Primer not working

simtech

simtech

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Simtech
My primer had been hard to use and over time got to where it took a lot of pumping. The last flight I had the primer didn't do anything. So I bought a primer rebuild kit and it works like butter. But...it still is not drawing any fuel up. The copper tubing looks good and it is pushing air to the cylinder just not drawing fuel up. This is on a piper Cherokee 180D. I pumped it up like 50 times and no resistance was ever felt.. Any ideas?
 
Mine did the same thing, the A&P that fixed it just replaced the O-ring and it was all better. Primer "overhaul" kits are like $20 if that.
 
Sounds like an O ring, that did the trick on my Archer.
 
I am in the same boat. Replaced O-rings. Made sure the lines were clear. Gonna put a "new" primer in it.
 
Greg Bockelman said:
I am in the same boat. Replaced O-rings. Made sure the lines were clear. Gonna put a "new" primer in it.
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Ugh..hope my mechanic can figure something out. We are going to look at it tomorrow. By the way, the primer overhaul kit was under 5 bucks at spruce. So,es with the 2 o rings and silicone lube. The primer is so easy to move now, it's a shame it won't draw fuel.
 
simtech said:
Ugh..hope my mechanic can figure something out. We are going to look at it tomorrow. By the way, the primer overhaul kit was under 5 bucks at spruce. So,es with the 2 o rings and silicone lube. The primer is so easy to move now, it's a shame it won't draw fuel.
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If its easy to pull you must not be making a vacuum to draw in fuel.
 
FuelLube.....a lil dab will do ya....on each o-ring.

united-ez-turn-fuelube-5-oz.jpg
 
Mine is easy to push and pull, like real easy. And both o rings have been lubed with silicone lube that came with the overhaul kit.
 
There are only three moving parts in a primer pump, the plunger and two balls in the check valves.

when you pull the plunger out, the inlet check valve opens allowing fuel to enter, when you push the plunger in the inlet check valve closes and the discharge check valve opens and the fuel trapped in the pump is delivered to the engine intake system, that's all there is to the pump.

when the fuel selector is off, the primer pump can't draw fuel. so it will be difficult to pull and very easy to push (if you got it out any at all) when the primer nozzle is plugged the plunger will be easy to pull, and difficult to push.

Before you buy a new pump, always remove the two lines connected to it, and see if the plunger is easy to operate. IT might not be the pump.
 
Can't you take the hole thing out, take it apart to remove the o-ring then soak the body of it in MEK or some sort of carb cleaner? Then take a rubber tipped blow gun and air compressor and blow out the ports/check valves?

There's gotta be a way to clean gunk out of them.
 
Today I disconnected the line going to the gascolator and disconnected it from the primer. The line broke off with ease at the compression fitting. Ugh!!

With that off I put my finger over the inlet hole and pulled out the primer and I got suction. So at this point I am sure it is not the primer and my mechanic agrees. With it disconnected from the gascolator I hit the boost pump and fuel came out. Hooked the line back up to the gascolator and in the cockpit I hit the boost pump and no fuel came out of the broken line.
I was able to blow air all the way through from gascolator to the primer. Though it was very hard to do so.

So at this point I think I had a small hole in the line at the primer sucking air. I'm going to source the copper tube and a flair fitting and install a new hose. Hopefully that fixes it.
 
Greg Bockelman said:
Neither. No resistance at all in either direction.
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stuck discharge check valve, its an easy fix. (remove and replace)but try this prior to replacing it.
remove the pump by shutting off the fuel or disconnecting the feed line, disconnect the two lines attached to the pump, remove the knerled nut holding the plunger into the pump cylinder, pull the piston out, then remove the large nut holding the pump to the instrument panel. the pump then can be removed from the instrument panel.

now find a can of 100LL/stoddard solvent/alcohol/acetone or the like. put the plunger in the fluid far enough to cover the ports of the pump. stroke the plunger and see if it pumps, (warning Stroke slowly) you can see the fluid flowing into and out of the pump.
When the fluid flows into and out of the same port. that check valve is stuck open. remove that check valve by removing the straight slotted plug nearest the port. do this on a white towel, and don't loose the little steel ball. clean the ball and passage ways with a Q tip and alcohol.
reassemble, try it again, if it doesn't work get a new one.
The one you need.
http://www.univair.com/piper/piper-j-3/view-all/u451-100-piper-engine-primer-pump-assembly/

The one at Spruce is a gerties, will not work.
 
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simtech said:
I was able to blow air all the way through from gascolator to the primer. Though it was very hard to do so.

The fitting at the gascolator only has a #60 hole thru it, it may be clogged.

So at this point I think I had a small hole in the line at the primer sucking air. I'm going to source the copper tube and a flair fitting and install a new hose. Hopefully that fixes it.
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The copper line has work hardened, have your A&P anneal it and reflare it. then your good to go again
 
We replaced the whole line from the gascolator to the inlet port on the primer. Bam works like money now! So smooth and draws in like never before. If I had to bet the primer hasn't worked the whole year Ive owned it so far. It took the rebuild kit to find it. But all is good now. And mine had no resistance pulling or pushing so Greg that could be your problem.?
 
