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Where does/should BDR ground ? Car won't start
My car just stopped running. About three weeks ago now.
I have air (carb) and fuel (squirts, and can smell when cranking); what I don't seem to have is spark. I have 11V at red wire in to MSD, and 8-9V when cranking. The trickle charger reads full when the battery has 11-12V. I'm about to verify continuity for wires to +/- for the (new) coil, and for the distributor trigger green/orange (the pickup is new). That's still to-do The wiring used to work a month ago, but I'm trying to think of everything. The power-in to MSD starts at the battery, and the ground wire connects to the battery. The battery grounds to the roll-bar that bolts to the frame. IS there another important ground for the engine etc ???? I just need a couple more things to check. Help my understand how a BDR grounds. I don't seem to get spark OUT of the coil. I stick a screw driver in the coil wire and place it by the frame. I get no spark when jumping the trigger wire. OH, one more thing. It did fire right up one day during this process, but would not restart. YESTERDAY I got spark and she went to start, but hasn't fired since. |
I'm going to see if I can borrow a DC inductive ammeter to help me test each wire.
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How old is your battery? What type of battery is it - AGM, wet, etc? You said the battery shows 11-12VDC with the charger on it, but drops to 8-9VDC when cranking? Has the car been sitting up over the winter?
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Well, I drove it some this spring.
Several short trips. I just got back from Autozone, having the battery tested a second time. They said it has 12.7V and passed all tests. Second different store to say so. Typical Autozone 665cca. The battery is two years old. |
"11-12VDC with the charger on it, but drops to 8-9VDC when cranking"
This was at the ignition lead (BDR green) to the MSD red ignition wire. |
Coil wires
verified continuity from MSD to coil on orange and black wires Dizzy wires verified continuity from MSD to distributor on green and purple wires Ignition wire verified 12V at key on, and 8-9 when cranking with electric fuel pumps on I trust the main power and ground lines, did not do continuity test there. |
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Ozzie,
What number is your car? I have 499 and had the engine rebuilt last summer. Soon after I got the car back I fried the jumper wire from the fan relay to the starter relay when attempting to start the car. I ended up rewiring the fuse/relay box power wires and installed a Bus Bar to eliminate the problem. When repairing the wiring I discovered just how funky the wiring was. Backdraft jumpers (or did on my car) ALL of the power wires on the relays and used in my opinion under-sized wiring. The grounds were also daisy chained. I cleaned up all of the wiring (went back to my aircraft days) and wired it up properly - No more problems. It definitely sounds like you have a bad ground, or possibly the same issues I had in the wiring at the fuse/relay block. Good Luck! |
Thanks Doc
#576 from 2008 So frustrating, I don't have good ole airplane days to draw from |
Quote:
https://www.msdperformance.com/suppo...ng_techniques/ |
1 Attachment(s)
Ozzie, Not sure if you have this diagram. It's not very detailed, but it may help with running wires if you come to that.
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Hey Brian
Yes. I tried tripping purple/green on the box with a paper clip. Did not get a spark. For grins, disconnected purple/green and grounded white wire No spark Roy |
It sure sounds like a battery with a dead/dying cell. I'd try another battery before delving into wiring gremlins. If you have a battery cutoff switch keep it in the OFF position until the terminals are connected. The MSD is sensitive to circuit bounce and one of the wires is an "always on".
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Quote:
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The battery has been replaced.
Now shows 12V at battery, ignition wire and starter Turns over like crazy, just doesn't catch Thanks fellas |
Quote:
Once I opened up the old box I found a slew of tin whiskers shorting it out internally. https://nepp.nasa.gov/whisker/ |
Thanks so much for some choices going forward
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I'm going to hand off to the professionals next week
Neither trigger method results in the box producing spark. I'm holding a spark plug against the exhaust header or frame. MSD said I need to show ground for the engine block, I don't see a grounding strap anywhere. I think this -new- 6AL might also be bad, but I have nothing left to check before sending the car in. |
Ozzie
On my car (BDR 168) the "engine" ground strap was actually from the transmission to the frame. I have since relocated the strap to the bellhousing, and have an additional smaller strap from the alternator to the frame. Don't know if this will help. FWIW I went from a MSD setup to a DUI distributor. Not as pretty but pretty reliable. |
Thanks Bill
That's exactly what I needed. I didn't see anything off the engine block, and gave up. I'll check that, but don't expect it's the root cause. |
Found the strap tucked under the starter, block to frame.
I can't wait for the shop to tell me: what I missed what the original cause was all the things I didn't do right since then Just cannot figure out why the 6AL box won't spark the distributor; even with the trigger test. New box, zero trigger spark. |
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