MSD box, second one dead in two days?

Casper302

Casper302

Club Member
Ok first off we wired it per MSD instructions, car fires up fine and runs. Drove it to telegraph and all around, no issues! Car sits over night and I go to start it Saturday morning and it won't start. Box was getting power to it but nothing coming out, swapped boxes (First was a 6al, swapped for a 6a) and drove the car again Saturday night and again no issues! Car sits over night again and on Sunday morning no fire WTF? So my brother moves the ground and the car fires right up... Neither one of us drove it so it sat until this morning. Car fires up and dies. Wont start, left me stranded.

I ran the power direct to the battery and the ground to. Still no fire, I've tried different grounds, even had two hooked up and still no power. The tach bounces around like crazy and the shift light does not come on when I turn the key on. Anyone have and similar issues? Thanks.
 
igotaneed4speed said:
You guys have some bunk grounds...


Number one killer of ignition boxes is a shity ground.
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X2.

If there isn't a constant 12V going to the MSD boxes, they will shit out on you.

Sounds to me like you have something in the system that is causing a draw that drops you below 12V.
 
Casper302 said:
How should the box be grounded? Direct to the battery? It seems no matter where its grounded in the engine bay it kills the box. I am lost.
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You prob have a crappy ground from the battery to chassis.


Grounds work both ways, so even if the box is grounded perfect but the ground to the chassis is only so so you can have the same problem.

I used to weld the head of a bolt to the floor pan (if trunk mount battery) for the ground then also run a second from that to a seat belt bolt hole.

I also put a heavy ground from the engine to the body (4 gauge wire or larger)
 
You are suppose to ground it right ot the battery if the battery is mounted up front. If you have the battery out back in the trunk/hatch then it's best to tie the battery to the frame and then ground the MSD to the frame as well. On a unibody car you need a good solid ground coming from your battery to the body and engine block. Many people don't realize that when your battery is mounted up front the groung had a nice fat cable going to the block before it was moved. Most thing they can just ground the battery to a seat bolt and expect the ground to carry through the cheap braided cable that goes from the back of the head to the firewall...that's a big NO NO. With a trunk mounted battery all the cables need to be bigger cause of the distance it has to travel. MSD's produce a hotter spark...to do this they need more power that your normal Duraspark box requires. The box is going to try and produce that powere no matter what and if the ground is shot then soon will be the MSD as well.

Something to keep in mind is that the MSD case does not ground any of the componets in side of it. The only source of ground for the components in that fat black wire itself.

Things to check:
Clean the grounds
Clean the positive
Check all connections
Upgrade your wiring to a bigger size if you have a trunk mount battery
Make sure your ignition line is not staying on even after the car is shut off.

If all else fails get ahold of me and i'll come by and look at it.
 
are you running a ballast resistor, i don't know about msd, but some ignition systems don't like to push huge amperage.
 
Ok I took the box off the fire wall and laid it flat and reconnect the ground and it fired right up. With the box off the fire wall it read 11.5 volts, the ground was reading .03. Attach the ground and the box grounds to zero. I am stumped LOL.
 
glh_turbo22 said:
Yeah but did you change the ground location or did you just un-mount the MSD and lay it flat?
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after i layed the msd flat it fired up at the same ground location as before, but i went to try and start the car this morning and it was dead again. im gonna move the ground around again and see what it does..
 
Teef racing said:
after i layed the msd flat it fired up at the same ground location as before, but i went to try and start the car this morning and it was dead again. im gonna move the ground around again and see what it does..
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dude bring it over,we will do it rite.i dont want any excuses when i bust your ass,lmao
 
Teef racing said:
after i layed the msd flat it fired up at the same ground location as before, but i went to try and start the car this morning and it was dead again. im gonna move the ground around again and see what it does..
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Sounds like you got some shity crimp job or wire connectiona nd from "laying the box flat" your pulling on the wire just right to make a connection. Double check your shit, I've seen some of the stuff you guys have done on your brothers car, not to be mean but maybe you should have someone else look at it for you guys.
 
igotaneed4speed said:
Sounds like you got some shity crimp job or wire connectiona nd from "laying the box flat" your pulling on the wire just right to make a connection. Double check your shit, I've seen some of the stuff you guys have done on your brothers car, not to be mean but maybe you should have someone else look at it for you guys.
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triple checked everything, box is gettin power and got power goin to the coil but still no spark. tried a different coil and ran the ground right to the battery and it still didnt fire..and what the fuck you talking about?
 
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