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Discussion Topic:
Will not start when hot
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46merc |
05-26-2013 @ 4:35 PM
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Member
Posts: 22
Joined: May 2013
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I have a 1946 Merc 69m convertible which has a habit of being hard to start when hot in fact it will not start at all until left to cool down. It has plenty of battery and spark so appears to be in the fuel supply. Can anyone point me in the right direction as to the cause and how I can remedy this. Cheers Mike.
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supereal |
05-26-2013 @ 8:24 PM
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Senior
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Joined: Oct 2009
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Even though the spark appears OK, if you have an original, unrebuilt ignition coil, it is more than likely that is the cause of your problem. When they get hot, the intensity of the spark drops until the coil cools. You can test this by cooling the coil with an ice bag when you try to start it hot. We install a simple hot start circuit to offset the system voltage drop caused by the starter. I can post the instructions if you wish.
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46merc |
05-26-2013 @ 9:29 PM
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Hey thanks for your prompt reply supereal. Yes I would appreciate your instructions for a hot start circuit. Cheers Mike.
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supereal |
05-26-2013 @ 10:01 PM
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Senior
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OK, Mike. I'm attaching the "quick start" instructions. It is a derivitive of a circuit used years ago by manufacturers to aid starting. Some used the start part of the ignition switch, others used a terminal on the starter solenoid. This was before solid state diodes came on the scene. The problem is that the starter, in drawing 100-200 amps, saps the battery to the point the coil is starved. The coil needs about 3 volts, and the starter can reduce it to the point that the coil fails to generate adequate spark. When the coil is heated, both by operation and under hood heat, this causes high internal resistance that further interferes with starting. This device costs almost nothing, but will aid in starting, hot or cold, if your coil is in good condition. If not, send it to Skip Haney for a rebuild. ALL old coils are bad.
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TomO |
05-27-2013 @ 5:38 PM
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Before you install the hot start fix, check your spark. If you have 1/2" spark, the fix will not make a difference. You may be flooding the engine due to a high float level or a power valve gasket leak. Try starting the car with the accelerator pedal pressed to the floor.
Tom
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supereal |
05-27-2013 @ 7:05 PM
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If you want be sure, carry a clip lead. When the car won't start hot, clip the lead between the coil input and the battery. Checking voltage at the coil is tricky, as it is pulsed by the points, requiring a special (RMS) reading to determine the actual coil input when the starter is activated. If the car starts with the jumper in place, you have the answer. Check the spark plugs. If they are black, you have a fuel leak at the carb. If not, the spark is insufficient when the starter is running, my best bet.
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46merc |
06-06-2013 @ 7:53 PM
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Joined: May 2013
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Thanks for the quick start diode instructions Supereal. Can I attach the other end of the wire (not the coil end) to the starter button or does it have to be attached to the starter motor. As the Coil is on the left hand side of the car and the starter motor on the other side it would look better if it was attached to the Starter button if possible. Or can it be attached to any hot wire on the firewall. Cheers Mike.
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supereal |
06-09-2013 @ 3:00 PM
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The reason the quick start is fed by the starter side of the solenoid is to activate the boost only when the starter is energized. When the starter is off, it removes the full battery voltage to the coil. The diode is a "check valve" to prevent the regular coil feed from being applied to the starter. The device must be attached exactly as our instruction shows. For appearance, we conceal the wire across the firewall behind wires already there. The starter button only furnishes ground to activate the solenoid.
This message was edited by supereal on 6-9-13 @ 3:02 PM
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46merc |
06-09-2013 @ 8:33 PM
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Posts: 22
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Many thanks for your words of wisdom. Will connect the diode as per instructions. Just on another matter I am about to replace a noisy bearing on the 6 Volt generator. Would you recommend doing anything else while I have it apart? Cheers Mike.
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40 Coupe |
06-13-2013 @ 3:16 AM
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There should be no need to attach additional jumpers or special circuits for you car. The above are band aids and may help your car to start, due to a problem, but are not necessary for a properly operating vehicle, and do not FIX a problem. I too, like Tom, suggest a Carb. problem, you may want to have the Carb. rebuilt by someone with a lot of experience such as Charlie Schwindler, see V8 Times ad section. If you believe your spark is the problem have the coil tested and if the distributor has not been looked at in some time have it checked. Jim Lindner at Bubbas Hot Rod Shop does a good job, on the electricals for the ignition.
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