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Hard Starting,Fuel Issue

  • Thread starter Thread starter JB
  • Start date Start date
MartyC asked me in a PM about my Post#24 - flame speed and burn rate vs air/fuel ratios. Here's a quote from a test paper. Less thermal energy = less power:

"The fuel air ratio has a very significant influence on the
flame speed. The highest flame velocities are obtained
with somewhat richer mixture. When the mixture is
made leaner or richer the flame speed decreases. Less
thermal energy is released in the case of lean mixtures
resulting in lower flame temperature. Very rich
mixtures lead to incomplete combustion which results
again in the release of less thermal energy [Ganeshan ,
2010]."

Also, a simplified pic that shows the ideal air/fuel ratio (Lambda; 14.7:1 A/F, 1.0) versus flame velocity in the combustion chamber. Likely not the main problem discussed here, but it can affect performance. Pre-carb heater days I was told old time pilots would lean the mixture until the slow burning fuel caused a backfire through the carb when the intake valve opened to start a new power cycle, melting some ice if lucky.
 

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bad impulse mag or key switch short

I was taught by a well know alaska bush pilot for hand prop.

Prime twice or three depending on temperature
Mags OFF !
Pull through the prop 4 complete revolutions
start, should bang first blade if iit does not then

I's say ignition problems somewhere.
 
Left mag like most everyone has advised.
My i0360 was hard starting when hot even with proper procedures. I just knew it was fuel related, after a extended conversation with a gentleman in Tulsa that rebuilt injection systems he said its your left mag. I had the left mag overhauled and yep it was the left mag! Its the left mag...



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My cold weather hand prop plan…when I built my engine…two impulse coupled mags. Haven’t had the need to hand prop it yet. When I bought the engine it still had the old bendix mags with the flat spot on the armature. Those were phased out in the 70’s…. The impulse coupler didn’t work very well cold…super gummed up with crud. Sometimes would snap, sometimes not. BTW there are three different thickness mag spacers for the impulse coupled mags. If you add a second impulse mag…double check the gear engagement like you would on a ring and pinion gear.
8f0561eebaccb0da4c7f5de1a3c2e967.jpg



My son recently bought a Pacer. I’ve installed the skytech starter and odyssey battery. Has the original mag switch, a more modern start solenoid and a push button switch. It came with three starting check lists…. They’re all wrong I say……but it says mag switch to both. It only has one impulse coupled mag. I did tell him there’s a backup shear pin just incase you have it on both and it kicks back when starting it. You’ll find it under the starter, after you pull the spinner, the prop and cowl. Don’t forget and change the start check list.
26d1862ccd07b2af29a6d15f81f0852a.jpg



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:smile: If JB tires of this I'll trade him airplanes. My Taylorcraft with new engine starts 2nd blade. Hope he gets it fixed.

Gary
 
Pulled the mags this evening. Will be sending them off for overhaul. Will provide update when they get back. Thanks for all the input.
 
Very good. Once the ignition is resolved revisit the fuel. Ensure the idle is set, idle cutoff rises as desired, acceleration is without burps, and in flight near sea level the rpm rises in cruise some with leaning. If ever carb heat helps suspect lean. Best wishes for a smooth engine.

Gary
 
......plugs cleaned, tested, and gapped....

Tested how?
I've heard that plugs can sometimes test good in a bomb type tester but still be out of spec.

Years ago, my old C170 was getting hard to start.
It finally refused to start one day & left me stuck one day (thankfully just at a friend's airpark home).
I was sure it was the slick mags, had them checked out & they were good to go.
Turned out that although they still looked good, with about 550 hours on them the (champion) plugs had too much resistance.
A new set of tempest plugs & all was well.

This might be worth a read....

magneto troubleshooting, aircraft magneto troubleshooting (aircraftmagnetoservice.net)
 
There was a discussion here a while back about plug resistance testing and the affect of high resistance. I’m a real believer. Seems like one of the simplest and least expensive places to start when trying to track down poor performance.

Jim
 
Ive had really great service from Aubrey (owner):https://www.magworx.com

They stand behind their work without question and the Bendix mags that everyone else told me weren't worth overhauling, are now running perfectly in my Vagabond, with a C-90.
Can't say enough about them.

Steve
 
Tested how?
I've heard that plugs can sometimes test good in a bomb type tester but still be out of spec.
I would like to know if anyone has a had a spark plug pass a bomb test and fail a resistance test and at what pressure was it tested. 100 psi is what I test to.
 
I would like to know if anyone has a had a spark plug pass a bomb test and fail a resistance test and at what pressure was it tested. 100 psi is what I test to.
I have,mostly champion plugs and never tempest. Mostly fine wire but sometimes a massive. Generally they will fire but very hard on magnetos.
 
I asked Joe Logie who had been with Slick for many years and then Champion when they sold out and he told me if a spark plug passed a bomb test it would pass the resistance test. Of course the resistance test doesn't work on those old carbon pile resistor plugs. 8)
 
Sent the magnetos to aircraft magneto service in Montana.

They received them on Monday and diagnosed the problem the next day. The internal timing on the left mag was -3 degrees which they said should be +6 to +12 degrees. Mine were 2013 edition which had an issue of moving out of time from the manufacturer. Right mag was +3 degrees. I should have them back next week and will let you know the outcome on starting.
 
sent the magnetos to aircraft magneto service in montana.

They received them on monday and diagnosed the problem the next day. The internal timing on the left mag was -3 degrees which they said should be +6 to +12 degrees. Mine were 2013 edition which had an issue of moving out of time from the manufacturer. Right mag was +3 degrees. I should have them back next week and will let you know the outcome on starting.
bingo!
 
