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frans(at)privatepilots.nl
Guest

Posted: Tue Mar 13, 2012 12:07 pm Post subject: Rotax 914 starting problems when hot

Hi everyone,



I guess I'm not the only one having this problem. The main problem here

is that I don't understand why it is happening.



If I arrive at an airfield in hot weather, I can restart either right

away, or after a considerable time. If I just refuel without having a

meal, I get into a time window where the engine has difficulties starting.



It is a vapour lock problem of some sort, but I don't know how this can

happen. Sure, the inside of the cowling is hot and residual heat from

the turbo is, without the large fan upfront turning, cooking the fuel.

But I thought that the 914 is supposed to be immune from the problem.



Up to the pressure regulator the fuel is recycling when I switch on the

electric fuel pump. Any vapour up to the pressure regulator is directed

back into the tank and being replaced by fresh and cold fuel.



The carb bowls might have been cooked empty, but then the floats will

have dropped and fresh fuel will pour in as soon as I switch on the

pumps. The fuel line between the pressur regulator is not recycled but

if it contains vapour then it will escape via the opened carb needle and

not raise the floats, so it will gently escape until being replaced by

liquid fuel, being driven there by the electric pumps.



So... why won't then darn thing just start?



Yesterday I was exactly experiencing this problem. After arriving at an

airport to go to the service center for the bi-annual pitot and static

systems test, and with the engine switched off for about ten minutes I

couldn't restart it. No matter how long I kept the fuel pumps running,

applied choke, (just in case the mixture was too lean) or was just

cranking with the throtthle wide open to vent the cylinders (in case it

was too rich), the engine would just crank without even a faint single hit.

So I abandoned the plan to taxi to the refueling station, and had a

lunch instead. Of course after that the engine started up right after

just a half turn of the prop...



So... why is this happening? I'm interested in solving this problem, but

primarily I want to know why this is happening because according to my

reasoning it shouldn't be happening in the first place. What am I

missing here?



Oh BTW, on the return home I got caught by non predicted early set in of

night fog, with a very rapidly dropping cloud base (never seen it

falling that fast). With my home base being the closest and most

promising airfield once I got forced down to 500 feet I advanced the

throttle to 100% (not 115%) and got over 155 knots IAS worth out of it

on my freshly calibrated ASI, which was quite an experience so low over

the ground. At my homefield I arrived less than 15 minutes later with

the local cloud base still at 1000 feet (as announced/predicted by ATC

half an hour earlier), but I was thankful nevertheless to have been able

to speed out of that threathening situation that fast. If it weren't for

the obligatory static/pitot test to renew my airworthiness review

certificate I wouldn't have been flying at all that day, so much for the

bureaucrats that want to enforce my safety this way. Anyway, the

pitot/static systems worked flawless (I would have had noticed it myself

it if they weren't) and I'm good to apply for renewal of the desired

certificate.

All this while I had unwittingly broke my smallest toe by bumping into

my wife unintentionally (honestly!) and was undergoing this flying

experience with some discomfort to enhance the flying experience even

further. At least the latter problem has been diagnosed correctly today,

so now I just want to get diagnosed the vapour lock problem as well. Who

can shine some light on this mystery?



Frans

ward.t(at)xtra.co.nz
Guest

Posted: Tue Mar 13, 2012 1:23 pm Post subject: Rotax 914 starting problems when hot

Frans,



Don't have a 914 but I know others who have suffered the same problem with 

the 912S and , for what it is worth, they always

open their oil and coolant doors on top of the top cowling to allow faster 

cooling of the engine compartment during stopovers.



Otherwise don't mention starting problems to me! I have now got to replace 

my Sprag Clutch due to cold starting problems with my 912S

at 300 hours!! Always had it and got worse with time. So watch out when 

trying to persist in trying to start the motor as it quickly destroys your 

Sprag Clutch. I have also the

old mono "classic" engine frame which doesn't allow enough room for the new 

Heavy Duty Starter which Rotax suddenly decided was

necessary for the 100 HP 912S. So, after replacing the Sprag Clutch, the 

Rotax man is going to look at how to fix the starting problem

in cold weather. Maybe a case of redesigning the engine frame to allow for 

the HD Starter?

Once it is going there is no problems with starting, so I haven't got the 

vapour lock problem.

All a bit frustrating as you have found out and expensive. Might as well 

throw in the 912iS, but that may unleash a different set of problems.



