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JL2A
Joined: 07 Apr 2015
Posts: 113
Location: Australia
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 Posted: Tue Jan 31, 2017 2:31 am Post subject: Hard starting.. help required from round engine pros |
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Gentlemen,
We have a Jacobs R755 powered Agcat used for commercial Joy Flights.
We also have two CJ6s, and realise this is a eastern bloc forum but hopefully there's a few of you here that have experience with other types of round engines (paging George Coy??!)
The aircraft has not done multiple flights in a day for many years, however we are working the aircraft quite a bit lately (which is great!) and it is proving to be a real sob to start, at seemingly random times.
Once running, the thing is great and purrs smoothly and runs well, however the starting sequence has many quirks, the most frustrating of which is the ‘Im not going to start at all’
We have tried everything!
- prime like crazy while cranking. nothing
- flooded start, idle cut-off, throttle open, crank. nothing
- every possible variation of prime, from nothing to too much with all combinations
And when I say nothing, I mean nothing! Not a chug, cough, smoke, nothing. It is like there is actually no spark at all. Unlit fuel vapour can be seen coming from the exhaust whilst cranking.
The only thing that does seem to work is walking away, coming back 30 minutes later and then she’ll start second blade! Unfortunately by then the customers have been refunded and have left.
We have had the magnetos overhauled, shower of sparks inspected and all found serviceable.
We had some drag car racers as customers the other day and their comment was 'it's like there's no spark'. Which is what it 'feels' like to us too. Too rich/lean starting mixtures engines behave differently, with some cylinders firing or not etc. This one is either perfect all 7 cylinders start, or absolutely nothing.
Obviously there is a spark, otherwise nothing would happen - but I'm thinking maybe it is such a weak spark from the shower of sparks that the mixture has to be juuuust right in order for it to go.
Would the starter be taking so much voltage that the SoS is not getting it's required amount?
Any ideas are welcome!
Thanks in advance!
Anatole Mills
PS Sometimes while starting one jug will fire way early and drives the engine backwards against the starter which makes us wince. Fear for the life of the starter. This may be an independent problem. The R755 is timed to 31°BTDC (running, static)
PPS After operating the R985 and R755 the HS6A looks more and more like an engineering masterpiece!
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dsavarese0812(at)bellsout
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| Posted: Tue Jan 31, 2017 5:06 am Post subject: Hard starting.. help required from round engine pros |
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You mentioned a shower of sparks as a possible culprit. We have seen the same thing with the Huosai and M14 (not with M9-35's which are timed AFTER TDC and in theory do not require a shower of sparks) engines as well and yes, a weak shower of sparks will cause the engine not to start.
What I typically do on the M14 and Huosai engines is test the shower of sparks by removing the shower of sparks lead from the magneto cap and placing the tip of the wire about 3/8" to 1/2" inch from a metal surface. The next step applies to an air start engine. We'll discuss your Jake shortly. We make sure the air system forward of the main air valve is bled off completely. This eliminates any residual air in the air lines from rotating the engine when the start button is pressed. Next we turn on the battery and the ignition switches and press the start button. With the shower of sparks held (by a second person) or held in place close to a metal surface in the engine compartment, the shower of sparks lead should jump a spark from the tip of the wire to the metal surface. If the spark does not jump about 3/8" and we have to move the wire tip closer to the metal to see the spark jump, we must conclude the shower of sparks is weak and not generating enough energy to fire the spark plugs. Luckily on the Huosai and M14 engines with their shower of sparks (ie: starting coil which is identical on both engines) we can clean and adjust the points inside the unit and improve the spark.
Remember, whatever you see at the tip of the shower of sparks lead has to travel down the spark plug wire to the spark plug. If the spark is weak at the tip of the wire, you can be assured it does not have enough energy after traveling down the plug wire to the spark plug.
As for the Jake, don't assume because you recently had the shower of sparks checked that it is outputting adequate spark. I would (if possible) remove the magneto caps from the magnetos and then remove the shower of sparks lead from whichever magneto it is affixed to. Next do the same thing as described above: place the shower of sparks wire close to a metal surface. Then turn on the battery and ignition switches and press or engage the start switch. Yes the engine will rotate, but it can not start with the mag caps removed. But the shower of sparks wire should jump a spark to the metal surface it is close to. Again, if the spark is weak, then the shower of sparks/starting coil is also weak. The weak spark will not fire the spark plugs.
