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Is it my ignition or engine?

Old 06-08-2012, 11:29 AM
  #26  
raptureboy
 
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Default RE: Is it my ignition or engine?

I disagree, RCxel ignitions are very reliable. What size battery are you using? Lot's of guys try using 6v which can damage the ign module, all thats really required is 4.8v. Your sensor could be going bad. You can buy an ignition tester from many of the gas engine suppliers. Go back to the last thing you changed before the problem.
ORIGINAL: All Day Dan

George, that's one of the most popular and unreliable ignitions around. Borrow one from one of the guys that you know is working. Dan.
Old 06-08-2012, 02:11 PM
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triumphman49
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Default RE: Is it my ignition or engine?

Hey GAGA,
If new ignition is needed, you might give Adrian a call at C H Ignitions. 240-888-5902.

A great guy and many have been served well by him here on RCU.

T-man49 in Al
Old 06-08-2012, 03:23 PM
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Default RE: Is it my ignition or engine?

Well everuone I was wrong I am running 2 rx packs, and 1 6V ignition battery, used the 6v regulator to keep the voltage below the 6v max.

So.. I took that out and put in one 4.8V battery pack, no difference. I will stay with one pack though.

I also messed up, the stock ignition module was crap, not the RCexl that is on their now, that is a good ignition, I thought this one was the stock one.

I will give that guy a call in the post above.

Thanks
George
Old 06-08-2012, 03:24 PM
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Default RE: Is it my ignition or engine?

I remember reading something Jedi wrote once, at 6v your ignition uses more current and therefore drains the battery faster so in fact a 6v pack of equivalent mah actually lasts less time than a 4.8.
Rcexl are fine, just use the correct voltage and mount them with some kind of cushion so it doesn't vibrate to bits.
I saw one fellow who cable tied it directly to the stand offs close to the muffler, when I asked if that was a good idea he snapped at me, so I dropped it.
His ignition will fail and he'll blame rcexl for it being crap.

Back to the topic, take out the regulator and try that first, check the voltage on your battery, 4.8v 2000mah is more than enough.
Your 6v supply may have already fried the ignition though.
If that fails, pull the jug off and look at the ring, a repeated "ta ta ta"sound coupled with low compression leads to that.
You said it had low compression, did it just start or was it always like that?
Old 06-08-2012, 03:34 PM
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Default RE: Is it my ignition or engine?

Now I am using one 4.8v ign. pack, 6v, and regulator gone. No difference.

If the ignition fails would it work at all? The plane starts, idles great, when throttle is applied I get the RATATATATATATATATAT..... nothing else, the the motor starts back firing, and spiting until the throttle is lowered back to idle and then it is fine, until throttle is applied again.

I also asked a couple companies who sell this engine, parts etc... about its comepression, they said it is not a high compression anyway. It does have compression, but I am used to a 1/4scale HPI baja with a 2-stroke gas engine, when you start that, if youdo not hold the buggy down you will lift it right off the ground, and it weighs at least 20lbs.

Grrr......This sucks!
Old 06-08-2012, 05:27 PM
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Default RE: Is it my ignition or engine?

The ignition coil went bad. Unfortunately you can't replace just it. They put it inside of the ignition module.

I have had the COP coils (coil on plug) go bad and behave exactly like that. The engine would idle and run up some RPMs and then flake out. But since the coil was outside of the ignition module I could measure its coil resistances and see that it had gone bad. The model airplane CDI units are all sealed up and potted with epoxy, so one cannot just open them up and check or measure anything. Even on the few that they didn't use epoxy to seal them up good with, if you try and take them apart they sort of get all mangled in the process.

One cause for the coil to go bad is an excessive spark gap.Where the spark has to jump a distance greater than the small gap on the spark plug. That large air gap causes the voltage levels to increase or spike tremendously. A example is looking to see how long of a spark one can get, or quite common is the spark plug cap coming loose on the spark plug. Most modern cars state to never ever pull a coil off of the spark plug as it will destroy the coil immediately. usually our model engine ignition systems tend to have a bit of a delay effect when the coil has that happen to it. The coil goes bad later on you.

The COP (coil on plug) design is where they use a higher voltage to drive the coil with. Such as 80 volts or more. The CDI system has a voltage multiplier circuit inside of it that boosts the battery voltage up to some pretty high levels. The higher the voltage you use to drive the coil with the smaller you can make the coil in size. The COP coil does not have to be mounted right on top of the spark plug, but that is the more ideal location for it, all the car engines have pretty much gone to that method as they eliminate the need for a distributor then. So the small coil can be separate and still use a spark plug wire. Since the model engine CDI modules are sealed up and potted, I can't measure any of them to see what the voltages are that are generated inside of them. But they do generate a pretty healthy spark across the spark plug though.

Old 06-08-2012, 06:01 PM
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Default RE: Is it my ignition or engine?

Hi

Quote : if youdo not hold the buggy down you will lift it right off the ground, and it weighs at least 20lbs.

