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Chasing a gremlin. Precisely at which point do the ground straps attach to,,,,well....ground? I'm assuming they are bolted to the dash but before I get my broken old back contorted under there, I want to go right to where I need to be.
point do the ground straps attach to the chassis? I'm assuming they are bolted to the dash but before I get my broken old back contorted under there, I want to go right to where I need to be.
That and I have used an extra visor mirror to lay back towards the firewall facing the back of the dash pad to get the view you see up there in your pictures.
In the upper right diagram, the ground strap wire between the pods screw directly to small flanges that are attached to the pods with 1/4" drive screws. The flat metal piece on the left-most side connects to a similar flange on the lower side, toward the rear portion of the gas/gauge pod, while the bottom of the flat strap attaches as shown at the headlight and wiper bezel, to the rear of the metal dash frame (shown in the bottom right diagram).
The upper left diagram shows the flat metal strap attaches to the right-most side, toward the rear, of the clock/tach pod.
Grounds on the firewall, core support, and gas tank are on fresh clean metal. The gremlin i'm chasing is a momentary loss of power. It is intermittent, but current draining actions seem to trigger it. Any of these actions may trigger it, but not always: Left turn signal. Reverse Lights. Turning on the headlights. Engaging the brights. And sometimes it just does it randomly.
I have a theory that the sealed module in the MSD Ready to Run distributor is very sensitive to current fluctuations and is barfing upon any extra drain. But I want to make sure the dash is grounded properly before I fork out any more cash. I thought it might be the coil so I bought another and now I have a spare coil because it didn't change anything.
Think this through. The metal cases for the instrument pods are the ground for everything in that pod. They screw into a plastic dash. Obviously there is no conduction there. The ground straps simply connect the metal instrument pod case to a metal body piece. As shown in the PIM drawing, the factory straps use the screws that hold the pods to the plastic dash to also serve as the electrical ground path between the straps and the metal instrument pods. That's not the lowest-resistance design, by the way.
Think this through. The metal cases for the instrument pods are the ground for everything in that pod. They screw into a plastic dash. Obviously there is no conduction there. The ground straps simply connect the metal instrument pod case to a metal body piece. As shown in the PIM drawing, the factory straps use the screws that hold the pods to the plastic dash to also serve as the electrical ground path between the straps and the metal instrument pods. That's not the lowest-resistance design, by the way.
Joe, I appreciate the insight. I've verified the absence of resistance to ground for each strap behind the dash. The one thing I'm having problem reaching/seeing is the little wire between the fuel gage assembly and the instrument cluster assembly. As soon as I can limber up enough to see it, verify it's screwed in tight and no resistance to ground, then I will work with MSD to swap that dizzy out. I'm pretty convinced it's the distributor module. I should provide y'all a video to see this on the tach...it's quite weird.
I do have another option which was going to be my winter project--Holley Sniper EFI and the Hyperspark ignition and distributor. If the car is going to be out of commission swapping out a distributor, MIGHT AS WELL (you warned me long ago about those) go ahead and dive in.
You haven't mentioned if the charging system was tested to ensure proper output (amperage). Before the MSD unit gets blamed I would test the charging system output under normal conditions. If ok I would retest it while the problem is occurring. If that is satisfactory I would test the power and ground circuits to the MSD unit(s) while the problem is occurring. If all is ok a call the MSD tech help line would be my next move.
Sorry to hear about your medical issues. I'm in a similar situation. After turning wrenches for forty five years I too have trouble getting under the dash board. Its is because of my condition I would test as I suggested before I go under the dash to check grounds for dash board accessories. Just my two cents. Please keep us posted on your progress.
If you're having trouble with grounding running an MSD distributor I would be hesitant to go to EFI. I've read those systems aren't forgiving when it comes to shabby grounds and EMI. That being said, what condition are the grounds (i.e. negative battery cable, alternator case ground and black wire running from the distributor) in on your Olds? How did you route the wires to the MSD distributor? They might be picking up EMI from something in close proximity.
December 7th, 2021, 05:05 PM
Dash ground straps
