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Fuel primer. I'm in Canada, do I need one?

Paul Tuttle

Well Known Member
Do I need a fuel primer for cool weather here in Canada? I have an O-360 with carb and will not likely be flying during the sub freezing winter months.

I've been going over the threads discussing copper primer lines and from what I've read have reservations about using them. I've also considered the braided lines, but don't want to spend the money if I don't really need a primer at all.
 
I built my 8A in Minnesota and flew there for a year and a half. I used preheat whenever possible in the winter but there were a few times I was glad I had put in the primer system as I may not have been able to get started with the accel. pump only.

As far as the lines, I used copper and AN fittings and they've been fine. Last year at inspection I replaced them all just for good measure, it's cheap and easy preventive maintenance.

Paul Danclovic
Jamestown NC
RV-8A N181SB
 
Paullie, noooo...

Billie's -6 has one and i NEVER use it.

With the correct technique it really isn't necessary.

My two...

:rolleyes: CJ
 
Primer

Yes......I have one and use it.
Remember what you are doing without a primer. The accelerator pump, which is not really designed for starting, is spraying a line of fuel into the carb throat, which is vertical, so guess where this raw fuel goes, if the "proper" technique is not used? That is right, it pools in the air box.
As far as installs go, the SS is like FI quality, it is best and most expensive.
Copper is very good if installed correctly. The braided line should at least connect the firewall fitting to the engine assembly because of vibration and engine shake on any installation.
Installation of Van's electric system is pretty straight forward and keeps the entire primer line assemblies FWF, other than the switch.
Just my opinion.
 
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I agree with Bob. I put in my primer solenoid and am glad I did...I use it for every start.

If you want proof of the accelerator functionality, just pump your throttle 2 or 3 times and watch raw fuel dump into your airbox! Not good in my opinion...but like CJ said it can be done with the right technique. I'd prefer to not have that margin of error, though. Just my 2 cents.
 
Can someone tell me what the correct technique is? Especially for colder mornings, say near freezing?

Thanks,

Very simple - pump ONLY when the engine is cranking (the huge suction pump pulls the atomized fuel/air into the cylinders). NEVER pump when you aren't cranking or, as was said, you will simple make a pool of fuel in the FAB. A backfire can easily lead to an engine fire.

As to the need for a primer in the north? I'll leave that to folks that haven't lived in Houston for 30 years.....
 
Thanks, Paul, that makes perfect sense. Another question; does the throttle have to be pushed full forward for the pump to function? Or halfway? I can imagine that if the engine fires with the throttle full open that would be exciting!! :rolleyes:

My procedure WAS full rich, pump full twice, back to about 1/4 throttle, then start. I will change that procedure now.

Thanks,
 
Several years ago my one primer line fatigue cracked. The entire system was removed and I have not missed it.

I live in Colorado, keep my plane in an unheated hangar but do preheat in the winter.

Start cranking. Then a quick pump. Sometimes I have to repeat.

If you install a primer system, do not cheap out on the lines. If braided offers far superior resistance to cracking compared to copper, then either install braided line or pre-emptively change out copper lines at some reasonable interval.
 
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Start cranking. Then a quick pump. Sometimes I have to repeat.

Thanks, Ron, that is what I will try. I'm heading out to ID and MT on the 23rd, and last year when it was cold it could be difficult to start. Perhaps it was my technique, hoping this will work better.
 
Several years ago my one primer line fatigue cracked. The entire system was removed and I have not missed it.

I live in Colorado, keep my plane in an unheated hangar but do preheat in the winter.

Start cranking. Then a quick pump. Sometimes I have to repeat.

If you install a primer system, do not cheap out on the lines. If braided offers far superior resistance to cracking compared to copper, then either install braided line or pre-emptively change out copper lines at some reasonable interval.

This is a good point...I wish I knew what a good interval for changing the copper lines was.

Also, Ron, your post made me wonder something about primer vs. no-primer. When you start cranking, how long do you have to crank before it's running? I've never tried without the primer, so I don't know. But when I prime, my engine is running in less than 1 revolution.
 
Primer

You have to look at the entire system, when it comes to fatigue. I have seen people use 1/8 aluminum primer lines and wonder why they kept breaking, but kept replacing with alum because that is what the original builder used and he must be right?..(kidding here, well about the builder must be right that is.) The line that fatigues is the line that runs from the firewall to the engine and has the most movement or vibration. If that one line is done in a flexible SS line, the other lines should be long lived. Some people say, and I have seen lots of examples of the copper tubing with a coil or two between the firewall and the engine. I think this will last for a short period of time and that is why I say the weak link is between the firewall and the engine connections. The lines attached to the engine and move with the engine are not as prone to wear out from fatigue. My opinion as always.
 
If you install a primer system, do not cheap out on the lines. If braided offers far superior resistance to cracking compared to copper, then either install braided line or pre-emptively change out copper lines at some reasonable interval.
As I understand it (or don't understand it), the only line that is always pressurized is the one between the gascolator and the primer solenoid. Per plans, I have copper there, and am slightly uneasy about it, but don't know why I should have any concerns about using copper from the primer solenoid to the cylinders given that they are not pressurized except for the couple seconds the primer is on. Should I be more concerned?

FWIW, and though I have very little experience with it, when I use 1-2 seconds of primer before starting, my Aerosport with regular mags starts on the 2nd or 3rd blade everytime, including on first start. I've been very pleasantly surprised.
 
Do I need a fuel primer for cool weather here in Canada? I have an O-360 with carb and will not likely be flying during the sub freezing winter months.

I've been going over the threads discussing copper primer lines and from what I've read have reservations about using them. I've also considered the braided lines, but don't want to spend the money if I don't really need a primer at all.

