Hot start problem

[John C. Noone]

Hey Guys,
I have been having some problems getting restarted
when stopping for fuel or whatever and want to start back up.
I have even waited around for 1/2 hour and still have run into
problems. I have to go to mixture off and half throttle and then
alot of cranking to get her started. Can this be avoided and can
anyone give me any helpful hints on a better procedure for
restart as I do not like alot of starter cranking-it is very hard on the starter motor.
Thanks so much
John

[hharney]

I HAVE A 1968 337C. I DON'T KNOW IF THIS IS THE BOOK METHOD BUT FOR HOT STARTS I NORMALLY PULL MIXTURES TO IDLE CUT OFF, THROTTLES FULL FIREWALL, AND RUN HI BOOST PUMP FOR ABOUT 5 SECONDS. PUMPS OFF AND ENGAGE STARTER AS SOON AS IT FIRES BRING THE THROTTLE BACK AS YOU ADD MIXTURE. IT'S A LITTLE TRICKY WITH THE LEVERS BUT WORKS EVERY TIME.

Hi John,

If I've got this right the problem is that the fuel lines get hot and the fuel vaporizes in the lines. This makes it hard to get restarted. By waiting the 1/2 hour, the fuel lines cool down and thus returns the fuel in the lines back into its normal form. Regardles off whether or not i've got this theory correct (please chime in anyone), here is the recommended solution...and one that I have been using for years.

1. pull the mixture back in cut off position
2. push the throttle lever full foward (prop is probably already forward but has nothing to do with this).
3. turn on your electric fuel pump for about 15 to 20 seconds or more (longer cannot hurt)
4. when ready to restart the engine, pull the throttle back to normal starting position.
5. start cranking and slowly advance the mixture control from full off to full on while cranking.
6. the end should start right up.

What happens here is that fresh cool fuel is pumped through the lines and cools off the hot lines and replaces the fuel vapor with cool fuel. Naturally, with the mixtures closed, the fuel simply recirculates through the system creating an endless loop.

Please let me know how this works for you.

best of luck,

Chris

[GMAs]

You haven't said much about the shape of the engines... and mags... spark plugs etc...and times on these items... they will make a differance...

As to fuel... shuting off the mix.. idle cutoff... is not what you want to do... sorry...

as it is the spider assembly on top that may have the fuel boiled out of it... and full of just "air"...

By holding off the mix control.. to cut off... you are not doing anything except circulating the fuel in the pump kinda thing... as no fuel is going to the rice valve on the throttle or the spider/injector lines/injectors...

instead may I suggest that you attend the meeting in May at LV and we will go over exactly how to start the engine... but, till then go from full rich to lean... i.e mixture control full forward... throttle 1/2 inch forward.. boost for a count of 5... then idle cut off...on the mix control.. boost pump off... and throttle 1 inch forward... count to 5 slowly... and crank... once the engine starts mixture full forward...

don't worry about the excess fuel.. as it will go out the overflow vents on the bottom of the cyc heads... make sure the line is clean though.. else you will hydrolic lock the cyc and that is damaging... those lines should be checked at annual for being open.. but, sometimes a little bug can block one up thinking its a new home... kinda thing... so a good way to check is to boost and then get out of the plane and go look for the fuel on the ground... ... again come to the meeting in may.. see other thread.. and we will show you how to do it.. on the ramp... along with the others... who are interested... that and a lot more...

Hope this helps.. G.M> GMAs

[Bob Cook]

Chris

It is my understanding there is a fuel return line at the Injector fuel control unit. By running the pump(s) with mixture closed it does circulate the fuel to the control unit and back to the tank.

This action can eliminate any air and hot fuel in the lines over top of the engine. I understand this is regular practice for the P versions and comes from a well qualified source. It has worked for me in the pass.

Recommended time is not less than two minutes and not more than four depending on temp and length of time on the ground.

The lines on my AC are insulated (that run over top of the engine). I think this was standard on later version.

Since the fuel lines from the spider to the injectors are rather small and contain little fuel, normal priming of the engine clears these rather quickly.

I double check this when I get back to my notes and manuals.

bob

[GMAs]

I have removed this message and sent it to Gmas to ask him to edit it. I hope he will repost it with technical content only.

Kevin

[GMAs]

I see you removed my message... and started censorship.. fine... I told you what would happen if it did start... good luck to you all... I'm out of here.. look for the new board to start... thanks Bye.. G.M> GMAs..

[FRED-E]

John
Could you tell us the year and model of your A/C, there are so many different fuel systems. Mine is a 1967 337B and there no return line from the spider the the tank, so Bobs method wouldn,t work on my A/C. I am sure someone on this site has the same A/C as yours and can tell how they HOT START theirs.
Fred N358

[John C. Noone]

Hey guys,

Thanks so much for all of the info. I have a 1964 336.
It is very nice to have you guys to refer to--I would love
to make it to LV..might be a little tough for me as I am in
NJ.....but hope to meet with you guys soon...Im sure I
will learn alot as I am a new skymaster owner and hope to
own these type birds for many years to come.
Thanks again
John
PS Ill keep you posted on what works for my plane.

