Priming a Piper Warrior in Cold Weather below 40 degeess

CPARMERNC

Does anyone have suggestions on how many primes to give a 1976 Piper Warrior in cold weather?

Starting Procedures

Scott Sherer

I have an electric pump primer in my Arrow. I do 6 - 7 seconds when very cold, 15 to 25 degrees F outside. 4 -5 seconds between 25 to 35 degrees F and 3 - 4 about 35 seconds. When it starts and it's rough I'll give it another second or two. I'm thinking that each second of electric priming would be about one push on your manual pump.

empannin

Scott, do you have the alternate prime with the fuel prime solenoid? I do exactly as you for this for the TSIO-360.

n36601

CPAR:

When starting my -161, below 40° F, I will use 4-5 strokes on the primer. I don't count the strokes that are needed to reach the point where I feel the pressure of the primer actually doing something. Then, I let it vaporize for about 15 seconds before attempting to start. Of course, FULL RICH and throttle only slightly forward.

If you're having difficulty, make sure your primer lines and cylinder orifices are clear. They are easily plugged up with carbon. When that happens, the cylinder does not get primed.

VFRs,

jacobsja

From the take it for what its worth category, I was in a club that had a PA-28 about that age with the O-360. Rather than use the prime pump, the automotive style was used. Also, we let the spark plugs warm prior to introduction of fuel.

Procedure was, ZERO fuel, mags ON, and crank 8 blades worth of revolution. After stopping the crank, fuel pump On, mixture full rich, apply two quick pumps of the throttle from idle, to WOT and back. Then start as normal. Engine reliably started each time without using the prime plunger. Only time this process did not work was when the oil was too cold and the engine needed a preheat.

planewrench

CP, start with the 4-5 as noted above. Of course, varies with temp and or preheating. Would not recommend throttle pump. You want the fuel at the intake port, not vaping in the airbox and lower sump. Save that for emergencies. Have already seen like 3 starting fires on the web this year, totaled the planes. Carl

griff390

https://piperowner.org/talk/discussion/156767/priming-a-piper-warrior-in-cold-weather-below-40-degeess

Cparmernc;

There's some good advice above.

I've owned my '78 Warrior for 25 yrs. in the Chicago area, so my plane and I have seen weather extremes. I'll share my procedures.

Cold engine:

Master on. Mixture rich. Aux fuel pump on, wait until you see fuel pressure rise. Pull the primer out slowly allowing it to fill. Push it in briskly, which helps atomize the fuel. I use 4 shots of primer when the engine is cold. Crack the throttle, then crank the engine.

Warm/hot engine:

Master on. Mixture rich. Aux fuel pump on. Throttle closed (not cracked). Crank engine.

A word of caution: The carburetors on our engines are updraft, and require airflow to draw the fuel into the engine, so if you're going to pump the throttle, ensure the engine is cranking.

The number of shots of primer can depend on your engine, primer, primer lines and nozzles. Lines can kink or leak, and nozzles can get clogged up over time. I'd start with 4 pumps when cold, and adjust +/- when you find out what your engine likes.

planewrench

Engine fire on start. OOOPs

carl

griff390

Jacobsja;

I have to ask:

Did the flying club ever explain their "automotive style" of engine start rather than the "airplane style" (Lycoming) procedure?

I've never started a street or race engine using their method. Second, as hard as I tried, I couldn't see any advantage to dry cranking the engine, stopping it, and then racking the throttle. That method causes fuel to pour out and puddle up below the carb. It's a textbook recipe for an engine fire. The pics Carl posted are proof.

I don't understand why the flying club was reluctant to use primers. They were put there for a reason.

I'm also genuinely interested in hearing why they chose a non-aircraft starting method that has devestating risks and no advantages (in my opinion).

PS - I'm very happy you never had an engine fire!

empannin

Jim,

I think some of this comes from a confusion on how the systems work. Obviously the primer was the much safer route but they convinced themselves otherwise and picked the worst case approach...

The TSIO-360 alternate prime is effective as it has spray jets for the intake runners but it also has a big liability as there is a solenoid that can shut down all fuel to the engine (aside from prime). There is a SB to take out the solenoid and then it is more a traditional prime via the injectors. (Should be a SB to convert the unused primer spray to fogging oil spray jets for use during shutdown...)

