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Discussion Topic:
51 Mercury w/BW overdrive not working
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Tracker |
02-11-2014 @ 8:32 AM
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New Member
Posts: 157
Joined: Oct 2009
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I think the kickdown switch has been installed wrong. Is there any I can check ? Its a stock 6 volt. The symptoms are when the kick down is activated by pressing on the accelerator, the car begins to act as tho there is an electrical problem...begins to shut down the engine and begins backfiring. Letting off the accelerator restores the engine to running smoothly. mechanic who installed this supposedly had BW experience but doubtful and I 'm not going back. The system does not appear to be down shifting. Prior to the installation, I had operated the car with the OD off since I don't drive it much. It did not start this shutting down /backfiring etc until I had this work performed. Any suggestions would be appreciated . Tracker
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cliftford |
02-11-2014 @ 10:34 AM
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Senior
Posts: 845
Joined: Jan 2014
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Go online to the Ford V8 techno scource. They have a post on trouble shooting overdrives. That should help you solve your problem.
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supereal |
02-11-2014 @ 2:44 PM
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Senior
Posts: 6819
Joined: Oct 2009
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The pupose of the kickdown switch is to briefly interrupt the ignition to allow the OD to release. It does this by grounding the coil, allowing the OD to release. If you need a circuit diagram, I'll post one for you.
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Tracker |
02-12-2014 @ 6:15 AM
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New Member
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Excellent site ...thanks for the suggestion...I had not seen this before.
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supereal |
02-12-2014 @ 10:43 AM
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Senior
Posts: 6819
Joined: Oct 2009
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Here is the circuit diagram of the overdrive. The kickdown switch does two things: First, it opens the control circuit, causing the solenoid to de-energize. Because the pawl is held due to torque, and can't release until the torque is removed, the kickdown switch also completes the igntion grounding circuit thru a second set of contacts, bypassing the ignition points, thus interrupting the ignition long enough to allow the pawl to fall back. This lasts only about one-half of the rotation of the crankshaft. If the connections of the kickdown switch are not correct, it can cause the problems you mention. It is also important to know that the oil supply of the OD is sparate from the transmission, and should be maintained.
This message was edited by supereal on 2-12-14 @ 10:45 AM
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Tracker |
02-12-2014 @ 12:51 PM
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New Member
Posts: 157
Joined: Oct 2009
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Thanks a million SR...I checked the KD switch wiring against the diagram and it isn't even close to the proper sequence of wire colors. I would have never fixed this on my own. When it warms up tomorrow, I will make the necessary corrections and get back to you with the results. The problems I described earlier felt just like the ignition switch had been turned off and then on again. The engine would almost quit but came on again when I completely released the accelerator. Pretty sure just by looking this diagram will solve the problem. Can't tell you how much I appreciate your help on this. Tracker
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supereal |
02-12-2014 @ 3:36 PM
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Senior
Posts: 6819
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You are welcome. In tracing the wiring, the colors are not always visible, and need to be traced from end to end. At our shop, we use a special trace tool, but an ohmmeter will work as well. Just one wrong connection will usually result in loss of overdrive.
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Tracker |
02-13-2014 @ 6:07 AM
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New Member
Posts: 157
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SR...got the kickdown switch rewired per the diagram but I have a question on the coil connection This car is positive ground 6 volt stock....shouldn't the wire from the Od go to the negative side of the coil ? Right now it is connected to the positive side. I have read that the coil would work either way but nothing on the OD. Thanks again. Tracker
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TomO |
02-13-2014 @ 7:25 AM
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Senior
Posts: 7250
Joined: Oct 2009
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The purpose of the wire is to ground out the ignition points during the kickdown process, so it needs to be connected to the coil terminal that goes to the points.
Tom
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supereal |
02-13-2014 @ 10:50 AM
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Senior
Posts: 6819
Joined: Oct 2009
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Tom spelled it out. The wire from the kickdown switch is connected to the distributor side of the coil. As for polarity, in a positive ground system, the distributor is attached to the output (positive) side of the coil. That is also where the condenser is connected. Remember that "circuit" means a circle from one battery pole to the other. In the positive ground old Fords, the flow is from the negative terminal of the battery to the positive pole thru the system. In reality, efficient current flow is the other way, the reason the switch to negative ground was eventually the rule. If the polarity of an old Ford is changed, such as in going to a 12 volt negative ground system, the connections at the coil must also be flipped. Almost all accessories, such as radios, use negative grounding and, as such, have to be isolated if the chassis is used as the ground terminal. Old Henry was noted for his staunch beliefs, and resisted change in most cases. Thus, positive ground was the rule until years after he went to the "great garage in the sky".
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