primer system

According to Van's accessories catalog, a fuel primer system is only needed in cold climates. How many of you have installed a primer system after finding it was needed anywhere? Anyone not install one and have no regrets?

Scott, Every engine is different. I have a primer system on my -6 and live in Texas. The first flight of the morning I need 1-2 shots. After that not needed for the rest of the day (regardless of temp). Even if you don't need it at your home base, sometimes you will fly to colder climates. Unless you are fuel injected, I would recommend a primer.
Mel...DAR

primer system?

Scott,
This was the subject of a thread a couple months ago and the jist of it was that it's better to have it and not need it, than need it and not have it. I live in middle Ga. and was planning on not having one, but broke down yesterday and ordered it from Vans. From my training days in a 172, I needed to prime in order to start on cold winter mornings in Georgia. Of course that plane was stored under a open shelter and was more exposed to the environment. I plan on keeping my -9 hangared, but there will probably be an occasion when I will overnight somewhere with the plane tied down outside and will need to start on a chilly morning. (most of my relatives live up north).

Bruce
-9 F/F

I built an RV6 in Missouri and included the primer. Then, I moved to Texas and the primer colelcted a lot of dust on it's knob. However, on cold days I did need primer to help start the engine. Using the accelerator pump in the carb to help start usually works but sometimes you need a shot of fuel in the cylinder to get it started when things get cold.
Primers can be expensive and I went to a salvage yard for mine and was able to get a brand new looking unit for half the price of a new one. After a new O-Ring was installed, it was like new.
Many people forget that you can get like new stuff from a good salvage yard at an attractive price. If you can build up a good rapport with a salvage yard near you, they will usually look out for better quality parts for you, if you ask them to. Anything from engine parts to avionics and everything in between. Just be sure your parts are yellow tagged, etc. and in airworthy condition. Most reputable yards do this anyway and guarantee their parts. I have bought quite a few instruments and radios that were removed, sent to a shop and sold to me as a used/OH unit and they provided great service. (For radios, you can always buy new faceplates or knobs to get that factory fresh look or have instruments refaced.) I can't begin to count the number of parts such as primer, etc. that I have purchased for my past projects in this manner with out sacrificing quality or aesthetics.

Go with fuel injection instead...

OR if you must go carbed, install the fuel primer.

Scott,

I had one in my -6 in the Midwest. I enjoyed the convenience of it and used it a lot. I have friends that don't have them and they don't have any problems getting it going in the cold, so it's not absolutely necessary. I would do it again. It just makes things a lot easier.

One drawback to pumping the throttle to prime is that fuel can collect in the elbow and can potentially cause a fire if the engine backfires. It happens, but is probably not that big of a deal.

I had a primer in my Cherokee 180 and never used it in 12 years. I didn't put one in my 7A with an 0-360 A1A and haven't needed it. I live in Wisconsin and have always hangared without heat. I generally didn't fly when weather was below 10 deg F. The accellerator pump in the carb was all I ever needed.

JME

Roberta

Cost and weight

Leaving it off will save weight, cost and potential failure point.

Weight: fuel lines, nozzles, solenoid, fittings brackets
Cost: nozzles and solenoid are not cheap
Potential failure point: primer line fails, causing a rough running engine

With out a primer you pump raw fuel into the carb (and drips into the airbox). It evaporates as it sits and gets drawn into the engine as you crank. With real cold temps you will not evaporate the fuel as easily, making starting harder but not impossible without primer. You may just have to wait to let the fuel vaporize and may be give it a pump while cranking. When you get in pump the throttle 1 or 2 times in cold weather by the time you strap in and are ready to "CLEAR" the fuel is ready to do its thing. Most of the stories about hard cold start problems are from the fact engines crank over slower. Slow cranking is not because there is no primer. In fact primers lead to flooded engines and raw fuel in the cylinder washes the good oil away, which is not good for the engine.

The big down side of no primer, fire danger
If you are not careful and realize you are blowing raw fuel into the carb (and into the airbox), over do it, have a backfire, you can have a fire. One or two pumps are plenty. If you do have an induction fire you need to keep cranking to suck the flame into the engine. No problem. However I have seen people over due it to where they are blowing fuel out the air box drain, down the cowl and on the ground. Use common sense and fire is not an issue.

I am going with no primer on the O-360A1A (180HP) in my RV-7. Keep in mind some small Lycomings like the O-235 (O-320?) don't have accelerator pumps in the crab to get that shot of fuel for starting. They need a primer system. Also to add a primer later would be a easy. G

Possible positive safety aspect of primer

I heard a story somewhere about an instructor that would make his students get back to the airport under a simulated engine out by stroking the manual primer. If you primed at least two cylinders I could see extending your glide pretty good.

Of course it would only work if the engine had died due to a fuel or carb problem, and then only in certain cases depending on where the primer got it's fuel source.

Any thoughts?

I had planned to install a pump type primer in my RV-7A, but it sounds like you can get by without it even up north. We'll see.

Mark

Myth?

Mark Burns said:

I heard a story somewhere about an instructor that would make his students get back to the airport under a simulated engine out by stroking the manual primer. Mark

Click to expand...

This sounds like an urban legend. I have heard this claim before. By the way what flight instructor, plane, place date, etc......

