Page 1 of 1

Will only run when cranking

Posted: Thu Nov 10, 2016 6:28 am
by broncovet
Hi Everyone.
302 motor with recently installed Fitech EFI, Pertronix billet distributor and coil and then entire new Painless wiring harness. All ran incredible for about 2 weeks. Then... I lost it. The motor will turn over and fire when cranking but as soon as I turn the key back to the on position, the motor stops. My radio still has power, so I don't think its the ignition switch. My fuses are good, it's not a fuel issue because the motor runs if I keep the key in the start position.
Seems to me there is either an issue with a connection or short in the wiring harness or something that has gone wrong in the Fitech computer? Not sure where to start looking first from here. Any help is great!

Thanks in advance

Posted: Thu Nov 10, 2016 9:52 am
by Stan
Normally i'd say starter relay then ignition switch but i don't know how your FI tech is wired.
Are you controlling the timing with the FI Tech ?

Posted: Thu Nov 10, 2016 12:07 pm
by broncovet
Timing is controlled by distributor. Brand new ignition switch from painless

Posted: Fri Nov 11, 2016 1:50 am
by DirtDonk
It could still be the switch because the radio and the ignition are two separate circuits.
It could still be a fuse because the engine can run from the Brown wire connected to the starter relay while the starter is cranking. Once you let off the key back into RUN, the "I" post on the starter relay/solenoid is not longer active.

Unfortunately new no longer means working properly, so you can't rule out the switch or the harness.
But check the fuses first. Another guy on Classic had the same issue and it was a fuse.
Or was that you?


Posted: Sun Nov 13, 2016 9:31 am
by broncovet
I have checked all the fuses and they are all good. When I have the key to the on position I don't have any turn signals either...but I do have power to the windshield wipers. Any tips on getting the ignition switch out to check or replace?

Posted: Sun Nov 13, 2016 10:00 am
by broncovet
There is also 0 volts to the distributor with the key in the on position.

Posted: Sun Nov 13, 2016 1:17 pm
by DirtDonk
With a Painless setup, it has to be either the switch, the Red w/green wire to the coil, whatever wire you have to the distributor, or a fuse.
The exception could be a faulty wire or connection from the manufacturer (Painless) but that would be very unusual. Unfortunately, nothing is impossible. Just unlikely.
Luckily though, the fact that it was running at one point makes a fault with the harness less and less likely.

What wire do you have powering the distributor? Same one from the coil, or a separate one?
What color wire is on the center post of the ignition switch? Yellow I think in the Painless? Originally it was Black w/green, but they changed it in the new harness. I just don't remember which color.
What else works and what doesn't? The Ignition is run from one post on the switch, while the turn signals are run from the center post. Two different circuits entirely. Can you check power distribution at the switch itself? That might be the easiest way to determine where to go from here.

Did you do the harness install? What about the switch? You asked for tips, so here's a basic rundown.
You can leave the harness attached to the switch and pull it from the dash. It doesn't have to be grounded to the dash for anything except the Brake Warning lamp on the dash, so every other function is testable.
We have a video on our website on how to remove a switch ( ... Kit#videos I think?) but basically you'll need a medium sized paper clip or small poker of some kind. Let us know if you need a more detailed rundown.
Remove the switch assembly from the dash, let it hang down, put the key/lock cylinder back in, connect the battery and use your tester to make sure power is coming into the switch (Red wire?) then going out on all the others in the different positions. Red w/blue is in START only, but the rest work either in RUN, in ACC, or both.

Not sure why the wipers would work and not some of the other things, so it looks like you'll be doing some deep-cover detective work!

Good luck.


Re: Will only run when cranking

Posted: Wed Dec 26, 2018 8:48 pm
by brncofan
Maybe the internal pump is broken. Try to check it.