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Fuel pump question!!!!

PerfTech

PerfTech

Well Known Member
...Can anyone suggest where I can purchase a engine mounted lycoming fuel pump that has a diaphragm impervious to ethanol fuels or a supplier that possibly sell a rebuild kit with the appropriate diaphragm. This has proven to be harder than I first thought. Regards all, Allan
 
A couple of months ago, I spoke with Tim Henderson at MSA Carbs (current owner of the design), & had a very enlightening conversation. I'd suggest that you try it, too. You might like it. :)

Charlie
 
I can't speak for him, but I found him very willing to discuss both the hazards and advantages of 'non-avgas', and also willing to discuss the evolution of materials used to make the diaphragms, seals, etc in both their carbs and mechanical fuel pumps.

He wants us end-users to know that MSA want's to help & is willing to discuss applications with us.

I've tried to convey what he said about non-avgas use in their products, without risking misquoting him. Again, just look up MSAcarbs & give him a call to hear 'from the horse's mouth'.

Charlie
 
dougmattson said:
So what did he say?
Click to expand...

Most of these guys are not going to be comfortable offering information online for fear of being sued if/when something goes wrong. They will be much more willing to discuss it openly one-on-one over the phone "off the record" and give you some information so that you can make your own informed choice.

It's a funny thing about facts - they are stubborn and hard to change. They can be hidden only with great effort, and the aviation industry as a whole has a lot of lawyers putting out a lot of effort. Fear is contagious - but it doesn't change physics.

Research and knowledge is your best friend and will never lie to you, that's all I can offer.
 
The reason its harder than you thought is because using automotive fuels with a mechanical fuel pump is not the best idea.

Even if you do change out the components of the fuel pump, that fuel pump is in the wrong place hydraulically speaking and is way to near the hairy edge of vapour lock.. Thats why low wing airplanes are not universally certifiable to run autofuel.

In fact (IMHO of course) the only reason we have mecahincal fuel pumps at all is because nobody in the certified world really trusts an electric fuel pump. How many cars do you see pulled over these days with dead fuel pumps?..Just doesn't happen. So if you use two and wire them properly then the mechanical fuel pump should be in the same place as the vacuum pump..in the dumpster!

Realistically the electric fuel/Mechanical fuel pump combo is really a single electric pump system if running autofuel off a baking hot airstrip with a heat soaked engine.

I understand the elegant simplicity of the mechanical pump..But its simply a poor hydraulic solution looking for a vapour lock accident.

Its a shame cus, the engine LOVE autofuel..with or without ethanol, not counting the internals if the carb if you have one

Frank
 
Arent automotive fuel pumps installed INSIDE the gas tanks? Any chance that could be feasible on our planes? Heresy I know, but that IS the best place from a hydraulic viewpoint, correct?

erich
 
No, you can't put an automotive fuel pump in your aircraft fuel tank. If you did that, you'd be way too close to having an automotive engine in your aircraft. And we all know that doesn't work, right?

You can't use an inline automotive pump as your a/c fuel injection boost pump, either. (Just don't look too closely at the Airflow Performance unit that Van sells...)

:)
 
Yes its the hydraulically correct place, but the miantenance access would be a nightmare.

Using a 3/8ths line though is very big so even if you put the fuel pumps on the floor in the middle the press drop would be miniscule, as long as you don't have any restrictions.

Mine ae in the wing roots and thats works out OK..if you have flop tubes to make the plumbing work.


Doing it again I might be tempted to put them on the floor in the middle.

Frank
 
erich weaver said:
Arent automotive fuel pumps installed INSIDE the gas tanks? Any chance that could be feasible on our planes? Heresy I know, but that IS the best place from a hydraulic viewpoint, correct?

erich
Click to expand...

Mostly, but not always. Ford, among others, built a variety of vehicles with external, frame-mounted pumps. In fact externally they are identical in appearance to the Van's-supplied AFP electric boost pump, though usually contained in some sort of padded metal shield. As noted though, they don't like to pull very much. Ironically that's less of an issue in our airplanes than in a truck application (the ones I'm most familiar with) because the height difference between tank and pump is minimal.
 
PerfTech said:
...Can anyone suggest where I can purchase a engine mounted lycoming fuel pump that has a diaphragm impervious to ethanol fuels or a supplier that possibly sell a rebuild kit with the appropriate diaphragm. This has proven to be harder than I first thought. Regards all, Allan
Click to expand...

