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Author Topic: Engine will not run with battery disconnected??????????????  (Read 2626 times)

Offline frank mccune

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Engine will not run with battery disconnected??????????????
« on: March 18, 2015, 03:22:16 PM »
     Hi Gang:

      Well it finally happened to me! I have an engine issue that I can not rectify.

       I got an older Fox .29 stunt that is in great shape to be used in an old Veco airplane.  I wanted to bench run it before I put in the airplane.  Lo and behold, it will not run without the battery being connected! I used fuel, 3 different blends known to be good, switched glow plugs,nva and props.  Same thing each time,the engine stops when the battery is disconnected!

     The engine appears to be carbon and varnish free, no compression leaks, and a great P&C fit! It starts first flip hot or cold but stops if the battery is disconnected.  There are no air leaks in the nva, tank or fuel line.  It will run a great 4 and then a 2 cycle as long as the battery is connected.

     Any ideas as to how I may cure this curse?

                                                           Tia,

                                                          Frank McCune

Offline Tim Wescott

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Re: Engine will not run with battery disconnected??????????????
« Reply #1 on: March 18, 2015, 03:28:26 PM »
All I can think of (and I'm not a huge expert) is that it's down on compression ratio -- not compression seal.  Particularly if you got it used, take the head off and see if it has multiple head gaskets stacked up in there.  If there are -- take some out, and try again.  Someone may have been confused, or flying with tons-o-nitro, or both.  While the head's off, make sure that the liner is in correctly, both seated correctly on the case, and oriented correctly (as the piston goes down it should uncover the exhaust port first, then the transfer port).  Piston, too -- the baffle should be away from the exhaust side (I think).

I assume you're using a hot glow plug -- using a cold plug shouldn't cause that severe a problem, though.

That's it, I know no more, unless it's a primary compression (crankcase) leak.
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Offline dennis lipsett

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Re: Engine will not run with battery disconnected??????????????
« Reply #2 on: March 18, 2015, 05:03:56 PM »
Throw the plug your using in the task it is wasted effort and put in a new one. Also change your fuel if it runs erratically. water in fuel or stale fuel is not going to run well at all. I'd say if your engine is firing up with the igniter then there is nothing wrong with it especially is it ran well before.
Dennis

Offline frank mccune

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Re: Engine will not run with battery disconnected??????????????
« Reply #3 on: March 19, 2015, 06:14:36 AM »
     Hi Again:

     After a good night's sleep, I got the idea of flushing this engine with carb cleaner and rinsing with fuel.  I will attempt to run it again today.

     Allow me to repeat what I have checked:

     Compression is VERY strong.

     It  will hold compression for a very long time.

     No base compression leaks.
 
     Cylinder is installed correctly.

     Tried different props, plugs, nva and fuels.

     The engine will run very rich and will scream in a 2 cycle as long as the plug is connected to the battery. It quits as soon as the battery is disconnected.  This leads me to believe that all of the plugs that I tried, were faulty.  However, they all ran well in other engines??????????????

     Will keep you posted after today's test runs.

                                                           Stay well my friend,

                                                           Frank McCune

     

     

Offline Dennis Toth

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Re: Engine will not run with battery disconnected??????????????
« Reply #4 on: March 19, 2015, 10:40:09 AM »
Frank,
I assume you are running this "Open Face" so there is nothing squeezing the case (this can cause the case to distort and will in some cases create enough friction to cause your described problem). You indicated that you ran through the usual culprits, cleaning with the solvent is I think in the right directions. It might have varnish build up on the upper cylinder liner and you may need to put the head to see this. A quick check is to remove the plug and put a few drops of fuel in the plug hole then slowly turn it through a full stroke a couple times. You might feel it get a little tight near the top of the stroke, that would be the varnish which gets worst when it gets hot. I would first pull the head and see if there is any varnish there, then pull the sleeve and piston for de-varnishing. I have used a small piece of Scotch Brite green pad to run it up and down in a twisting motion. Go slow and check the fit often (this method was from GMA). Once clean, wash out with soap and water, dry and oil up. Also while you have it out make sure the con rod is feel on the wrist pin and that the wrist pin clips (small circular spring clips) are in place and seated properly.

Best,     DennisT

Offline Steve Helmick

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Re: Engine will not run with battery disconnected??????????????
« Reply #5 on: March 19, 2015, 01:39:14 PM »
"Engine will not run with battery disconnected??????????????"

That's the usual sign that the glowplug is not nearly hot enough. There are some very good (and suitable) glowplugs available. None made by Fox, IMHO. Thunderbolt R/C long reach (with idle bar) and Thunderbolt 4-Cycle (discontinued) are all I stock. So, what brands and heat ranges are you using?

Another possible potential problem is that you're using a short reach plug in an engine designed for long reach plugs. I'd pull the head and check to be sure the glowplug is at least flush with the chamber surface, if not a little "proud". I've seen that in a Fox .35 Stunt...very touchy on NV, didn't want to run rich, didn't want to run lean, and the clicker type NV didn't have a suitable detent. A Thunderbolt long/idle bar fixed it.    H^^ Steve
"The United States has become a place where professional athletes and entertainers are mistaken for people of importance." - Robert Heinlein

In 1944 18-20 year old's stormed beaches, and parachuted behind enemy lines to almost certain death.  In 2015 18-20 year old's need safe zones so people don't hurt their feelings.

