Minor Oil Leaks, Mech. Fuel Pump

I am chasing a few minor oil leaks. +- 400 hours.
I don't know enough about the inter-workings of the mechanical fuel pump to know this but it appears that oil is seaping around the gaskets that are sandwiched around what I assume is the diaphram? There are two gaskets here, an upper and lower. It might be oil migrating from where it bolts to the acc. case, but it sure looks like it is coming directly from the pump itself.
Experiences with this? Do I need to exchange this for a rebuilt pump?
It seems that most of my accessories on this Aerosport Engine have some kind of small leak or another; acc. drive (fixed), governor pad, etc...
Not enough oil to even mark its spot in the hangar but I want them fixed.

Jon, mine too

is leaking exactly where you described. Mine is on a Lycoming IO-390 with about 700 hours on the tach. It took me a long time to find the leak. I called a FAA repair station and was told that this leak is not uncommon and was advised to tighten the screws. This helped, but there is still some oil seepage at the top gasket. I am going to replace to fuel pump.

The fuel pump is vented to the crankcase so there's nothing to stop oil from accumulating on the top plunger diaphragm. Check and make sure the screws around the circumference of the pump are tight.

My engine-driven pump dripped oil from day one until I replaced it at about 100 hours. Not a lot, but really annoying. I tried tightening the screws to no avail. Haven't seen a drop from the fuel pump since the replacement (about 300 hours ago). Before turning it in for core I took the old one apart to see if there was an obvious defect causing the leak, no joy.

Exactly....

I have a O-360 A1A with exactly the same problem. I did tighten the screws a couple of times and the leak seems to have stopped although the pump itself around the gaskets is oily. It never leaked enough to make a mess or show on the dipstick but I could see a drop accumulating on the lower screw heads after a couple of hours flying.

Flying 42 hours now and I am going to leave it alone unless it actually begins to drip.

Bill S
7a flying
Got the Grin

I may have the same problem but I think in my case it is leaking from the gasket where the fuel pump mates to the engine case. A quick look over tells me it will be a tough job removing the pump while the engine is still mounted. Can this be done?

tkatc said:

I may have the same problem but I think in my case it is leaking from the gasket where the fuel pump mates to the engine case. A quick look over tells me it will be a tough job removing the pump while the engine is still mounted. Can this be done?

Click to expand...

Yes, it can be done but it is not easy. I helped change one last week. You may need to remove some oil lines and other obstructions to access the pump. It helps if you glue the gasket onto the new pump with some permatex gasket cement so it will stay in place while you try to get the bolt threads to engage. Rotate the propeller until the plunger is fully retracted to make it easier to position the pump lever as you line up the bolts. Be patient. It can be done!

Enjoy...

Removing the old and putting in the new is not too much of a problem. However!!! You don't get to simply place the pump in position (minding the plunger and lever), and then put the bolts in. The main problem is that you cannot start the bolts into their threaded holes while the pump is its final position. There needs to be a gap between the pump and the engine when the bolts are started into the threads on the engine. This of course means the plunger drops... For more entertainment, see this thread. Good safety comments in that thread also.

Mine would have to be dropping a lot of oil for me to bother with it.

Ugh. Sounds like a new roll of shop towels will do the trick for me!

In all seriousness, it isn't a bad leak but it is very annoying. It doesn't take a lot of oil to make a YELLOW airplane look bad. I will keep an eye on it and make a decision from there. I'm not CERTAIN that is where the leak is but I really do suspect it.

pump

Changeing the fuel pump was covered in great detail in a previous thread. Mahlon had some very good tips on this. A ball end allen wrench and/or a custom allen wrench is the most important thing.

AlexPeterson said:

Mine would have to be dropping a lot of oil for me to bother with it.

Click to expand...

Me too! I did replace my fuel pump recently because it was exhausting gray stuff out its vent and had 2000+ hours on it, I figured it was dying. The old pump always had a few drops of oil hanging off it and the new pump after one oil change interval has the same drops hanging off it. I have a buddy that will get all bothered and spend lots of time chasing the smallest oil leak, I look at mine like it?s a small block Chevy, they almost all have leaks if there used and they have oil in them. If drips suddenly become lots worse then start looking, last time that happened with mine it had a cracked crank case! Every one of these fuel pumps I have seen have oil hanging off of them.