Heard of the show Myth Busters on Discovery channel? Well anyone with a primer system want to give this a try? Go up pull the mixture to cut-off and try to milk that airplane back to the airport with the primer providing fuel. I would love to hear how that goes. I think it is bogus, but lets say it is true, it works. When would this come in handy? I'll offer up the throttle linkage breaks. Most loss of power is from fuel starvation because there is air in the fuel tanks and no fuel; the primer will not help you with no gas in the tanks. I feel like I am going to risk it and not put the primer on. As a former CFII, I never heard of any instructor teaching this, read any emergency procedure promoting this or heard of it being done. Not saying it can't work, practical power that you could effectively use but I would have to see it to believe it. G

Just one data point

I have a fairly complex fuel supply system and I want the engine to fire immediately so my experience may not be typical. My O-360-A1A engine is not easy to start without a prime. I have a LASAR ignition and hand proping is not an option - in other words a weak battery is a serious problem. I have one of the little solid state (that's what the catalog calls it - I have no clue what's inside the housing - it makes noise so something is moving) Facet aux fuel pumps with a "T" downstream with the side tap going to a primer solenoid. On the console there is a toggle swith to activate the aux pump and a momentary pushbutton switch to activate the primer solenoid. The output of the solenoid routes to three of the four cylinders (the fourth is used for the MP source). The only thing that was new in the fabrication process was silver soldering the AN800 union cones onto the primer lines (p.114 in Aircraft Spruce's new catalog) but it was a clean and easy job with the Portasol Cordless Butane Soldering Tool Kit (p.563). I used 1/8" copper lines for the actual runs to the cylinder inputs. Oh yes I forgot about the 1/8" flaring tool - forget about the the nice tools used on the 1/4" and 3/8" tubes, that little $19.35 flaring block (P/N 17010 p.515) is all that would work for me on the 1/8" tubes. The beauty of the solenoid arrangement is you don't have mount that hand pump in the panel with the fuel lines etc. I put a full loop in all of the primer lines where appropriate for strain/vibration tolerance.

Bob Axsom

Bob,
Copper will work for primer lines and many people use it. But be aware that copper work hardens with vibration, so watch for broken lines at the connections. Ive seen copper last for years when properly strain relieved, but I've also seen them break within months. Just a word of caution.
Mel...DAR

Copy that

I will watch it and I aknowledge the good info. My Archer had the same copper primer lines for 25 years but you never know the lessons learned and incorporated into their manufacturing processes. I looped the lines and let them cool in ambient air but there are no guarantees. When I was a young Quality Engineer for McDonnell Aircraft many years ago, one of my jobs was certifying the controlled processes and facilities for manufacturing our airplanes (F-4, F-15, AV8B, F/A-18 and subs for the DC-9 and DC-10). I was very surprised and impressed with the great number of closely guarded heat treating processes and the associated process control instrumentation, destructive and nondestructive test methods rigorously applied to achieve correct and consistent results. My formal technical education was electronics and computer science so mine is an acquired sensitivity.

Bob Axsom

Work Harden and annealing copper

It is recommended that you anneal copper lines after you form them (bending them work hardens them) and periodically while in service (vibration work hardens them).

To anneal your copper lines (soften them), you heat them to 600F to 850F and let them air cool or you can water quench them; The cooling rate has no effect.

If you have a torch (gas only) you can anneal them at 1000F. At this temp the tube will glow red in a low low light shop. The tube will show rainbow colors. The trick is to heat it evenly and not over heating. (Beware, around 1200F can start to get real soft, above 1650F you will start to melt it.)

If you water quench you need to have a large enough water source to submerge the entire tube length at one time.

G

PS Bob, F-4, Cool. My first engineering job at Boeing was for a former McDonnell F-4 engineer. He told me that when they had a bunch of vertical stabilizer profiles laid out on a table, Old man McDonnell walked by and pointed to one and said, "That one looks nice". Thus the Vertical stabilizer on the F-4. In the wind tunnel, the F-4 exhibited serious deficiencies in lateral-directional stability characteristics at supersonic speeds, including unstable dihedral effect (wing has none) and marginal directional stability. To cure these problems, McDonnell introduced 12 deg of geometric dihedral into the outer wing panels (which were foldable for carrier planes). The rest is history as they say.

More on the 4

The plane started out as an unsolicited proposal by MAC in plain vanila configuration in 1953. It was a long development process from there to the first flight of the F4H1 at Lambert Field St. Louis in May of 1958. I was fresh out of the USAF in 1957 and I was working on the F-101B and I got to watch that first flight. I thought all models of the F-101 were beautiful and considered the F-4 kind of ugly at the time but it grows on you. The plan view is quite elegent actually. We still had F3H Demons coming off of the line and it was a striking looker (though origionally at least way underpowerd) so the Phantom II had some formidable competition when viewed normal to BL 0.00. I was assigned to Project Mercury in early 1959 so I didn't work on the F-4 until the mid 1970s. Now when I see one it gets my undivided attention. That wing by the way is awesomely strong. The structural testing was conducted in Building 102 where we built the first Mercury Capules. The wing center section was built as a single structural assembly from tip dihedral break to tip dihedral break and mated with the fuselage in final assembly. When I finally got to work on it I gained a lot of respect for it even though I was working on the F-15 at the same time. Those were the days but then these are pretty good too. The last 19 years of my work life were at JPL in Pasadena - totally different world but space is where it's at now in my opinion. Being on console for Genesis mission ops was a great way to end 50 years in aerospace.

Bob Axsom

P.S. Mr. MAC was such an influence on everyone on the team (That's what he called us) I'm not surprised that the decision was made to use the design he liked. He was a giant in our world and every teammate would do whatever it took for the company to succeed. We took a lot of internal pride in what we did. No mickey mouse awards etc., just the personal knowledge that you did everything you could to the best of your ability and we produced some very special jet fighters was what drove us. That and our leader. I'm talking from the grass roots perspective because that is where I worked - down on the floor - and I loved it! When old uncle MAC (J. S. McDonnell) died the magic died with him - he was truely a very special "one of a kind."

Bob