Van's Air Force
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Primer line failure...again
- Thread starter Skint
- Start date
Kyle Boatright
Well Known Member
There has been lots of back and forth on this, but I removed my primer a decade ago and haven't looked back. My starting procedure is to give the throttle two pumps while running the starter, wait about two blades, and turn the impulse mag to "on". My engine starts great with this procedure, never backfires, and there is no primer system to fool with.
LifeofReiley
Well Known Member
+ 1 with Kyle, only difference... I never installed a primer system.
Andrew M
Well Known Member
primer
I have removed three primer systems from O-320 engines. My clients don't use it, they use the accelerator pump built into the carburetor. I find either cracked lines, or the plugs come loose from the cylinder. I do not plan on using one on my O-320E2D for the RV-9.
I have removed three primer systems from O-320 engines. My clients don't use it, they use the accelerator pump built into the carburetor. I find either cracked lines, or the plugs come loose from the cylinder. I do not plan on using one on my O-320E2D for the RV-9.
Kyle Boatright
Well Known Member
$25 bucks and I'll sell you one so you can see what you've been missing. ;-)
Yeesh. One airbox fire coming right up. If the prop isn't spinning, the fuel isn't going into the engine.
Lionclaw
Well Known Member
The primer setup I removed from my engine had lines that were clamped to the intake pipes and met at a flared "T" that was clamped to the bolts at the rear of the sump. I would assume it then used a flexible line to go to the primer pump.
Perhaps this would be a more robust setup?
Perhaps this would be a more robust setup?
alpinelakespilot2000
Well Known Member
I just pulled my primer system out a couple weeks ago for the same reason. Cracked copper line.
I need to learn the proper way to start an engine with the accelerator pump. I really, really don't want to start a fire with an airbox full of fuel. Can anyone enlighten me regarding the best method to safely start without a primer, especially in regions where it actually gets cold?
I need to learn the proper way to start an engine with the accelerator pump. I really, really don't want to start a fire with an airbox full of fuel. Can anyone enlighten me regarding the best method to safely start without a primer, especially in regions where it actually gets cold?
As Snowflake said, key is to ensure the prop is spinning prior to pumping the throttle. Hard to give an exact procedure, as each engine - even if same setup - tends to have its own idiosyncrasies and preferred starting routine. You will quickly learn the tempo your engine prefers - e.g. mine likes a smooth movement as soon as my prop is turning. Almost without fail, I give a slight pause on the second pump of the throttle (full throttle), she fires right up, and then quickly retard throttle to idle. FWIW, I have a primer, but do not use it, however I do live in the SE and the coldest I've cranked is probably about mid 30sF.
Sam Buchanan
been here awhile
Guess I've been lucky....for fourteen years its been one or two shots of throttle immediately followed by hitting the starter button (that's for a cold start, hot start doesn't need any help). No fires. I've never had a primer on my O-320.
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DanBaier
Well Known Member
If you pump the throttle, this is a way to safely start. If you have a key switch, first go to Start and keep it turning before doing the two pumps.
Raw gas dropping into the airbox is not good. Not an automatic fire, but if any other fault should cause a backfire, it could get interesting.
As to the primer line - there's such a thing as being too secure. The engine moves around in the mount pretty good on start and shutdown. Can the primer line stand that or is it too anchored in place?
Dan
longranger
Well Known Member
Same primer line on my 170 for at least the 1800 hours I've flown it, probably closer to the 3000 since new. I guess they don't make copper like they used to... or maybe it's just that 6-cyl. Continentals are a bit smooother than 4-cyl. Lycomings.
I had an air box fire on a O-200 cold start because I pumped the throttle without the prop turning and had a backfire. It was after several failed start attempts which probably helped my chances of a fire. Post air box fire I only pump the throttle while the prop is turning.
Sam Buchanan
been here awhile
Yes, repeated pumping of the throttle before the engine is running will create a considerable puddle of fuel and increase the odds of something bad happening.