Anyone have some input to my problem? Tried new battery, preheating the 

engine which has helped, haven't tried the soft start module,

and kicking the tyre!!



Cheers,



Tim



Tim Ward,

12 Waiwetu Street,

Fendalton,

Christchurch 8052

New Zealand



Ph; 03 3515166

Mob; 0210640221



email; ward.t(at)xtra.co.nz

--

paul.the.aviator(at)gmail
Guest

Posted: Tue Mar 13, 2012 4:21 pm Post subject: Rotax 914 starting problems when hot

Hello Frans,

I have the same problem. �I find if I turn the fuel pump off when I crank and the turn them on after the engine starts works well for me.

BTW, I have called a couple of times, have you been away?

Cheers, Paul

On Tuesday, March 13, 2012, Frans Veldman <frans(at)privatepilots.nl (frans(at)privatepilots.nl)> wrote:

 	  Quote: 	
		   --> Europa-List message posted by: Frans Veldman <frans(at)privatepilots.nl (frans(at)privatepilots.nl)>

 >

 	  Quote: 	
		   Hi everyone,

 I guess I'm not the only one having this problem. The main problem here

 is that I don't understand why it is happening.

 If I arrive at an airfield in hot weather, I can restart either right

 > away, or after a considerable time. If I just refuel without having a

[quote] meal, I get into a time window where the engine has difficulties starting.

   	  Quote: 	
		  [b]

paul.the.aviator(at)gmail
Guest

Posted: Tue Mar 13, 2012 4:26 pm Post subject: Rotax 914 starting problems when hot

Tim,



I have found setting the plug gap to the minimum specified helps with cold starting.



Paul



 	  Quote: 	
		   Otherwise don't mention starting problems to me! I have now got to replace my Sprag Clutch due to cold starting problems with my 912S

 > at 300 hours!! Always had it and got worse with time. So watch out when trying to persist in trying to start the motor as it quickly destroys your Sprag Clutch. I have also the
	


 	  Quote: 	
		   old mono "classic" engine frame which doesn't allow enough room for the new Heavy Duty Starter which Rotax suddenly decided was

 > necessary for the 100 HP 912S. So, after replacing the Sprag Clutch, the Rotax man is going to look at how to fix the starting problem
	


[quote] in cold weather. Maybe a case of redesigning the engine frame to allow for the HD Starter?

 >    	  Quote: 	
		  [b]

daseitz(at)cfl.rr.com
Guest

Posted: Tue Mar 13, 2012 6:12 pm Post subject: Rotax 914 starting problems when hot

OK, I'll put my two cents in on this one. Ever since my 914 was new it has had this problem. Starts right away oe after half hour, but not after ten minutes. When this happens it is flooded. it will start firing with the throtle almost full open and finally start running. This is with both pumps off. After it starts turning the pump on will flood it again. I have to bump the pump on for a moment at high RPM wait till it clears and bump again until it will stay running then all is well.

I have asked when down at Lockwood and all they would say is the carbs need to be rebuilt. If this is the case it was sold to me new with bad carbs since it has done it from day one.

I have given up trying to figure it out. If anyone can let us know. In the meantime I an making my own fuel injection system for it. So far I have it running from 2000 to 4000 rpm on the ground tests. This will be able to run on the carbs or the injection. I hope to make it available when it is finished for under $4000.00  It will still be a while before all the desiging and testing will be completed though.



Be nice if someone could figure the flooding problem out in the meantime



Dean Seitz

---- Frans Veldman <frans(at)privatepilots.nl> wrote: 

 	  Quote: 	
		   

 

 Hi everyone,

 

 I guess I'm not the only one having this problem. The main problem here

 is that I don't understand why it is happening.

 

 If I arrive at an airfield in hot weather, I can restart either right

 away, or after a considerable time. If I just refuel without having a

 meal, I get into a time window where the engine has difficulties starting.

 

 It is a vapour lock problem of some sort, but I don't know how this can

 happen. Sure, the inside of the cowling is hot and residual heat from

 the turbo is, without the large fan upfront turning, cooking the fuel.

 But I thought that the 914 is supposed to be immune from the problem.

 

 Up to the pressure regulator the fuel is recycling when I switch on the

 electric fuel pump. Any vapour up to the pressure regulator is directed

 back into the tank and being replaced by fresh and cold fuel.

