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What Engine Priming System Do You Use?

Saville

Saville

Well Known Member
A priming system is going to be installed in my plane this week. You have to pump the throttle otherwise and I don't like that so hence the priming system.

Mine will be a Piper-style hand pump. But I was wondering what other people have for that?

Electrical priming?
Hand Pump?
Other?
None?
 
No priming system in mine other than the carburetor accelerator pump. Works fine on every start, but I’m very cautious to only pump the throttle when the prop is turning; I don’t want pooled fuel in the airbox to go “poof!” if I get an accidental backfire.

During my build I was going to install a separate electric solenoid primer system, but decided against it. I still have the primer solenoid, unused, new in the box… anyone want it for 50 bucks plus shipping?
https://www.aircraftspruce.com/catalog/appages/elsolprimer.php?clickkey=8418
 
jbDC9 said:
No priming system in mine other than the carburetor accelerator pump. Works fine on every start, but I’m very cautious to only pump the throttle when the prop is turning; I don’t want pooled fuel in the airbox to go “poof!” if I get an accidental backfire.

During my build I was going to install a separate electric solenoid primer system, but decided against it. I still have the primer solenoid, unused, new in the box… anyone want it for 50 bucks plus shipping?
https://www.aircraftspruce.com/catalog/appages/elsolprimer.php?clickkey=8418
Click to expand...

Everything he said! Except I have no idea where the priming system I removed might be now - I installed it in the original build, but it was in the way, and plumbing cracked - so since I wasn’t using it, I took it off.

Paul
 
None

Accelerator pump on carburetor works very well

Like Paul, I have found them to be prone to failure, so they need very regular inspection and repairs.
 
I’m not a fan of primer systems in general. Too much added plumbing, complexity and failure modes. For an airplane with no accel pump or starter like my Taylorcraft, sure. It helps. For the typical RV, not required.
 
My SDS system automatically gives an extra shot of fuel when the engine is cold.

Fuel pumps on and 40 PSI in the system. Turn on the ECU and (magic happens :D) and push the start button.
 
Accelerator Pump. Me Too.

Here in warm SoCal, we just pump the throttle twice, crack it open a bit, twist the key and watch for oil pressure. Lycosaurus 0-320, Slick on the left, Lightspeed Plasma III on the right. Have never operated in really cold weather but I’m pretty sure it would start about the same with preheating.
 
JDeanda said:
Here in warm SoCal, we just pump the throttle twice, crack it open a bit, twist the key and watch for oil pressure. Lycosaurus 0-320, Slick on the left, Lightspeed Plasma III on the right. Have never operated in really cold weather but I’m pretty sure it would start about the same with preheating.
Click to expand...

Pumping the throttle without the engine cranking, is greatly increasing the risk of an induction system fire.
The recommended procedure is start cranking the engine, and then pump the throttle till it fires
 
Electric

I have the Vans sold electric solenoid priming system. I installed it with the same lines made for fuel injection. It gets close inspection but in five years I have not had a problem.

I used a MOM switch and as I crank the engine I press the prime MOM switch for just a second or two depending on temperature. Starts great every time.
 
Saville said:
A priming system is going to be installed in my plane this week. You have to pump the throttle otherwise and I don't like that so hence the priming system.

Mine will be a Piper-style hand pump. But I was wondering what other people have for that?

Electrical priming?
Hand Pump?
Other?
None?
Click to expand...

I had a used Piper hand pump on hand so installed it when I built the airplane over 26-years ago. In the past 3,500 hours of flying the airplane, I have used the primer about a half dozen times.

IF you live in a cold climate, an engine primer may be something nice to have.

The electric solenoid primer would be the cheapest option.

My engine typically starts quick and it if it not trying to fire, a quick pump of the throttle while the engine is turning over typically will get it running.

Starting at 17 F in the morning after sitting on the ramp at Lake Tahoe, I used the primer and it started without a lot of cranking.
 
I have the Vans sold electric solenoid priming system. I installed it with the same lines made for fuel injection. It gets close inspection but in five years I have not had a problem
Click to expand...

Same here. Only used when the aircraft hasn't flow for a long time, like a week or so.
 
I live where we get cold winters (Ontario Canada). No primer system on either of my 4s or my 7 (all carbed). Two were O-320s and one an O-360. Start cranking and pump the throttle when cold. No pumping required when warm. Usually one shot in summer and 2 or 3 in winter (after preheating). Never a starting problem in 1200+ primer less hours.
 
