Having to choke engine to start after warmup.

[dvd]

My atomic 4 engine seems to run well and starts right up when cold with full on choke. After it starts within approx. 20 seconds the engine begins to lope (like the choke is On) and I push the choke all the way back in and the engine smooths right out. If for some reason the engine dies or it is turned off after warmup I have to choke it to get it started again. It seems that it should start when warm without having to choke.

Also, I am still having the vibration problems but I've been told that they are not severe and I think I will just wait on that issue until the boat comes out of the water again so that the shaft and prop can be inspected.

Any Suggestions.

DVD

[jayw]

What you describe is almost exactly how my engine behaves. Unless the engine has been run hard for at least 20 minutes and I restart within 5 min after shutting down, I'll have to briefly use full choke.
I'm now in the habit of choking whenever I start without regard as to how "warm" it is and then slowly moving to no choke as soon as it fires up.

[rigspelt]

I found this in the old guest log:

Don Moyer comments: Because of the updraft design of the carburetor, Atomic 4s almost always require full choke to start easily - even when warm. In general, any time an engine starts a bit hard, but then runs fine after it starts, the problem is usually caused by the choke not closing completely. Every now and then we hear of an engine that requires no choke after it warms up, but it is far more common for an Atomic 4 to require full choke (if only for a second or two) to start quickly, even after it is warm.

[s/v Dearbhail]

rigs is right about the engine needing choke to start. I can't speak for everyone, but mine has always worked that way and there are several other posts throughout the forum about that.

After it's warm, choke it and it should fire right up.

[dvd]

thanks for the info. I thought maybe it needed a tune or a carb adjustment. I guess I can live with it. When the engine is warm I need to choke it for only a second or so just to get her started and she then runs fine.

dvd

[keithems]

you also can try no choke but pumping the throttle once or twice before hitting the starter

that works for mine....

[ndutton]

Keith,

Pumping the throttle shouldn't make a difference and I'm surprised you report it does. Unlike automotive carburetors of old our carbs do not have accelerator pumps.

[keithems]

dunno -- it does on mine

that's my story and i'm sticking to it -- and not complaining either

just like for some reason....maybe cuz the block is in good shape or because the raw water cooling here is fresh not salt --- anyhoo -- for some reason my a4 always runs cool -- even at 80% power -- meaning it's warm -- manifold is almost too hot to touch, but temp reading rarely is more than 120, unless run hard then shut down, then ig switch put on with no starter to get temp reading -- no plug fouling so far -- so again, i'm not complaining.

just a quirky engine, i guess, like her owner....

[just thinking of when i used to fly the piper navajo chieftain in commuter service on hot days....it had twin turbocharged lycoming 350 hp's -- and if u ever flooded them -- especially when hot -- good luck on getting them started!]

[JOHN COOKSON]

DVD
Your choke operation is normal. I guess you've checked the tightness of the motor mounts?
The throttle control lever is attached to the throttle butterfly only. I don't see how pumping it would have any effect on starting.

TRUE GRIT

[keithems]

dunno..but it do! it do!!

how's about a few of you all try it [warm engine] and let me know if it do?

[JOHN COOKSON]

Keithems
R\E apparent cool running:

Have you had the temp sending unit out in the last few years? I took mine out a few years ago and found:
The sending unit coated with lots of white mineral crud. I removed this with lime away and a tooth brush.
Lots of crud in the sending unit area. I reamed as much out as I could then put a nipple in place of the sending unit, attached a hose and clamped it, started the engine and reved it up, clamped the bypass hose, unclamped the hose on the nipple, and blew a lot of stuff out.

Also are the temp sending unit and gauge matched?

If you want to peruse this further we can do so in a new thread.

TRUE GRIT

[Dave Neptune]

If yur A-4 requires the choke to start when warm you have the idle set about right. One of the problems I have encountered constantly with peples A-4's is that the mechanics and most owners set the idle to rich so they do start easier both cold with the choke and warm without. My engine will literaly idle all day on the stock cold J8-J plugs and is quite hard to start without the choke when warm.
As Don has stated this is normal in an updraft carburator!!!!!!!!

Unsiezed A-4 42 years running original except one exhaust valve 26 years ago when unsiezed!

Dave Neptune

[keithems]

i dunno

mine's just quirky, i guess

as u know, it was just r, r, and r'ed

was that way before

and it's running great now, so i'm not gonna mess with it

and as the chief [and only] mechanic on this boat, i set the carb as lean as i could--any leaner and i get hesitation upon acceleration or an unreliable idle

seeing as i'm using about 1 gal / hr now at 80% power, i don't think i'm running too rich.

btw -- i am curious if pumping works for other a4's -- and i'm gonna try starting warm without pumping and see what that does..

also - don't agree that the pumping does nothing -- may not be an accelerator pump, but there are jets that uncover as you accelerate -- thus the pumping may be a manual accelerator pump...pls don't jump on me; i'm no expert on this...

however, i do remember from my vw beetle and non-jet pro pilot days -- you never want to use choke if you can avoid it -- raw gas washes oil off the cylinder walls, etc. -- and in a hot gas a/c engine, pumping was s.o.p.--usually to avoid flooding -- on my vw, i actually disconnected the auto choke

[keithems]

Originally Posted by JOHN COOKSON

Keithems
R\E apparent cool running:

Have you had the temp sending unit out in the last few years? I took mine out a few years ago and found:
The sending unit coated with lots of white mineral crud. I removed this with lime away and a tooth brush.
Lots of crud in the sending unit area. I reamed as much out as I could then put a nipple in place of the sending unit, attached a hose and clamped it, started the engine and reved it up, clamped the bypass hose, unclamped the hose on the nipple, and blew a lot of stuff out.