 

 The carb bowls might have been cooked empty, but then the floats will

 have dropped and fresh fuel will pour in as soon as I switch on the

 pumps. The fuel line between the pressur regulator is not recycled but

 if it contains vapour then it will escape via the opened carb needle and

 not raise the floats, so it will gently escape until being replaced by

 liquid fuel, being driven there by the electric pumps.

 

 So... why won't then darn thing just start?

 

 Yesterday I was exactly experiencing this problem. After arriving at an

 airport to go to the service center for the bi-annual pitot and static

 systems test, and with the engine switched off for about ten minutes I

 couldn't restart it. No matter how long I kept the fuel pumps running,

 applied choke, (just in case the mixture was too lean) or was just

 cranking with the throtthle wide open to vent the cylinders (in case it

 was too rich), the engine would just crank without even a faint single hit.

 So I abandoned the plan to taxi to the refueling station, and had a

 lunch instead. Of course after that the engine started up right after

 just a half turn of the prop...

 

 So... why is this happening? I'm interested in solving this problem, but

 primarily I want to know why this is happening because according to my

 reasoning it shouldn't be happening in the first place. What am I

 missing here?

 

 Oh BTW, on the return home I got caught by non predicted early set in of

 night fog, with a very rapidly dropping cloud base (never seen it

 falling that fast). With my home base being the closest and most

 promising airfield once I got forced down to 500 feet I advanced the

 throttle to 100% (not 115%) and got over 155 knots IAS worth out of it

 on my freshly calibrated ASI, which was quite an experience so low over

 the ground. At my homefield I arrived less than 15 minutes later with

 the local cloud base still at 1000 feet (as announced/predicted by ATC

 half an hour earlier), but I was thankful nevertheless to have been able

 to speed out of that threathening situation that fast. If it weren't for

 the obligatory static/pitot test to renew my airworthiness review

 certificate I wouldn't have been flying at all that day, so much for the

 bureaucrats that want to enforce my safety this way. Anyway, the

 pitot/static systems worked flawless (I would have had noticed it myself

 it if they weren't) and I'm good to apply for renewal of the desired

 certificate.

 All this while I had unwittingly broke my smallest toe by bumping into

 my wife unintentionally (honestly!) and was undergoing this flying

 experience with some discomfort to enhance the flying experience even

 further. At least the latter problem has been diagnosed correctly today,

 so now I just want to get diagnosed the vapour lock problem as well. Who

 can shine some light on this mystery?

 

 Frans

klinefelter.kevin(at)gmai
Guest

Posted: Tue Mar 13, 2012 8:19 pm Post subject: Rotax 914 starting problems when hot

Hot start on my 914 is no choke, closed throttle, start cranking and slowly advancing the throttle untill it fires up.

Kevin

914 mono 400hrs.



On Mar 13, 2012, at 1:01 PM, Frans Veldman <frans(at)privatepilots.nl> wrote:



 	  Quote: 	
		   

 

 Hi everyone,

 

 I guess I'm not the only one having this problem. The main problem here

 is that I don't understand why it is happening.

 

 If I arrive at an airfield in hot weather, I can restart either right

 away, or after a considerable time. If I just refuel without having a

 meal, I get into a time window where the engine has difficulties starting.

 

 It is a vapour lock problem of some sort, but I don't know how this can

 happen. Sure, the inside of the cowling is hot and residual heat from

 the turbo is, without the large fan upfront turning, cooking the fuel.

 But I thought that the 914 is supposed to be immune from the problem.

 

 Up to the pressure regulator the fuel is recycling when I switch on the

 electric fuel pump. Any vapour up to the pressure regulator is directed

 back into the tank and being replaced by fresh and cold fuel.

 

 The carb bowls might have been cooked empty, but then the floats will

 have dropped and fresh fuel will pour in as soon as I switch on the

 pumps. The fuel line between the pressur regulator is not recycled but

 if it contains vapour then it will escape via the opened carb needle and

 not raise the floats, so it will gently escape until being replaced by

 liquid fuel, being driven there by the electric pumps.

 

 So... why won't then darn thing just start?

 

 Yesterday I was exactly experiencing this problem. After arriving at an

 airport to go to the service center for the bi-annual pitot and static

 systems test, and with the engine switched off for about ten minutes I

 couldn't restart it. No matter how long I kept the fuel pumps running,

 applied choke, (just in case the mixture was too lean) or was just

 cranking with the throtthle wide open to vent the cylinders (in case it

 was too rich), the engine would just crank without even a faint single hit.

