Eliminating fuel pumps

shortfielder · Post by **shortfielder** » Tue Oct 08, 2013 1:59 am

I recently purchased a '52 C-170/Avcon conversion. I have been told that you could eliminate the fuel pumps if you ran a larger size supply line to the gascolator.
Anyone have any experience with this procedure?
Thanks Gary

Post by **Bruce Fenstermacher** » Tue Oct 08, 2013 2:52 pm

Gary, you can be told a lot of things. But unless the STC installation allows it or there has been a subsequent approval you can use for it, you can't just do it without seeking your own approval.

shortfielder · Post by **shortfielder** » Tue Oct 08, 2013 3:04 pm

Good morning Bruce
Thanks. I had heard that it had been done by 337, and I had hoped that if that were so and anyone had been involved in the process they may be able to get me copies of the paperwork. My understanding is that the fuel selector and the lines coming into it are the same as that on the 180 which typically runs the O-470. The only difference being the line going to the gascolator on the 170 is smaller.
So...practically speaking, if that is true, should be no problem supplying the O-360 with sufficient fuel by increasing the size of the supply line from the fuel selector valve to the gascolator ending up with the same setup as the 180.
I am aware that practically doesn't always come into play.
Gary

Post by **GAHorn** » Wed Oct 09, 2013 10:51 pm

Which exact model 170 did you purchase?

shortfielder · Post by **shortfielder** » Thu Oct 10, 2013 3:36 am

It's a 1952 B model ser# 25411 Avcon O-360 conversion

bigrenna · Post by **bigrenna** » Thu Oct 10, 2013 3:46 am

delete

N419A · Post by **N419A** » Mon Oct 21, 2013 3:52 am

Gary is this what you are looking for? It has been done here in AK at least once.
Paul

shortfielder · Post by **shortfielder** » Mon Oct 21, 2013 9:53 am

I think that is pretty much it, I would like to see something that speaks to the removal of the fuel pumps.
And if anyone else has has done something similar I would like to see copies of their paperwork too, just to have more supportive evidence of what has been done and approved.
Thanks Gary

DaveF · Post by **DaveF** » Mon Oct 21, 2013 4:49 pm

Why do you want to eliminate the pump?

N419A · Post by **N419A** » Tue Oct 22, 2013 2:13 am

Found this old thread that discusses the same topic of removing the fuel pumps.

Paul

http://www.cessna170.org/forums/viewtop ... ing#p17169

and this:
http://www.cessna170.org/337Library/077 ... onv%20.pdf

same 337 I have.

Dooley · Post by **Dooley** » Wed Dec 18, 2013 3:05 am

Mine has been working fine for years at all attitudes and altitudes. Winter and Summer and towing a glider over and over on the hottest of days. I changed the fuel line from the fuel selector all the way to the Carb including a new gascolator. The Alaskan paperwork inspired me and I don't miss my fuel pumps. Don't ask about my paperwork.

minton · Post by **minton** » Tue Mar 11, 2014 9:32 pm

This discussion has missed all of the other flow restrictions within the fuel supply system. IE, fuel tank outlet sizing, fuel selector port sizing ??. As the fuel "Head" pressure drops (min1.5 psi)(Lower fuel quantities) the size of the fuel lines, inlets and outlets do matter! That's why the fuel pumps are in the system, to aid in fuel flow and head pressure at the carb inlet regardless of the fuel line and orifice sizes and fuel state vs. larger fuel flow requirements.

The next question is, what's with this complexity of one switch and 4 lbs.??? I'm puzzled. The cost is not just a field approval but a new weight and balance is required for the weight removed. (Any weight removed or added over 1lb. for A/C empty weight of less than 5000 lbs.) Looks like a few $$$ to me.

You might look at that last issue pertaining to adding or removal of radios, big tires, landing gear, etc. How many of us have blown that W/B requirement off ??

Yes, I know others have differing opinions

corefile · Post by **corefile** » Fri Mar 14, 2014 5:07 pm

Why is this thread in the "Trademart"?

Moderator- Likely because that is where the OP started it and we didn't catch it. Thanks it is now in a better place.

DaveF · Post by **DaveF** » Mon Mar 31, 2014 3:19 pm

I thought of this thread as I was waiting to take off yesterday. It was a bit warm and I was taking off after a half-hour fuel stop. The fuel pressure normally indicates a solid 6 psi, but idling in the runup area I saw it occasionally dropping into the 3 psi range, then back up to 5. A few vapor bubbles, maybe. I put on the electric pump for takeoff as usual, and the pressure went back up to 6, and it stayed there after takeoff after I shut the pump off.

Marvel-Schebler calls for a minimum of 1.5 psi inlet pressure, I think, so I was still well above that, but considering how sketchy the Avcon design is, why would you mess around with your fuel supply for such a minor return? The AC fuel pump is $350 new outright, the electric pump is less than $100, and both will last a full TBO run.

Just sayin'.

ghostflyer · Post by **ghostflyer** » Mon Mar 31, 2014 9:37 pm

It has been asked why remove the fuel pump? My fuel pump has been a god send once when I had heavy contamination of the fuel . I have 2 fuel pumps on my aircraft . One mechanical on the engine and 1 electrical . Plus I run a -8 fuel lines . These fuel lines were in the aircraft when I bought it . They are -8 from the tank all the way down . I am convinced this was put in by Cessna at manufacture . I only just found this out recently due to a cracked fuel line from the r/h door post to the fuel selector valve . This problem had been with me for some time as I was thinking it was a leaking selector valve . There was stain everywhere until there was fluid everywhere . Selector valve out (%#€£ job ) and then a crack in the line was found . YAHOO . Easy fix.

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