Van's fuel primer system

My plane has no fuel priming system. Apparently no one in over 20 years has ever felt the need for one. I give it a pump or 2 with the throttle depending on how cold it is, none if the engine is warm. It generally starts just fine for me.

OTOH, a couple times I've had to cancel a flight because it simply wouldn't start or even fire. One time, there was lots of gas on the ground, but it wouldn't even fire. In these cases. I try until the battery is too weak, then I just push it back in the hangar, put the battery charger on it, and try it again next time.

At my last annual, the A&P mentioned I have no priming system, and said it must be hard to start. I told him about pumping the throttle, but he said the vast majority of any gas I pump that way just falls down into the air filter. True - I hadn't thought of that; with the carb upside down on the bottom of the engine. So that technique isn't amounting to much. He said in case of any backfire, it will also start a fire. He said I really should have a priming system that uses the priming ports provided by Lycoming.

So I ordered the Van's electric priming system. One thing I really liked about the idea of it was that all fuel stays forward of the firewall, rather than run back to a hand pump. It was also vastly cheaper than even a used priming system from/for a certificated plane.
http://vansaircraft.com/cgi-bin/store.cgi?ident=1492416080-132-612&browse=engines&product=eng-prime

I got it, but it came with next to nothing in the way of instructions; just a block diagram showing how it gets plumbed in from the gascolator.

Do any people on VAF have and use this system? The main question I have is how long to pump for. I assume I'd put a guarded momentary switch on it to activate the pump (interesting that the pump has a label on it that says it's for non-flammable liquids). But since there's no tactile feedback to using it, and no way to tell if I pumped too much or nothing at all, what are people with this system using to determine how long to hit the switch? What equals a "shot"? A full second? Half a second? Is it worthwhile to install it?

And does anyone have any installation tips or things to do or not do or things to watch out for?

Many thanks,
brian

Hi Brian,

I installed the Van's priming system on my RV-8 when I built it, but eventually removed it because of fractured lines. Priming with the throttle is easy and effective - but from what you wrote, I think you are doing it wrong - dangerously wrong!

You should only pump the throttle WHILE CRANKING THE ENGINE - this will suck all the fuel sprayed out into the throat straight in to the cylinders. If you pump while not cranking, the fuel falls into the air box and yes - can easily start a fire.

We have two carbureted RV's at our house, and both start this way just fine - and any system that isn't installed can't fail - so that's a plus.

Paul

I had a priming system on my RV6A but removed it also cause of fractured lines. I was afraid of fuel leaking.
I do the pumping thing also, however be CAREFUL...over pumping caused an engine fire when it backfired.. That was a bummer day...!

Brian---we do our primer systems in teflon hose, mainly. Email me and we'll design something that fits your needs. We've also done some in stainless tubing, but the line from the firewall to the engine is still teflon.

Tom

thanks!

Many thanks to all for the great advice. I have always pumped, then cranked, so I certainly won't be doing that any more. I'll probably just go with Paul's advice and pump smarter. If it ever refuses to start again, I'll probably revisit the primer idea, but with TS Flightlines hoses.

I had terrible trouble starting my O-320 by pumping the throttle as I cranked the engine.
No problems now, but I give several pumps of the throttle, wait about ten seconds and then crank it over. Usually start straight away.
It is never very cold here in Queensland, just South of the tropic line and I assume that the fuel that descends into my air box rapidly evaporates and is drawn into the cylinders.
Never had any hint of a fire, but in case it did happen it should be sucked in if i keep cranking.

Yen said:

I had terrible trouble starting my O-320 by pumping the throttle as I cranked the engine.
No problems now, but I give several pumps of the throttle, wait about ten seconds and then crank it over. Usually start straight away.
It is never very cold here in Queensland, just South of the tropic line and I assume that the fuel that descends into my air box rapidly evaporates and is drawn into the cylinders.
Never had any hint of a fire, but in case it did happen it should be sucked in if i keep cranking.

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The problem with waiting for a hint of a fire is that by the time you get the hint, it will be quite well developed. I've seen it happen from outside the plane, and it took a long time (with the developing fire) to get the pilot's attention.

Pumping, then cranking, with an updraft carb and a fiberglass air box, is just plane dangerous.

Paul

Agree on all above... Here's my hot engine start sequence that really works:

Doing a start after a flight (engine hot soaked).
Do not give it any prime, leave the throttle out, mixture in cut off, all as it was when you shut down.

