Piston Slap: You Spin Me Right Round Edition

Sajeev Mehta
by Sajeev Mehta
piston slap you spin me right round edition

Captainzerocool writes:

Sajeev, I’ve recently acquired a 1969 Ford F100. It is a solid truck with the 360FE and three on the tree. It does, however, have an electrical problem that I can’t nail down. Apparently, the key or the ignition switch isn’t needed to get the motor to attempt to turn over. Once I attach the positive terminal, the starter motor begins to rotate and will not quit until the battery is disconnected. The starter and starter solenoid have been replaced. Is there some random wire that isn’t/needs to be grounded? Any and all help is appreciated.

Sajeev answers:

For older vehicles in unknown condition, replace your battery cables and clean the mounting surfaces for your chassis/engine ground wires. That’s probably not the source of your problem, but new cables are great fire insurance and keep your cranking/charging system happy. And it’ll cost $20 or less.

But it won’t cure the problem. Probably. So now it’s visual inspection time.

Check for homemade hack jobs. I’d recommend getting a Ford (or Helms) shop manual with a wiring diagram for 1969 Ford trucks. You can spend less for a cheaper manual, but they are harder to use and never as comprehensive. Several on-line places (like eBay) sell reproduction paperback manuals, but you might prefer the cheaper CD-ROM equivalent.

With book (or laptop) at hand, check the wiring harness around the following parts: ignition switch, solenoid, starter, ignition module and starter relay (if equipped). Look for frayed, rotted or spliced wires near these components. As you probably know, these components are grounded, which somehow connects to the negative battery cable.

[Send your technical queries to mehta@ttac.com]

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4 of 14 comments
  • Tony7914 Tony7914 on May 09, 2009

    You can find wiring diagrams for your truck here. http://www.fordification.com/wiring.htm

  • Tyler D Tyler D on May 09, 2009

    @tony7914: Frackin' A! That is what I needed. Thanks! @Paul Niedermeyer: That is what I am hoping for.

  • SCE to AUX SCE to AUX on May 09, 2009

    @Captainzerocool: You have stumbled upon the secret technology that will permit the Chevy Volt to go 40 miles without its gas engine starting. Every Volt will be fitted with an ignition switch from a '69 F100! Heh.

  • GS650G GS650G on May 11, 2009

    Red with a blue stripe is the wire that triggers the solenoid. If it is loaded with 12 volts it will try to start all the time. Shorts can develop in the firewall connector over the years from overheating. Are you sure you have the correct solenoid? Some solenoids are pass through designs and have two connectors for signal. If you have one of these, move the red/blue stripe wire to the other terminal .