Hope this helps.
Dennis
From: JL2A <info(at)flyingwarbirds.com.au>
To: yak-list(at)matronics.com
Sent: Tuesday, January 31, 2017 5:31 AM
Subject: Yak-List: Hard starting.. help required from round engine pros
--> Yak-List message posted by: "JL2A" <info(at)flyingwarbirds.com.au (info(at)flyingwarbirds.com.au)>
Gentlemen,
We have a Jacobs R755 powered Agcat used for commercial Joy Flights.
We also have two CJ6s, and realise this is a eastern bloc forum but hopefully there's a few of you here that have experience with other types of round engines (paging George Coy??!)
The aircraft has not done multiple flights in a day for many years, however we are working the aircraft quite a bit lately (which is great!) and it is proving to be a real sob to start, at seemingly random times.
Once running, the thing is great and purrs smoothly and runs well, however the starting sequence has many quirks, the most frustrating of which is the ‘Im not going to start at all’
We have tried everything!
- prime like crazy while cranking. nothing
- flooded start, idle cut-off, throttle open, crank. nothing
- every possible variation of prime, from nothing to too much with all combinations
And when I say nothing, I mean nothing! Not a chug, cough, smoke, nothing. It is like there is actually no spark at all. Unlit fuel vapour can be seen coming from the exhaust whilst cranking.
The only thing that does seem to work is walking away, coming back 30 minutes later and then she’ll start second blade! Unfortunately by then the customers have been refunded and have left.
We have had the magnetos overhauled, shower of sparks inspected and all found serviceable.
We had some drag car racers as customers the other day and their comment was 'it's like there's no spark'. Which is what it 'feels' like to us too. Too rich/lean starting mixtures engines behave differently, with some cylinders firing or not etc. This one is either perfect all 7 cylinders start, or absolutely nothing.
Obviously there is a spark, otherwise nothing would happen - but I'm thinking maybe it is such a weak spark from the shower of sparks that the mixture has to be juuuust right in order for it to go.
Would the starter be taking so much voltage that the SoS is not getting it's required amount?
Any ideas are welcome!
Thanks in advance!
Anatole Mills
PS Sometimes while starting one jug will fire way early and drives the engine backwards against the starter which makes us wince. Fear for the life of the starter. This may be an independent problem. The R755 is timed to 31°BTDC (running, static)
PPS After operating the R985 and R755 the HS6A looks more and more like an engineering masterpiece!
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=465595#465595
="http://www.matronics.com/Navigator?Yak-List" target="_blank">http://w -->
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GeorgeCoy
Joined: 02 Dec 2010
Posts: 310
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| Posted: Tue Jan 31, 2017 7:20 am Post subject: Hard starting.. help required from round engine pros |
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It is most probably ignition problems. Either timing or weak spark at starting.
The Jacobs that I had was on a Cessna 195 had one magneto and one distributor (like on a car). The distributor had an mechanical advance built into the rotor, used a coil, points and capacitor. I recall the Jacobs on the Bamboo Bombers ( Cessna Bobcat) also had the same ignition system.
I also found out when the engine was warm or hot it was often hard to start with the starter, but would easily start by hand propping. I suspected the voltage to the coil was low during start and made a weak spark.
I replaced the coil, the capacitor, the lead from the coil to the distributor on mine to help starting. I also installed fine wire plugs to help starting. I had a friend with a 195 who had a reluctor wheel made to replace the cam, replaced the points with a pick up from a Toyota and installed a capacitive discharge system (the FAA did not know any better). It fired up every time.
The Franklin B9F engine on the SeaBee had a similar system and we always replaced the coils and =with modern coils.
George
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Viperdoc
Joined: 19 Apr 2014
Posts: 484
Location: 08A
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| Posted: Wed Feb 01, 2017 8:08 pm Post subject: Hard starting.. help required from round engine pros |
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Weak battery is another source for weak spark from the shower of sparks. Also the wiring harness break down is a source too. Broken insulation allows the spark to ground out. A problem if the original harness is still on the A/C.