[davidh]

Excerpt from TCM IO-360 Seris Operators Manual:

The operator can take certain steps to cope with problems associated with hot weather/ hot engine starting. The primary objective should be that of permitting the system to cool. Low power settings during the landing approach will allow some cooling prior to the next start attempt. Ground operation tends to heat up the engine, therefore, minimizing this will be beneficial. Cowl flaps should be opened fully while taxiing. The aircraft should be parked so as to face into the wind to take advantage of the cooling effect. Restarting attempts will be the most difficult during the 30 minutes to one hour after shutdown. Following that interval, the fuel vapor will be less pronounced and normally will present less of a restart problem. The starting procedure for a hot engine is the same as the normal starting procedure except that the throttle should be opened more while cranking.

If the above procedure does not effect a start, proceed as follows:

a. Ignition switch off.
b. Throttle open
c. Mixture Idle Cut-Off
d. Fuel pump on high 15 seconds
e. Normal start procedure

This usually works on my 336. If it's a particurly hot day, I'll leave the boost pumps on "low' during cranking.

I knew that I had read something before on this topic that had actually worked for me, and I got it at OSH last year from the TCM booth. It's an article that was reprinted with permission by the National Pilots Association.

The title of the publication by TCM is "Tips on Engine Care", Form X30548, Copyright 2000 Teledyne Technologies Incorporated, 00 TP/OPSTIPS/CAL 10K 07/00. Pages 5-9. (Uh oh, I don't do intellectual property law, but I think we're covered now, credit has been given, where credit is due!) None of this is my material, it's all TCM, thus there is no pride in authorship. If it's wrong, that's fine. I'm just passing along info I received from TCM.

I'll skip through the majority of the beginning of the article and get to what they say about how to fix a typical fuel-injected "hot" engine. I'll be quoting quite a bit here, so forgive the long-winded diatribe. Again, it's all TCM. You have to read all of this to get to the real answer. . . sorry.

Assuming the engine has been shut down for approximately 20 minutes and the ambient temp is 90 degrees F, the STANDARD procedure for a ROUTINE engine start "would consist of:
1. Mixture control -- full rich.
2. Throttle -- "cracked" or slightly open.
3. Magneto switches - on (if separate from starter switch)
4. Starter engage."

"Usually a small amount of liquid fuel will remain in the injection lines leading to the nozzles. As the engine begins cranking, this retained fuel is injected into the intake valve ports and drawn into the cylinders. Upon ignition, the fuel ignites and the engine bursts into life; then, just as suddenly as it started, it dies. A false start and the prima facie indication that a 'hot start' situation exists."

"Since the fuel lines inside the cowling are full of vapor rather than liquid fuel, the engine driven pump will not pump or 'remove' the vaporized fuel in sufficient quantity to support combustion. Therefore, the engine's refusal t continue running after the initial start up is simply due to fuel starvation."

. . . .

"There has to be a better way -- and here it is, in three easy steps:

1. Mixture control -- full lean or cut-off.
2. Throttle -- full open.
3. Electric auxiliary fuel pump -- on high."

"Relax for approximately twenty seconds and while you are waiting, here is how the solution is working for you. " (apparently, this author was never in my plane sitting on the ramp it hot temps, it's not too easy to 'just relax for 20 seconds ed.)

"The electric fuel pump is taking liquid fuel from the tank selected and pumping it through the heat-soaked lines under the cowling. In its cut-off position, the mixture control prevents this fuel from reaching the cylinders. This is exactly what is needed at this moment: Now the fuel takes the alternate path and returns to the tank or header from which it came."

"During this process, the continual flow of fuel will purge the lines forward of the firewall of all vapors. Also this continued flow will reduce the wall temperature of the lines through which it passes. After approximately twenty seconds the fuel lines will have cooled sufficiently to retain the fuel in a liquid state after the pump is turned off."

"After twenty seconds, turn off the electric pump and make a normal start as follows:

1. Mixture control full rich.
2. Throttle cracked partially open.
3. Starter engage."

. . . .

"Just remember:

1. The mixture control must be full lean -- to prevent flooding and to force the circulating fuel to flow back through the return system.
2. The throttle must be full open -- because some single engine fuel injected aircraft incorporate switches in their throttle linkage to prevent the auxiliary pump from operating in the high position when the throttle is retarded.
3. The auxiliary pump must operate in the high position for approximately twenty seconds -- to provide sufficient time to adequately cool the fuel lines and components inside the cowling."

So there you have it folks. My fingers are tired from typing. That's the best info I have, and it worked for me on my 337A.

Keven
________
Ipad Accessories

[kevin]

Interesting. I'm headed to Palm Springs later this week for AOPA Expo, I'm sure I'll get a chance to try Keven (TCM'S) technique. FWIW, what I have been using successfully on both my '65 337 and my '73 P337 is (in "hot start" conditions, usually after trying to start the engine with a very small amount of prime and normal procedure, which fails):

1.) Mixture full rich, throttle full forward.
2.) Run boost pump on Hi until normal fuel pressure value is reached, about five to ten seconds. (Small amount of fuel will dump on ground through overflow line.)
3.) Immediately, mixture idle cutoff, throttle cracked
4.) Crank engine
5.) When engine fires, mixture full rich, fuel boost pump on and off intermittantly as needed until engine smooths.

This works all the time, very reliably, with no having to wait for anything to cool. But I am intrigued by the TCM procedure provided by Kevin, as it seems more "peaceful".

Kevin