About two years ago, I spoke with a guy in the tech department at

http://www.aeroaccessories.com/index.html

At the time they were testing a Lycoming fuel pump built with materials impervious to ethanol. He commented the results were very encouraging. The purpose of the testing was to certify the pump for mogas.

About a year later I called again to ask what the progress was with the ethanol testing. The program had been cancelled. He commented there was a problem with acquiring materials for the effort. I believe someone higher up in the company pulled the plug on the project. I called back sometime later in an attempt to determine what the problem really was and he would not say.

There was an aerobatic pilot from North Dakota who did an air show burning pure ethanol. I found out where he had his engine built up, called them about the fuel pump used and they would not give me any information about it except to say they would call back but never did. I concluded everyone is concerned about the liability, but clearly there are sources to get a pump with ethanol proof materials if one has money and an inside track.

The aero accessories pump may well have upgraded materials but they won't say so. The same guy I talked to in the beginning would only say there were pilots flying with their pumps, using mogas, and having no problems that he knew of. That's all he would say. He would not comment on the materials they were using. One would think that since the pump is certified, changing the materials would be a certification issue.

Don Rivera at AFP has been building his stuff with materials impervious to ethanol and states his FI system is OK with mogas.

I suppose if there were enough "money in the deal", someone would build up a mechanical pump for experimental use and sell them but so far they are none available that I know of. If I were younger and less cautious, I would go with the aero accessories unit and see what happens. So there is another forced landing.... no thanks, not just to burn mogas. :)
 
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erich weaver said:
Arent automotive fuel pumps installed INSIDE the gas tanks? Any chance that could be feasible on our planes? Heresy I know, but that IS the best place from a hydraulic viewpoint, correct?

erich
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Its not hearsay. If the suction = the vapour pressure of the gas the fuel will boil. The less suck the pump does the less risk of vapour lock. With a high vapour pressure liquid the closer it can be to zero the better. Thats why fuel pumps are in the tanks on modern vehicles. On airplanes this is impractical so we can take say 0.05psi of suck in favour of improved maintenace access.
 
heresy not hearsay

"heresy" : opinion or doctrine at variance with the orthodox or accepted doctrine.


Had to chuckle at the confusion. See what can be learned on this forum?

erich
 
rv8ball said:
For those of you that run elec only fuel pumps.What pumps are you using.
Barry
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Do a search under my name and there is a complete photo guide of my system.

The pumps came from NAPA for the fuel injected set up..For the carb set up they were the little Facet cube pumps.

Frank
 
frankh said:
Doing it again I might be tempted to put them on the floor in the middle.

Frank
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Hmmmm... How about on the firewall?

Fuel lines go from tank, straight through fuse to firewall (minimal tubing in cockpit) penetrate firewall and attach to pump. From pump to fitting with fuel pressure sensor, to one-way valve, to gascolator. Duplicated on both sides.

I'm planning on a carb, so the small Faucett pumps for me.

No valves in the cockpit. Switching tanks is electrical, and pressure sensors give health status of pump.

Would that make the pumps too far from tank?

Dkb
 
Well

Its further from the tanks.. Its also a little up-hill.

But the big killer is its its on the hot side of the firewall. Hot (or warm fuel) boils much more easily than cold fuel.

remember on a hot day parked outside the fuel could in theory be close to 100F inside the tank..Likely?..No but..

The other thing to remember is that "hydraulically close" is not the same as "geographically close".. I.e if you were to short narrow tubing and tight bends then you will have a lower pressure at the inlet to the pump.

Clser you can get to no suck at all the better.


Frank
 
P-T

FrankH,
Funny thing. I am a Pressure temperature guy (A/C contractor) and I have never taken the time to relate P-T to vapor lock. Now it makes sense.
So I Google Gasoline P-t chart and can't find one. Only that the boiling point of petrol is 203F. As you say, under a negative pressure/vacuum this would come down. Kinda like the light bulb just went on.
Thanks,
 
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David-aviator said:
There was an aerobatic pilot from North Dakota who did an air show burning pure ethanol. I found out where he had his engine built up, called them about the fuel pump used and they would not give me any information about it except to say they would call back but never did.