Well it turns out no primer system will be installed.

So I could use some advice:

I've never really gotten the knack of the technique of pumping the throttle when the engine is turning to make it work regularly. So I have a few questions:

1) How soon after the prop starts to move you do start pumping the throttle?

2) How many pumps does it take?
-If I pump the throttle before the engine is turning it usually takes 2-3

3) How fast should the throttle be moved through it's range from closed to full open back to closed?

4) Any delay between successive throttle pumps?

Thanks for your advice.


P.S. I preheat in the Winter with the Reiff Turbo XP System on all 4 cylinders with the sump heater. I get the oil pretty warm before trying to start.
 
Last edited:
Before I switched to injection: O-320-D2A on an RV-6 with no primer:

1) right away.

2) one pump.

3) pretty quickly. Less than 0.5 seconds from cracked to full, then right back to maybe half-travel.

4) no need for successive throttle pumps. If you use more than one, maybe wait a couple of turns of the prop?

It might help to see what's happening in the carb when you pump it:
https://photos.app.goo.gl/bTjBNXmZXwUMRw7L6

If the engine isn't turning, almost all of that fuel ends up in the FAB, waiting to catch fire. If it is turning, you end up with a pretty rich mixture in the intake manifold, and then the only challenge is to suck it past the valves.

When it's very cold, my belief is that the fuel condenses to liquid on the inside walls of the intake manifold, which doesn't help anyone because it needs to be in vapor phase to burn. Might need a second pump then.

- mark
 
For me, it sometimes takes three or four pumps in colder weather, or one or two in warm weather ALWAYS during cranking.

I use fast pumps fairly close together. Dunno if this is right, just what seems to work.

I imagine in cold weather climates a primer may be more worthwhile - I'm on the OR coast so while it can get kinda cold, it rarely gets into the 20s / teens.
 
jbDC9 said:
No priming system in mine other than the carburetor accelerator pump. Works fine on every start, but I’m very cautious to only pump the throttle when the prop is turning; I don’t want pooled fuel in the airbox to go “poof!” if I get an accidental backfire.

During my build I was going to install a separate electric solenoid primer system, but decided against it. I still have the primer solenoid, unused, new in the box… anyone want it for 50 bucks plus shipping?
https://www.aircraftspruce.com/catalog/appages/elsolprimer.php?clickkey=8418
Click to expand...
Have you sold the primer yet? Id be interested in it.
 
Saville said:
Well it turns out no primer system will be installed.

So I could use some advice:

I've never really gotten the knack of the technique of pumping the throttle when the engine is turning to make it work regularly. So I have a few questions:

1) How soon after the prop starts to move you do start pumping the throttle?

2) How many pumps does it take?
-If I pump the throttle before the engine is turning it usually takes 2-3

3) How fast should the throttle be moved through it's range from closed to full open back to closed?

4) Any delay between successive throttle pumps?

Thanks for your advice.


P.S. I preheat in the Winter with the Reiff Turbo XP System on all 4 cylinders with the sump heater. I get the oil pretty warm before trying to start.
Click to expand...

Try this other thread currently discussing the same subject.
https://vansairforce.net/community/showthread.php?p=1734091#post1734091
 
newt said:
Before I switched to injection: O-320-D2A on an RV-6 with no primer:

1) right away.

2) one pump.

3) pretty quickly. Less than 0.5 seconds from cracked to full, then right back to maybe half-travel.

4) no need for successive throttle pumps. If you use more than one, maybe wait a couple of turns of the prop?

It might help to see what's happening in the carb when you pump it:
https://photos.app.goo.gl/bTjBNXmZXwUMRw7L6

If the engine isn't turning, almost all of that fuel ends up in the FAB, waiting to catch fire. If it is turning, you end up with a pretty rich mixture in the intake manifold, and then the only challenge is to suck it past the valves.

When it's very cold, my belief is that the fuel condenses to liquid on the inside walls of the intake manifold, which doesn't help anyone because it needs to be in vapor phase to burn. Might need a second pump then.

- mark
Click to expand...

Thanks for the info. If you need a second pump, do you first move the throttle to closed and then pump? Or can you start from the half-way point where you stopped the last pump.?
 
