Broken Fuel Primer

wa4jr · Post by **wa4jr** » Sat Dec 30, 2006 12:36 am

I went to pull out on the primer today for a nice shot of fuel, and found that the primer pulls out freely without taking in any fuel. Feels as if the plunger has disconnected from the handle, as there is no friction or sound as I pull out on the unit. Fortunately, pumping the trottle worked today and I was able to go flying. Are the primer units rebuildable, or are they best replaced as a unit

Tom Downey · Post by **Tom Downey** » Sat Dec 30, 2006 2:09 am

You have a stuck discharge check valve. try this.

remove the plunger and fill the cylinder with as nuch WD 40 as you can and replace the plunger and work it in and out a few times.. see if that will dislodge the speck of dirt that is holding the check valve off its seat.

WD 40 will not harm your engine if injected as primer fuel on the next start.

Post by **Bruce Fenstermacher** » Sat Dec 30, 2006 2:18 am

John

I'll try to describe this from memory and will also assume you have a primer the same type as 99% of the rest of us.

First pull out your primer like your going to prime the engine.

Look at the base of the primer with the slots that you have to pass the stubs through to open the primer. This piece with the slots is usually a knurled nut. Turning it counter clockwise will spin it off. You may have to use a pliers for this. Sometimes this nut has flats like a regular nut in which case a wrench can be used.

When you have this nut off the primer will pull apart. You will see or should see 2 o-rings at the end. Replace them and look inside the primer and clean out anything inside like old o-ring. Sometimes there is old gummy lubricant inside the tube which you should also clean out.

After cleaning and replacing the o-rings just reverse the assembly. I like to use a little dab of fuel lube on the o-rings but didn't last time I replaced mine.

The o-rings are common but need to be for use in a fuel system.

That is it.

wa4jr · Post by **wa4jr** » Wed Jan 03, 2007 1:43 am

The problem was indeed the O rings at the end of the plunger. Just to be sure that there was not a problem with the check valves, I coated the old O rings with silicone grease, reinstalled the plunger and was able to draw fuel into the primer tube. The O rings had shrunk and become hardened with age. I'm sure the nice NAPA man will have just what I need tomorrow

Now if he only had all the mystery springs for my door latch rebuild

bradbrady · Post by **bradbrady** » Wed Jan 03, 2007 3:23 am

John,
Do me a favor and go to your ACE hardware store and check out there O-rings. I know that NAPA dosn't have MS29512 or 29513 o-rings, My local ACE does! It dosn't make any differance in legality because I'm sure you are not going to make a log book entery! But for me I need a 8130 form to make the transaction legeal. Just to give you the heads up!

brad

Post by **Bruce Fenstermacher** » Wed Jan 03, 2007 2:30 pm

John do yourself a favor and get the right 0-rings which are made from the correct compound.

Think you primer doesn't work now what till those AceAeromotive or NAPAero o-rings swell and you can't pull out your primer.

Not saying these sources don't have o-rings that will work. Just that if your not sure of the compound of the o-ring don't waste your time.

I've already done the research for you.

wa4jr · Post by **wa4jr** » Fri Jan 05, 2007 12:52 am

Well by now I have two O rings from NAPA on my work bench. NAPA confirmed that they are indeed suitable for use in fuel systems...if they were not suitable for fuel, NAPA would be in a bad situation since these O rings are used all over automotive engines with fuel, oil and hydraulics. BUT, since Brad dropped a couple of aviation part numbers, I just might go by ACE tomorrow and throw them a curve ball. I still remember being able to go to the BigA auto parts store in Alpine TX to find the dual filament 28V lights for use on an old Queenair that I flew on a freight run. Just never know what you will find until you ask

Fri Jan 05, 2007 12:55 am

Yes John they might be made for mogas but as George will point out are you running 100LL in your car?

