Leaking primer

How to keep the Cessna 170 flying and airworthy.

Moderators: GAHorn, Karl Towle, Bruce Fenstermacher

VernH
Posts: 84
Joined: Wed Jan 04, 2017 8:49 pm

Leaking primer

Post by VernH »

Hello All,
Hope everyone had a Merry Christmas!

I recently replaced the O-rings in my primer. All was well for about a month. Now, when I use the primer, it blows fuel out the back! I took it back apart, ORings look fine, used a very small amount of fuel lube, checked the bore and reassembled, same thing.
Any suggestions?
Fly safe!

Vern
1950 C-170A N5453C sn 19487
Based in Pensacola, FL. 82J
User avatar
GAHorn
Posts: 21145
Joined: Fri Apr 12, 2002 8:45 pm

Re: Leaking primer

Post by GAHorn »

What do you mean by “blows fuel out the back”?

Do you mean the B-nuts on the connecting lines? Or do you mean the body of the primer?

Is it possible you cracked a B-nut when over-torquing it?l. Or perhaps the copper fuel-line has cracked at it’s flare (such as copper often does after long service and re-use due to hardening.)
'53 B-model N146YS SN:25713
50th Anniversary of Flight Model. Winner-Best Original 170B, 100th Anniversary of Flight Convention.
An originality nut (mostly) for the right reasons. ;)
User avatar
canav8
Posts: 1006
Joined: Thu Sep 25, 2008 2:34 pm

Re: Leaking primer

Post by canav8 »

Use Fuel lube(EZ Turn) on the O-rings. D
52' C-170B N2713D Ser #25255
Doug
VernH
Posts: 84
Joined: Wed Jan 04, 2017 8:49 pm

Re: Leaking primer

Post by VernH »

gahorn wrote:What do you mean by “blows fuel out the back”?

Do you mean the B-nuts on the connecting lines? Or do you mean the body of the primer?

Is it possible you cracked a B-nut when over-torquing it?l. Or perhaps the copper fuel-line has cracked at it’s flare (such as copper often does after long service and re-use due to hardening.)
The fuel is coming from the hole in the back of the barrel. Not sure, but I think it’s a vent. When the primer is pushed in, there is pressure then the fuel comes out the back.
The B nuts have not been disturbed and are not leaking.

I used a very small amount of Fuel Lube on the o Rings.
Fly safe!

Vern
1950 C-170A N5453C sn 19487
Based in Pensacola, FL. 82J
User avatar
GAHorn
Posts: 21145
Joined: Fri Apr 12, 2002 8:45 pm

Re: Leaking primer

Post by GAHorn »

Sound like one of the o-rings has a cut in it that is difficult to see by inspection, or is “rolling” during re-insertion.
'53 B-model N146YS SN:25713
50th Anniversary of Flight Model. Winner-Best Original 170B, 100th Anniversary of Flight Convention.
An originality nut (mostly) for the right reasons. ;)
VernH
Posts: 84
Joined: Wed Jan 04, 2017 8:49 pm

Re: Leaking primer

Post by VernH »

Thank you. I have some new O rings on the way. We will see what that does.
Fly safe!

Vern
1950 C-170A N5453C sn 19487
Based in Pensacola, FL. 82J
User avatar
170C
Posts: 3182
Joined: Tue May 06, 2003 11:59 am

Re: Leaking primer

Post by 170C »

"O" ring gaskets from Harbor Freight (they carry an assortment box with multiple sizes) work well on our primers. I have had them on mine for 7+ yrs and no problem plus the assortment will fit many other things around the hangar and house.
OLE POKEY
170C
Director:
2012-2018
User avatar
sfarringer
Posts: 311
Joined: Wed Jan 12, 2005 10:49 pm

Re: Leaking primer

Post by sfarringer »

I do not have one of these primers in front of me to examine.
But, I wonder if the "hole in the back of the barrel" is open because some check valve parts have fallen out of that hole.
Ragwing S/N 18073
User avatar
bsdunek
Posts: 425
Joined: Wed Feb 11, 2004 6:42 pm

Re: Leaking primer

Post by bsdunek »