I'm out in the wilds of Saskatchewan; I preheat in an unheated hangar, and have a carbed O-360 in my 6A. I have a primer and use it on every cold start, and wouldn't be without it. Having said that, my hangar partner also has a carbed O-360 in his 8, no primer, and seems to do fine as well. Go figure. Personally, I think it makes life easier. As for flying in the winter in general terms, I do realize that you're on the East coast and that your winter weather is quite different from my prairies, but don't automatically cheat yourself out of some great flying; nothing like a clear cold winter day in the air! I put 25 hours on my plane this winter; just need a little preheat and hopefully a hangar to keep out of the wind while you preflight, and life is great:)
 
As for flying in the winter in general terms, I do realize that you're on the East coast and that your winter weather is quite different from my prairies, but don't automatically cheat yourself out of some great flying; nothing like a clear cold winter day in the air! I put 25 hours on my plane this winter;

I've flown a lot here on skis, love it! The big problem being there's no winter maintenance on the field, one big storm and it's pretty much over until spring.

Looks like we're running neck and neck on the primer question :confused:

I have the solenoid attached to the firewall already so I may investigate the stainless steel idea further. Can anyone tell me what SS line I need ? I see ACS has two wall thickness' listed. Also will I need a special flaring tool or technique to install stainless lines?
 
As I understand it (or don't understand it), the only line that is always pressurized is the one between the gascolator and the primer solenoid. Per plans, I have copper there, and am slightly uneasy about it, but don't know why I should have any concerns about using copper from the primer solenoid to the cylinders given that they are not pressurized except for the couple seconds the primer is on. Should I be more concerned?

I have my primer solenoid mounted next to my fuel pressure sensor with a tee from the sensor to the solenoid. A firesleeved fuel line connects the two. The only time there is any pressure in my copper lines is when the primer is on. I would also be uneasy having a copper line always pressureized.

Paul Danclovic
Jamestown NC
RV-8A N181SB
 
I'm not even worried about the short copper line from the gascolator to the solenoid. I put a loop in mine, and it's about a 6" distance. In the heating and air conditioning business, we have these small copper lines running all over the place, to feed high pressure refrigerant to evaporator & condensor coils. The outside A/C unit is vibrating, and the furnace motor may also be out of balance with an A/C coil above it. I also ran loops from the solenoid out to the engine, and as mentioned, these lines are not always under pressure. These A/C lines are also seeing pressures that could be in the 300's and are tested for 450 lbs. pressure.

And..............I think the prime system is great. I'm also one, who wouldn't want to be without it.

L.Adamson
 
I've flown a lot here on skis, love it! The big problem being there's no winter maintenance on the field, one big storm and it's pretty much over until spring.

Fair enough! Good luck with the rest of your project, whichever way you go on the primer;)
 
No

No, you don't need it. Preheat a bit and it will start immediately. Better burn that primer money on gas. Preheat the battery if you can.

I flew a hundred hours during winter time no issues with start even in Canada. I have new O320. Well, not new anymore :)
 
Primers

Hey Paul....I would install the primer, I have lines to three cylinders, copper with a vibration loop to the firewall. I worry about fatigue as well but you must remember that the only time the primer lines have fuel in them is when you pump the primer.

Much more of a concern is if you have a copper line to your fuel pressure gauge. Old school I know if you have a glass cockpit and use a sender behind the firewall.

I can confirm this, mine cracked and I fortunately discovered it on the ground. I have stainless now and would like to replace with a braided line. Where can you source 1/8 braided lines?

Joe
 
For the primer line fittings - do a search on AN780-2 on AS. You attach the fitting to the line with silver solder.

Dan
 
For the primer line fittings - do a search on AN780-2 on AS. You attach the fitting to the line with silver solder.Dan
Definitely not saying you shouldn't solder (because I wouldn't know) but, as far as I can remember, Van's just has you flare like any other fitting. No soldering in their instructions.
 
Sorry - I was responding (I thought) to how to handle the stainless steel primer lines. For that - high temp silver solder with the fitting. (Be careful not to plug the fitting.)

Dan
 
I have a fuel primer on two cylinders and from my experience if I use it the engine starts in less than a blade or two. If I don't use it, because I have tried it on occasion I have to crank a few revolutions. I think it saves on some wear and tear. The plane has seen winters in Idaho, Reno, and Nebraska.
 
Sorry - I was responding (I thought) to how to handle the stainless steel primer lines. For that - high temp silver solder with the fitting. (Be careful not to plug the fitting.)

Dan

Can you use the brass fittings that are sold by ACS with the SS lines? I thought you had to use the SS fitting with the stainless lines. If the ACS fittings are ok that would be a big help, the SS version is not cheap!
 
It has worked for me. As I recall that was recommended by the (very reputable) engine shop.

Dan
 
When I installed my primer system over 12 years ago I used the following parts.

DISCHARGE NIPPLE AN4022-1
UNION CONE AN800-2
BRASS UNION NUT AN805-2

I used copper lines silver soldered to the AN800-2 Cone. The Discharge Nipple has a tiny orifice and internal baffle so the fuel sprays in the intake port. If you use the primer fittings supplied by Van's flow is not a spray but more like a little hose. Both will work but I prefer the Discharge nipple spray pattern. I tested both.

With that said it is still very easy to overprime using the Discharge nipples and guess where the fuel ends up; yup, the airbox. The primer port in the heads are on the carb side of the intake port so any fuel whether it is sprayed or hosed in starts running down the intake tubes through the carb and into the airbox. So we must be carefull even if we use a priming system.

My technique is; Boost pump on, Short prime to clear the lines of air, press starter button and prime at the same time. Fires in one to two blades every time no matter what the temp (if the battery is good).

My $0.02 worth.
 
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