I've got a 5.0 EFI engine in my 66 and am trying to get my tachometer hooked up. The wire i need to connect goes either to the coil or the EEC-IV, the directions for installation said to connect to the tach connection on the computer if available but i looked and did not see any connection. I cannot determine which wire to connect to on the coil itself. I know it is supposed to go to the negative side of the coil but am not sure which one is negative. I would appreciate some help on identifying the difference in positive and negative. I looked at a pin table for the computer and it shows what pin the wire is coming from but i havn't traced it back but suspect it will go back to the coil. Any help is appreciated

 

Since you don't mention which 5.0L EFI you have & there are different set ups, tach sensor wire should go to terminal of coil recieving pulse signal from crank sensor.

This can be marked test or tach. If you have a coil pack you'll need to intercept pulse signal data going to ECM, since P-ROM chip "sorts out" distribution to which coil, and most all tachs req' "gross" pulse number, or total pulse count to calculate RPM.

If you have CFI you should have a "tach" terminal at end of coil harness, it's moulded into the plastic connector. If you have SEFI/ EECIV with TFI, or MAFS/EFI with EECIV & TFI look for "Test" terminal. If you have a coil pack, good luck w/out a schematic! AND don't probe or guess as that could be costly in terms of ECM/ Prgrm Integrity.

FBp

 

I puled the coil connector and looked down inside the female side and found positive and negative stamped into the bottom. I connected to the negative side which were the yellow with dark green wires and it works fine. Your right i did not want to guess in fear of burning somethin up. I have EECIV with TFI. Is the test plug your talking about connected to the TFI. If so thats what i thought that was for but wasn't sure. Thanks FBP for your help.
Jim

 

Well yeah it[sic test port] is, but it should be accessable to "technician" at your coil connector. However since the powertrain is a retro fit perhaps the OEM style Ignition harness is not there anymore, which is quite understandable.

I run a 64 Falcon, Sprint, Faria, 6K RPM, electronic tach, off my 88 5.0L Roller eng'n with SEFI & TFI in EEC IV Logic and I pick impulse rate up at coil like we talked above. Some people "flip out" because I run a 40 year old tach on an engine thats 24 years older than my instrument.

Too many folk shy away from new tech from lack of knowledge & clear understanding. It's not "Rocket Surgery", and it certainly improves everything on the performance plate [IMHO] I still read posts about this carb or that, and "performer intake versus a "torker intake". Everytime I look at runners of a TP/ EFI System, I gotta wonder why anybody still messes with carbs, but
"Hey" that's only my take on the whole thing.

It's not as easy as I make it sound tho. I'm trying to workout MAFS/TP/EFI using an EEC IV & SIDS on a 460 & not have it Bank Fire like OEM [nor speed density logic like OEM either]. I've eliminated HPSI, in-tank, pump & return line. I short looped HPSI confining all high PSI operation to engine bay using a reservoir instead of return line system OEMs use. Problems come with dual fuel rails for SIDS set up. Since I'm not fond of big lb/hr injectors or how they don't idle well.
Never the less as I intimated, it's easier to work out an EFI system than dial a carburetor in, keeping it dialed in and getting good performance & economy across the "Op-Range" if you get my drift.

Are you familiar with E-Legal drag racing? That's where I'm headed with this whole scheme. I think it's neat getting in sub 12 sec et brackets with street operated, and completely Emissions Legal engine/ powertrain, ergo "E-Legal".
But I admit many of my "cohorts" avoid me because guys my age won't even try to use "Digi Tech", let alone make a stab ever understanding, tinkering or attempting to refine & improve on it. Hah! their world's shrinking & they don't realize it's even happening. . . .

Guess I been "Rodding" too long! These same folks laughed when we bolted disc brakes off light Aircraft on a narrowed rear of our fuel rail drag car in late 50s. Ha!..... now everybody wants disc brakes, and on everything they own, my John Deere Yard Tractor has disc brakes! It sure goes to show ya huh?

. . . . "Oh Well!"
FBp