my tach has stopped working, so i tested the output on the MSD box. i thought it was supposed to have a steady 5V, but it was all over the place, so i wanted to put my old analog box in just to test.

i have the main set of wires from the box on a connector for easy removal, so simply did the swap. now the car won't start. it sometimes catches, fires, and then immediately dies, kind of like when a ballast resistor goes bad, but of course that is disconnected.

strange thing is when the old analog box is in it act differently. sometimes when i hit the key it almost sounds like a ton of initial advance when the starter struggles to turn the engine over the first few revolutions, and then kicks in. sometimes it fires, only to die immediately.

i have done the test for both boxes, and they do show spark.

i can't imagine what else could have changed, as i said, all the wires out of both boxes are on the same type of connector, so it's just that and then the 2 wires to the distributor, which are on MSD's connectors.

at the moment, i don't know where to go from here. any thoughts?

Tach not working with MSD. subbed in non MSD ign & it started/ran but when cranking the starter sounded labored like the MSD was either on purpose or not supposed to, retarding the start function. Put MSD back in & it wont start? Wanting to clarify plus a BTT for ya since you ain't getting any love on your Q

i'm glad i don't use'em!

no, sorry, subbed in an MSD analog box. both are 6AL's. the one in there was a digital, the subbed in one is an analog.

neither starts and runs. sporadic, but both will fire at times but always dies immediately.

with the analog box in, starter seems to stall and catch as if the initial was very advanced, digital box does not do that.

ok, my problem. one of the pins was loose in the connector, and when changing boxes it was partially pushed out, making partial-sometimes contact.

an easy one... thanks for tuning in!

that was TOO easy!. Sometimes we need things to go our way

as well you should be. yes, they work great for many people, and while i'm still using mine, i've had countless hours of issues. some operator error, but not all, by any means...

Just something to keep in mind if any more problems arise in the future...I have seen a tachometer go bad and cause it to run rough and misfire. Unplug the tach and it ran fine.

i've heard that before as well. tach isn't working correctly, but doesn't seem to have an effect on the engine. thankfully... sigh...