Fuel Pump Leaking Oil?

[krw5927]

Each time I remove the cowling on my RV9A, I notice that the top diaphragm of the low pressure mechanical fuel pump has a bead of oil around it. Also, a few of the bolt heads on the bottom of the pump will have a drip of oil clinging to them. I always wipe the oil up with a paper towel but it reappears every time - even if it's just one flight around the local patch. Not sure how long this has been happening - I'd say at least a year.

The engine is an ECI Titan O-340 with about 300 hours, and it has a Tempest fuel pump. The amount of oil is not a concern, a few small drops at most. The pump continues to operate just fine. I tightened the bolts and screws on the fuel pump that I could reach just a bit to see if that would solve the issue, but no luck.

Should I look into replacing this pump, or leave well enough alone? If I replace it, should I go with another Tempest or the more expensive Lycoming pump?

[petehowell]

Hi Kurt,

I'd make sure the oil is from the pump - mine seemed to collect oil there from the engine breather hose swirl until I finally routed it out of the cowl entirely. Yours may be different, but worth checking.

If it is the pump - they are "fun" to change!

Good luck!

[AX-O]

I had the same issue. It took a while to diagnose because it was also getting oil on the case and firewall. I bought a rebuilt one and turn the core in. The installation was a PITA but now everything is nice and clean. Good luck.

[krw5927]

Originally Posted by petehowell

Hi Kurt,

I'd make sure the oil is from the pump - mine seemed to collect oil there from the engine breather hose swirl until I finally routed it out of the cowl entirely. Yours may be different, but worth checking.

If it is the pump - they are "fun" to change!

Good luck!

Interesting - this seems to imply that the air flow local to the breather exit (very near the left exhaust on mine) may be forward and slightly upward toward the fuel pump. I had never considered that as a possibility, but I suppose it seems plausible.

Trying to envision a way to block that flow as a test.

[9GT]

I would find out for certain where the oil is coming from before trying to "fix" things by process of elimination. Wash and rinse the engine and engine compartment down to get rid of all the oil and oil film with your favorite degreasing product safe for aircraft. Let it dry. Add a oil leak dye and run the engine until you find where the leak is coming from. Like Pete mentioned, oil mist can blow all over and collect and pool in certain areas, not where the leak actually is.

[JonJay]

Mine leaked as you described, but I am not saying that yours is. It did this almost from day one. Not a lot, just enough for a drip or two to collect on the bolt heads. I just lived with it. The diaphragm eventually showed signs of a fuel leak out the vent so I replaced the pump at that time. This was after several hundred hours. Dry as a bone after it was replaced and has been since.

[krw5927]

For those of you who replaced a pump for this issue or another, and the problem of oil drips went away: what brand was leak-free for you?

Naturally I'm a little shy to order another Tempest since that's what's currently suspected to be leaking, but the price is right. Given an equal likelihood of leaks, I'll take the cheaper route.

[JonJay]

I went from tempest to another tempest. I believe part of the issue is normally we buy an engine and have it delivered way early as we need to fabricate/install all of the FWF stuff associated with it. Meanwhile, things sit, seals and gaskets may dry out, and we have leaks. That's my theory.
I just installed a pump on another airplane and a "new" Lycoming pump from AS was cheapest.

[turbo]

wrap the lower pump with something to protect it. go flying then remove the wrap and see if the pump is leaking. pure genius.