I can say about this is that redesigning the Van's fuel system should not be taken lightly. I would caution anyone making such changes as noted above to proceed with extreme caution, and personally I do not recommend the above alterations! The only thing I do recommend is a prefilter after the fuel valve of 74 microns which is also recommended by Facet.

osxuser said:
On an injected setup, they pumps have to be in series because of the higher pressures involved, unless you want to spend the extra money on some high quality check valves. The pressure on the outlet of the electric pump when it is turned off is enough to start fuel back-flowing through that pump and dropping the system pressure. The high pressure electric pump has a bypass built into it so fuel can be drawn through if it is plugged.
Click to expand...

Sorry to disagree again but this is not accurate, either pump is 100% capable of suppling the required flow and pressure if the other fails. They are in series in both FI and carburator systems as designed for a reason and I caution anyone about redesigning the fuel system without EXPERT advice.

Looking at some of those install examples on that Zenith make me cringe !!!
 
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Diagram/Photos?

Hey on the parallel pump set up do you have any photos or diagram of such a set-up? Where does the parallel plumbing occur exactly?
 
Junglepilot said:
...this Zenith site has some of the best FFW fuel line routing info which should for the most part transition to the RV program.
Click to expand...

I'd suggest the line from electric pump tee to engine pump inlet is a bit short.

The line to the carb is zip-tied to an engine mount tube about 6 inches from the carb....too little slack; something is going to be sawed.

The mixture cable is attached to a motor mount tube with a pair of adels....when the engine shakes due to torque reaction the mixture lever is going to move with it. The shaft into the carb will wear out quickly.
 
Walt said:
Sorry to disagree again but this is not accurate, either pump is 100% capable of suppling the required flow and pressure if the other fails. They are in series in both FI and carburator systems as designed for a reason and I caution anyone about redesigning the fuel system without EXPERT advice.

Looking at some of those install examples on that Zenith make me cringe !!!
Click to expand...

Yes either pump can supply full pressure, I made no claim otherwise. IF the high pressure pumps were in parallel, AND the electric is turned off, the pressure from mechanical can bleed back through the electric, and thus reduce the total system pressure to lower than acceptable. That is why certified aircraft FI fuel systems are in series.

As for the low pressure pumps being in parallel for a carb'd setup, most if not all certified airplanes are set up this way. Van's setup is actually the anomaly here.

Check out the fuel diagram in this Cherokee 180 flight manual as an example.

http://www.freewebs.com/defence_aeroclub/Manuel PA28E.pdf

Fuel systems should be modified with caution, but I've had experience with an RV-6 that had a partial loss of power due to the Van's design, that would've never had that problem if they had been parallels. It's a pretty small modification all things considered, you don't have to change the routing of anything, just mount the pump to the firewall, and use a T at the inlet of the electric pump and at the inlet of the carb.

And I also think that we can all agree the craftsmanship on the Zenith isn't A+ work, hopefully that was just testing, not flying that way. I don't see the mixture as being a problem honestly. Once again, that is pretty standard with certified airplane, and I don't see them wearing out carb mixture shafts often... I think I've only ever replaced one, on a Cessna 150. The should have a wire type control on it though, not the stiff shaft type, that would probably absorb more vibration.
 
Actually the fuel system design in the pdf is p***-poor. If one of the two diaphragms in the mechanical pump ruptured and failed open, there would be no way for the electric pump to pressurize fuel going to the carb...it would just recirculate.

If the check valve in the Facet pump failed....it would also cause a lack of pressurization.
 
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Bob, I respectfully disagree. I've seen a diaphragm fail, and the electric kept up just fine. I've also seen the Facet get plugged on an RV, which the mechanical couldn't do anything about. The pilot was lucky to make it around the pattern and land.

Once again, I reference the way certified airplanes do it... there is a reason they do it that way. I suppose a catastrophic failure of the mechanical could induce enough of a problem that pressure might drop. But remember, all you need is 3 PSI at the inlet of the carb with some volume, and you are fine. The problem with the series setup is the failure mode doesn't provide for any volume.
 