 So I abandoned the plan to taxi to the refueling station, and had a

 lunch instead. Of course after that the engine started up right after

 just a half turn of the prop...

 

 So... why is this happening? I'm interested in solving this problem, but

 primarily I want to know why this is happening because according to my

 reasoning it shouldn't be happening in the first place. What am I

 missing here?

 

 Oh BTW, on the return home I got caught by non predicted early set in of

 night fog, with a very rapidly dropping cloud base (never seen it

 falling that fast). With my home base being the closest and most

 promising airfield once I got forced down to 500 feet I advanced the

 throttle to 100% (not 115%) and got over 155 knots IAS worth out of it

 on my freshly calibrated ASI, which was quite an experience so low over

 the ground. At my homefield I arrived less than 15 minutes later with

 the local cloud base still at 1000 feet (as announced/predicted by ATC

 half an hour earlier), but I was thankful nevertheless to have been able

 to speed out of that threathening situation that fast. If it weren't for

 the obligatory static/pitot test to renew my airworthiness review

 certificate I wouldn't have been flying at all that day, so much for the

 bureaucrats that want to enforce my safety this way. Anyway, the

 pitot/static systems worked flawless (I would have had noticed it myself

 it if they weren't) and I'm good to apply for renewal of the desired

 certificate.

 All this while I had unwittingly broke my smallest toe by bumping into

 my wife unintentionally (honestly!) and was undergoing this flying

 experience with some discomfort to enhance the flying experience even

 further. At least the latter problem has been diagnosed correctly today,

 so now I just want to get diagnosed the vapour lock problem as well. Who

 can shine some light on this mystery?

 

 Frans

g-iani(at)ntlworld.com
Guest

Posted: Wed Mar 14, 2012 1:07 am Post subject: Rotax 914 starting problems when hot

Frans

 

This problem drove me mad for a couple of years until I discovered the magic trick Ivor described.

 

Turn off both pumps and start the engine with about a 1/8in to �in of throttle. �It will fire up and run but you must

leave the pumps off until she starts to falter (say 5 to 10 seconds).� �Then turn on the main fuel pump and she continues to run.

 

This has worked well on both G-IANI and G-IRON (both 914) for the last six years.

 

 

Ian Rickard G-IANI XS Trigear, 300hours

Europa Club Mods Specialist

e-mail g-iani(at)ntlworld.com 

 

   [quote][b]

watervet(at)mweb.co.za
Guest

Posted: Wed Mar 14, 2012 1:45 am Post subject: Rotax 914 starting problems when hot

Hi Frans



Have exactly the same problem with my 914 - ok straight away but short break very difficult to start - but have found if I do 2 things

I can get it to start agin with little extra effort.

1. Open both inspection hatches once you have landed - allows some of the under cowl heat to escape.

2. To start - switch on a fuel pump till you have good fuel pressure ( i have a fuel pressure warning light - wait till it goes out) then switch OFF the fuel pumps - open throttle to about a 1/4 +/- and crank till it fires - once engine is running - switch on fuel pump but be prepared to switch off again if engine starts to die - soon running smooth and fuel pump can be left on as normal

Regards

Mike



 Dr Mike Toft BVSc

083 654 6655

P O Box 602

Linkhills 3652

watervet(at)mweb.co.za (watervet(at)mweb.co.za)

 

 

On 13 Mar 2012, at 11:22 PM, Tim Ward wrote:

[quote]--> Europa-List message posted by: "Tim Ward" <ward.t(at)xtra.co.nz (ward.t(at)xtra.co.nz)>



Frans,



Don't have a 914 but I know others who have suffered the same problem with the 912S and , for what it is worth, they always

open their oil and coolant doors on top of the top cowling to allow faster cooling of the engine compartment during stopovers.



Otherwise don't mention starting problems to me! I have now got to replace my Sprag Clutch due to cold starting problems with my 912S

at 300 hours!! Always had it and got worse with time. So watch out when trying to persist in trying to start the motor as it quickly destroys your Sprag Clutch. I have also the

old mono "classic" engine frame which doesn't allow enough room for the new Heavy Duty Starter which Rotax suddenly decided was

necessary for the 100 HP 912S. So, after replacing the Sprag Clutch, the Rotax man is going to look at how to fix the starting problem

in cold weather. Maybe a case of redesigning the engine frame to allow for the HD Starter?

