FAST + Holley Annihilator Ignition System = No Tach

[Stk1520]

I had a Holley Strip Annihilator ignition system sitting on the shelf and decided to install on my '89 Mustang (with FAST FI system). I wanted to use the Annihilator's 3-step rev limiters (main, stage and burnout) so I installed the box in place of the trusty old MSD 6A.

Everything works except the tach (the VDO tach worked fine with the MSD box). The Holley manual says most aftermarket fuel injection systems require a tach signal amplifier. I just wanted to see if anyone else has run into this problem before I order the signal amplifier.

Thanks,

Jim K.

 

[Craig Smith]

I'm not sure I get what you are asking. If the car runs OK, the issue is strictly between the tach and the ignition box. The only connection to the ignition box that should come from the FAST is the points control output. Since the car runs, we know that isn't a problem.

At least I think so.

If no one here can verify this for you I would post this EFI forum on chevytalk.com, which is moderated by a guy from Holley named Doug Flynn. He would definitely know.

 

[Stk1520]

Hey Craig,

I had the same Holley ignition box previously installed in my Mustang with the factory Ford computer and the VDO tach worked fine. I then went to an MSD 6A box and later installed the FAST system on my car and again the tach worked.

I'm now going back to the Holley ignition (need the 3-step rev limiters built into the Holley) with the FAST system in the car and the tach doesn't work. The car does start and runs fine, just no tach. The Holley manual states that "most aftermarket fuel injection systems that connect to the negative side of the coil" will require a signal amplifier. That got me thinking that I needed the signal amplifier to get the tach to work. On my Ford TFI system the points wire from my TFI module connects to "either the (-) coil lead or the points input on the ignition system" (from the FAST installation manual). The tach gets its source from the ignition box, the ignition box gets its source from the TFI/FAST . . . whew . . . I'm getting dizzy . . .

I see your point, though (i.e., most likely a problem between tach and ignition box). I did order the appropriate signal amplifier from Holley, so hopefully that will solve the problem. I'll post the results when I get it installed. I just wondered if anyone had run into this before.

Thanks for your input!

Jim K.

 

[Craig Smith]

Just don't connect anything from the FAST directly to the coil! The ignition control output from the FAST should be going to the TFI module. If FAST=connected to coil then Jim K.=owner of blown-up FAST box. We certainly don't want that.

I'm not yet sure why your tach isn't working yet but I don't know if the amplifier you are describing will do the trick. It sounds like they are describing a thingy that goes between the ECU and the coil. In your case that would be the TFI module. It sounds to me like either the tach output or the tach itself isn't working properly.

 

[Stk1520]

Don't worry, Jim K = owner-of-still-good-FAST-box (coil is connected to the ignition box, not the ECU). Sorry for the confusion. I'll try the signal amplifier when it comes in - if it doesn't work, I'll probably yank the Holley box out of the car and have it checked out.

Thanks again,


JK