No one has mentioned the use of an aluminium fitting on the carb inlet shown in the pdf...a BIG no no, should be a steel fitting. Thought you guys would have picked that one up straight away. :D
 
airtractor8 said:
No one has mentioned the use of an aluminium fitting on the carb inlet shown in the pdf...a BIG no no, should be a steel fitting. Thought you guys would have picked that one up straight away. :D
Click to expand...

I picked it up right away, and mine is steel (because of the location). But there are those who say that every fitting should be "steel" firewall forward...... including the fitting on the firewall. Mine are not.

L.Adamson --- RV6A
 
MC2 said:
This picture shows the inlet and an aluminium fitting on my engine. I'm guessing the risk here is a vibration induced failure and subsequent major fuel leak and fire. What should this be replaced with and what thread sealant should be used on the fitting?

Yes. The safest practice is to use steel fluid fittings on the engine due to possible failure from vibration. You need steel elbow, flared tube and pipe thread,45deg, AN823-6. I just used one of the locktite pipe sealants..can't remember which one.
That is not the only thing wrong in the picture. The fuel line tie wrapped to the engine mount does not leave enough slack for the engine to move on start up and will probably ware the mount after some time and as Dan pointed out the mixture cable adel clamped to the engine mount like that is beyond words in my book.
Click to expand...
 
osxuser said:
Bob, I respectfully disagree. I've seen a diaphragm fail, and the electric kept up just fine. I've also seen the Facet get plugged on an RV, which the mechanical couldn't do anything about. The pilot was lucky to make it around the pattern and land.

Once again, I reference the way certified airplanes do it... there is a reason they do it that way. I suppose a catastrophic failure of the mechanical could induce enough of a problem that pressure might drop. But remember, all you need is 3 PSI at the inlet of the carb with some volume, and you are fine. The problem with the series setup is the failure mode doesn't provide for any volume.
Click to expand...

Lets ignore the mechanical fuel pump for a moment. If we replaced it with a straight section of hose, do you think that would work fine?
 
With the pumps in series, you could parallel each pump with a check valve if you are concerned about pump blockage. This adds a bunch of extra plumbing for an unlikely event, but would be acceptable.

A "pre-filter" (before the electric facet or FI pump) eliminates this blockage issue except perhaps in the case of a catostophic pump failure (which I've never seen but is "theoretically" possible).

If you are going to parallel the pumps, then each pump would require a seperate check valve to ensure no back-flow can occur.
 
airtractor8 said:
No one has mentioned the use of an aluminium fitting on the carb inlet shown in the pdf...a BIG no no, should be a steel fitting. Thought you guys would have picked that one up straight away. :D
Click to expand...

Sorry to pile on here, but doesn't page 8 show a bass-akwards safety wire on the fuel pump attach bolt?
 
szicree said:
Sorry to pile on here, but doesn't page 8 show a bass-akwards safety wire on the fuel pump attach bolt?
Click to expand...


Great observation. didn't notice that one.
Did you notice that none of the fire sleeve in any of the pics is terminated with clamps or safety wire...another big no no.

A lot of things in the pics are a good example of what not to do in your engine installation. Something we can all learn from and not repeat I hope.

Any more mistakes anyone or can we stop picking it to bits now?
 
Great example of what not to do.

Critique:

1. Chafe issues as hose is tie-wrapped to engine mount. As engine moves its going to move the hose back and forth against the mount. There needs to be more distance between the carburetor and the tie-wrap. Use a proper clamp "DG" instead of a tie-wrap.

2. Firesleeve ends are not sealed nor clamped. Fluids will wick under the firesleeve causing deterioration and a fire hazard.

3. page 7-11. Firesleeve in picture is too short and pulling off of fitting. Again not clamped or sealed.

4. Cables attached to hose with tie-wraps. Hose should not be used as support for cables.
 
My PA 28-151 came from the factory with the fuel pumps in series. But, it also had an alum firewall!!!!


I guess the really sad part of this thread is that these pictures are actually posted in a factory manual.

Looking at pictures of engine installations here during the past several years, I continue to wonder why builders make an effort to clutter up the back side of the engine. This is a service area....... Mags or EI's need to be serviced. And the oil filter needs to be serviced. Let's not forget the lower oil screen.
 
