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carb primer

P

paul romine

Registered User
indy
Any of you Experimental Super Cub builders doing anything different from the stock 1/8 copper line for the primer system?
I would like to use a bulkhead fitting thru the firewall instead if just a pass thru line.
How about plastic line? Do they make a bulkhead fitting that will work with plastic?
Thanks,
PR
 
Took mine off. No primer, no starter, no problems.
If you don't have it, you never have to fix it.
 
OK,
So now maybe the question is:
How many guys with 0-360 engines and hopped up compression are not using a primer, in the Winter?
Maybe I just don't need a primer.
PR
 
It never gets real cold here, but I've flown it at around 20F. I keep it heated in the winter--100watt bulb, a blanket and a thermostat set at 60.
8.5:1 compression, 160HP
Less stuff under the hood=less stuff to worry about.
I prop start a 10:1, O-360 in a Pitts quite a bit. No worries.
 
I hear pilots all the time talking about starting engines without prime, but they don't explain their procedures. How's about you guys who hate primers so much explain your cold start procedures for the guy so he can make an informed decision?

I know how I start engines, which is generally WITH a primer. The alternative is often to use the accelerator pump in the carb to deliver a blast of fuel to the carb. Since these are updraft carbs, unless the engine is turning over (and sucking gas into the cylinders) while you blip that accelerator pump, some of that gas drips down into the airbox, and a backfire, while uncommon (particularly if the start procedure is just right), can ruin your day, as well as your airplane.

I've started engines using the accelerator pump many times, but I'd rather use a primer any day.

Primers require very little maintenance and if properly installed in the first place, they are trouble free for years.

I use primers, my own self. Call me a wuss if you like, but I think they are worthwhile :lol: .

MTV
 
I have always used the primer on Cubs, and even though my 450 Stearman has an accelerator pump on the carb, it is also an updraft carb. If you don't prime it the first start of the day or if has cooled all the way down, you can pump the throttle all day and it aint gonna start.
I have heard you don't have to prime 0-360's but I would hate to get out on the lake with a breeze and that baby woun't start!!
PR
 
mvivion said:
I hear pilots all the time talking about starting engines without prime, but they don't explain their procedures. How's about you guys who hate primers so much explain your cold start procedures for the guy so he can make an informed decision?

I know how I start engines, which is generally WITH a primer. The alternative is often to use the accelerator pump in the carb to deliver a blast of fuel to the carb. Since these are updraft carbs, unless the engine is turning over (and sucking gas into the cylinders) while you blip that accelerator pump, some of that gas drips down into the airbox, and a backfire, while uncommon (particularly if the start procedure is just right), can ruin your day, as well as your airplane.

I've started engines using the accelerator pump many times, but I'd rather use a primer any day.

Primers require very little maintenance and if properly installed in the first place, they are trouble free for years.

I use primers, my own self. Call me a wuss if you like, but I think they are worthwhile :lol: .

MTV
Click to expand...


Geez Mike I didn't mean to stick a burr under your saddle... I just said I don't use mine... I think they work well if you already have one and use it thats great but the only time I have realy needed to use mine is when my batt was very low and it needed to hit the first time and not make an all day project out of starting... Mine normally starts after two blades so it just has not been a big deal. I guess I just haven't had a hard start issue with mine :)
 
Hello Paul
I don't think I would use plastic line for fuel delivery.Asking for fire in my opinion.

Primer has worked the best for me when the nozzles are pointed at the back of the intake valves and priming is started once the engine is turning.

I don't prime my 0-200.I pull it thru half a dozen blades and leave it at tdc.It will start in 1/2 turn every time. Bill
 
mvivion said:
I hear pilots all the time talking about starting engines without prime, but they don't explain their procedures. How's about you guys who hate primers so much explain your cold start procedures for the guy so he can make an informed decision?
MTV
Click to expand...

First of all, 5 Pawnees and 6 Supercubs and NONE with primers. It's just JUNK in our opinion, if your accelerator pump is working you don't need it.
I have NEVER had trouble starting even at -30 F.

Starting Procedures

Warm temps - 2-3 jabs of the throttle, then push starter button.
Cold Ass Temps -30 F (plugged in) - 6-7 jabs of the throttle, then push starter button.
Just landed and shut down to drop someone off and go again (Warm Engine) - 1 jab, then push starter button.
99% of the time they pop right off and I've NEVER had a back fire.
The 1% when it didn't pop right off I gave it 1-2 more jabs while turning it over, otherwise Throttle First , Starter Button Second.
0-360 or 0-540 both the same. (Edit) and they're hopped up :D
No troubles here. Hope this helps.

