Hot start woes...

I am experiencing major difficulty starting my PA18, most recently yesterday at Ely during the Fall Colors Tour. I am going to have a great engine shop look it over tomorrow, but would like any wisdom you might offer.

Here is a scenario that has happened beginning about a month ago (really no problems before that). When I pull the aircraft out of the hangar for the first flight I typically pull the throttle back, mixture full rich, pull and push the primer 3-4 full shots, lock in the primer, turn on the magnetos and ignition and within 4-6 turns of the blades the engine fires right up. No problem. (My starter switch is one of those keyed type with which the first click is one mag, the next is the other, the next is both, the next engages the starter). I burn 100LL. The engine runs up nicely, both right and left mags have only a small drop (50-100 rpm), the carb heat check pulls down rpm (even as much as 400 rpm), full power is applied smoothly and the engine runs great.

Upon landing I typically lean the mixture while taxiing to parking, and upon reaching the parking spot I pull the mixture to full lean, the engine promptly shuts down, I turn off the mags and the electrical system, get out of the plane.

If I get back in the plane shortly thereafter (30-45 minutes) I do the hot start procedure I have always used: throttle cracked 1/2 inch, mixture full rich, NO PRIMER, engage the starter and the prop turns over, and over, and over, and over....no start. So I figure it must be flooded, so I pull mixture to full lean, throttle full forward and crank it several times. Stop cranking, pull throttle back to 1/2 inch open, mixture full rich, crank it over and over (once in awhile it fires, but doesn't start). I repeated this ad nauseum until good ole Pat Angelo comes to my rescue and points out that it may be flooded and he shows me how to clear a flooded engine by putting mixture to full lean, throttle full forward, mags off (duh), pull the prop backwards 10-20 times (I don't understand why this should help, but I've been told this helps by others, too) and sure enough fuel runs out onto the pavement for the first few turns. Then tried the mixture full lean, throttle full forward, crank a number of times, then mixture full rich, throttle cracked and....crank and crank and crank. No start. We tried this until the battery was wearing down and we were tired of turning the prop backwards.

I should also mention that Pat slowly turned the prop to listen for the clicking of the impulse coupler, and we heard it click nicely.

I asked Pat to leave me there, go on to Anderson's (which he reluctantly did), and it was my plan to let the plane sit in the cool air and try to start it when it was cooled down. Hooked a jumper battery to the aircraft about an hour later, tried the start using full rich, cracked throttle, no prime and it fired right up! I called Pat to tell him the good news, I battened things up (wheels were chocked) and flew back home.

I don't understand this at all. It seems as though it is flooded, but I don't understand how that could be after those attempts to clear a flooded engine. Anyone have suggestions/explanations?

I want this thing to start up easily to fly down to East TN in a couple of weeks and it is making me real nervous. Thanks.

Randy

Oh, yeah, I flew the airplane today, it started right up cold, but had a devil of a time getting it to start warm. grrrrrrr.

Randy

Check your plug gap. Harder to jump the gap when hot. Also, how many hours on your magnetos and what brand? At about 6-800 hours Slicks get hard to start. I reset the "E" gap (internal timing) at 500 hours to compensate for point wear.

Randy,, my warm start is either to jump in and crank it, push throttle forward about half and then back all the way.. while cranking... or do this before cranking.. Dosent seem to matter, just which hand hits either the throttle or key first.. Mine is keyed like yours.

If it starts to go low on rpm,, I hit the throttle just a little,, not much at all.

Randy,

I like your procedure, EXCEPT when hot, I crank and after one blade or so, I give the throttle two VERY quick shots all the way to the forward stop, back to idle, back open and back to 1/2 inch open.

My engine and a bunch of O-320's I've operated seem to start just fine that way, but just cranking when hot doesn't seem to work as well.

It sounds to me like you may have some small problem, like Steve says--plug gaps, or??

But, I'll bet if you blip that throttle a couple times while cranking, it'll start.

Maybe.

MTV

Thanks, Mike and SteveE. I'll give those a try.

Steve Pierce, why are you thinking magnetos? I need to look at the logbooks tomorrow and see how old they are and what brand. How do you check the mags?

Randy

Randy,

Remember, when you shut the plane down you robbed it of all its gas by pulling the mixture. You have to give it some gas to start on. Unless gas is dripping out of the carb, its probably not flooded (yes, I have done this, and yes it was at night, and yes when I say the glow of the flames on the ramp I kept cranking until it sucked out the fire).