Offline frank mccune

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Re: Engine will not run with battery disconnected??????????????
« Reply #6 on: March 19, 2015, 03:46:59 PM »
    Hi Steve:

    By golly I think that you may be on to something! You described the running characteristics to a tee! I put a new Fireplug Long in it today and it and that did not help. It is a real kick in the head that the hobby store is 55 miles away from me!

    I was wondering if the engine is not "broken in" yet?  There was a bit of carbon on the cylinder above the travel of the piston and on the head so it has been run for a period of time.  It really starts well, first flip each time!  It seems to have become a bit better today with more running time on the engine.

                                                       Stay well my friend,

                                                       Frank McCune

    I am afraid to strip it down to remove the carbon from the innards.  In the past, I never got a good piston and cylinder fit after I did that.

Offline bob whitney

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Re: Engine will not run with battery disconnected??????????????
« Reply #7 on: March 19, 2015, 03:58:39 PM »
have u seen this engine run .i would pull a head shim ,or just pull head and see how many shims it had

one year we brought a nelson 15 good year to Munciie that ran great here at sea level in FL. .in Muncie it would not run with the bATT DISCONNECTED EVEN AFTER A LENGHTYworm up , we pulled a shim and it ran great taking 3rd
rad racer

Offline Steve Helmick

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Re: Engine will not run with battery disconnected??????????????
« Reply #8 on: March 20, 2015, 07:44:02 PM »
    Hi Steve:

    By golly I think that you may be on to something! You described the running characteristics to a tee! I put a new Fireplug Long in it today and it and that did not help. It is a real kick in the head that the hobby store is 55 miles away from me!

    I was wondering if the engine is not "broken in" yet?  There was a bit of carbon on the cylinder above the travel of the piston and on the head so it has been run for a period of time.  It really starts well, first flip each time!  It seems to have become a bit better today with more running time on the engine.

                                                       Stay well my friend,

                                                       Frank McCune
    I am afraid to strip it down to remove the carbon from the innards.  In the past, I never got a good piston and cylinder fit after I did that.


What's the color (colour?) of the insulator in that Fireball glowplug? If it's not red, it may be too cold. I used a lot of Fireball glowplugs in the olden days, and wouldn't buy them now, Frankly (pun intended!). Had a lot of seal failures back then. Bob could be right about compression shims...but I can't imagine any reason for anybody to put any extra shims into a Fox .35 Stunt...they're already extremely low C/R. There might be a chance that somebody just figured that would be a safe place to store some extras, however, especially if they didn't intend to use the engine themselves. Much more nitro would probably fix the problem, if you happen to have some 15%-25% nitro with 25% castor. Probably not!  y1 Steve 

"The United States has become a place where professional athletes and entertainers are mistaken for people of importance." - Robert Heinlein

In 1944 18-20 year old's stormed beaches, and parachuted behind enemy lines to almost certain death.  In 2015 18-20 year old's need safe zones so people don't hurt their feelings.

Offline frank mccune

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Re: Engine will not run with battery disconnected??????????????
« Reply #9 on: March 21, 2015, 08:41:30 AM »
     Hi Steve et al:

     No, I do not have anything other than 10% nitro fuel at the time. I do have the fixins to brew whatever blend I wish.

     I pulled the engine down and saw that there was only one aluminum head gasket installed. I ran the engine through my ultrasonic cleaner and reassembled it.  Of course, I now have a poor piston and cylinder fit that I hope will improve after I break in the engine again! I can never reassemble an engine that had a great p&C fit to quality of the original fit! Perhaps there is just not enough metal left to establish a new seal. It may also be that toe p&c are not concentric and will never fit the same way again tto form a good seal.  Perhaps varnish will seal up the new p&c to form a good seal. Lol  A friend of mine suggested to place a 10x6 prop on the engine and feed it a pint of 35% nitro with about 30% castor oil to form a new varnish seal.  Run it hot but not over lean on the test stand.

      I will run it for awhile today to see what happens.

      Of course I had to play musical screw to get the head/crankcase seal to stop leaking.  I think that those old Fox heads always needed to faced to true them before attempting to reassemble the engine.  Three thousands of an inch or more was often required to get them straight. 

      I wanted to use this engine in an OTS plane as it had such a great p&c seal.  Talk about easy starting!  It is an older Fox with the filleted piston baffle and the brass end pads on the wrist pin. Any idea as to when it was made?
                                                               Stay well my friends,

                                                               Frank McCune
p.s.
     The prices that are on the Fireball Plugs reads 39 cents.  I must have bought them in the 70's! Lol

Offline frank mccune

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Re: Engine will not run with battery disconnected??????????????
« Reply #10 on: March 21, 2015, 03:20:57 PM »
      Hello All:

      I ran the Fox .29 Stunt again today and here are the results:

      The engine will only run in a fast 2 cycle mode.

