I posted this in another thread relating to MSD, but not getting any responses and im looking for an answer pretty quick so i figured id post it here. ive done some searching and havent found a conclusive answer yet. the car in question is a 1984 GSL-SE.

im installing an msd 6AL running 2 msd Blaster 2 coils on leading ignition, and disabling trailing. the install is happing tomorrow (today, saturday). Ive got the wiring for the msd figured out, no big deal. The thing im trying to find out is, where is the wire for the fuel pump circuit (and any other wires of importance for that matter) that ties into the trailing ignition. I dont wanna get all this crap installed only to find my car wont crank cause there is no fuel pressure. any help would be appreciated.

 

Black wire comes out of a shielded gray coax and goes into plug on the negative terminal of the trailing coil (with the Yellow/green from the ignitor).

 

Alternately you can bypass the fuel pump cut relay under the dash. Then your fuel pump will do what the 79-83 cars did, which is pump whenever the ignition's in the "ON" position regardless of whether the engine is running. I had to do that on mine for a few months because I blew that relay. It wasn't a big deal, once you got used to the idea that your fuel pump was OK to be pumping without the engine on.

Jon

 

The GSLSE has a "circuit opening relay" next to the ECU under the panel on the passenger floor. They also have the "fuel pump short connector". It is a black, rubber shrouded plug just behind the air filter box. If you jump the two terminals the FP comes on when the key is turned to on.

BTW the gray wire from the coil goes to the ECU. The tach signal is used for other things besides just the fuel pump circuit.

 

so can i assume that while i CAN bypass these circuits and make the FP come on with the ignition, that my tach will not work if i do this? can I just put the gray wire on one of the leading coils that ill be using?

 

Why delete the trailing ignition? You can run the leading direct fire through the MSD and the trailing in the stock mode. Then the tach and all the other things that depend on the coil signal would work properly. I believe the ECU uses the coil signal as one of the inputs to determine properly timed injector opening. I'm not sure how it would work on leading.

 

I have several reasons for not using the trailling.

1. I dont want the extra clutter in the engine bay. by just using leading i can mount the msd coils in the same location as the stock ones without modification.

2. I want to fully utilize the rev limiting capability of the 6AL. From what i have read, trailing is still enough to overrev and blow a motor (no i dont PLAN to over rev my motor and blow it, hwoever, its going to be getting some nitrous, and it wouldnt be the first time ive missed a shift)

3. after searching, it seems the only REAL purpose of the trailing is for emissions purposes, which i no longer have to worry about, therefore worst case scenario its just a bit of weight savings and less clutter in the engine bay.

 

I would love to see how you do this setup since i have been keeping up on reading the same post you have ;p

can you take pictures of the work as u go along, that way i can replicate or even be able to make a (howto) stickie. ;p

take lots of pictures of the step by step.. ect..

 

I will make sure and do a writeup when im dont with pictures. I was gonna work on it today and got sidetracked with some minibike projects a buddy of mine and i have going on. ill probably end up doing it monday.

 

That can work. Have you downloaded this manual? Section 4b explains a lot about the 13B emission control systems and how they interact.
http://www.jimrothe.com/mazda/84_training_manual

 

I will take a read later today, thank fellers, hopefully i can get enough info out of that to get everything done tomorrow.

 

So don't direct-fire them.

Trust me, you don't. Hitting the rev limiter while under load is the fast train to blown engineville. I learned that lesson the fun way.

I do use a 6AL, but I use it in conjunction with a two-step. 6000rpm with the clutch pushed in, no limit otherwise.

There is a definite purpose to trailing ignition. It's not as important as leading but it is still there for more than emissions. I run MSD box firing both coils through the distributor. Zero split. I had to emergency-wire my car to direct fire leading and the engine felt a LOT softer, made a lot less power and wouldn't idle.

Since I don't think it's been said: Doesn't the fuel computer need trailing igntion to function?

If clutter is the problem, why not just empty everything out of the engine bay? That way it's totally clean