I always have to give it a couple shots of throttle to get it going hot or cold - for the record, I have not used the primer in my plane since 2001.

sj

SJ, do you just pump the throttle to 'prime' for cold starts? I thought the advantage of the primer is to deliver the fuel directly into the cylinders, not the carb...

Randy

Yup,

Two or three quick full shots immediately before hitting the starter - not a few shots and then wait. Right or wrong, this has always worked way better for me than the primer.

sj

hot starts

I agree with Steve,s When in doubt flood it,,,, at least you then know its flooded and as stated I also never use the primer except on round engines or in cold weather. I know others will say it will catch fire using the accelerator pump in the carb if it back fires and they are right it will and I have but never on a carburated Lyc. only on injected Continentals and if it does just keep cranking it will suck it out or blow it out when it starts. Randy I think you have a weak spark caused by the mags, ignition wires or plugs... If you have Slick mags they never start quite as good and Bendix but it should start every time if you hit on the right combo of fuel/air.

Try giving it 2-3 full jabs of throttle next time you cold start either right before you start cranking it or during and maybe 1 0r 2 when its hot then slowly advance the throttle forward while your cranking till it finds what it likes and starts firing, start it there then bring the throttle back to idle.

Dave

hot starts

This what I was taught to do: Cold Starts--crack the throttle about one half inch. Fuel on , full rich, mags off, 3 shots of prime, turn over by hand six blades, then mags on and start. Shut down--full rich then left hand turn off both mags and right hand full throttle. Hot start crack throttle and turn over with mags on. But the skytec inline starter has been a big improvement.

When my old SF4 mag coils were failing on my PA12, it would start cold but not hot.

I always give them three shots with the throttle, while the engine is cranking. Seems to me carbureted engines are not nearly as finicky as injected engines on hot start, so I just do the same, cold or hot.

On the hand start Continentals, I crack the throttle for a hot start, then it usually starts on the first blade. If it doesn't start, sometimes I simply try the cold start procedure. Maybe 45 minutes on a normal day is enough cool down time for a carbureted engine?

I have owned the AEIO360 for eight years now, and always expect it to not start on the hot start - so far it has never let me down, but it used to be quite scary. I now let a little fuel in there with the goose pump on, then do a normal hot start, and about nine blades later it is off to the races.

When I have had trouble with my c-90 I shut off fuel and mags full lean, full throttle turn back 12 blades. Mags on, fuel off, throttle cracked, mixture full lean, and prop, I found if I didn't leave the fuel off it would flood itself before I could reach the controls. mixture to full rich and a little throttle when it fires up, usually one or two blades then fuel on. Most of the time it was in front of a crowd of people . I just shut down with the mags now instead of leaning and don't seem to have a problem, that is with the small contintal and I know the Lycoming is a diffrent animal.

Hot starts

If you are using the hot start method you have always used and now it won't, I see no need to start changing your procedure. My vote goes for the mags. In the last five years, I've seen maybe six or seven doing just what yours is and it was mag issues. These were 0320's and one 0360 and all were fine cold but would not start hot until they cooled off. I did notice that the issue seemed worse in cold weather. Good luck, will be interesting to see what you find,Reid

Randy,, I was having trouble starting this last winter... aggravated by the cold.. it was the mags..

I agree that there has to be something that's changed if you used one procedure for a long time and suddenly it doesn't work.

That said, using the accelerator pump instead of the primer when hot seems to be a good procedure with every little Lycoming (not necessarily every ENGINE) that I've run.

I DO NOT blip the throttle UNLESS that prop is turning over with the starter, though--that's how to get fuel pooled in the airbox and a backfire. Granted, continued cranking SHOULD suck the fire back into the engine, but....why put yourself in a position where you have to worry about that?

When you start cranking the starter, THEN move the throttle briskly through it's full travel TWICE (okay, maybe three times if you're really enthused, but NO MORE) the accelerator pump sprays raw fuel into the throat of the carburetor. Since you're cranking the engine over, air is being drawn into the carb inlet, and that air goes into the cylinders.

