| jfarrell | -- 03-18-2017 @ 1:55 PM |
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I know this subject has been covered before in this forum but I can't find it in a search. so here goes. Our 49 Ford V8 runs great when it starts up. engine was recently rebuilt using a 4" Merc crank by someone I consider a well qualified flathead mechanic. Everything on the car is also recently rebuilt. Gas tank was cleaned, carb is new from Carpenter (I changed carbs and it made no difference), fuel line is new, battery is new, just replaced coil and condenser (haven't run the car since changing them), reset and filed points, cleaned plugs and am using only non-ethinol gas. Flex line between fuel pump and carb is also new. Everytime car is taken out it runs great for several miles, then starts missing, then after a few more miles of running rough, quits. Right after it quits the bowl on the fuel pump is observed to be full with no residue showing at bottom. Let it set for hours or overnight and it starts right up. I know I need to do some testing, and I need to go back to the bonehead stuff. I'm missing something and with me it's usually something simple (hopefully). Can someone walk me through exactly what tests need to be done and how to do them? Thanks you
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| carcrazy | -- 03-18-2017 @ 2:16 PM |
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It sounds like your coil is going bad. I have had similar problems with coils, even new ones that would stop working after about 10 minutes of engine running time. Install a new coil and check to see if you still have a problem.
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| supereal | -- 03-18-2017 @ 2:39 PM |
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You said you "filed the points". If points are burned or eroded, they should be replaced, not filed. That produces a rough surface on the contacts that will fail after a short time, particularly if the condenser is weak.
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| TomO | -- 03-20-2017 @ 8:01 AM |
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Also, before you change your coil, check your spark, when the engine is running good and when it is running rough. It should be a nice blue spark when idling. if the spark is good when the engine is cold and bad when it is warm, then the coil is probably bad. If the spark is a weak orange spark under both conditions, check your condenser and point dwell. Replace bad parts. Tom
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| trjford8 | -- 03-20-2017 @ 1:06 PM |
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Does your car have an internally resisted coil or is there an external ballast resistor?
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| jfarrell | -- 03-20-2017 @ 3:25 PM |
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The new coil I installed had written on it that it had an internal resister. I understood the prior coil to be the same. Thanks. Jim Farrell
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| rotorwrench | -- 03-20-2017 @ 3:49 PM |
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The coils for the 1949 cars were just plain Jane coils. There was no need for an external resistor and the primary resistance was set up to work well with a 6-volt system current draw. The later type higher resistance coil may be hard on the current draw and causing a weak spark. The internal resistor primary types are OK for 12-volt conversions but not so much for an old 6-volt car. One of the most common problem these days is very poor quality condensers. Manufacturer's in 3rd world countries don't care if they work or not. It has to be able quickly build a charge and boost its charge rapidly to the coil or the points will burn up. It also has to have enough capacity to increase the induction of the coil giving a stronger and longer lasting spark at the plug tip. If is doesn't do its job, your spark will be weak and the points won't last. They can also be temperature sensitive as much as a coil can.
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