Brad
 
I'm with Brad,my 0-320 has always started with 2 or 3 jabs of the throttle, depending on the temp., and never a backfire. Forget the primer.

Tim
 
They've always said "you can't teach an old dog new tricks :D "
TJ, you work way to hard to start an airplane. I like to jump in, jab the throttle and go. This thread will go like all the others, everyone has their own way and that's fine with me :wink: .
But please don't start agreeing with MTV :eek: , that scares me.

Brad
 
Okay, okay, okay--I'll have to change my procedures if TJ is going to go and spoil my day by agreeing with me :lol: .

Actually, using the accelerator pump to start DOES work okay, EXCEPT the time you get in an airplane where the timing is maybe a mite off, or you select BOTH mags in an airplane with only one impulse coupling.

That's when a backfire (and believe me it doesn't take much) could ruin your day.

I watched an absolutely beautiful Beech Model 17 burn to the ground because that pilot insisted on using the accelerator pump to start the engine instead of using the primer. He got a little bitty backfire, the engine didn't start, and it went up like a torch from all that fuel pooled in the airbox, as TJ referenced. Granted, a 985 is not an O-320 or 360....but. Physics is physics.

Using the accelerator pump, you are just one backfire away from a serious fire, potentially. These little engines really tend NOT to backfire, but. If it's your engine, you may be fairly certain the timing is set right, etc, but....things change.

The only down side to a primer that I can see is that it does require a tiny bit of maintenance.

I use em on 985's and on anything else with a carburetor.

MTV
 
Thanks for all the advice (and opinions)
This site is the best for getting info (and stirring it up a bit)
I got some -3 aluminum line and pretty anodized bulkhead fittings and B nuts,
so I am ready to install my primer.
Thanks for the good words.
PR
 
mvivion said:
I watched an absolutely beautiful Beech Model 17 burn to the ground because that pilot insisted on using the accelerator pump to start the engine instead of using the primer.
MTV
Click to expand...

Mike that wasn't in Lewistown many years ago was it? my boss there used to tell of a gorgeous 17 burning up after rebuild.

TJ, I gotta admit I kinda like the primer system too. But unlike Brad, its probably cause we run old worn out junk that takes everything we can muster to get them fired up. 8)
 
S2D,

Nope, Kodiak, on floats. Broke my heart.

I also lit a Beaver on fire once using the accelerator pump. Got the fire out quick, but still gives me the shakes.

MTV
 
Is it legal to take the priming system off a certified cub? Had this discussion a few years ago with a guy and he says it isn't because the aircraft was type certificated with it installed. I said its not in the type certificate as required equipment? Anyhow don't really care just wondering. Only time I use my primer is if the engine is really cold with no preheat.
 
First radial I Sprayed with was low time but had sat about 10 yrs. so everything was dried out. Every time I would land on some rough ground and get to bouncing a little bit,(Snows don't have much for shock absorption) it would start sloshing some gas out of something in the carburetor and I'd get a big fire out the exhaust. Usually adding a little power would make it quit burning. One day as I was landing on an old crested wheat grass strip, I got to bouncing a little too much and the fire got to belching out the the exhaust.I added power and the engine died. as luck would have it, my starter wire was on the fritz so I couldn't Crank the engine over. Thinking the fire was only in the exhaust, I didn't figure there was much panic and got out to crank the engine over by hand. As I got near the front, I could see the whole carburetor was engulfed in flames. Then panic did set in. Tried to prop it but that wasn't working quick enough so I started trying to scrape up some dirt in the rock hard ground until my finger nails were bleeding . Finally I just threw up my hands in defeat and started to walk away. After a couple steps, I realized I couldn't do that and went back and made a few more feeble attempts at getting a little dirt on the fire. It finally fizzled out without any damage. After a few minutes to get my adrenalin and heart beat lowered, it fired up and I went back to spraying. And I did replace the carb and fix the starter wire not long after that.

I still use lots of prime and the accelerator pump to start the 1340's when they are cold, but if I ever get a back fire, I don't quit cranking.
 
primer

{ Call me a wuss if you like}

Mike, you a wuss :D

I only use prime on little lycomings if it is very cold and even then it seems that with nothing but raw fuel and not enough air you will get wet plugs, then you either have to crank the hell out of it with the throttle open to dry the plugs or open the throttle,get out and pull it through backwards 8 or 12 blades before it will start. I have never had a O320 on fire but I have had several 520s lite off and I agree with Brian that the round engines need about 2 dollars of prime to get them to fire the first time in the morning. Best insurance if one ever does catch fire is to have a good battery/starter and sit there and keep cranking and get it started,that will suck the fire into the engine and put it out.

