Starting engine without primer

[JohnW]

Rodg; I'd go so far as to say that having "regular old tube to IP brass fittings" rather than [MODIFIED regular old tube to IP brass] pirimer nozzles is ONE POSSIBLE REASON for a "loosey-goosey" primer. The absolute number one reason is usually ROCK HARD o-rings (or...some of the older style primers -like Lunkenheimers- didn't even USE o-rings). This usually means that to begin with, the out stroke doesn't "suck in" any fuel into the primer, so you're just pumping AIR back and forth (or not, even). Not too unusual is another "malfuction" that can occur (and has probably resulted in more unnecessary primer replacements that COULD have just been fixed with some simple benchtop maintenance) is this...MOST primers (the Kohlers that Piper used, particularly) have two itsy bitsy ball bearings inside them that act as "check valves" when the primer is stroked. When you "pull our" the plunger you (by design) "suck shut" the ball-bearing check valve in the discharge line of the primer. When you "push it back in", you shove that one open (with the fuel you are pushing) and close off the one in the inlet line of the primer. A quick look at the primer in place will reveal a brass SCREW (plug) on the primer body directly opposite each of "cast in" primer line "bosses". This open/closing action clearly provides "one-way directionality" to the flow through this "pump" (the primer), and just as clearly, you can see the effect of one or the other -or both- not seating. Unless there is some obvious "damage" to a primer, troubleshooting usually goes "install new 50 cent o-rings and check; remove BOTH lines to the primer, clamp your thumb and forefinger over the tune connections and operate the primer and see if you can make a hickey on one, and blow the other one off the fitting. This pretty much is all there is to finding a problem with most primers. If you have the "no o-ring" type (my -15 still has it's original Lunkenheimer; s/n 290) you need to get to Lowe's and buy a #2 pack of silicone faucet packing, pick all the dried up jute out from around the plunger, and repack so as to stop the primer from sucking air around the assembly nut (around the plunger). This is usually first "noticed" as a problem area by either "a primer that stays wet with fuel all the time", or a "sewing machine engine" that idles rougher'n a cob, even though a really good engine guy has ripped his hair out trying to get it to "idle right". I've had people tell me that the Lycoming 65 "just idles that way, and that is part of why it is JUNK!" (I disagree vehemently with both those propositions!). One you have "eliminated" the primer itself as the Bad-Boy, there isn't too much more that CAN BE causing your "loosey-goosey" primer, so finding what IS the issue gets easier. Mostly, you will find an air leak into the inlet tube (gascolator to primer) or somewhere else, or a PLUGGED inlet line. "Crud" in the lines (and trapped by the check valves in the primer) can "be a problem for YEARS", especially in the LOVELY starting O-145-B2 engines.

All said, lightplane primers should all work "just about the same"...get 'em filled up good (first pull when you start means everything is JUST RIGHT), and then the harder (quicker) you push them in, the firmer they should feel. Good and hard means "better atomization" at the business end. ANd when everything else is all said...you still have to learn EACH AND EVERY ENGINE before you know just what to do to get it to fire on the first or second blade (what you gots ta do to KEEP IT RUNNING when it first fires is a whole 'nother discussion -and a whole 'nother bunch of variables.

My Colt "Daily Driver" will virtually NEVER start without at least ONE shot of primer, "cold"... even in 95-100 degrees F. It's more like four or five when its 10 degrees F or less. But once it's "hot", and for 20-30 minutes after shutdown (in the SUmmer, 5-10 minutes in the dead of WInter, you better not stroke that primer... or you WILL be outside in a short while, flippin' the prop backwards!

[pacerman]

Interesting. What serial number is your 17?

The only thing Piper seemed to be consistent on was being inconsistent.

Would love to see some pictures of your PA-17 and it's panel.

Sorry, for the late reply. It's been wet here and CA and I didn't go to the hangar last weekend. I checked yesterday and there is no sign that there was ever a primer in my plane. Serial is 17-13. I'm sure it has the original panel. There are no extra holes and it's very basic with no extra controls or instruments. Joe

[BrettL]

Joe,

I'd love to see that. Very unsual for an original panel not to have a bunch of extra holes cut in it. Mine is 17-119, and it has a bunch of extra holes in what I'm 99% sure is the original panel. People just can't seem to resist putting a turn and bank in here, a clock in there, etc. Seems like in the 60s people would put 100 lbs of extra instruments in what started as a VFR panel without batting an eye.