I had this failure mode happen on a rental Seneca where the prime button was stuck active. Started fine and ran well at idle and a bit above... If you did not hear it or see it you would flood the intake with fuel (and hope the drains are working vs hydrolocking the cylinders...) During pre-flight and before start it is important to listen to what is running...

griff390

Eric;

Excellent response as usual.

I'm a little confused because you referenced the TSIO-360 (6 cyl Continental), whereas Jacobsja mentioned an O-360 (4 cyl Lycoming). I don't know a ton about the TSIO-360's, but I believe they use different primer systems.

Going back to Jacob's post, regardless of carb or injected version, I don't see the advantage of dry cranking with fuel off. That completely puzzles me. He mentioned the procedure was to then stop cranking the engine and run the throttle full travel 2 times before cranking again.

For those who aren't familiar: Most of our carbureted aircraft engines use what is known as an updraft carburetor. Updraft carburetors are typically mounted below the engine and require airflow to draw fuel upwards into the engine. Airflow through the carb requires the engine to be turning (either running or by the starter).

Every time the throttle is advanced, the accelerator pump squirts fuel into the carburetor venturi. Even if there is no airflow (zero RPM), fuel is dispensed, but instead of being drawn into the engine, that fuel (obeying gravity) runs down and out the throat of the carb creating a fuel puddle beneath it. Any spark or backfire results in the pics Carl posted.

I made a presumption from Jacob's post referencing the O-360 that the engine was not fuel injected. If it was, then dry cranking becomes even more questionable.

Eric: I'm more curious than anything else, and agree with you 100% that they chose the worst case approach.

Yes, I realize we've diverted from the OP's question and gone down a rabbit hole. 😆

jacobsja

Doc, correct. Carburetor.

Toward the throttle pumping, am not clear on what inspired the deviation from using the prime plunger as I do not recall any concerns with the plunger's operation. The club also had a carburetor Cessna and they used it's prime plunger. The O-360 Piper is still flying under different ownership, but do not know whether the new owners went back to plunger use.

Regarding automotive use of starting a carburetor engine by pumping the throttle, I actually have experienced this in cool to cold weather. Both were carburetor V8s by US manufacturers and popular street rides for their time. One was a manual choke where the throttle pumping actually had to occur while cranking: no pumping while cranking, no start. The second was with an automatic choke where the pumping both introduced a squirt of fuel, and set the choke: no pump before crank, no start.

Regarding cranking prior to introduction of fuel in cool to cold weather, reminder is that the club did not use preheat (unless the oil was so cold that it would not allow the engine to turn). From what I recall of the theory, it was to warm the plugs to minimize any chance of frost/ice formation on the plugs and maximize the opportunity to ignite the fuel (once introduced). So the dry crank occurred with the fuel pump off and mixture at cut-off. This procedure was done in both the Cessna and Piper. Tried to find some reference material on this and nothing is readily appearing in the search engines. Do not see where this method has value when using preheat.

And, FWIW, this thread started down the rabbit hole when responses for injected engines were provided for the carburetor engine. Just say-in 😋

empannin

Jim,

I brought the TSIO-360 prime up as an example of how it is important to understand how the priming system works and that some are more complicated than others. ;)

Eric

griff390

Jacobsja;

Thank you for the clarification!

I cut my teeth on carburetors, so we're definitely on the same page. [Warning: another rabbit hole coming up] You're correct about the chokes. Automatic chokes had a bi-metallic spring that (when cold) held a cam against the throttle stop. When the driver pressed the gas pedal, the cam slid under the regular throttle idle stop and simultaneously set the choke and high idle.

Standard procedure when cold was 3 pumps on the gas pedal to get fuel into the manifold before cranking. Once the engine was warm, another press on the gas pedal disengaged the choke plate and the high idle simultaneously, resuming normal operations. It was a rather ingenious system when it worked. Ahh, good memories! [Exit rabbit hole].

Dry cranking to put a little heat in the plugs makes sense, but I have to admit that's the 1st time I've ever heard of it (I learned something new!). Our flying club simply required an external pre-heat any time the temp was below 32F.

My engine has a Tannis heater that I leave plugged in all winter. It ensures that the oil and plugs are always warm.

Thanks for the response!

Happy Holidays!