Bad Fuel Pump Diaphram

N

nvracer

New member
I flew to the Golden West EAA fly in at Marysville CA yesterday which is a fairly short hop from Carson City, NV where I am based. It is a very large event and had a great air show. When they reopened the airport for traffic , I took off to go home. I then noticed liquid collecting on my windshield. I decided that I had better look at it and set down at Lincoln, CA. There was oil every where and it was at least 2 quarts overfull. I called my fellow Bellanca owner Tom Cross who lives close to Lincoln. He came to the airport to help me & brought some tools. We figured out that fuel was getting into the crank case from the fuel pump. We removed a plug on the engine side of the fuel pump, turned on the electric fuel pump and watched large quantities of fuel pour out. Tom had a rebuild kit at his house. We ended up installing a new diaphram in the existing pump without removing the pump from the engine. This is tricky, but easier than removing the pump. Everything was working in well when I flew home today & had to land in a 70 degree 20 knot crosswind. That was tricky & I ran out of rudder and ended up going thru a little grass. Nothing damaged.

I feel fortunate that I landed when I saw the oil on the windshield. A bad fuel pump diaphram can cause some serious problems. Has anyone else experience the same problem?

Thanks,

Ray N33GM
 
I also had the oil on the windshield and I knew that it was the fuel pump as the pressure was low.

Unfortunately my outcome was not as good as yours. I set a normal full flap landing, wound up short of the runway when the engine quit and would not re-start, Tore off the landing gear and did some major damage to the wings flaps and ailerons. Luckily didn't get the Aeromatic prop.

Big plus, no cuts nor bruises just a very short step to the ground.

So check your engine driven fuel pump. The present pump setup has a oil drain into the engine thru the pump adapter.
Larry D'Attilio had a pump body with the internal drain holes heli-arced closed so he could put an external drain on the pump. Lycoming does this and even has a secondary diaphram to keep the gas out of the engine.

Now I had a early warning from the pump that I didn't undertand.
The fuel pressure gage fluctuated just like it does when there is a vacuum leak on the suction side. This time it was sucking air thru the diaphram and I did "fix" the fluctuations temporarily by bleeding the gage line.
 
Cy,

Thanks for the info. I am convinced that the electric fuel pump that I use for take off & landing was pumping enough pressure into the diaphragm pump that it was leaking fuel past the worn diaphragm. I tested & found it to be the case. I need to plumb the electric pump differently so that it will not go through the engine driven pump.

Thanks,

Ray N33GM
 
I had the same problem with the bad fuel pump diaphram. I had lots of clues that it was going bad but didn't pick up on them. The wobble pump would pump up the pressure, but it wouldn't hold it long. I had a slight drop in oil pressure during climb and it would come up after level off and I didn't think it was quite right, but the summer temps were pretty high and I excused it. My fuel pressure flucuated and was at the very bottom of the green. I checked for leaks but there was no sign and I just kind of shrugged it off. During the annual I put the full eight qts of oil, mainly to check my dipstick..I have three for the Franklin 150 and they are all marked differently. When I ran the engine and shut it down there was oil everywhere. As we sat there looking at it I noticed what I thought was water coming out of the breather hose. Looked like water, smelled like fuel. Of course now the oil level was really high..So I lucked out. I know it had been leaking for awhile.
 
Thanks McCruisair,

I didn't think that I was the only one who had the fuel pump problems. I am going to re-plumb the electric pump so that it doesn't go through the engine pump. I don't understand why it was plumbed the way that it is.

How much oil do you normally run in the Franklin? Have you found that it blows oil out the crank seal above a certain amount?

Thanks,

Ray N33GM
 
Hi, Ray
I have never blown a crankcase seal..I generally run 6 to 6.5 qts of oil. My wobble pump goes through the engine driven pump..I should do what you are doing and change..along with installing a electric pump. My logs show my aircraft has had one in the past.
Mike
 
I've got low compression noticed when pulling the prop through on pre-flight. I'll be taking it in to the shop on Wed. to have that looked at.

I noticed alot of oil on the belly and windshield after my last hour and a half flight. I didn't check oil after the flight, but on the next preflight I noticed it was down a full quart! After reading your posts I'm wondering if the fuel pump diaphram is leaking and possibly causing overflow, but when cooled and evaporated a week later shows the lowered oil level.

Any thoughts? :shock:
 
mr. wolf!

low compression on jug(s) and oil on the belly (presumably from the crankcase breather tube) sounds an awful lot like classic blow-by past the rings. the idea about gas past the pump diaphram filling the crankcase and then evaporating is possible, but not very probable.

i'd check out why you have low compression first. is it whistling past the rings or valves? (listen up when doing a compression check; hissing from the crankcase breather is leakage past the rings. hissing from the carb is leakage past the intake valve (rare) and hissing from the exhaust pipe is leakage pas the exhaust valve (more common)).

hope this helps. :D
let us know what you find!

blue skies,
vic & N522A
 
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