Once it is going there is no problems with starting, so I haven't got the vapour lock problem.

All a bit frustrating as you have found out and expensive. Might as well throw in the 912iS, but that may unleash a different set of problems.



Anyone have some input to my problem? Tried new battery, preheating the engine which has helped, haven't tried the soft start module,

and kicking the tyre!!



Cheers,



Tim



Tim Ward,

12 Waiwetu Street,

Fendalton,

Christchurch 8052

New Zealand



Ph; 03 3515166

Mob; 0210640221



email; ward.t(at)xtra.co.nz (ward.t(at)xtra.co.nz)

--

bill.sue(at)orcon.net.nz
Guest

Posted: Wed Mar 14, 2012 1:57 am Post subject: Rotax 914 starting problems when hot

Franz,



I sometimes have this problem during hot weather. My solution is to turn 

OFF both fuel pumps and then it starts easily. As soon as it starts turn 

the pump back on and all is OK.

Sue&  Bill

On 14/03/2012 9:01 a.m., Frans Veldman wrote:

 	  Quote: 	
		   



 Hi everyone,



 I guess I'm not the only one having this problem. The main problem here

 is that I don't understand why it is happening.



 If I arrive at an airfield in hot weather, I can restart either right

 away, or after a considerable time. If I just refuel without having a

 meal, I get into a time window where the engine has difficulties starting.



 It is a vapour lock problem of some sort, but I don't know how this can

 happen. Sure, the inside of the cowling is hot and residual heat from

 the turbo is, without the large fan upfront turning, cooking the fuel.

 But I thought that the 914 is supposed to be immune from the problem.



 Up to the pressure regulator the fuel is recycling when I switch on the

 electric fuel pump. Any vapour up to the pressure regulator is directed

 back into the tank and being replaced by fresh and cold fuel.



 The carb bowls might have been cooked empty, but then the floats will

 have dropped and fresh fuel will pour in as soon as I switch on the

 pumps. The fuel line between the pressur regulator is not recycled but

 if it contains vapour then it will escape via the opened carb needle and

 not raise the floats, so it will gently escape until being replaced by

 liquid fuel, being driven there by the electric pumps.



 So... why won't then darn thing just start?



 Yesterday I was exactly experiencing this problem. After arriving at an

 airport to go to the service center for the bi-annual pitot and static

 systems test, and with the engine switched off for about ten minutes I

 couldn't restart it. No matter how long I kept the fuel pumps running,

 applied choke, (just in case the mixture was too lean) or was just

 cranking with the throtthle wide open to vent the cylinders (in case it

 was too rich), the engine would just crank without even a faint single hit.

 So I abandoned the plan to taxi to the refueling station, and had a

 lunch instead. Of course after that the engine started up right after

 just a half turn of the prop...



 So... why is this happening? I'm interested in solving this problem, but

 primarily I want to know why this is happening because according to my

 reasoning it shouldn't be happening in the first place. What am I

 missing here?



 Oh BTW, on the return home I got caught by non predicted early set in of

 night fog, with a very rapidly dropping cloud base (never seen it

 falling that fast). With my home base being the closest and most

 promising airfield once I got forced down to 500 feet I advanced the

 throttle to 100% (not 115%) and got over 155 knots IAS worth out of it

 on my freshly calibrated ASI, which was quite an experience so low over

 the ground. At my homefield I arrived less than 15 minutes later with

 the local cloud base still at 1000 feet (as announced/predicted by ATC

 half an hour earlier), but I was thankful nevertheless to have been able

 to speed out of that threathening situation that fast. If it weren't for

 the obligatory static/pitot test to renew my airworthiness review

 certificate I wouldn't have been flying at all that day, so much for the

 bureaucrats that want to enforce my safety this way. Anyway, the

 pitot/static systems worked flawless (I would have had noticed it myself

 it if they weren't) and I'm good to apply for renewal of the desired

 certificate.

 All this while I had unwittingly broke my smallest toe by bumping into

 my wife unintentionally (honestly!) and was undergoing this flying

 experience with some discomfort to enhance the flying experience even

 further. At least the latter problem has been diagnosed correctly today,

 so now I just want to get diagnosed the vapour lock problem as well. Who

 can shine some light on this mystery?