Post by **GAHorn** » Fri Jan 05, 2007 2:12 am

wa4jr wrote:...I still remember being able to go to the BigA auto parts store in Alpine TX to find the dual filament 28V lights for use on an old Queenair that I flew on a freight run. Just never know what you will find until you ask

Hey, John! When did you fly that UPS run? I used to spend a lot of time out there at E-38, Alpine-Casparis. Did you know the guy that hit the water over at Lake Ivie? Or the guy that rolled the Bonanza at E-38 and hit the dirt across the hiway? (George Miller? I think was his name...had a nice visit with him and thought him a reasonable guy... hated it when I realized who did that silly stunt...)

bradbrady · Post by **bradbrady** » Fri Jan 05, 2007 2:27 am

N9149A wrote:John do yourself a favor and get the right 0-rings which are made from the correct compound.

Think you primer doesn't work now what till those AceAeromotive or NAPAero o-rings swell and you can't pull out your primer.

Not saying these sources don't have o-rings that will work. Just that if your not sure of the compound of the o-ring don't waste your time.

I've already done the research for you.

Bruce,
My post was realy toung in cheek. But what I couldn't belive was looking for a sink part for the house, and found MS29513 O-rings at my local ACE, this just blew me away! I wouldn't use these because there is no cure date on the O-rings coming from ACE. But an MS number is an MS number and is better than a NAPA number! And if I need the part yesterday???????? By the way I could buy the O-rings cheeper through Aviall.

brad

Post by **GAHorn** » Fri Jan 05, 2007 2:40 am

No matter the source, O-rings are too cheap to buy the correct ones anywhere other than an approved source.

bradbrady · Post by **bradbrady** » Fri Jan 05, 2007 2:47 am

gahorn wrote:No matter the source, O-rings are too cheap to buy the correct ones anywhere other than an approved source.

George,
My thoughts exactly!!!
brad

wa4jr · Post by **wa4jr** » Sat Jan 06, 2007 11:27 pm

I went ahead and tried the NAPA rings, but they are too high in profile to let the primer plunger go back into the tube. I'll visit my A&P on Monday and see if I can get the correct number. Have not tried ACE yet. I run both mogas and 100LL. Was on the Genuine Aircraft Hardware sight looking at O ring specs and all of the four materials listed are suitable for fuel use, including the nitrile NAPA rings I had intended to use.

George, my days running between Midland and Alpine were back in 1995, and I only stayed three months because of the low pay and scary MX work on the old Queenairs. Yes, I knew the British fellow that went into the lake....was one of the mechanics that worked for Talon Air Service and also flew a route between San Anjelo and Lubbock. Also knew George Miller. What a nice guy! Sorry to see him try a stunt so low to the ground. I remember leaving E-38 and he was just coming in...jumped me over Alpine and we engaged in a nice 5 minute dogfight! No contest with his acro Bonanza and my unsecured UPS freight in the back...yes I KNOW the cargo net doesn't do any good wadded up in the back of the cabin. Boy could I tell some hangar stories about Talon Air and the things we were instructed to do that went so far afield of FAA regulations....well....I'll just stop here. Fun times though. I'll let you know how many dollars these MS 29513 O rings run me

Post by **GAHorn** » Sat Jan 06, 2007 11:42 pm

I landed about an hour after he crashed, and had the sad experience of helping his son endure the ordeal of identifying the body while still in the wreckage. There was speculation about a breakup with a girlfriend contributing to the behavior, but I never heard the conclusion...
George seemed like such a nice guy, and it seemed so uncharacteristic of him that he'd try such a stunt. (Others: On a low ceiling day, the Bonanza came down the runway at about 200' and attempted a roll and, just passing he departure end of the runway, crashed while inverted. The pilot enjoyed a by-the-book reputation and it made no sense to anyone he'd do such a thing. He was a single parent with two boys, the oldest in his early teens.)

cfiatzph · Post by **cfiatzph** » Tue Jan 09, 2007 9:51 pm

What are the correct o rings? and how many do I need to rebuild the primer. I don't think my parts manual shows this.