Tom-D said:
That's the stuff that contaminates the discharge check valve making it stick open. people use way too much.
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Works great, lasts long time. Just use enough to make the o-rings shiny.
 
simtech said:
We replaced the whole line from the gascolator to the inlet port on the primer. Bam works like money now! So smooth and draws in like never before. If I had to bet the primer hasn't worked the whole year Ive owned it so far. It took the rebuild kit to find it. But all is good now. And mine had no resistance pulling or pushing so Greg that could be your problem.?
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I've followed this with interest. So the faulty primer line was encased in a sheathing? Did this prevent you from detecting the hole? Did you buy a replacement from A/C Spruce or similar? Just curious what this all looked like as there aren't any photos and I don't want to make any assumptions about the fault or the cure.
 
iflyvfr said:
I've followed this with interest. So the faulty primer line was encased in a sheathing? Did this prevent you from detecting the hole? Did you buy a replacement from A/C Spruce or similar? Just curious what this all looked like as there aren't any photos and I don't want to make any assumptions about the fault or the cure.
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The line is not encased. It is just 1/8" bendable cover tubing purchased from a local supply house. It ran from the bottom (inlet) side of the primer and ran straight to the gascolator. Gascolator side was flared and primer side had a compression fitting. Upon visual inspection it all looked good. But when I unscrewed the fitting at the primer the copper tubing snapped so easy at the compression fitting. So...we assume it was sucking air and not allowing the primer to prime. Like Tom thought a line was crushed and maybe it was from the compression fitting and that's why it broke. I don't know. But since the line broke that was the first thing to fix. All good now.

I'm going out to the plane today. I'll try and take a picture of the back side of the primer for you.
 
Fuel Lube (or EX Turn) should NOT be used in primers. I have tried it several times and in every case it eventually gummed up the primer bore and made it almost impossible to move. I have had the best results putting NOTHING in there. The fuel is lubrication enough.

Getting Fuel Lube out of that bore is a pain. After 20 years I finally discovered last week that acetone will dissolve it.

Fuel Lube is great on fuel valves or pipe fittings. Nothing but trouble in a primer.
 
iflyvfr said:
Awesome, thanks for the explanation and future pic Simtech.
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Sorry it's not a good picture, standing on my head under the panel and taking a picture is harder than I thought. Haha the top copper line is the outlet going to the cylinders, the bottom copper line is the inlet from the gascolator. Hope this helps.
 

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simtech said:
Sorry it's not a good picture, standing on my head under the panel and taking a picture is harder than I thought. Haha the top copper line is the outlet going to the cylinders, the bottom copper line is the inlet from the gascolator. Hope this helps.
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Do you see the 2 slotted screws? they are the check valves, back them out and you'll find a chrome Ball that controls the direction of fuel flow.
 
Tom-D said:
Do you see the 2 slotted screws? they are the check valves, back them out and you'll find a chrome Ball that controls the direction of fuel flow.
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I saw those but chose not to mess with them. As soon as I put in the new line it worked like magic.
 
Norman said:
Wise idea. They can be almost impossible to find in the carpet.
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Even harder to find are the little tempered copper springs that seat those little balls.
 
After removing the primer; Can the pump be checked for correct operation by placing the inlet/outlet in a container of fuel and operating the plunger in the normal way, to observe if it draws and ejects as if it were connected to the inlet/ outlet in the aircraft?
 
Twainsmark said:
After removing the primer; Can the pump be checked for correct operation by placing the inlet/outlet in a container of fuel and operating the plunger in the normal way, to observe if it draws and ejects as if it were connected to the inlet/ outlet in the aircraft?
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Yup. Would work fine.
 
bluerooster said:
Really, one tube of it should last a very busy A&P a lifetime.
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I went through a pound or two of it in the last 20 years. It works well not only as an O-ring and plug valve lube but also as a thread sealant (easy to get apart again) and for sticking small nuts and washers to the blades of long screwdrivers to get them into difficult spots and onto a stud or whatever. Rotate the nut with another long screwdriver pushing the corners of the flats while holding the nut against the stud with the sticky screwdriver. Or put it on a fingertip and stick the hardware to that. Or a little gob of it on a long screwdriver to snag stainless (non-magnetic) screws that fall into tight places. Or a bit on an O-ring to make it stay put while you assemble the rest of some component; the Cessna fuel strainer bowl O-ring is one of those. It wants to fall out, or partly out, and get pinched between the bowl and housing and create a big leak when the fuel is turned back on. Or a bit on the end of a length of lockwire (make a tiny loop in the business end) to check for rust inside steel-tube assemblies, like the Cessna control yoke SB that demands a check of the inside of the bottom end of the yoke for corrosion caused by water getting into the top of the yoke after getting past bad windshield seals or the like. SB01-3: https://support.cessna.com/custsupt/contacts/pubs/ourpdf.pdf?as_id=17090
I used to put some Fuel Lube on that wire and poke it into the hole to see what the sticky goop would pick up.

While we're at it, note that the control yoke is NOT that thing that the pilot holds to fly the airplane. That's a control wheel, not a yoke. Everybody calls it a yoke, but if you asked Cessna for a new yoke for your airplane you'd get a nasty bill for it. A yoke is used to join two systems together. The term comes from the device that was used to link two oxen to drag a plow or wagon.
 
yup....kick the tires...n.....light the fires. lol ;)
 
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