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03-28-2021, 12:26 AM | #21 |
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Re: Ignition Problem or Carb Problem
As I have stated previously you can measure voltages and resistances till the cows come home but to really know what is going on in the coil primary circuit the current draw needs to be measured with the engine not running and dist timing points closed so as to complete the circuit and then with the engine running at idle speed. Use a good quality digital multimeter with a 10 amp capability. Engine not running with ignition switch ON should be 3 to 5 amps. Test quickly so Ign. is not on longer than a minute. Run engine at idle speed and reading should be about 2 amps. If you are in this ball park then all is good. These readings are for both 6 volt and 12 volt systems. Regards, Kevin.
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03-28-2021, 12:28 AM | #22 |
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Location: MN
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Re: Ignition Problem or Carb Problem
I don't know anything. But Pertronix?
Spiral wound wire for electronic ignitions, solid for points. |
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03-28-2021, 02:48 PM | #23 | |
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Re: Ignition Problem or Carb Problem
Quote:
The bad news is that the engine will still barely run; stumbles; won't take throttle and build up rpm past about 1200. Will swap condensers next. It is not shorted, but if the capacitance is too far off, the mismatch with the inductance of the coil could cause a problem. Will report back when checked out. |
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03-28-2021, 04:37 PM | #24 |
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Re: Ignition Problem or Carb Problem
For what it's worth, we made the first prototype "Trash Can" reproduction condenser with a .047 micro-farad capacitor (it was all we had that would fit). The engine (a flathead, of course), ran fine. I wouldn't make a large bet on point life, but that's really not that important. Unless you are concerned with the difference in point life to be 20K miles vs 25K, don't worry about the exact capacitance. A .22 and a .36 are virtually interchangeable on these engines.
If you are going to test condensers, heat cycle them. (You should also check for voltage spikes above the rated value of the condenser being evaluated. I don't know how to do that, so I use capacitors that are designed withstand 600 volts, which seems to be enough.) Last edited by tubman; 03-28-2021 at 04:42 PM. |
03-28-2021, 07:05 PM | #25 |
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Re: Ignition Problem or Carb Problem
You state that the spark is erratic when cranking like it is not hitting every cylinder. I still think that the points need looking into for spring tension and closing or binding. Points hanging open? I have had that happen - tightened the spring tension solved the problem. And you might put s drop of oil on the pivot point.
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03-28-2021, 10:44 PM | #26 | |
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Re: Ignition Problem or Carb Problem
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Quote:
With good advice from members of this board, I pulled the Tubman condenser out of the "return" pile and mounted it so it connects to the coil end of the black wire to the distributor, instead of on the distributor itself. Still need an all out road test, but in the garage it is running like a champ! Thought I knew something about flathead ignition. What I did not know is that a nice blue spark when cranking does not necessarily mean that the problem with running rough is in the carburetor. The other thing I learned is, like starter switches, never buy a condenser from just anywhere. |
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03-29-2021, 12:21 AM | #27 |
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Re: Ignition Problem or Carb Problem
Good news. Sounds like that condenser would work on start up but then fail immediately.
But I think you are not done yet. You said: "I am running a brand new Bosch blue coil which I measured as having very close to 1.5 Ohms. That should not need any other resistor, right?" With your 12V, that will allow too much current, will cook things. You want about 3.0 ohm, either a 3 ohm coil with no resistor, or use your coil with a 1.5 ohm resistor. |
03-29-2021, 08:07 AM | #28 |
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Join Date: Dec 2013
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Re: Ignition Problem or Carb Problem
Thanks, "drolston". I have been looking for that returned condenser for a while, but it never showed up. I guess I now know why. I'm glad it worked out for you.
"squirrel" on the "H.A.M.B." did a little research on the "intermittent condenser problem" mentioned and found that the connection from the lead wire to the the internal workings of the condenser was faulty. It was held in contact only by the crimping together of the condenser body. It would be fine when tested statically or with the engine not running, but when the engine was started, the vibration from the running engine would cause the connection to become intermittent and fail. This why you can run into failures with multiple new condensers. I do mine differently. |
03-29-2021, 08:16 AM | #29 | |
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Re: Ignition Problem or Carb Problem
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03-29-2021, 08:40 AM | #30 |
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Join Date: Dec 2020
Location: Ellensburg wa
Posts: 58
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Re: Ignition Problem or Carb Problem
I’ve been reading these posts and when I saw erratic spark I thought the problem might be the distributor cap. A crack in a cap can be hard to see and a manufacturer defect even harder. What ever it is I know you can solve it. Good luck
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03-29-2021, 11:28 AM | #31 |
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Re: Ignition Problem or Carb Problem
Pleased that you found the problem. I have had straps break off condensers, and a new condenser fail with a no start, but your problem was an education for me too.
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03-29-2021, 08:08 PM | #32 |
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Re: Ignition Problem or Carb Problem
Final report. (maybe)
Did the road test and it runs like a scalded dog. Wound right up to 4800 in first and second without a miss. Got a little spark knock at full throttle in second. Because that "ping" could have been detonation, I first will go back on the heat range on the plugs from the NGK B5HS to the B6HS. If that doesn't take care of it, I will pull back from 4 degrees advanced to 2 degrees advanced. Thanks again to all who walked through this with me. |
03-29-2021, 10:03 PM | #33 |
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Join Date: Dec 2013
Location: Minnesota, Florida Keys
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Re: Ignition Problem or Carb Problem
Since you have a modified engine (heads, carbs, etc.) I will indulge in a little shameless self-promotion and say it looks better too.
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07-05-2021, 02:53 PM | #34 | |
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Re: Ignition Problem or Carb Problem
Quote:
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07-05-2021, 11:30 PM | #35 |
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Location: Shawnee, Ks.
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Re: Ignition Problem or Carb Problem
I'am running a "H & C" ignition with ( 2 ) "Bosch Blue" coils and two "Tubman" condensers. Engine temp got to 200 dg. shut off and would not start. ( No fire at the plug.) Engine cooled down to 180 dg. and fired right up and ran fine.!! We are still looking.??
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