Start cranking, SLOWLY push the mixture in, when it starts, quickly give some throttle..

If you push the mixture in too fast, you'll miss the opportunity.

If you do the pumping, just make sure your cranking first! Ask me how I know.

Sheldon

Ironflight said:

The problem with waiting for a hint of a fire is that by the time you get the hint, it will be quite well developed. I've seen it happen from outside the plane, and it took a long time (with the developing fire) to get the pilot's attention.

Pumping, then cranking, with an updraft carb and a fiberglass air box, is just plane dangerous.

Paul

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When you pump the throttle while cranking, how far do you go on the throttle? Fully forward and then all the way back? Half throttle?

Thanks

Saville said:

When you pump the throttle whole cranking, how far do you go on the throttle? Fully forward and then all the way back? Half throttle?

Thanks

Click to expand...

Every engine/condition will want something a little different, but generally, I use full pumps to get full stroke on the accelerator plunger.

Ironflight said:

Every engine/condition will want something a little different, but generally, I use full pumps to get full stroke on the accelerator plunger.

Click to expand...

Thanks! Sorry - I should also have asked this for posting efficiency:

About how fast do you pump the throttle? About one pump (zero-to full - to zero) per second?

Interesting comments. I've always used a primer until now, my RV doesn't have a primer either.

My technique has been to turn on the fuel boost pump, until it reaches 5 lb PSI (max), then turn the pump off, push the mixture in and crank, while back and forth on the throttle. Usually starts within a couple of props, even at 40 deg. F.

Heading to Alaska, and plan to have a primer installed.

I am in the throes of installing an engine priming system on our O-360. Many of the opinions expressed here need to be read carefully, with special attention being paid to the location of the person posting the opinion. For somebody in CA or TX, a "cold" start is about the same as a "warm" start for those who live in more northern climes. This is a critical detail.

Also, note that battery performance decreases with decreasing temperature (assuming a lead-acid battery). For some of us, a cold start means that we not only have a cold engine but also a cold battery with very limited cranking capacity. "Missing" a start might mean spending a night in a place one would rather not. It's for this reason that I am installing primer nozzles on three cylinders (I don't have injection ports on the cylinders, otherwise I'd have primers on all four cylinders).

If you are looking to install a priming system, I would advise you contact one of the reputable engine builders and ask if they have "spare" priming hardware. Many engines come with primers installed which the builder removes in order to install fuel injection equipment. This makes for good (and potentially less expensive) access to Lycoming or similar factory-made stainless steel primer lines and the appropriate brass Tee fittings etc.

If one wishes to use the Lycoming steel lines but doesn't want to run a copper line from the electric primer valve to the Tee located at the aft end of the engine, there is a reasonably good solution available... Install an AN917 1/8 NPT Tee. On the left and right ports install AN780-2 brass fittings (1/8 NPT to AN800-style ball fitting). In the aft-facing location install an AN816-3D fitting (1/8 NPT to male AN-3 flare fitting). Now you can connect a nice AN-3 sized stainless braided teflon hose to connect to the primer solenoid.

This allows the use of nice, light and small stainless lines on the engine itself while also accommodating the use of a flexible braided stainless line in the location which is subject to the greatest level of relative motion between shaking engine and stationary airframe.

Ironflight said:

Hi Brian,

I installed the Van's priming system on my RV-8 when I built it, but eventually removed it because of fractured lines. Priming with the throttle is easy and effective - but from what you wrote, I think you are doing it wrong - dangerously wrong!

You should only pump the throttle WHILE CRANKING THE ENGINE - this will suck all the fuel sprayed out into the throat straight in to the cylinders. If you pump while not cranking, the fuel falls into the air box and yes - can easily start a fire.

We have two carbureted RV's at our house, and both start this way just fine - and any system that isn't installed can't fail - so that's a plus.

Paul

Click to expand...

Hi Paul,

How fast do you pump the throttle? I've tried this and it seems to take much longer for the engine to catch. But maybe I'm pumping the throttle too fast.

Can you give any hints on how to do this effectively?

Thanks!

Saville said:

Hi Paul,

How fast do you pump the throttle? I've tried this and it seems to take much longer for the engine to catch. But maybe I'm pumping the throttle too fast.

Can you give any hints on how to do this effectively?

Thanks!

Click to expand...

As the owner of such a system on an RV-9A, I'd say maybe a single, quick, half-pump once the engine is cranking. In winter, maybe a couple half-pumps. That's if you have a MA-4SPA carburetor, anyway.