| March40 | -- 05-29-2015 @ 1:42 PM |
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I have a stock 1940 flathead v8. It misses, and cuts out when accelerating. It runs ok for the first 15-20 miles then runs progressively bad. Finally stalls at red light and will not restart. After complete cool down it will operate again for 15-20 miles. Been doing this for 18 months. Here's the history: Engine rebuilt about 5 years ago (everything stock). Ran fine for 3-4 years. In last 18 months I replaced round 6v coil & condenser 3 times (all Echlin), coil gets full 6 volts, replaced distributor twice, replaced high tension copper wire 2 times, replaced coil to distributor adapter. Have tested ignition switch by bypassing with wire direct from battery coil. Cleaned and gaped plugs, rebuilt carb 6 months ago and rechecked float level yesterday. New mechanical fuel pump, new flexible fuel line. Coil output is 10K volts. Copper spark plug wires are 4 years old. Fuel tank and steel fuel line replaced about 8 years ago. Tried electric fuel pump both connected and disconnected. Fuel is always fresh. Seems to run better on cool mornings than hot afternoons. After all these changes over last 18 months it still runs like cr*p today! I would like to hear any suggestions.
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| carcrazy | -- 05-29-2015 @ 2:29 PM |
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The symptoms you describe could be caused by coils or condensers going bad or a weak fuel pump. I have experienced trouble with several round coils (12 V with internal resistor) before going with a Bosch 12 V coil for a VW Beetle which seems to have solved the problem. If you are running a 12 V system, you might want to do the same. If you are running a 6 V system you might want to get a Bosch 6 V coil for an older VW Beetle. Does your coil replacement adapter have a spring behind the carbon piece that contacts the rotor to ensure a good contact as the engine warms up and the distributor expands with the increasing temperature? Does the engine overheat before you experience the engine running problems? Do you have any coolant leaks into the cylinders that increase with temperature contributing to problems with combustion? Are all of your secondary ignition wires (spark plug and coil lead) solid core metal items? When resistance type (carbon core) ignition secondary wires go bad the resistance of them can go to infinity as they warm up.
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| pauls39coupe | -- 05-30-2015 @ 6:03 AM |
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You did not mention replacing the ignition resister under the dash. Heat will cause them to fail, then reconnect after they cool. Also try taking the ignition switch apart to be sure everything inside is bright and shiney. If you go back to the stock coil have one rebuilt by Skip Haney, they work and fit your distributor correctly. Some of the adapters have had problems not lining up with the contact in the distributor.
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| TomO | -- 05-30-2015 @ 7:39 AM |
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How are you checking the coil output to determine that it is 10K volts? I would check the spark when the engine is at normal operating temperature. You can make this test in your driveway. Let the engine run until it is at normal operating temperature for your car. Use a fuse puller or other insulated tool to remove a plug wire and hold it close to a head nut. You should be able to see a 1/2" blue spark. If you have this, go onto fuel delivery tests. If the spark is orange in color or not at least 1/2" long: Cheek the input to the coil, it should be 6 volts with the points closed. If it is in the range of 3-4 volts with the points closed, your ignition resister is not bypassed or your ignition switch is bad. Check the wiring of the coil. The + terminal should go to the distributor on a 6 volt POS ground system. If the coil has been connected backwards, replace it as it has been damaged. Check the distributor resistance by connecting the POS or red lead of your ohm meter to ground and the black or COM lead to the + terminal of the coil. Tap the starter until the lowest OHM reading is obtained. The points will be fully closed at this time. The reading should be less than 1 ohm. if it is more , remove the adapter plate and check from the copper contact for the points. This will let you know if it is the adapter plate or the distributor. If this is all OK, come back with the results and I can give you more tests to help isolate your problem. Tom This message was edited by TomO on 5-30-15 @ 7:40 AM
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