Doc
Sent from my iPad
| Quote: | On Jan 31, 2017, at 9:19 AM, George S. Coy <george.coy(at)gmail.com> wrote:
It is most probably ignition problems. Either timing or weak spark at starting.
The Jacobs that I had was on a Cessna 195 had one magneto and one distributor (like on a car). The distributor had an mechanical advance built into the rotor, used a coil, points and capacitor. I recall the Jacobs on the Bamboo Bombers ( Cessna Bobcat) also had the same ignition system.
I also found out when the engine was warm or hot it was often hard to start with the starter, but would easily start by hand propping. I suspected the voltage to the coil was low during start and made a weak spark.
I replaced the coil, the capacitor, the lead from the coil to the distributor on mine to help starting. I also installed fine wire plugs to help starting. I had a friend with a 195 who had a reluctor wheel made to replace the cam, replaced the points with a pick up from a Toyota and installed a capacitive discharge system (the FAA did not know any better). It fired up every time.
The Franklin B9F engine on the SeaBee had a similar system and we always replaced the coils and =with modern coils.
George
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hkgibby(at)yahoo.com
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| Posted: Wed Feb 01, 2017 8:26 pm Post subject: Hard starting.. help required from round engine pros |
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Don't forget the oft-forgotten and under appreciated start solenoid (QDF-1) as the culprit. Can get pretty fugly on the lower "air" section of the valve.
Hoot
Sent from my iPhone
| Quote: | On Feb 1, 2017, at 8:07 PM, Roger Kemp <f16viperdoc(at)me.com> wrote:
Weak battery is another source for weak spark from the shower of sparks. Also the wiring harness break down is a source too. Broken insulation allows the spark to ground out. A problem if the original harness is still on the A/C.
Doc
Sent from my iPad
> On Jan 31, 2017, at 9:19 AM, George S. Coy <george.coy(at)gmail.com> wrote:
>
>
>
> It is most probably ignition problems. Either timing or weak spark at starting.
> The Jacobs that I had was on a Cessna 195 had one magneto and one distributor (like on a car). The distributor had an mechanical advance built into the rotor, used a coil, points and capacitor. I recall the Jacobs on the Bamboo Bombers ( Cessna Bobcat) also had the same ignition system.
> I also found out when the engine was warm or hot it was often hard to start with the starter, but would easily start by hand propping. I suspected the voltage to the coil was low during start and made a weak spark.
> I replaced the coil, the capacitor, the lead from the coil to the distributor on mine to help starting. I also installed fine wire plugs to help starting. I had a friend with a 195 who had a reluctor wheel made to replace the cam, replaced the points with a pick up from a Toyota and installed a capacitive discharge system (the FAA did not know any better). It fired up every time.
> The Franklin B9F engine on the SeaBee had a similar system and we always replaced the coils and =with modern coils.
>
> George
>
>
>
>
>
>
>
>
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JL2A
Joined: 07 Apr 2015
Posts: 113
Location: Australia
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| Posted: Thu Feb 02, 2017 3:19 am Post subject: Re: Hard starting.. help required from round engine pros |
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Thanks all - going down to where the aircraft is based tomorrow with a multi-meter and I'll start with seeing if the sos can jump a spark 3/8" first and work from there.
From other suggestions - when you say wiring harness grounding out / poor etc, the engine RUNS perfectly, so you'd think if it was this we would have big mag drops rough running etc or am I missing something.
I understand it could be an earth issue in the shower of sparks itself, or the lead that goes to the mag is bad...
Not a battery problem, plugging a ground cart in (2x12V in parallel) doesn't make any difference
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wlannon(at)shaw.ca
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| Posted: Thu Feb 02, 2017 8:42 am Post subject: Hard starting.. help required from round engine pros |
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I hope "2 x 12V in parallel" is a typo. If so that is your problem, you
are getting only 12V.
--
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GeorgeCoy
Joined: 02 Dec 2010
Posts: 310
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| Posted: Thu Feb 02, 2017 9:24 am Post subject: Hard starting.. help required from round engine pros |
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Hmmm, I guess I am confused. I thought this thread was about a Jacobs engine
on an Ag cat...
--
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JL2A
Joined: 07 Apr 2015
Posts: 113
Location: Australia
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| Posted: Thu Feb 02, 2017 12:29 pm Post subject: Re: Hard starting.. help required from round engine pros |
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Series! Sorry, yes, typo. Agcat is 12V system.
