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| Ballast Resistor Readings https://www.slantsix.org/forum/viewtopic.php?t=38693 |
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| Author: | manco-capac [ Mon Jan 18, 2010 4:47 pm ] |
| Post subject: | Ballast Resistor Readings |
Hi All! In trying to cure a hard start condition on my 1963 Dart after setting for a few hours, I started taking voltage readings on the + terminal of the coil. My understanding of the ballast resistor is that in the run position of the ignition switch, 6-7 volts actually is fed to the coil for running. It is only during cranking that the full 12 volts are fed to the coil. The lower run voltage saves point wear and seems to be sufficient for normal engine performance. My readings during the run position (engine off) is 6-7 volts. Cranking is 7-8 volts and running is 10-11 volts. A new ballast resistor made no change. The ballast resistor wiring is all stock as is the whole car. What am I missing here? Mis-wired ignition switch? Thanks! |
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| Author: | SlantSixDan [ Mon Jan 18, 2010 5:13 pm ] |
| Post subject: | Re: Ballast Resistor Readings |
Quote: My readings during the run position (engine off) is 6-7 volts. Cranking is 7-8 volts and running is 10-11 volts.
What is your voltage across the battery while cranking? These readings look OK to me other than a potentially low line voltage while cranking which might suggest a weak battery or voltage drop in the battery cables and/or elsewhere in the wiring harness. But on the whole, if you are trying to chase a hard-start-after-sitting condition, you are likely barking up the wrong tree looking at the ignition system. It's probably fuel-related. What are the (exact) symptoms?
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| Author: | emsvitil [ Mon Jan 18, 2010 5:25 pm ] |
| Post subject: | |
The 6-7 volts makes sense if the points are closed while you're testing. I think you're fine. |
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| Author: | manco-capac [ Tue Jan 19, 2010 8:30 am ] |
| Post subject: | Ballast Resistor Readings |
Hi Guys! Thanks for the input. When cranking, battery voltage at the battery, is a little over 9 volts. That's a bigger drop than I expected out of a newer AutoZone battery with 460 cold cranking amps that someone just put in. So cranking voltage at the coil of 7-8 volts seems to be in line. But why am I getting 10-11 volts at the coil while running? Shouldn't this be about 7-8 volts to protect the points? The hard start problem occurs after setting overnight or even after only 3-4 hours. Need to crank about 15 revs before starting. I am getting spark at the plugs. The fuel pump, while discharging into a container is putting out a lot of fuel. The carb is a Holley Reman #64-1205 and has a sticker date of 2-23-09 so someone replaced it recently. Before cranking, operating the linkage and looking into the carb shows a little gas coming out of the accelerator pump. After it starts, it will restart on the first rev. So there! |
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| Author: | SlantSixDan [ Tue Jan 19, 2010 9:20 am ] |
| Post subject: | |
"Remanufactured" carburetors tend to work poorly — I still think your starting difficulty is fuel-related. Carburetor operation and repair manuals and links to training movies and carb repair/modification threads are posted here for free download. (Also, going forward, keep in mind that Autozone's parts tend to be of poor quality.) Voltage at the coil with the engine runninng will vary with line voltage and ballast resistor temperature, which will vary with engine RPM. I'm not sure I like your 1-2v drop between battery and coil while cranking, but I still don't think that's the source of your starting difficulty. |
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| Author: | WyoCowboy [ Tue Jan 19, 2010 11:10 am ] |
| Post subject: | Leaking fuel |
This sounds a lot like my problem with a leaking fuel bowl. When left overnight, the fuel leaks out of the bowl, then the next time I crank it up, it takes awhile to get fuel from the pump to the carb sufficiently to start the engine. Thereafter, there is fuel in the carb, and it starts right up. But let it sit for a day, then we're back to cranking for 15+seconds. Look for dripping fuel from the bowl, stained intake, dust/dirt on the intake. These symptoms are exactly what I had. |
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| Author: | manco-capac [ Sat Jan 30, 2010 1:53 pm ] |
| Post subject: | |
Hi Guys, Sorry to be so late with this but had other matters that pulled me away from the starting problem. As suggested, I measured battery voltage while cranking and it was 9 volts! Big drop. Load testing showed bad battery. New battery only drops to 11 volts and now have 9+ volts cranking. Still losing voltage somewhere but car starts a little better. But I think S6Dan is right about carburation. After driving, I notice a gas smell in garage and outside of carb around air horn gasket (actually has two gaskets installed! A Holly reman Carter.) is a little moist from gas leaking. So I have a carb rebuild gasket set coming. I hope I don't have some major warping going on. Just came in from rolling around under the car installing four new seat belts. I'm getting too old for much of that stuff! Thanks |
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