My 17-119 was completed on July 6, 1948. Final approval for the Type Certificate wasn't until August 26, and I bet yours was completed much earlier than mine. Being completed that early under a tentative type approval, I wouldn't necessarily be surprised if it was delivered without a primer. I'd still be interested to see if there's any sign of the steel reinforcing tab behind the panel though. That would tell a better story than basing the conclusion on the panel alone. Good replacement instrument panel blanks have been and continue to be available for the Vagabonds. They would be difficult to positively differentiate from an original panel.

Brett

[justin]

i was going to delete my primer to save weight

Joe,

I'd love to see that. Very unsual for an original panel not to have a bunch of extra holes cut in it. Mine is 17-119, and it has a bunch of extra holes in what I'm 99% sure is the original panel. People just can't seem to resist putting a turn and bank in here, a clock in there, etc. Seems like in the 60s people would put 100 lbs of extra instruments in what started as a VFR panel without batting an eye.

My 17-119 was completed on July 6, 1948. Final approval for the Type Certificate wasn't until August 26, and I bet yours was completed much earlier than mine. Being completed that early under a tentative type approval, I wouldn't necessarily be surprised if it was delivered without a primer. I'd still be interested to see if there's any sign of the steel reinforcing tab behind the panel though. That would tell a better story than basing the conclusion on the panel alone. Good replacement instrument panel blanks have been and continue to be available for the Vagabonds. They would be difficult to positively differentiate from an original panel.

Brett

[this-is-steve]

I have found on any engine whether equiped with a primer or not that you can really help cold weather starting by pulling the engine through at least one blade for every cylinder. I pull my 0-320 through 4 blades every time. Then prime about 3 shots and it will start on the second blade just about every time. And I usually don't prime above 50F. IT really doesn't do any good to pump the throttle until the engine is turning. If you pump it before rotation you are taking a big risk of an intake fire. (updraft carb)

All of that being said, I agree that you should have a primer. It was original equipment. Also, for safety sake, if you have a weak battery, replace it. If you crank slow then, put new cables on.

Steve

[joewcasey]

Don't know if this will help, but this is the technique I used in an R-1340 powered Agcat:

Mags off, starter on, pump four or five full throttle shots while the engine was turning over and mags on. Worked like a champ everytime. Provides suction so the raw fuel has a place to go, and if it's too rich, while you're pumping air in and out of the cylinders, it should find it's proper lean setting on its own in a few blades.

The Agcat's book wanted 10-12 shots of primer for start, and let me tell you, sitting there waiting for the primer to fill and then spray it in 10-12 times took FOREVER. This was a much more efficient and incredibly reliable way to start that engine. Maybe it would work in this case, provided you have a seperate starter and mag switch like my old PA22 did.

[krwill]

Pulling up an old one here, but seems to be the best place to ask. Is there and difference in a O-290 and O-320 primer system? Mine (O-320) has none and just want to make sure that I can use the system off a O-290 before getting it.

Thanks!
Ken

[Tailwind_Fan]

Humm, I’ve not got a primer in my Tri Pacer, nor the Cherokee that I’ve been taking lessons in. I’ve had zero problems starting, I just crank and pump the throttle 3-5 times and it fires right up....

-Alana

[Steve Pierce]

Pulling up an old one here, but seems to be the best place to ask. Is there and difference in a O-290 and O-320 primer system? Mine (O-320) has none and just want to make sure that I can use the system off a O-290 before getting it.

Thanks!
Ken

I would be willing to bet but ceck the parts manual and drawings.

[smcnutt]

Humm, I’ve not got a primer in my Tri Pacer, nor the Cherokee that I’ve been taking lessons in. I’ve had zero problems starting, I just crank and pump the throttle 3-5 times and it fires right up....

-Alana

We have a primer in our 0-290D2 and I always use it when starting. 3 pumps if cold and either 1 or none if warm and it fires up after 1-2 blades.

My brother on the other hand almost never uses the primer and pumps the throttle instead. It might take him an extra blade or two to start. I've tried to get him to stop but to no avail. I think it's just out of laziness or something. I tried to explain that the primer goes straight into the cylinders where the carb hangs under the engine and so the fuel has to be sucked up into them by a cylinder that's barely moving -comparatively to actual running conditions. He's never had an issue arise from doing it his way -so far.

I just think that if you have a working primer you should use it. I've not heard of a catastrophic problem being created by priming but I have from people pumping the throttle.