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wlannon(at)shaw.ca
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| Posted: Thu Feb 02, 2017 8:36 pm Post subject: Hard starting.. help required from round engine pros |
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Probably me that's confused. I assumed he was referring to an M14P or
Huosai, must have missed an earlier post.
If he was posting about a Jake 12V would be correct.
Walt
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JL2A
Joined: 07 Apr 2015
Posts: 113
Location: Australia
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| Posted: Fri Feb 03, 2017 3:15 am Post subject: Re: Hard starting.. help required from round engine pros |
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Hang on parallel was correct. 12V, made me doubt my shaky knowledge of this stuff.
For the record, if anyone with Jakes stumbles across this in the future, and for any other electric start SoS engines I guess..
- voltage going to shower of sparks whilst cranking 8 volts. weak sparks
- ran 12 volts through shower of sparks. many sparks
- ran 6 volts through shower of sparks. no sparks. (we couldn't do 8V on bench, only had 100W landing light handy to drop voltage)
- off the very big starter solenoid there is heavy cable to starter motor and little lead to SoS, off two separate terminals
- connected SoS on same terminal as starter motor
- many sparks while cranking (the voltage drop through the solenoid must've sapped a lot of juice from the SoS, as well as the starter motor)
- it now starts
Thank you Yak-Listers!
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Viperdoc
Joined: 19 Apr 2014
Posts: 484
Location: 08A
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| Posted: Sat Feb 04, 2017 4:05 pm Post subject: Hard starting.. help required from round engine pros |
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If memory serves, if the battery is delivering less than 18 volts can cause difficult starts. At least that seems to be true for M14.
Glad you found the issue.
Doc
Sent from my iPad
| Quote: | On Feb 3, 2017, at 5:15 AM, JL2A <info(at)flyingwarbirds.com.au> wrote:
Hang on parallel was correct. 12V, made me doubt my shaky knowledge of this stuff.
For the record, if anyone with Jakes stumbles across this in the future, and for any other electric start SoS engines I guess..
- voltage going to shower of sparks whilst cranking 8 volts. weak sparks
- ran 12 volts through shower of sparks. many sparks
- ran 6 volts through shower of sparks. no sparks. (we couldn't do 8V on bench, only had 100W landing light handy to drop voltage)
- off the very big starter solenoid there is heavy cable to starter motor and little lead to SoS, off two separate terminals
- connected SoS on same terminal as starter motor
- many sparks while cranking
- it now starts
Thank you Yak-Listers!
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=465683#465683
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Viperdoc
Joined: 19 Apr 2014
Posts: 484
Location: 08A
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| Posted: Sun Feb 05, 2017 5:58 pm Post subject: Hard starting.. help required from round engine pros |
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Missed the 12 X 12v in parallel. True. That is part of problem. Not getting 24 V.
Doc
Sent from my iPad
[quote] On Feb 2, 2017, at 10:23 PM, Walter Lannon <wlannon(at)shaw.ca> wrote:
Probably me that's confused. I assumed he was referring to an M14P or Huosai, must have missed an earlier post.
If he was posting about a Jake 12V would be correct.
Walt
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Lancer
Joined: 21 Apr 2016
Posts: 30
Location: Cairns, Australia
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| Posted: Mon Feb 06, 2017 10:41 pm Post subject: Re: Hard starting.. help required from round engine pros |
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| JL2A wrote: | Hang on parallel was correct. 12V, made me doubt my shaky knowledge of this stuff.
For the record, if anyone with Jakes stumbles across this in the future, and for any other electric start SoS engines I guess..
- voltage going to shower of sparks whilst cranking 8 volts. weak sparks
- ran 12 volts through shower of sparks. many sparks
- ran 6 volts through shower of sparks. no sparks. (we couldn't do 8V on bench, only had 100W landing light handy to drop voltage)
- off the very big starter solenoid there is heavy cable to starter motor and little lead to SoS, off two separate terminals
- connected SoS on same terminal as starter motor
- many sparks while cranking (the voltage drop through the solenoid must've sapped a lot of juice from the SoS, as well as the starter motor)
- it now starts
Thank you Yak-Listers! |
Yep that'll do it.......The CJ is a 28V system
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