Also are the temp sending unit and gauge matched?

If you want to peruse this further we can do so in a new thread.

TRUE GRIT

maybe--

actually right now i'm using the dave neptune method of temp control

your points may be right also. though my sender is new--not sure if it's matched

truly, my personal method of temperature reading is:

is water spitting out the exhaust? we're good to go...

and at least on my a4, the few times the intake hose crimped or the intake got weeds in it....as the motor heated up, the oil, grease, etc. resident on the outside began to smoke, and i quickly smelled it and shut down.

as a former jet pilot [b727] i learned that your nose is your best gauge --

think about it -- way up in front of the 7-2, you really can't hear the engines, and you can't see them, seeing as they're on the tail.

any smoke or fire will go back behind you, again out of sight

yes -- you have gauges, but by the time something happens there, it may well be too late. the earliest warning you have that something is happening is when that peculiar smell of coffee, puke, sweat, kerosene, plastic, airline food, whatever.....begins to change.

[Dave Neptune]

Pumping will indeed work if you do it properly. As you are cranking moving the throttle from off the stop and back to idle causes a big suction (vacuum) to build behind the butterfly when on the idle stop and when you advance the throttle this suction aids in "lifting" the fuel for an easier start. This also works on my engine, however I usually just hit the choke and then there are no issues of a prolonged starting sequence.

Kiethems your a RWC without a t'stat right?

Dave Neptune

[keithems]

thank you ... u took the words right out of my mouth

yes -- rwc, no thermo -- and i do think the fresh water here is a better cooling medium than salt water -- so maybe that makes her run a little cooler?

re. the choking....remember, as mentioned elsewhere, my choke has the famous keithems modification....meaning no choke lever in the cockpit -- only a bungee cord on the choke itself -- u want choke? free the bungee, once she starts and warms? go put the bungee on da hook...

since i don't really relish running up and down to do that, i use the pump method when warm

also -- i pump because it is a habit by now to never use choke if not necessary.

[edwardc]

Originally Posted by keithems

... as the chief [and only] mechanic on this boat, i set the carb as lean as i could--any leaner and i get hesitation upon acceleration or an unreliable idle ...

I had this situation too. But what I found when I installed a fuel/air ratio gauge was that I was indeed too rich. The solution was to advance the timing a little more. This cured the unreliable idle, eliminated the hesitation, and let me get the mix close to the ideal 14.7:1.

[ndutton]

Originally Posted by keithems

thank you ... u took the words right out of my mouth

Was this in response to Dave's comment?

Pumping will indeed work if you do it properly. As you are cranking moving the throttle from off the stop and back to idle causes a big suction . . . . .

I read the post sequence about 5 times before this reply and concluded it was. If so, wait a minute - you said

you also can try no choke but pumping the throttle once or twice before hitting the starter

that works for mine....

Before hitting the starter. No cranking, just throttle exercise. I wanted to be sure I hadn't missed something when I made the 'no accelerator pump' comment.

Speaking of comments, when Thatch joined me for our day of chasing the U.S.S. Iowa we broke off and sailed for a few hours in the afternoon. Reaching my preferred area for dousing the main I started the engine with no choke. Tom did a double-take and shot me a two word comment, "No choke??" I said no, I admit she's on the rich side.

[roadnsky]

Here's an older post from Don...

"There is no accelerator pump or other mechanism within the carburetor which has any capability to move fuel through the carburetor, no matter what you do with the choke. Therefore I have no clue why an engine would respond better to opening and closing the choke than simply by closing it and then opening it when the engine starts."

[keithems]

i pump the throttle, not the choke

maybe once or twice before i hit the starter, then once or twice while i hit it....

whatever works..and it usually does...

remember, my choke has the special, exclusive, hi-teck keithems mod on it; thus no pumping of choke

though, really, it does enhance safety, seeing as once it starts, you have to go down to the motor to set the bungee, and while doing, the old captain [me] insists you look everything over, esp. any fuel leaks, and of course, shut down immediately should there be any.

how many of you remember sitting in a dc-6, behind schedule, on a hot day, while the crew tried to start her up?

anyhoo....all i know right now is my a4 starts and runs like a charm...so i have bigger fish to fry --- like getting her to run off the main tank

which i think i did tonite -- drained the main to the bottom a few times thru the fuel level sender plate. just like jeff said to ....seems fine so far....

also found a place to take the 4 gal of drained fuel..

.but that will be another thread...