 Frans

raimo.toivio(at)rwm.fi
Guest

Posted: Wed Mar 14, 2012 3:44 am Post subject: Rotax 914 starting problems when hot

Great Frans



"I advanced the

throttle to 100% (not 115%) and got over 155 knots 

IAS worth out of it

on my freshly calibrated ASI,"



Congratulations for that; next upgrade your very 

speedy cannon to Mono and meet even VNE (165 

knots) during the low level flight.



"broke my smallest toe by bumping into

my wife unintentionally (honestly!)"



I recommend you to try next time your biggest tool 

intentionally instead of a smallest toe 

unintentionally.



Raimo



do archive

-----Alkuper�inen viesti----- 

From: Frans Veldman

Sent: Tuesday, March 13, 2012 10:01 PM

To: europa-list(at)matronics.com

Subject: Rotax 914 starting problems 

when hot




<frans(at)privatepilots.nl>



Hi everyone,



I guess I'm not the only one having this problem. 

The main problem here

is that I don't understand why it is happening.



If I arrive at an airfield in hot weather, I can 

restart either right

away, or after a considerable time. If I just 

refuel without having a

meal, I get into a time window where the engine 

has difficulties starting.



It is a vapour lock problem of some sort, but I 

don't know how this can

happen. Sure, the inside of the cowling is hot and 

residual heat from

the turbo is, without the large fan upfront 

turning, cooking the fuel.

But I thought that the 914 is supposed to be 

immune from the problem.



Up to the pressure regulator the fuel is recycling 

when I switch on the

electric fuel pump. Any vapour up to the pressure 

regulator is directed

back into the tank and being replaced by fresh and 

cold fuel.



The carb bowls might have been cooked empty, but 

then the floats will

have dropped and fresh fuel will pour in as soon 

as I switch on the

pumps. The fuel line between the pressur regulator 

is not recycled but

if it contains vapour then it will escape via the 

opened carb needle and

not raise the floats, so it will gently escape 

until being replaced by

liquid fuel, being driven there by the electric 

pumps.



So... why won't then darn thing just start?



Yesterday I was exactly experiencing this problem. 

After arriving at an

airport to go to the service center for the 

bi-annual pitot and static

systems test, and with the engine switched off for 

about ten minutes I

couldn't restart it. No matter how long I kept the 

fuel pumps running,

applied choke, (just in case the mixture was too 

lean) or was just

cranking with the throtthle wide open to vent the 

cylinders (in case it

was too rich), the engine would just crank without 

even a faint single hit.

So I abandoned the plan to taxi to the refueling 

station, and had a

lunch instead. Of course after that the engine 

started up right after

just a half turn of the prop...



So... why is this happening? I'm interested in 

solving this problem, but

primarily I want to know why this is happening 

because according to my

reasoning it shouldn't be happening in the first 

place. What am I

missing here?



Oh BTW, on the return home I got caught by non 

predicted early set in of

night fog, with a very rapidly dropping cloud base 

(never seen it

falling that fast). With my home base being the 

closest and most

promising airfield once I got forced down to 500 

feet I advanced the

throttle to 100% (not 115%) and got over 155 knots 

IAS worth out of it

on my freshly calibrated ASI, which was quite an 

experience so low over

the ground. At my homefield I arrived less than 15 

minutes later with

the local cloud base still at 1000 feet (as 

announced/predicted by ATC

half an hour earlier), but I was thankful 

nevertheless to have been able

to speed out of that threathening situation that 

fast. If it weren't for

the obligatory static/pitot test to renew my 

airworthiness review

certificate I wouldn't have been flying at all 

that day, so much for the

bureaucrats that want to enforce my safety this 

way. Anyway, the

pitot/static systems worked flawless (I would have 

had noticed it myself

it if they weren't) and I'm good to apply for 

renewal of the desired

certificate.

All this while I had unwittingly broke my smallest 

toe by bumping into

my wife unintentionally (honestly!) and was 

undergoing this flying

experience with some discomfort to enhance the 

flying experience even

further. At least the latter problem has been 

diagnosed correctly today,

so now I just want to get diagnosed the vapour 

lock problem as well. Who

can shine some light on this mystery?



Frans



browse

Un/Subscription,

FAQ,

http://www.matronics.com/Navigator?Europa-List

Forums!