When I started in Aviation my boss called slick's throw away mags. He liked them for that reason just put a new set on.

Back then they were real cheap. I do not run them anymore , they let me down to many times.
 
When I started in Aviation my boss called slick's throw away mags. He liked them for that reason just put a new set on.

Back then they were real cheap. I do not run them anymore , they let me down to many times.
They use to literally be throw away mags. I still have a set of those. They were decent mags in my experience until Champion bought them, darn near doubled the price and started out sourcing (changing) everything that worked. Those points were wearing enough in less than 100 hours to change the timing enough to cause detonation if it started. They changed 8 things in the points at one time and sent them out the door. Ask about warranty and they laugh.
 
When I started in Aviation my boss called slick's throw away mags. He liked them for that reason just put a new set on.

Back then they were real cheap. I do not run them anymore , they let me down to many times.
I bought a new 185 which came from the factory with Slicks...they literally fell apart. Out they went to be replaced with Bendix. Never again would I use a Slick. Even when after listening to a presentation by a Slick rep at an IA meeting.
 
I would like to know if anyone has a had a spark plug pass a bomb test and fail a resistance test and at what pressure was it tested. 100 psi is what I test to.

I have, do them at 100 as well. I resistance check then clean gap and pressure check. The caf has a pt-23 here after they figured out how to time the mags it wouldn’t make static rpm. Told them to resistance check the mags. They said they pressure checked them after cleaning and the spark looked good. They eventually changed the plugs after a handful failed resistance. They were champion. Now tempest.


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I agree with all on the Slicks...just throw them away and INVEST in Bendix. So many problems just go away. I've had so many problems, with so many Slick mags, I've quit counting.
Just had Magworx, rebuild a 50 year old set of Bendix, dual impulse coupled setup for my hand propped Wagabond & C-90....and they simply could not be better.

I have nothing but good to say about the Surefly also....great product.

Steve
 
We are still running some slick mags around here, but have to keep after them. Shouldn’t have to do that. I still have a slick mag on the right of my old 360 but have been using the Sure fly on the left side for a couple years and have been very happy with it. When I have any issue with it, I will find something else for the right side.
 
That was supposed to say 0360. That is a new engine. I just put in an August and I am very happy with that also.
 
Mags came back looked brand new. Installed and it started on the second blade. Yippee. Now to dive into the issue of no rise when pulling the mixture. How many turns rich on the idle/mixture knob before you should be looking into carb getting checked out?
 
Go here https://www.lycoming.com/sites/default/files/attachments/O-320%20Operator%20Manual%2060297-30.pdf page 5-5
  1. [FONT=&quot]Idle Speed and Mixture Adjustment.[/FONT]
    1. [FONT=&quot](1) Start the engine and warm up in the usual manner until oil and cylinder head temperatures are normal.[/FONT]
    2. [FONT=&quot](2) Check magnetos. If the “mag-drop” is [/FONT][FONT=&quot]normal, proceed with idle adjustment.[/FONT]
    3. [FONT=&quot](3) Set throttle stop screw so that the engine [/FONT][FONT=&quot]idles at the airframe manufacturer’s recommended [/FONT][FONT=&quot]idling RPM. If the RPM changes appreciably after making idle mixture adjustment during the succeeding steps, readjust the idle speed to the desired RPM.[/FONT]
    4. [FONT=&quot][FONT=&quot](4) When the idling speed has been stabilized, move the cockpit mixture control lever with a smooth, [/FONT][FONT=&quot]steady pull toward the “Idle Cut-Off” position and observe the t[/FONT][FONT=&quot]achometer for any change during the leaning process. Caution must be exercised to return the mixture cont[/FONT][FONT=&quot]rol to the “Full Rich” [/FONT][FONT=&quot]position before the RPM can drop to a point where the engine cuts out. An increase of more than [/FONT][FONT=&quot]50 RPM while “leaning out” indicates an excessively [/FONT][FONT=&quot]rich idle mixture. An immediate decrease in RPM (if not preceded by a momentary increase) indicates the idle mixture is too lean.[/FONT][/FONT]
      [FONT=&quot]If step (4) indicates that the idle adjustment is too rich or too lean, turn the idle mixture adjustment in direction required for correction, and check this new position by repeating the above procedure. Make additional adjustments as necessary until a check results in a momentary pick-up of approximately 50 RPM. Each time the adjustment is changed, the engine should be run up to 2000 RPM to clean the engine before proceeding with the RPM check. Make final adjustment of the idle speed adjustment to obtain the desired idling RPM with closed throttle. The above method aims at a setting that will obtain maximum RPM with minimum manifold pressure. In case the setting does not remain stable, check the idle linkage; any looseness in this linkage would cause erratic idling. In all cases, allowance should be made for the effect of weather conditions and field altitude upon idling adjustment.

      I would do it on a 30 [/FONT]
      [FONT=&quot]degree day. That should kind of cover winter/summer temp swings.
      DENNY
      [/FONT]
 
Flew to Valdez yesterday where it was 20deg cause its been -36F at my place. Adjusted per your recommendation and can not get a rise. Seems to have the least problems at 3 turns rich. Fourth turn the screw is about to come out. Up at my place in the cold temps it is popping when I drop to 1000-1400 rpm from 2200.

Leaving vdz from sea level to 5000 feet full rich at 2450 the rpms increased to 2500 without throttle adjustment. Shouldnt I be loosing rpm?

When leaning at cruise I don’t get a slight rise either it just falls off once I get to a certain point.

Thinking either intake leak or carb issues.
 
Is there a carb shop that has the equipment to test a carburetor.
 
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