Fuel Pumps and '48s

[Fearless Tower]

I have been looking at a '48 170 and am trying to find out about the fuel pump issue.

I must 'fess up that I have apparently gone about things slightly backward - I found aircraft first and then went and located an A&P not associated with the plane to do the pre-buy (he seemed knowledgeable about 170s, but I never thought to ask if he was knowledgeable about '48s specifically).

So, pre-buy is done and while there were certainly some hits here and there, it didn't uncover anything that made me want to run away....well maybe until now. After reading some about the required fuel pump on '48s vs A's and B's, I am now left wondering. I cannot say whether there was a fuel pump or not - I wasn't specifically looking and the A&Ps write-up did not mention anything good or bad about such a pump. I know it has a carb accel pump, but don't recall if a separate fuel pump was installed.

I have asked the owner if there is a pump and waiting for a reply.

Was the fuel pump on '48s electric or engine driven?

If there is no pump, can this be resolved? From the forums, it sounds like they are impossible to come by. Were there any authorized fuel modifications on '48s that legally did away with the pump?

Mucho thanks,
Andrew

[3958v]

Andrew There is no legal way to do away with the fuel pump. That said in past years people use to remove the pumps and fly with out. I have heard two different reasons for the fuel pump. The first and I suspect the correct one is that the fuel lines run down the front door posts as opposed to the later models they ran down the rear door posts. That created a situation were if the plane was in a nose up attitude it might be difficult to restablish the flow of fuel if the line were to suck a little air. The other reason had to do with the size of the fuel lines and that does not make sense since some ragwings had the larger fuel lines from the factory but still had the fuel pump. The factory pump is located on the right side of the front of the engine and is readily visable through the right cowl opening. If you dont have a pump you will need a pump, check valve, fuel pressure gauge and all associated lines. The cost of the pump will be a small part of the total costs which ran me about two thousand dollars ten years ago. The check vaulve is necessary because the backup for the pump is gravity. Just be careful when you get the check valve that the cracking pressure is very low because the head pressure of gravity from the fuel in the tank needs to open the valve if the pump fails. Another problem some have experienced in the past is check valve that are installed backward. They work fine till the pump fails. Some have repaced the engine driven pump with an electric pump although that is probably more dificult to get approved today than it use to be. Bill K

[GAHorn]

Andrew, the reason for the pump/check-valve is indeed due to the delivery lines running down the forward doorposts. When airplanes are certified they must be capable of delivering 150% of max-power fuel-flow in all normal attitudes. Since the lines run up the fwd doorposts (remember the ragwing is a copy of a 120/140 fuel system) the fuel system's flow rate ...designed for 85-90 hp....could not meet with the increased fuel demands of a 145 hp engine without a fuel pump. The check valve is for the purpose of allowing the engine to continue to run (even at reduced power) via gravity alone, should the pump fail.

The pumps are available thru Aircraft Spruce or Univair. The PN is 40585 and can be bought for about $350 overhauled or new.
The check valve has an unusual installation instruction that MANY DO NOT KNOW to follow...which is to open the valve...and REMOVE THE INTERNAL SPRING! This allows gravity to operate the check valve in the event of pump failure. (Pump pressue closes the check valve, no spring is actually necessary.)

[Fearless Tower]

The pumps are available thru Aircraft Spruce or Univair. The PN is 40585 and can be bought for about $350 overhauled or new.

So you can buy replacement pumps? I've heard a couple different stories - one that it costs $2000 for a replacement pump and the other that there are no more such pumps to be found.

FWIW, I just called the shop and the A&P said that it did have the pump....so it may be good for now

[GAHorn]

The pumps are available thru Aircraft Spruce or Univair. The PN is 40585 and can be bought for about $350 overhauled or new.

So you can buy replacement pumps? I've heard a couple different stories - one that it costs $2000 for a replacement pump and the other that there are no more such pumps to be found.

FWIW, I just called the shop and the A&P said that it did have the pump....so it may be good for now

I stand corrected. (Not on availability...on pricing. Here's Univair's CURRENT online pricing.)
40585 AERO ACC FUEL PUMP - OVRHL $466.20
AF-40585 AERO ACC. FUEL PUMP $632.22 NEW

Here's Aircraft Spruce's current online catalog:

40585 FUEL PUMP - OVERHAULED
3.5 ~ 4.5 PSI (Spruce PN 05-02557) $306.95

AF40585 FUEL PUMP - NEW (Spruce PN 05-02564) $395.95

Here's the link: http://www.aircraftspruce.com/catalog/e ... ntfuel.php

Here's what it looks like so you can show the guys at the airport:


Whenever checking on such things it's always best to ask suppliers and distributors DIRECTLY ...not the wannabees at the airport who have probably never seen the actual part and may not recognize it if they did.

[3958v]

My price of $2000 included all the parts and labor. The installation includes some hard to find fittings. Based on my prevous life as a test pilot I can tell you I would be much more concerned with legal issues than I would be performance issues while flying with out a working pump. My biggest concern would probably be a possible problem reestablishing fuel flow if you unported an inlet. I do know that full power stalls were never a problem although we may never have done them while low on fuel. Based on my previous experience I sure don't lose any sleep worrying about "what if the fuel pump fails" Please do not consider that I am advocating in any way flying with out a working fuel pump because it is definitely require equipment. Another thing to check is the direction of the check valve. If they are installed backwards the engine runs just fine until the pump fails and the engine follows a few seconds latter. One of our previous members actually had that happen to him. Bill K

[indyav8n]

Andrew,

I have a good fuel pump core if your interested, you can send it out for O/H, PM me.

Wes McCallum

[cessna170bdriver]

Based on my prevous life as a test pilot I can tell you I would be much more concerned with legal issues than I would be performance issues while flying with out a working pump. ... Bill K

And therein lies the difference between an "airworthy" airplane and a safe one...

[blueldr]

Isn't there a CW song about "My wife left me because my ragwing didn't have a fuel pump"?