List Admin.

frans(at)privatepilots.nl
Guest

Posted: Wed Mar 14, 2012 3:54 am Post subject: Rotax 914 starting problems when hot

On 03/13/2012 10:00 PM, PHILLIPS I wrote:



 	  Quote: 	
		   I turn off both pumps with about a 1/4 throttle it will fire up and run

 but you must

 leave the pumps off until she starts to falter,


	


Thanks a lot! You, and of course everyone else who answered. Good to

hear I'm not the only one having this problem and good to hear there is

consencus about the work around to get the thing started.



Nobody came up with a suggestion why we are having this problem. Let's

see, now it is clear that the engine will start with the fuel pumps off,

we can draw some conclusions from it: It is not a fuel starvation

problem, so it is not vapour lock.



I think the best (if not only) explanation is:



After 10 minutes in a hot engine bay the fuel in the carb bowls has

vaporized completely and is then lingering in the airbox and manifold

with no easy way out, so it is still there when we try to start the

engine after these 10 minutes. The mixture is overly rich due to the

excessive fuel vapor and allowing the carbs to add the normal amount of

fuel will make the mixture so rich that the engine won't start. If we

start right after shut down the fuel in the carbs has not yet vaporized,

if we start much later the vapor has leaked away so it is not causing a

problem anymore.



Anyone else with a better explanation?



I thought of fixing this problem but now the work around is so easy I

think I will leave it at that.



Thanks everyone!



Frans

frans(at)privatepilots.nl
Guest

Posted: Wed Mar 14, 2012 3:58 am Post subject: Rotax 914 starting problems when hot

On 03/13/2012 10:22 PM, Tim Ward wrote:

 	  Quote: 	
		   So watch out when

 trying to persist in trying to start the motor as it quickly destroys

 your Sprag Clutch.


	


The 912S has a much higher compression than the 914 (and 912). Although

never owned a 912S it was my understanding that the starting issues have

to do with this higher compression, which makes cranking the engine much

harder with much more jolts and kicks.

I guess a larger battery and retarding the ignition during starting

might help a bit.



Frans

frans(at)privatepilots.nl
Guest

Posted: Wed Mar 14, 2012 4:01 am Post subject: Rotax 914 starting problems when hot

On 03/14/2012 01:20 AM, Paul McAllister wrote:



 	  Quote: 	
		   BTW, I have called a couple of times, have you been away?


	


Yes, I have been away yesterday and the day before. Now I first have to

get a pile of work done, I guess we can call later (when it is evening

here).



Frans

frans(at)privatepilots.nl
Guest

Posted: Wed Mar 14, 2012 4:17 am Post subject: Rotax 914 starting problems when hot

On 03/14/2012 03:11 AM, Dean Seitz wrote:



 	  Quote: 	
		   I have asked when down at Lockwood and all they would

 say is the carbs need to be rebuilt. If this is the case it was sold

 to me new with bad carbs since it has done it from day one.


	


Same here. It has always done that. And with only 150 hours on the clock

I think the carbs are still pretty new.



 	  Quote: 	
		   In the

 meantime I an making my own fuel injection system for it.


	


Great, I'm working on plans to do the same. You are also using the carbs

as throttle body (and for redundancy in case the injection fails?)



 	  Quote: 	
		   I hope to make it

 available when it is finished for under $4000.00


	


Are you working on it as a commercial project or is this a fun project

we can openly discuss? If it is the latter I would love to know where

and how you obtained adapted manifolds with injector bosses.



 	  Quote: 	
		   It will still be a

 while before all the desiging and testing will be completed though.


	


I bet! But it is worth the effort, I estimate a fuel reduction of 10%

and a slight increase of power. With the current fuel prices the system

will earn itself back.



 	  Quote: 	
		   Be nice if someone could figure the flooding problem out in the

 meantime


	


What do you think about my theory?



Frans

frans(at)privatepilots.nl
Guest

Posted: Wed Mar 14, 2012 4:32 am Post subject: Rotax 914 starting problems when hot

On 03/14/2012 12:44 PM, Raimo Toivio wrote:



 	  Quote: 	
		   Congratulations for that; next upgrade your very speedy cannon to Mono

 and meet even VNE (165 knots) during the low level flight.


	


I think with proper fairings on the wheels the difference in drag

between a tri-gear and a mono wouldn't be that much. This year I plan to

replace the mickey mouse fairings by properly shaped fairings. The

frontal area of the outriggers, mono wheel and tail wheel might still be

smaller but I think these items are more difficult to clean up

aerodynamically.