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rocketbob said:
Lets ignore the mechanical fuel pump for a moment. If we replaced it with a straight section of hose, do you think that would work fine?
Click to expand...

Depends on the size of the hose I suppose, and the capacity of the pump. I've flown hundreds of hours behind this system in the certified airplanes, and feel perfectly comfortable continuing to do so. I also plan to build my airplane that way if it ends up being carb'd (unlikely). Just my opinion, but I think it's the lesser of two risks.
 
I have a parallel flow fuel system, tee'd off the fuel strainer/drain to a facet pump and the lycoming mechanical pump. Both pumps' discharge hoses tee into the carb with a fuel pressure tap on the same tee.
I get very low - to no fuel pressure at altitude on any kind of a warm day. As a result, I never run without the facet electric pump on. Yes I do check the electric pump discharge pressure before engine start, and the mechanical pump alone while the engine is running to verify each pump is working.
I recycled this thread because I'm considering converting to a series pump arrangement for this reason:
I think the parallel pump system has twice as much fuel hose absorbing heat, with half the fuel flow thru each hose (in an ideal case) or no fuel flowing thru one pump and hose assembly while the lower pressure pump has no flow, gets hot and forms a vapor bubble which effects the other pump's discharge.
I have not figured it out totally, but I plan to remove a couple of hoses and cap unused legs on the tees and run the fuel thru the facet, then the engine driven pump, then to the carb so I can see if I get better fuel pressure at the carb inlet?
 
So I did switch from parallel fuel pump plumbing to the series circuit. During the switch, I noticed a check valve had been installed on the outlet of the mechanical fuel pump. I left it on there out of simplicity, as I was able to use the existing fire sleeved hose, and simply cap the tees.
The results were not spectacular, but they were at least 1 or 1.5 PSI on the mechanical pump alone. Better, never reading "0" as before.
I'm using a Holley liquid filled 1.5" fuel pressure gauge from, you guessed it, Summit Aerospace. I wonder if it is effected by 3 things:
1. Height of the gauge (on the panel) above the pressure tap (at the carb inlet)
2. Temperature
3. Altitude
Additionally, the check valve ball & spring must cause some pressure drop? It looks similar to an Andair check valve, threaded right into the mechanical fuel pump and safety wired. Isn't this valve is redundant?
 
I don't have an RV (yet) but have built and flown 2 LongEZ's with carbs and 1 with Bendix RSA Lycs. The EZ and RV's are similar in that they both have pumped (not gravity fed) fuel systems. Rutan's specs for carbs call for a Facet pump in series with the engine driven pump and no check valves. I have 3,000+ hours on these EZ carb systems with one mechanical pump diaphragm failure in flight, but was able to maintain reduced fuel pressure with the engine driven pump only and normal (about 4 - 4.5 psig) with the Facet on.

Facet makes these pumps both with and without internal check valves; Rutan calls for a specific model without an internal check valve. As in RV's, builders like to deviate from the plans but the EZ crowd found out the hard way long ago not to deviate from the plans plumbing. There are 2,000+ Longs flying, most of which are carbureted and have in-line, series pumps.

deek
 
Anyone have a good source for an inline filter before the electric fuel pump in the standard vans o-360 setup? I have a andair gascolator but its after the electric fuel pump. On the engine side of the firewall.
 
Having built alot of fuel hoses for RV's and others out there, I can say the very few follow the recommended plans. Mainly due to installing flow transducers, different servos, and sometimes completely different style injection.
That means different length hoses, different routing, and sometimes different fittings.
Dont make it complicated, and use good installation techniques.
If you're not sure, look on VAF for some pics of an installation that may be similar to yours. If you cant find one, ask. Even though experimentals are somewhat unique, basics are the same.
Tom
 
Flow Ezy series 3000

I used the same and installed upstream of the fuel pump.

Flow Ezy series 3000, 74 micron, very high quality product.
http://flowezyfilters.freestarter.com/

Carb 0-320.

For first start I added 0.7 gallons to each tank and did not pre-prime the fuel lines. I do not have a primer. The engine started after two 10 second start attempts. I ran the engine for about 5 minutes on the left tank and shutdown. I drained 0.25 gallons from left tank.
 
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