Dave
 
I got caught flooding today trying to start Miss Daisy. She has sat at the WAD this past month and a half since I got her back from Maine and off floats. She has a mixture of some 93 octane car gas fuel but mostly100ll.
I screwed up and because it was in the teens last night but 35* this afternoon. I got it in my thick mick head to prime it since I did not have a preheater available. The last time I primed it it was a bear to start so I asked the mechanic after getting her off floats what he thought. He told me if I was to prime at all I should do it while it was turning over. I am the first to admit I have not had a normally aspirated engine in years and what I do is to put in full rich crack the throttle few times for a normal start in warm temps. In cold I normally prime 5 pumps and crack the throttle with full rich. Today it did not work nor did it the last time I did it. I ended up killing the battery trying to jump it without any fuel to eventually giving up and going after the other plane a generator and an electric heater for preheat.
I suspect it was the lack of preheat that may have caused the issue.
John
 
When it is below 30 and I have not preheated I give it a few shots of prime, jump out spin the prop by hand a few times, and then prime once, load the primer for a second shot and give it the second shot while turning it over.

Tim
 
Yep, when they're cold it's sometimes hard to get them to run on anything BUT prime. Cold engines (as in ~30 to 40 F) I prime five shots, then load the primer, crank the engine. They almost always fire on the first couple blades. Then, push in that load of prime to keep it running till it'll run on vaporized fuel from the carb. Sometimes, you have to keep it running with primer for a bit.

It is VERY easy, however, to flood one of these engines when they are warm, as in even vaguely warm.

I don't like cold starting any engine, but every once in a while....

On my experience with the Beaver, the engine popped just a bit, ran for a second, then quit. I really didn't think it'd backfired. I pushed the door open to reach the primer to give it another try, and there were flames coming up around the cowl. Jumped out, halon extinguisher in hand, and turned that puppy loose with a full blast.

It was about 35 degrees in Kodiak and RH was REALLY high. When I pulled the trigger on that extinguisher, the whole area went 0-0 in dense fog. The tower sent the fire trucks down to investigate, though what they saw was the fog, not the fire...

Got back in and lit it up, internally this time, and spent the day flying.

MTV
 
Mike,
Just so I am clear the 5 shots you refer to is the throttle and to push in some more primer you are leaving the primer extended with a full load then shoot it in while the engine is turning?
Thanks
John
 
Daisy, primer extended is an old MLT trick for cold weather. Works well. You can tell as you are feeding it in how much it wants or doesn't want.
 
John,

NOPE! When I say five shots of prime, I mean five shots of the PRIMER, not the throttle. I use five shots of PRIMER when the engine is pretty darn cold (cold as in environmentally cold AND a cold engine--one that hasn't been run for a while), three or four when it has not been run (ie: cold engine starting procedure) but the temperatures are not so cold.

Blasting the throttle five times is a great way to flood one of these engines, and as I said earlier, if you pump the throttle prior to cranking (which activates the accelerator pump in the carb) most of the gas you pump in that carb just drips out the bottom. I'll bet you had a pretty good puddle under your engine after that episode. My bet is that if you pumped the throttle five times while starting you either a) Fouled the plugs by flooding the engine. or b) if it fired, and was really cold, you may have FROSTED the plugs. It's essential when temps are really low that you catch it and keep it running on the first firing.

This is why in my first post, I suggested that anyone discussing a starting procedure should describe their procedures fully to avoid confusion. Guess I didn't follow my own advice well enough. This procedure is outlined in the Cub Operators Handbook, as well.

As I noted, cold engine, I use primer ONLY most days. As to the question of legality of a Certified Cub with no primer--I'd bet that it's not legal UNLESS the removal was covered by a field approval. And, in this day and age, I'll bet it'd be hard to get one.

MTV
 
Also, for those of us with the MS carb, don't forget to open up the big old knob on the back of the carb a half turn or so for the colder air.

If I don't make this "seasonal" adjustment she starts and runs for about 10 seconds and then dies.....

I'm still a big fan of preheating.

Last year I bought a small 40,000 btu propane heater (with fan) at the local HD on sale. I think I paid 59 bucks for the thing. I rigged up some creative ducting and stick that sucker in the cowl under the oil sump and turn her on low for 15 minutes or so. I leave the engine cover on during preheat.

Works.
 
Hi Mike,
That is exactly how I was instructed on this engine to fire it up cold and for the first time these past starts she has been unwilling to take that procedure. I will admit I got onto the throttle after the prime did not take and I bet you are correct that the engine was good and flooded when I was done. This is the first I have heard of the keeping a loaded prime. I also know that on the spring annual the timing was changed but I saw the timing tool and she was adjusted dead on. Well she is good and cold now and I will attempt to give her another shot this Turkey- Day.Thanks
John
 
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