My brother's car was having an issue shutting off for a instant and then coming back on - very intermittent.
He changed the main power shutoff and ignition switch last week. He made 9 runs Friday, a few on Saturday and we called it fixed. Then Sunday morning no spark. So now we feel the intermittent has become permanent
It's a Grid 7730/7720 setup. Green light on 7730 pulses when cranking. When you put a test light on the coil + wire it lights dimly and does not pulse when cranking (our other cars show no light and then pulsing when cranking).
Over the past couple of weeks we checked grounds, connections, continuity checked the coil primary wires etc.
Originally posted by Greg Kelley:Over the past couple of weeks we checked grounds, connections, continuity checked the coil primary wires etc. Thoughts?
To help troubleshoot, enable all the Grid DA record channels and run the DA for 20 seconds starting when the Launch (TB) is activated.
Do a quick check of the small four pin Deutsch connector (red, black, white, orange) between the 7720 and 7730 for pins being seated properly. Pay attention to the male plug on the 7720 with female pins. The female pins need to be seated tight against the plastic cover.
Posts: 2681 | Location: 53056 | Registered: December 30, 2009
I know this sounds out there but make sure you do not have any power wires near the pickup or distributor. My buddy had an issue where his car would not start and it turned out after weeks of changing components, trying a million things... It turned out to be his starter power feed wire was passing behind the distributor and as soon as we moved it it solved the problem. It drove me nuts for weeks.
Posts: 1462 | Location: St Marys | Registered: January 12, 2004
Greg I had the same problem a few weeks ago.if you go into your msd view and crank the motor over but on the guage side it dosent show any rpm it's usually the black 7720 box
Posts: 1433 | Location: united states | Registered: January 16, 2006
Thanks for all the suggestions. It turned out it was a bad 7730. It did flash the light when cranking so we felt the 7730 was ok and started looking at 7720.
The reason we were mystified was that when we tested the 7720 per MSD instructions it tested bad. We swapped it out and still no go at the track. Which sent us down the road of possible bad coil, continuity testing the orange/black etc and he missed first round so we loaded up..
It turns out the MSD instruction to test the 7720 are IMO wrong/incomplete. You need the red wire to have 12/16 volts and then give the white 12/16.
Greg, Great Video showing what a working 7720 looks like during a bench test.
The first pic below is the pin out “From” the 7730 going “To” the 7720. The Orange wire is the pass through of +12v from the 7720 to the 7730. The red wire is +12 from 7730 to 7720 turning it on when Ign ON is present at 7730.
The second pic is of the Deutsch plug in connector that I use to test 7720 in the car.
In the Introduction to Grid that I posted many years ago, I explain how to make this plug-in and how it works. You’ll find it all at the end of that post.
Posts: 2681 | Location: 53056 | Registered: December 30, 2009
