Fuel pump question!!!!

[PerfTech]

...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

[rv7charlie]

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

[dougmattson]

So what did he say?

[rv7charlie]

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

[airguy]

Originally Posted by dougmattson

So what did he say?

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.

[170 driver]

http://www.classicpreservation.com/fuelpumpkits.html

Found this cruising the net,,,maybe this guy can help. Looks like he probably knows all about them.

[frankh]

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

[erich weaver]

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

[rv7charlie]

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...)

:-)

[frankh]

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