Primer information

[Hank Jarrett]

I got another start and run on the Continental, and another fuel leak out of the carburetor! The good news is she started on the first pull, ran strong with a smooth as silk idle and I didn't burn the plane up.

For all the fear the problem was in the newly overhauled carb it looks like the primer is leaking. Not a big problem........I have a spare and they are easy to overhaul, or at least I thought so.

I will be pulling the one that is leaking tomorrow and will see if it is identified, but my replacement also has some wear on the seals. Problem is it is the one in the old catalogs but there is no PN or manufacture marks. I have the old Taylorcraft part numbers, but they are not the manufacturers numbers.

Does anyone know who made them or have any overhaul information? Are there any tricks to taking the plunger apart to change the seals? Most important, are they "O" rings or cup seals and anyone know what part numbers are needed? Is there a kit available? Any information appreciated and photos are rubber attached. It is in beautiful condition, except for the rubber parts.

Hank

I will probably post the one on her tomorrow.

[Hank Jarrett]

Re: Primer information

Photo of plunger

[clear_prop1961]

Re: Primer information

Hank- I see that you are running the engine for the first time. If the engine is new overhaul you don't want to run the engine for more then about a minute, while you check for leaks, idle rpm, etc. and then let it cool to the touch before starting it again. After you do this 3 or 4 times you can go to about 2 minutes run time but no more before you put the cowling on and go fly it. Fly it at curse rpm, 2150, for 40 minutes and then 2200rpm for 20 minutes and your engine will be run-in. I climbed out at 70 mph so as not to over heat the engine. I did that recently and the engine is doing great with a qt oil burn for about 10 hours flying. I have about 18 hours on it now.

My point is you don't want to run it on the ground too long... one minute runs is all you need to check for leaks, idle, idle mixture, etc. I have found that everyone has a different approach to engine brake-in, but because it is important on first runs I thought I would mention it.

Jerry

[Hank Jarrett]

Re: Primer information

Good advice on an overhaul engine, but this one is mid time. Even so, we haven't run her for over a minute or so at a time. Good oil pressure and temperatures, just a stinking drip from the carb on shutdown that doesn't stop till the fuel is shut off and the gascolator is drained. It doesn't drip until the engine has run and been shut down, then is fairly fast, which is why we think it is fuel is being siphoned through the primer. Next step will be to prime and NOT start the engine to see if we can start the siphon and verify it is coming out the primer tube in the spider.

Hank

[woodmw]

Re: Primer information

I believe that was made by Imperial Brass Mfg.
Here are a couple of links, one about the patent for the primer, the second is a discussion about how it was originally used.

http://www.google.com/patents/US1396529

http://www.mtfca.com/discus/messages/179374/193159.html?1298586339

[Hank Jarrett]

Re: Primer information

That's it! Amazing how many car parts Taylorcraft used in our planes. Looks like it DID use cup seals and not "O" rings so I will need to go on a hunt for some new ones. The ones in there are working but are worn and I doubt they will last.

Going to airport today to remove teh one on the 41 now and will post what I find on that one. Hopefully the leak will disappear when the primers are out of the circuit and the lines plugged.

Thanks Mike and Jerry. This group is unbelievable!

Hank

[Ragwing nut]

Re: Primer information

Good advice on an overhaul engine, but this one is mid time. Even so, we haven't run her for over a minute or so at a time. Good oil pressure and temperatures, just a stinking drip from the carb on shutdown that doesn't stop till the fuel is shut off and the gascolator is drained. It doesn't drip until the engine has run and been shut down, then is fairly fast, which is why we think it is fuel is being siphoned through the primer. Next step will be to prime and NOT start the engine to see if we can start the siphon and verify it is coming out the primer tube in the spider.

Hank

I doubt its the primer leaking thru, they usually leak out the packing nut around the shaft first. More probably culprit is a leaking needle and seat. It may not have leaked on the bench check, but you may have the float level set to high so it leaks when it is sitting on an angle installed on the plane until the bowl drains down and the needle closes against the seat.

[3Dreaming]

Re: Primer information

Myself I would pull the primer line at the spider and see if it is dripping with the fuel turned on. I would also pull the primer fitting from the spider and plug it and run it to see what happens. While I know a leaking primer can happen I have never actually found one in 35 years of working on airplanes, except for the new style primers when they are left unlocked.

[Hank Jarrett]

Re: Primer information

Sounds like we are all thinking on the same lines. I talked to the shop that rebuilt the carb and they suggested unhooking the primer at the spider and gascolator (got the plugs last night) and running the engine. That would eliminate the primer as the cause. I know the primer is leaking because I have a series of fuel spots on my pants and it is leaking from the end fitting. It is off now for a repair.
They said that if it still leaks the first step would be to pull the screen and bottom plugs and flush out the bowl (hopefully to wash out whatever is under the needle). I did find the fitting to the primer pump a little loose and will put some thread seal on it before I put it back in. I also got the two check valves working smoothly again. I think one was sticking open.

Hank