      The engine will stop if it is leaned out or richened up a bit.

      The plugs used are Fireball Yellow, Fox 2v.,K&b std.

      There were also many unidentified plugs used.

      The nva was changed to a Fox .15.

      The engine will run with the battery disconnected with no loss of rpms.

      The engine will start first flip.

       I checked the plug and fuel in another Fox .35 Stunt and they performed perfectly.  Perhaps this engine needs more break in time, hotter fuel or plug.  It may have advanced timing for racing in the 50's and will not 4 cycle.  I could put it away and stop wasting time with it or put it an old Foxberg plane and fly it at high rpms with a small prop.  Perhaps a 9x4 or a 9x5 would be the cats's pajamas.  The p&c has made a good seal!

     Time to move on!

                                                        Thanks for all of the help,

                                                        Frank mcCune

p.s. When I started this engine for the first time and after I pulled it down to check the internals, a lot of black residue was emitted from the ehaust for awhile.  The only thing that I could think of causing this was aluminum on aluminum wear. Perhaps the con rod was rubbing on the back plate.  I will check for this potential problem.  This black rsidue ceased after about a minute of running time in each case.




   

 

Offline David Ruff

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Re: Engine will not run with battery disconnected??????????????
« Reply #11 on: March 21, 2015, 04:10:57 PM »
I'm thinking you should run the Fox 35?

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Offline bob whitney

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Re: Engine will not run with battery disconnected??????????????
« Reply #12 on: March 21, 2015, 04:25:16 PM »
one more thing to check is head or back plate leakage take i small cup and fill it with water or after run oil. stick the head in the cup ,up to the exhost port ,turn the engine over and see if there is any bubbles coming from the head or glo plug .if using water make sure to lube the engine when finished  can also just drip oil aound the case /head joint and turn over ,do the same for the plug

dont like the fact that u are getting black oil from an older engine
rad racer

Offline Bill Little

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Re: Engine will not run with battery disconnected??????????????
« Reply #13 on: March 21, 2015, 04:36:42 PM »
Hi Frank,

The only thing I can tell you is that the Fireball "Yellow" and K&B "Std" are NOT "HOT" plugs.  I know there can be an exception to every rule, but every 4-2 engine I have used had to have a HOT plug to run "correctly".

I would put more bench time on the engine.  Also at least 25% oil and mostly castor (as I am sure you know).  During bench time I would run 25% castor, 3% synthetic to get 28% oil and still keep it fairly clean inside.  Plus all that oil does have a cooling effect on the engine (as you also know) so a non broken in engine running a lot of oil at a constant air speed (0 mph forward) should really need a hot plug just to keep the fire lit if the temps are like they are here! y1

Also, bench run it with a 9-3 prop, or a prop 1" less diameter and 3"-4"pitch. George and Big Art recommended this.  I got a 10-3 1/2 Top Flite to break in the .35 and .40 engines I have on Big's recommendation.

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Offline frank mccune

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Re: Engine will not run with battery disconnected??????????????
« Reply #14 on: March 21, 2015, 07:46:10 PM »
     Hello All:

      Thank you for all of the very intelligent suggestions.

      Bob mentioned about checking for leaks by dunking the engine into a clear container of water.  I did this and found NO leaks.  This is how I solved the leaking head gasket problem.  I had to play with the head screws to get a perfect seal but I got it.  If I had not gotten lucky with the screws, a friend of mine offered to face the head to get a good seal.

     Bob, I must confess about the black residue the was emitted from the engine upon the inital start ups after disassembly. I think that I was forcing the con rod into the back plate with the electric starter.  I saw score marks on the back plate caused by the conrod or crankpin and I removed them.  I used to electric starter again and the marks were back again even though very light.

     I replaced the orginal paper backplate gasket with a newer cork gasket which is much thicker.  Perhaps now I may use the electric starter without scoring the backplate.  Perhaps I should have a thrust washer made to prevent the crankshaft from being moved via the electric starter.  It is much easier to cut an additional backplate gasket. Lol

     I know that it is nearly a cardinal sin to use an electric starter but due to health reasons, finger flipping and using a chicken stick have become difficult for me.

      Dave, perhaps you are correct.  Why keep beating my head against the wall whdn I have a large number of Fox engines that work well? 

    Again, thanks for all of the help.

                                                         Stay well my friends,

                                                         Frank McCune


Offline Jim Kraft

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Re: Engine will not run with battery disconnected??????????????
« Reply #15 on: March 23, 2015, 02:50:38 PM »
Frank, a couple of other things that could cause your problem. When using the electric starter I am sure you wiped a little aluminum off of the back plate. That will go right to the plug and destroy it in short order. The other thing, when you had it apart was the rod loose on the wristpin or frozen to it. They can get stuck on there from congealed oil and put the rod in a bind or push the wristpin into the cyl. wall. Just a couple of things to check other than getting a good hot plug in it. I hope you find your problem as I just went through one of these and it runs great on the test stand. Hoping to fly it soon in my Sterling profile Mustang.
Jim Kraft


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