This engine doesn,t have a 20 inch prop ,............................. it has a 1/2 inch spool . You can not compair this two .

Do what has been suggested to you .

CHANGE THE IGNITION

Michel
Old 06-08-2012, 07:02 PM
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Default RE: Is it my ignition or engine?

I just had a thought. Did you try a new spark plug in the engine?

Old 06-09-2012, 03:34 AM
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Default RE: Is it my ignition or engine?

Yup tried a new plug.

Well next to try is a new ignition......

Thanks everyone, I will keep you posted.

George
Old 06-09-2012, 04:31 PM
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Default RE: Is it my ignition or engine?

When you try a new ign go with tghe 4.8 volt batteries, 6volt is a killer
Old 06-09-2012, 06:06 PM
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Default RE: Is it my ignition or engine?

Yup, new ignition ordered, and going with 4.8V pack.
Old 06-09-2012, 07:21 PM
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Default RE: Is it my ignition or engine?

I was just breaking in a new gas engine today on my test stand. I ran the ignition unit off of a 4.8v 2000mah pack for a little over 2 hours and it still had plenty of power left in the pack. So unless you have one of the old style ignition units, you'll be able to fly for quite a while off of a 4.8v 2000mah pack.

Old 06-10-2012, 07:52 AM
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Default RE: Is it my ignition or engine?

I'm curious to what the plug gap is? If it is too large the ignition may not have the power to arc across the gap. I would check, it's a 5 min thing. Set it to .015 and give a try. Got nothing to loose.
Old 06-15-2012, 05:51 AM
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Default RE: Is it my ignition or engine?

Well problem solved! I think....

Bought a new ignition, no change.
New spark plug and ignition no change
New spark plug, ignition, 4.8v 2000mah battery (eliminated the 6v regulator, and 6v battery) no change
Cleaned carb, all new gaskets etc... no change
Tore engine apart to check for stuck or sticking ring etc... engine is not perfect but nothing worth replacing. I put the engine back together, when to start it, and it would not start, no spark. I checked my ignition with my ignition tester, and it worked. BAD HALL SENSOR!!!!!! ALL OF THIS FOR A BAD SENSOR!!!

Replaced that, started right up, and revved like normal. All that time, and money for a what would have been 10.00 fix.

I will keep you all updated to see if this "fix" lasts and was the problem from the get go. Still have not flown the plane since all of this.

Thanks everyone!

George
Old 06-15-2012, 06:49 PM
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Default RE: Is it my ignition or engine?

This has been posted here before by JediJodi, but here it is again. This time pay attention:
Troubleshooting guide for RcExl ignitions
If you have no spark or think you are having an ignition problem, carefully following this guide will test the ignition module, hall sensor, and spark plug cap components. This guide can be used for single or twin cylinder ignitions; it does not test the manual or any optical ignition switches that may be in the system. You will need a good fully charged 4 cell NiCd or NiMH battery, an old servo extension, and your trusty volt meter.


Take an old expendable servo extension and cut off the male plug end, separate the wires, strip a bit of insulation from each of the 3 leads and plug the other end into the sensor lead on the ignition module.

Put a good spark plug in the cap, doesn't need to be all the way seated but far enough for the hex of the plug to make good contact with the metal shell of the plug cap, plug a fully charged 4 cell battery directly into the ignition.

Test for battery voltage at the red and black wires of the test extension you made and plugged into the sensor lead of the module, if there is no voltage replace the module, if there is battery voltage:

Short the white and black wires together, every time you break this connection there should be a spark, if there is no spark or intermittent spark you have a bad module. If you get a good spark:

Remove the test lead and plug the sensor on the engine into the module and turn the engine over, if no spark, replace the sensor. If you have a good spark:

Remove the spark plug, look down into the plug cap and turn the engine over, if you see spark arcing through the silicone boot to the metal shell, replace the spark plug cap. If there is no visible spark but you hear a snap:

Put a small screw driver into the bottom of the cap, turn the engine over and you should observe spark jumping from the screw driver to the plug cap shell outside of the silicone boot, an arc of about 1/4"-3/8". If it does this there is nothing wrong with the ignition. If you hear an arc but it's not in the cap with the screw driver, it could be a problem with the resistor in the cap or the high tension lead where it goes into the cap, replace the plug cap.

All of this can be done on a bench; the plug does not need to be grounded to the engine.

As Jodi would say: Now go outside and play!
Old 06-15-2012, 06:58 PM
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Default RE: Is it my ignition or engine?

Glad you found the problem. I missed it earlier and thought you had already tested the hall effect sensor. Sorry.
Anyway, at least you got some extra ignition parts should you ever need them again.

Old 06-16-2012, 04:23 AM
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Default RE: Is it my ignition or engine?

Thanks everyone

Flew it last night since the fix all fine for now!

Thanks everyone.
Old 06-16-2012, 04:50 AM
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Default RE: Is it my ignition or engine?

Sometimes the dogs bark up the wrong tree... glad you got it flying well. And... thanks for informing the thread of the results. It is frustrating when a thread ends with no report of the outcome.

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