170C wrote:"O" ring gaskets from Harbor Freight (they carry an assortment box with multiple sizes) work well on our primers. I have had them on mine for 7+ yrs and no problem plus the assortment will fit many other things around the hangar and house.
With full respect, Ol Pokey, I wouldn't use anything from HF on my airplane, or lawn tractor, or even my pitch fork.
Bruce
1950 170A N5559C
User avatar
mschlender
Posts: 134
Joined: Mon Jun 03, 2002 1:27 am

Re: Leaking primer

Post by mschlender »

I wouldn't use them either,you can buy the kit cheap from spruce. $6.50 with lube
User avatar
n2582d
Posts: 2903
Joined: Mon Apr 29, 2002 4:58 am

Re: Leaking primer

Post by n2582d »

Vern,
“Chestnuts roasting on an open fire” is a lovely scene ... unless they are your chestnuts and the open fire is under the panel. 8O The primer is inches from electrical switches which have the potential to take on the role of a spark plug. I would ground the plane until you find and eliminate the source of the leak.

There is no vent on the primer. It simply has two one-way check valves, each made up of a spring and ball as shown here.
EE87B504-91FB-4C5F-8E25-F11EF80246A0.jpeg
If the primer isn’t leaking from one of the line fittings it must be that a screw cap holding the check valve in place is loose. I’d recommend your mechanic use Viton o-rings Cessna calls for in SE78-73. I’d also recommend your mechanic disconnect the AN4022-1 (or AN4002-1) primer nozzle from the intake manifold and confirm that it’s not clogged and has a good spray pattern.
Gary
User avatar
170C
Posts: 3182
Joined: Tue May 06, 2003 11:59 am

Re: Leaking primer

Post by 170C »

bsdunek & mschlender, I have no argument with your statements. The only reason I used the HF gaskets was that an AP/IA gave them to me and they were HF items. I never expected them to last, but they have so far.
OLE POKEY
170C
Director:
2012-2018
VernH
Posts: 84
Joined: Wed Jan 04, 2017 8:49 pm

Re: Leaking primer

Post by VernH »

Gary,
That isn’t my primer but it probably works the same way. I’ll see if that’s a cap at the end of the barrel. Makes sense to me.
Thanks guys!!
Fly safe!

Vern
1950 C-170A N5453C sn 19487
Based in Pensacola, FL. 82J
User avatar
GAHorn
Posts: 21145
Joined: Fri Apr 12, 2002 8:45 pm

Re: Leaking primer

Post by GAHorn »

170C wrote:bsdunek & mschlender, I have no argument with your statements. The only reason I used the HF gaskets was that an AP/IA gave them to me and they were HF items. I never expected them to last, but they have so far.
Most (black) HF O-rongs are Buna-N rubber and pretty fool-proof. I use them on agricultural equipment and have found them quite reliable. They also sell Viton and others in assortments. (Not disputing nor arguing with anyone who endorses genuine aircraft quality (AN or MS traceable ) O-rings for aircraft use... but for the average guy who simply wants an assortment on-hand for various uses they are easy and inexpensive.)
'53 B-model N146YS SN:25713
50th Anniversary of Flight Model. Winner-Best Original 170B, 100th Anniversary of Flight Convention.
An originality nut (mostly) for the right reasons. ;)
VernH
Posts: 84
Joined: Wed Jan 04, 2017 8:49 pm

Re: Leaking primer

Post by VernH »

This is the primer. Marked “Imperial”
This is the primer. Marked “Imperial”
D31B8FFC-18AA-4FD2-8A68-67AB71193EC6.jpeg (36.94 KiB) Viewed 22575 times
This is where the fuel is coming out.
This is where the fuel is coming out.
AC84CF70-F6BC-4F2A-B09D-DEA6B15A1C0D.jpeg (23.17 KiB) Viewed 22575 times
Disassembled
Disassembled
F29BA496-B629-4E31-B325-5E86B9E444C2.jpeg (32.13 KiB) Viewed 22575 times
This is the only thing I saw. Looks like the diaphragm is crushed.
This is the only thing I saw. Looks like the diaphragm is crushed.
D56996BA-E8D4-4741-BA7C-D7C1871F566F.jpeg (27.58 KiB) Viewed 22575 times
Fly safe!

Vern
1950 C-170A N5453C sn 19487
Based in Pensacola, FL. 82J
Post Reply