If I were younger and less cautious, I would go with the aero accessories unit and see what happens. So there is another forced landing.... no thanks, not just to burn mogas. :)
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The "aerobatic pilot from North Dakota" I suspect you are referring to the Vanguard Squadron. Gary was generous in his time about two years ago, and I wrote up what he told me about their experiences with ethanol. He reported no fuel pump problems (mechanical or electric) among their fleet. http://www.vansairforce.com/community/showthread.php?t=58334&highlight=vanguard+ethanol+stan

Forced landing? That seems a bit dramatic, considering the likely failure mode. If the primary diaphragm fails, the secondary diaphragm take over and you notice drips under your aircraft on the ground. Or, if the soft parts of the check valve are destroyed, they don't seal, you lose fuel pressure, and the electric pump is brought on line. Now if somehow the soft parts break into pieces, and head downstream, then OK, we've got a big problem, if there is enough to block off the fuel screen.
 
MarkW said:
FrankH,
Funny thing. I am a Pressure temperature guy (A/C contractor) and I have never taken the time to relate P-T to vapor lock. Now it makes sense.
So I Google Gasoline P-t chart and can't find one. Only that the boiling point of petrol is 203F. As you say, under a negative pressure/vacuum this would come down. Kinda like the light bulb just went on.
Thanks,
Click to expand...

Mark,
The "distillation curve" is helpfull to look at. Chevron has some really nice info in thei publication Aviation Fuels. Check the graph on page 47. http://www.cgabusinessdesk.com/document/aviation_tech_review.pdf
The different gasoline components have different jobs, the graph illustrates that very well.

There are distallion curves for mogas as well. One thing that you will see is that using a winter blend mogas during the summer is not the best idea. When you look at winter blend gasoline, there will be very early boiling components in that mix so cars start easier in the winter (the winter fuel will start boiling- making vapor- at a lower temperature than the summer blends). That means they are also more likely to vapor lock during high heat conditions. This is not a fuel I would want in my airplane in the summer on a hot day!! Best burn it up before summer, unless you are set up like Frank's airplane, his system would probably not even notice.

The fact that gasoline can be made of so many different components, puts a kink in the idea of "pure gas". The concept of "pure gas" might be good as a marketing term to explain there is no ethanol on board, but reality, the "pure gas" is right there on the shelf next to the pure trail mix and the pure gardening soil...:D
 
nomocom said:
Mark,
The "distillation curve" is helpfull to look at. Chevron has some really nice info in thei publication Aviation Fuels. Check the graph on page 47. http://www.cgabusinessdesk.com/document/aviation_tech_review.pdf
The different gasoline components have different jobs, the graph illustrates that very well.

There are distallion curves for mogas as well. One thing that you will see is that using a winter blend mogas during the summer is not the best idea. When you look at winter blend gasoline, there will be very early boiling components in that mix so cars start easier in the winter (the winter fuel will start boiling- making vapor- at a lower temperature than the summer blends). That means they are also more likely to vapor lock during high heat conditions. This is not a fuel I would want in my airplane in the summer on a hot day!! Best burn it up before summer, unless you are set up like Frank's airplane, his system would probably not even notice.

The fact that gasoline can be made of so many different components, puts a kink in the idea of "pure gas". The concept of "pure gas" might be good as a marketing term to explain there is no ethanol on board, but reality, the "pure gas" is right there on the shelf next to the pure trail mix and the pure gardening soil...:D
Click to expand...

Correct it doesn't care..Now about the only failure mode I could come up with was maybe fuel boiling in the tanks on a Winter bleand at altitude.

Kind of hard to prove it or not..as I wold need a camera insode my fuel tanks at 18,000ft.

Lets just say I never noticed any problems going up high...Like half my gas dissappearing ar anything like that.

Frank
 
MarkW said:
FrankH,
Funny thing. I am a Pressure temperature guy (A/C contractor) and I have never taken the time to relate P-T to vapor lock. Now it makes sense.
So I Google Gasoline P-t chart and can't find one. Only that the boiling point of petrol is 203F. As you say, under a negative pressure/vacuum this would come down. Kinda like the light bulb just went on.
Thanks,
Click to expand...

Good cus there have been a lot of actual "hey my fuel pressure went away on take off..but its fine when I run the boost pump" messages on this forum, even when using 100LL.

Classic vapour lock..sucking uphill with a mechanical pump bolted to the back of a hot engine.

Its a eally such a hokey solution

Frank
 
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