We all have a drain hole in our airbox, right?
Yes, but remember gasoline will not burn. It's the vapors. And the vapors don't drain. Even with the fuel drained from the air box, there is still a very real potential for fire.
deek
Well Known Member
Me too! Same drill, two accelerator pumps immediately before cranking; 3 if it's below 35*F. 30 years on the O-320 without a primer. If you take the airbox off and have someone pump the throttle you'll see it takes a few seconds for gas to begin dribbling from the carb throat.
deek
Mile High Relic
Well Known Member
This is always what I assumed was happening, and in reading through this thread I started thinking it would be a good experiment to run next time the FAB is off the plane.
My O-360 starts well cold with a single throttle pump immediately before cranking. No pumps when it is hot.
flyinmonque
Well Known Member
Did any of you......
.......Heat your copper lines to red hot and let slow cool?
.......Heat your copper lines to red hot and let slow cool?
YellowPeril
Well Known Member
Huh. I've been running an Ellison TBI (no accelerator pump) for 10 years and 1,000 plus hours. I have copper primer lines going to all 4 cylinders, and haven't had a single issue (save a small leak at a Tee once).
I couldn't possibly tell you what I've done right....would you be interested in photos?
I couldn't possibly tell you what I've done right....would you be interested in photos?
Resurrecting this old thread.
My O-320 has 1/8" copper primer lines to all cylinders. These have periodically broken, not a good situation to be inadvertently spraying fuel into the engine compartment.
Having just repaired a copper line again, I wonder if there is some other more flexible tubing available and suitable for this application?
[I know there is a common view here that priming is unnecessary, but let's put that to one side for a moment ....]
My O-320 has 1/8" copper primer lines to all cylinders. These have periodically broken, not a good situation to be inadvertently spraying fuel into the engine compartment.
Having just repaired a copper line again, I wonder if there is some other more flexible tubing available and suitable for this application?
[I know there is a common view here that priming is unnecessary, but let's put that to one side for a moment ....]
rmarshall234
Well Known Member
Yes, you might try annealing the copper as mentioned here. The reason they crack is they get work-hardened.
BillL
Well Known Member
Actually, it is the vapor that is burning. Example. Fill a quart milk bottle with gasoline, right to the top. Then make sure the outside is free of wetted area (no vapors , then take it to an area 30 ft from anything you don't want burned. Then take a match and light the top. It will burn the vapors coming off the liquid surface. A nice small flame. As the level burns down, and the liquid is heated, it will soon boil, then you have a roaring flame, but it is still the vapor that is combining with oxygen to burn, the liquid is still sitting down there in the container, just a reservoir. I had fun doing this test. It is not for the faint of heart. It could be hazardous to your future if handled poorly. Proceed at your own risk. etc etc.
To the topic - copper can live nicely if properly brazed/soldered and fastened to avoid vibration that will harden and fail the material. The focus should be on the attachment points. Not the material.
While I believe you are technically correct here, I still think it is wrong to give someone the impression that liquid gasoline won't burn, regardless of what is technically happening. I could also argue that it is not the gasoline burning, but in fact a combination of gasoline vapor with oxygen that is burning. That shouldn't fool me into thinking that gasoline won't burn. I believe the gasoline is continuously converting to vapor until the surrounding air is saturated and therefore always a risk unless you happen to be in a vacuum chamber.
Larry
I know the copper is getting work hardened - in my case in spite of it being well supported and with strain relief loops etc; it is inevitable that there is movement when attached to the engine. My earlier question was whether any of the pundits here can suggest an alternative material?
Stainless steel, as used on injector lines. Can be made into a direct replacement for the copper, as it flares nicely with your existing flaring tools. Or you can buy injector lines and use them.
Alternatively, you could contact Tom at TS Flightlines (forum advertiser) to make you some stainless braided Teflon-lined hoses.