And of course I don't think I'm a good enough flyer to keep the thing

under control in the various and sometimes challinging situations during

my travels.



 	  Quote: 	
		   "broke my smallest toe by bumping into

 my wife unintentionally (honestly!)"

 

 I recommend you to try next time your biggest tool intentionally instead

 of a smallest toe unintentionally.


	


I tried but something clearly went wrong... I will keep practising. 



Frans

raimo.toivio(at)rwm.fi
Guest

Posted: Wed Mar 14, 2012 5:00 am Post subject: Rotax 914 starting problems when hot

"I think with proper fairings on the wheels the 

difference in drag

between a tri-gear and a mono wouldn't be that 

much."



Maybe so but like all The Mono Pilots know they 

are flying a little fighter in fact and think it 

must be faster - then it also really is faster  



You know - the placebo effect works...as well as 

attitude.



Raimo

djaflyact(at)gmail.com
Guest

Posted: Wed Mar 14, 2012 8:11 am Post subject: Rotax 914 starting problems when hot

I have found, over the years, that if I run the engine taxiing in with the fuel pumps off and then shut it down as the engine starts to falter, that leaves the carb bowls empty. Then on start-up, the carbs are filled with fresh, cool fuel and with the techniques described, it starts right up. I do leave the pumps off during the start and then start them when the engine starts to falter.



Not sure why this has to be done, but it is necessary. I also leave the inspection doors open to help remove the hot air from the top of the cowl while it is parked.



Dave Anderson

480 hours

914 long wing.

frans(at)privatepilots.nl
Guest

Posted: Wed Mar 14, 2012 8:39 am Post subject: Rotax 914 starting problems when hot

On 03/14/2012 05:08 PM, DAVID ANDERSON wrote:

 	  Quote: 	
		   I have found, over the years, that if I run the engine taxiing in

 with the fuel pumps off and then shut it down as the engine starts to

 falter, that leaves the carb bowls empty.


	


That is a smart idea! I like this one. It should solve the problem, and

it also causes less residu to be built up in the carbs. (If fuel

vaporizes some residues from the various additions remain, if the carb

is drawn empty these residues can not built up in the first place).



 	  Quote: 	
		   Then on start-up, the carbs

 are filled with fresh, cool fuel and with the techniques described,

 it starts right up. I do leave the pumps off during the start and

 then start them when the engine starts to falter.


	


I'm not sure if I understand this right. You switch the fuel pumps off

on arrival and let the engine sputter to a halt due to fuel starvation,

and then you leave the fuel pumps still off at the subsequent start??? I

assume that you use either one of these options but not both at the same

time because otherwise there wouldn't be any fuel available for

starting? Please clarify?



Frans

neveyre(at)aol.co.uk
Guest

Posted: Wed Mar 14, 2012 11:31 am Post subject: Rotax 914 starting problems when hot

Hi Frans,

   I believe heat is the trigger to your [ and other 914 drivers] initial problem.

   Can you provide us with the under cowl temps you saw during your Flight Test Program ?

   The numbers you witnessed in cruise, climb out and after shut down / resting ? I was monitoring these temps in several places inside the cowl during development of the original 912 and 914 Installation, would be interesting to see how the removal of all through air flow has effected under cowl temps. Heat from the exhaust / Turbo has to go somewhere ?

   Cheers,

   Nev.

 

 

 

   --

frans(at)privatepilots.nl
Guest

Posted: Wed Mar 14, 2012 11:55 am Post subject: Rotax 914 starting problems when hot

Hi Neville,



 	  Quote: 	
		   Can you provide us with the under cowl temps you saw during your Flight

 Test Program ?


	


Nope, don't have that data. But I plan to do some measurements this summer.



 	  Quote: 	
		   would be

 interesting to see how the removal of all through air flow has effected

 under cowl temps. Heat from the exhaust / Turbo has to go somewhere ?


	


I bet it is much lower than it was before. The air leaving the radiator

blows right between the exhaust tubes and turbo. Air box temp (I have a

sensor there) is also lower than it used to be. And I have no signs of

elevated temps in the cowling (no discolourisation, no melted tie wraps,

etc).



Of course, once the engine is switched off the radiant heat will still

heat up everything and boil away the fuel.



Frans

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