You can do from mid point. I replaced my o320 carb last year. Once removed, I pumped the lever WOW …. shot a stream 10’ up ! I pump first start of the day, afterwards no need. It works well! I do have a manual primer system, but don't use.
 
Saville said:
A priming system is going to be installed in my plane this week. You have to pump the throttle otherwise and I don't like that so hence the priming system.

Mine will be a Piper-style hand pump. But I was wondering what other people have for that?

Electrical priming?
Hand Pump?
Other?
None?
Click to expand...

None. There is no priming system on either my current fuel-injected engine or my previous carburated engine and there has never been a hint of a problem.
 
To prime or not to prime.....

BH1166 said:
You can do from mid point. I replaced my o320 carb last year. Once removed, I pumped the lever WOW …. shot a stream 10’ up ! I pump first start of the day, afterwards no need. It works well! I do have a manual primer system, but don't use.
Click to expand...

Electric primer plumed into the primer ports of cylinders 1 and 2. Carburetor; mags with one impulse. Cold start: 3 potatoes of prime; 1/4 throttle without pumping. Start: slowly advance throttle while cranking; never goes past about half. 4 blades and The Noise begins. Hot: crank it without priming. Sometimes needs a little encouragement from the accelerator pump, depending on how long breakfast took! :p
 
newt said:
Before I switched to injection: O-320-D2A on an RV-6 with no primer:

1) right away.

2) one pump.

3) pretty quickly. Less than 0.5 seconds from cracked to full, then right back to maybe half-travel.

4) no need for successive throttle pumps. If you use more than one, maybe wait a couple of turns of the prop?

It might help to see what's happening in the carb when you pump it:
https://photos.app.goo.gl/bTjBNXmZXwUMRw7L6

If the engine isn't turning, almost all of that fuel ends up in the FAB, waiting to catch fire. If it is turning, you end up with a pretty rich mixture in the intake manifold, and then the only challenge is to suck it past the valves.

When it's very cold, my belief is that the fuel condenses to liquid on the inside walls of the intake manifold, which doesn't help anyone because it needs to be in vapor phase to burn. Might need a second pump then.

- mark
Click to expand...


Ok well I gave this a try yesterday. Didn't work.

The engine was cold (i.e. hadn't been started).

Temps maybe at 45 degrees.

Full mixture

Cracked the throttle.

Master on.

Started cranking.

Went from cracked to full throttle to half throttle as fast as I could. Nothing.

Waited 3-4 props (i.e. engine still turning.)

Tried sequence again - nothing

waited 3-4.

Tried sequence again. Nothing.

Now the thing to remember is that if you prime the engine the bad way (i.e. engine not turning) - 3 pumps and it starts right up. Every time.

I just must not be doing something right. I really want to figure this out. Not sure what to try next.
 
Manual prime

My RV3b has the manual primer pump plumbed into 3 of the 0-320's cylinders. During the pre-purchase inspection the plunger type primer pump was discovered inoperable, seized tight and requiring pumping the throttle while cranking in order to fire up the engine.. Freeing up the the primer pump was a top priority for me.
Having had the same primer system installed on a previously owned C-150 possibly saved me from an unplanned ocean landing.
While transiting over a wide body of water at 4500' the engine RPM suddenly dropped, to the point that only a 200 fpm decent could be maintained.
Full throttle, carb heat on, mixture rich, primer was in and locked, mag check showed two good mag's. Radio call was made, my passenger briefed what to expect when we landed in the water. Told him not to inflate the life jacket (always worn), until out out the aircraft.
As we carried on with our slow descent toward the ocean and multiple attempts regain full power, recalled an odd statement a very keen flight instructor once said to me.
This instructor was fond of pulling power at the least expected moment, announcing 'engine out'. During one of these engine out exercises and after my having done the requisite checks, (likely a third time) he asked what else could I do prior to the forced landing? I said 'I dunno. keep checking?' and his response being that I had already done all the checking I possibly could, what else could I do? Not knowing the answer, he informed me to do the 'fiddle f--- check'. He was a seemingly straight laced guy, so was a bit taken aback by the comment. He explained that I had done all the required checks, that I had nothing to lose and time remaining, so 'play' (not his words) with everything.
The instructors words came back to me as my friend and I were slowly descending to the ocean. As most know, C-150 is a pretty simple airplane and there isn't much to 'play' with on the panel. The only thing that came to mind was the primer, which had been checked in and locked.
Operating the manual primer gave surges of power and enough to maintain altitude! I pumped that thing for about ten miles and long enough to make it to a runway I had been 'cleared straight in'. We had 3 fire trucks waiting for us at the threshold of the Comox airport.
The problem was a bit of gunk in the gascolator (and likely my own dumb fault) and after clearing the gascolator the engine then developed full power. If memory serves, the primer pump inlet was plumbed upstream of the gascolator, bypassing the restriction in the gascolator.
In my view, having a manual primer pump installed on a carbed engine could possibly be a useful option and plan B for a fuel starved engine.
My friend had had enough flying that day and opted to take a taxi, buses and a couple ferry's to get home.
 
