Fuel Primer

[dkenney1]

Good morning. My bird is in annual and I had the A&P look at a persistent leak from the fuel primer. Not every time but often after using the primer a few drops would come out and continue for a few minutes during flight. Tightening the various nuts didn't do it take care of it and then I noticed more fuel was coming out the shaft of the plunger through the large nut that is on the face plate by my hand. He thought it no big deal, "we will just replace the o rings with a kit we have". However when he took the system apart the o rings looked pretty good and he noticed there was nothing inside that large top nut and he could not find a kit or ring for that, so he said I may have to get a whole new primer. After doing some quick seeking for a primer on the usual suspects, Univair, Aircraft Spruce, Wag Aero, I'm a little confused. First the price range is $20, $445. The cheapest really being a primer for a snowmobile engine, then all the rest are specific to say "not FAA/PMA approved, experimental only".

Does anyone in the tribe have experience or knowledge they could impart on either the old/original primer, or best means to repair or replace it? Thank you, Darrin

[Guest]

Re: Fuel Primer

Put the new o-rings in.

Then see if it solves your issue.

All there is (usually) is two 3/8" by 1/16" o-rings.

You can get o-ring for use with avgas or regular ones either will work but the ones for avgas are preferred.

I have never seen or heard of a primer repair kit before today but if it has the o-rings install them.

Dave

[dkenney1]

Re: Fuel Primer

Put the new o-rings in.

Then see if it solves your issue.

All there is (usually) is two 3/8" by 1/16" o-rings.

You can get o-ring for use with avgas or regular ones either will work but the ones for avgas are preferred.

I have never seen or heard of a primer repair kit before today but if ithas the o-rings install them.

Dave

Dave I had not heard of a kit either until looking in Aircraft Spruce, but I think they were specific to the primer manufacturers they carry. The shop where my plane is, he brought out two bags with two different size O rings but commented that they go further down. My point was for the fuel to be leaking out the facia nut wouldn't the fuel first have to be bypassing those two rings? For the couple of dollars of rings I may have him or I'll put them on and see what happens. It would be a lot better than a $450 primer.

On the good news side, everything else on the annual went well. Compressions in the high 70's, oil clean, nothing looked worn after 54 hours of flying. There was some discussion of whether to replace the gear bungees, but they are not fraid or worn looking, when push on wing tips they flex slightly but not a lot and there's no sagging. The most senior A&P there said, "leave them alone, they look good, it handles well on the ground, they're fine". The next challenge will be finding brake parts for next year's annual. It looks like it will be about time for them by then.

Thanks for your help

[Guest]

Re: Fuel Primer

I forgot to say that tightening the aluminum nuts on the primer do nothing for a leak.

[Guest]

Re: Fuel Primer

Dave I had not heard of a kit either until looking in Aircraft Spruce, but I think they were specific to the primer manufacturers they carry. The shop where my plane is, he brought out two bags with two different size O rings but commented that they go further down. My point was for the fuel to be leaking out the facia nut wouldn't the fuel first have to be bypassing those two rings? For the couple of dollars of rings I may have him or I'll put them on and see what happens. It would be a lot better than a $450 primer.

On the good news side, everything else on the annual went well. Compressions in the high 70's, oil clean, nothing looked worn after 54 hours of flying. There was some discussion of whether to replace the gear bungees, but they are not fraid or worn looking, when push on wing tips they flex slightly but not a lot and there's no sagging. The most senior A&P there said, "leave them alone, they look good, it handles well on the ground, they're fine". The next challenge will be finding brake parts for next year's annual. It looks like it will be about time for them by then.

Thanks for your help

Yes they do go further down and yes they must leak past them to come out at the shaft.

The primer check valve should be stopping flow when the primer is in (no leaks past o-rings then) so it makes me curious if your engine is drawing fuel flow thru the primer and causing rich mixture (black sooty plugs and exhaust?).

Perhaps that is why A&P suggests new primer??

Dave

[astjp2]

Re: Fuel Primer

I just bought 5 orings from Stoddards in Anchorage, MS29513-012, were about 1.25 each