71T Speed Sensor Causing No Spark?

[Stretch32]

I've got a '71 T with all stock 2.2 engine including ignition system. I just got the engine back in the car yesterday and could not get it to start. I intentionally left the speed sensor (located under the left carb cam) wires unhooked because I was told doing so eliminated the enrichment circuit from operating thereby making the carbs easier to tune. With that said after a friend and I looked at a wiring diagram we realized those 2 wires had to be hooked up for power to actually get to the distributor. After hooking them up the car started and ran. Today while driving my ignition began to miss intermittently and now the car won't run at all. It has the same symptoms from yesterday prior to hooking up the wires to the speed sensor. The CDI is buzzing so there is power and there's very weak power at the dizzy but no spark. My thought is the speed sensor has failed replicating the same issues as having it unhooked. Is this possible? Do you have to have the speed sensor hooked up in order to have the dizzy produce spark? Lastly is there a way to bypass this or trouble shoot to confirm this is in fact the problem? Any thoughts? Thanks in advance,

Stretch

[304065]

You don't have to have it hooked up, but the speed switch runs off a black/purple wire that also drives the tach and is connected to the points. Are you absolutely certain that the wires to the speed switch are not touching either ground or other wires? And that they weren't previously? It sounds like the breakup is due to CDI misfiring, which could be caused by these wires making contact when they shouldn't.

[Stretch32]

Thanks for the reply. I think I'm having ground issues related to the engine ignition wiring harness and the speed switch wires may or may not be the issue. I'm actually thinking, after pulling the wiring harness off a few weeks ago, that my overall wiring harness for the CD ignition and engine may be in poor shape since it's all original and doesn't appear to have ever been tampered with (so it's over 40 yrs old). I can tell you the black and purple wire was pretty dirty and coroded even after stripping some coating off looking for a clean piece of wire which I was unable to find. When the engine quit while driving the tachometer dropped to zero when the ingnition failed. After looking around I really think there is power to the CD box and coil and it's just not cleanly getting to the dizzy and points. I think a replacement harness for both the engine and CD Ignition may be the best solution to replace the frayed original braided ground straps for the CD Ignition and brittle original wires. Any thoughts and this?

Stretch