TheRabbit

Just wanted to give you guys a little story about an issue I've been having.

I have an MSD digital 7 (7530) in my truck. Installed it and it ran fine for probably 8 passes. Then I was at a race and I pulled up to the starting line hit the trans brake and it came off the line and it was like it was stuck on a rev limiter at 5,400. Checked everything (in the set up. ie; rev limiter 8,800, launch rpm 5,200, etc.) at least 10 times nothing wrong. Finally that night gave up and put it in the trailer. Pulled it out the next morning and the truck ran fine. Just as a precaution I cleaned and check every wire including all ground wires. It ran fine for about 3 or 4 more passes then it did this again. This time for some reason I unpluged the tach because it had started acting goofy. ( Just trying anything at this time) Truck made another pass same night and worked fine so I thought I had a messd up tach. After two or three more passes it did the same dam thing.
I know that 90% it's not the box it's something else, but by this time I was sure it was in the box so I called MSD.
Joe is one of the main tech guys, but he was gone to a race for a few days.
The guy I talked to was usless and told me to send it to them which I did.
I called yesterday to check the status and got Joe. He said that nothing was wrong which was the last thing I wanted to hear 'cause as you know that means I still have a problem! However, Joe is good tech guy and began to ask me some questions. Of course the first thing he ask is about the ground wire which I have checked and checked and re-checked
to make sure it was a good ground. With that being said like most guys I have my ground from the box going straight to the frame (actually roll cage.) Joe told me to run the ground straight to the battery (10 ga wire) and should solve my problem. No doubt, I understand that the battery is the ground and not the frame so I agree that I should have and will change it.
I'll have the box next week and will let you guys know if this solves my problem for good.

I posted this because I know most, like me don't run a ground wire all the way back to the battery and maybe it'll help someone else with a similar problem. I've been trying to get this problem fixed so I can add a little nos to it. No way can I until I know this is fixed.

suicidebomb

Rabbit, I'm curious, is your cage, chrome moly, or mild steel?

Tod74

msd ALWAYS blames it on the ground to the battery thing. Friend of mine went through a bunch of trouble with a 7AL-3 box missing out at 6000 rpm in his dragster. Did this with no chip in rev limiter also. He sent it back twice both times they say it's fine. He got mad and purchased another one.Hooked it up to the same wires and it worked great. Put the box in my car and guess what...missed out at 6000 rpm. Put my box back in and hooked it up to the same wires and it worked fine

TheRabbit

It's moly and I know that moly does not ground as well as mild steel and that may be part of the problem. I'm glad you mentioned that because I forgot to put it in my post. it was already pretty long anyway.
BTW I just learned that a few weeks ago.
The reason I didn't think that was the problem is because there was a different box wired to the exact same wires and ground for 2 or 3 years that worked perfect. I bought this box used (again I hate used parts) from a friend for half price of a new one and I know it worked fine in his truck.

Todd that's what I'm afraid I may have to do. If I do I'm not going back with the digital 7 eventhough I already have the hand help programmer mouted in my truck and like that part of it.

cepx111

It may or may not be your problem but ALWAYS ground a MSD box to the battery it might run that way for a while or even a good while but sometime down the road not grounding it to the battery will give you problems.

I hope you get it fixed whatever it is....


Why isnt this post in the electrical section?>Cp

TheRabbit

ops: whoops, didn't pay attention when I posted it.

Can one of the mods move it over for me?

I'll let you know how it does. Already ran a 10ga ground wire. Just waiting on the box to come in today.

cepx111

Yeah Rabbit they are the only ones who can move it. But you know how that goes, zzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzz.....


Me personally, rather than wait an enterity for them to do it I'd just re-post in the electrical section.


Cp

TheRabbit

Well I did make it down the track last night without any ignition issues.
However, I've thought I've had this issue fixed before. We'll see.

Track was craAAPY, but that's just my bad luck of the draw. It was way to dry and I was the 29th pass in the first round and they never dressed the track. Second pass I 'bout got the right guard rail TWICE! whoops.

Sorry for the poor video. If you think there's not much light in the video you should have been driving. Lets just say I sure would have liked to have had 10 more feet of stopping room :shock:


http://www.facebook.com/video/video....58302964184844

http://www.facebook.com/video/video....58304104184730

TheRabbit

Well it made 4 good passes and problem came back. Needless to say I'm buying a new box and I don't think it will be a digital box.
Called MSD and they want it back to check it again. All I can say is if it's not the box is at least I will have a spare from now on.

Scooterz

Dang Rabbit!! that is a hassle. I am sorry to hear about that. So if I understand you right- you are running a huge big-block (exceeding "700" cubes) w/ your rev limiter @ 8,800?? I assume alcohol right? going down a muddy track w/ the front wheels off the ground most/all of the time, trying not to hit the guard rails?? Do I have this right? Aside from pucker-factor, that sounds like a good damn time brutha!!