Setting base timing - TBI w/MSD

[Can Can]

I'm new to the whole TBI thing, and I need some help with this one.

On a TBI motor, I've benn told that you're supposed to unplug the tan/black wire to take the computer out of the mix in order to check the base timing. Well, my truck has an MSD box wired into the harness, and when I unplug the tan/black wire, the motor dies instantly. According to my mechanic buddy, it should idle a little differently, but not die.

So, how do I go about bypassing the computer to check the base timing?

 

[btolenti]

Are you sure you are pulling the right wire apart????

I would post this in the MSD forums. They are pretty good at getting back to you...

http://msdignition.com/

Have you tried bypassing the MSD unit and see if it works then?

 

[JEBSR]

Is it running poorly, like the timming is retarded? The reason I ask is that if your pulling the correct plug apart and it is dying it could be because someone else set the timming with the plug connected. This would cause the timming to be retarded enough that it may die when computer advance is not applied (wire disconnected). Just a thought anyway

 

[Hossbaby50]

I got rid of my MSD when I installed fuel injection. Therobzilla has MSD with his TPI and he said it has caused "ghosts" in the motor with codes and such other problems that go away when the MSD is disconnected. After running my TPI system without the MSD I saw no reason to run the MSD.

The MSD was on my truck with the carb to help with the inefficiency of the carb and to help the plugs from oil fouling or gas fouling from the carb running to rich. With the FI I have not had a problem with any plug fouling like I did with my carb. I have pulled my plugs several times in the last 2 years I have had FI and every time I just reinstalled them because the FI has made the motor run very efficiently and I have had no fouling problems with them.

I also removed the MSD to take out one more possible problem to have to trouble shoot if the truck wouldn't run. After doing the FI and running it for a few years I wouldn't even consider running the MSD even if I still had it. The FI with the HEI does its job really well and I am not going to mess with something that doesn't need it.

I wish I could help you with your problem but honestly I have no experience with the MSD and FI. Sorry

Harley

 

[MaxPF]

The way I have always done this is to enter the diagnostic mode by shorting the diagnostic pin in the ALDL to ground, and then start the engine. With the diagnostic pin shorted the computer will not apply any advance to the timing. Keep in mind this was on S-10's and Camaro's, but I believe the truck is the same way.

 

[4X4HIGH]

The tan/black connector is near the power booster and when disconnected should idle differently but not die like your friend said.

 

[Can Can]

Okay, why exactly is the truck dying the minute that connector is unplugged then?

 

[MTBLAZER89]

Does it instantly die, or does it stumble then die? Like mentioned above it may be retarded too much, and when you remove the computer advance it is way too retarded. I don't remember how much the computer advances it. Have you put a timing light on it to see where it's at before you unplug the wire. Is it running bad? Why are you adjusting the timing? I kinda set mine by feel. I advanced it a hair then drove it, and continued to play with it till I liked the throttle response and how it ran. Mine is 2 or 3 degress advanced over whatever the reccomended setting is. Good to see ya in the Garage buddy

 

[Can Can]

The motor dies the INSTANT the tan/black wire is unplugged.

We were checking the timing because in park, the idle is a little lumpy. IIRC, with the computer still hooked up, the timing at idle was around 16-20. We're pretty sure it's not a timing issue, as the truck runs smoothly at idle in gear, but we were trying to rule it out as a contributing factor to the "lump". FWIW, the truck performs absolutely beautiful otherwise- lots of power, no pinging, no hesitation.

Now that I have a new rig to play with, you can expect to see me in here more often. Of course, there are very few issues with the truck, and once I've got them straightened out, I'll be MIA again.

 

[mouse]

When I have base timing set to 0*, at idle and the computer controlling the timing, it usually is between 16-20*. You probably have it set very close.

 

[Can Can]

That's good to know. Thanks for your input, brother.