If, on the other hand you blast the throttle a couple times, THEN start cranking, much of THAT fuel coming out of the accelerator pump winds up dropping down below the carb in the air box, and isn't helping things much. REmember, these are UPDRAFT carbs, so if you're not cranking, fuel, being heavier than air, will settle, not rise. You'll probably get the engine to start, but you're putting the plane at greater risk with this technique.

I still use primer when the engine is cold, to avoid the possibility of induction fires completely. But hot starts are always with a couple quick shots of the throttle to energize the accelerator pump.

And, I have seen an airplane burned down from careless use of the accelerator pump. That was a gorgeous Beech 17 :x

One final note, Timing is critical when you start using a lightweight starter, because almost ANY backfire can shear those tiny little starter drives. And, shear that starter drive, and you no longer have the ability to suck that fire back into the induction by cranking the engine over.... :x

MTV

I have never had any problems with Bendix magnetos but have seen this time and time again with Slicks. The magnetos of a set of points inside that open and close to allow the built up spark out. These points wear and over time, anywhere from 500-800 hrs, they change the internal timing of the magneto making the engine hard to start. There is tool that goes into a jig hole in the rotating magnet that allows you to properly set the internal timing (E gap).

Another thing to look at is the primer nozzles. I have seen them clog over time and not allow fuel through.I soak them in Hoppes #9 gun cleaning solvent for a few hours and they come out as good as new.

I have had transient airplanes fly here from the Metroplex for an ice cream at the Dairy Queen across the street. They try to start the engine an hour or so later and it won't. Look at the spark plugs and the gap is way bigger then the .022" maximum. They always say "well it started fine when I left." I set the gap where a .015" gauge will slip through and those airplanes make it 100 plus hours until the next annual inspection and plug removal.

Start with the simple stuff and try others technique.

Hot starts

Personally, I'm with MTV. I use the accelerator pump almost altogether except in very cold weather, and I've been using the same light weight starter for 14 seasons without any trouble. When you find a system that works for you, stay with it. Reid

My 180 would not hot start and it was Slick mags. Replaced them and it worked great.

sj

Its your magnetos, fix them or replace them depending on the amount of time they have.
Doug

Little short on time right now so haven't read this whole thread. If someone has already mentioned this ---sorry !! Hand starting an 0-320 PA-18 for more than 20 years. Hot start procedure is to NEVER touch the mixture ---leave it in the cut off position--left mag hot----4th blade 99% of the time she fires up then qiuckly push mixture full rich. Works just like that on my electric start 0-320 PA-12 also.

Sounds like mags
Bill B

We'll find out soon. Larry Cassem is coming out to Randy's hangar in the morning. Then the left mag goes across the field to have Tim Hieb at Bolduc's work it over.
Darrel

two thoughts,
i agree mags,

specifically left mag (if pleads are wired right)

as mentioned above, also broken impulse spring left mag.....

cranking to fast?, does it start better hand propping?(worn impulse dogs & pegs)

pleads, cracked insulation under Plead nut(bendix)
noise filter on plead?
traces in mag switch( check this and above items with unhooked/hot plead adapter like used for timing, bendix)

also that little jumper on switch? if not installed you probably would notice kickback...not this...

ok maybe that was 10...

As Darrel mentioned, we are pulling the mags in the morning.

Question 1: why are Slick mags such a problem?

Question 2: Given that We are going to the trouble to pull the mags, how much more trouble would it be to replace with Bendix rather than fix (if they need fixing) the Slick mags?

Randy

As Darrel mentioned, we are pulling the mags in the morning.

Question 1: why are Slick mags such a problem?

Question 2: Given that We are going to the trouble to pull the mags, how much more trouble would it be to replace with Bendix rather than fix (if they need fixing) the Slick mags?

Randy

WindOnHisNose said:

As Darrel mentioned, we are pulling the mags in the morning.

Question 1: why are Slick mags such a problem?

Question 2: Given that We are going to the trouble to pull the mags, how much more trouble would it be to replace with Bendix rather than fix (if they need fixing) the Slick mags?

Randy

Click to expand...

1. track record.. rebuilt by a good shop they are fine then....

2. no more work but, see 1 above....

ps the left mag is the only one you start on...so...normally....

updates?

Very strange. My Scub is harder to start cold than hot. When it's hot, it will usually start with one spin of the prop! In cold weather (30-40 degrees) I have trouble getting it going, but after it's been running, it will crank right up.