Saville said:
Ok well I gave this a try yesterday. Didn't work.

The engine was cold (i.e. hadn't been started).

Temps maybe at 45 degrees.

Full mixture

Cracked the throttle.

Master on.

Started cranking.

Went from cracked to full throttle to half throttle as fast as I could. Nothing.

Waited 3-4 props (i.e. engine still turning.)

Tried sequence again - nothing

waited 3-4.

Tried sequence again. Nothing.

Now the thing to remember is that if you prime the engine the bad way (i.e. engine not turning) - 3 pumps and it starts right up. Every time.

I just must not be doing something right. I really want to figure this out. Not sure what to try next.
Click to expand...

Next time you pump while cranking, return the throttle to idle, then only crack it open a little bit.. I wonder if during your pumping, you are also allowing too much air.. I bet you crank, pump, and go to idle and it’ll fire right off.
 
That’s a great story Richard and supports one of my rationales for installing a primer system on my Ellison equipped 0-360. An alternative way to get fuel to the cylinders - just make sure the throttle is open too.

And as Michael pointed out, if you are injecting into the primer ports you can count potatoes before cranking to allow that fuel to vaporize. I think peeps cautioning about engine fires need to understand *where in that intake system the priming fuel is being introduced. If above the butterfly that’s one thing but one size does not fit all.
 
For several years with a 6A/O-320 combo I had no primer, even with one electronic ignition starting was difficult on cold days in North Texas. After one cold day, perhaps 25F, when I really needed to go fly and the engine would not start I installed a primer. I chose the electric solenoid with primer pipes to the left hand cylinders only. Solenoid only works with the boost pump on. Starting has been much better, sometimes a couple of pumps of the throttle are required to keep the engine going after it fires, but that's OK as at least it fires! I never had any problems with the pipes cracking in 15 years.

After a few years I moved back to the old country and had to deal with much longer damp and occasionally cold winters. Even with the primer I found starting was much more reliable if I stuck an old hair drier in the oil door for 5 or 10 minutes during the pre-flight.

My view is it depends where you are based and where you intend to fly. Somewhere not too cold then pumping the throttle is probably OK, and you don't need to add any additional parts. Cold and/or damp places probably need a primer and/or some pre-heat.
 
Last edited:
Saville said:
Ok well I gave this a try yesterday. Didn't work.

The engine was cold (i.e. hadn't been started).

Temps maybe at 45 degrees.

Full mixture

Cracked the throttle.

Master on.

Started cranking.

Went from cracked to full throttle to half throttle as fast as I could. Nothing.

Waited 3-4 props (i.e. engine still turning.)

Tried sequence again - nothing

waited 3-4.

Tried sequence again. Nothing.

Now the thing to remember is that if you prime the engine the bad way (i.e. engine not turning) - 3 pumps and it starts right up. Every time.

I just must not be doing something right. I really want to figure this out. Not sure what to try next.
Click to expand...

Try as you have been doing but with the throttle CLOSED and not cracked open. The richest mixture is with the throttle closed. As soon as it starts, open the throttle to 1000 RPM.

My O-320 start sequence:
1. Master on
2. Fuel selector on fullest tank
3. Mixture rich
4. Throttle closed
5. Boost pump on until pressure stabilizes then turn pump off
6. Turn key to start
7. Set throttle RPM to 1000
 
Sorry if already asked/suggested/answered/etc. How old is the carb or time since OH? Accel pumps do go bad and can be intermittent on their way out. Something I’d strongly consider.
 
The idea is to provide a rich mixture. Yes, you want the fuel swept up into the chamber and that takes airflow, but once that is up into the plugs, the throttle blade needs to be closed. To leave it half open is in essence the “clear a flooded engine” procedure…. It’s counterproductive.
 
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