Need help with ignition coil wires (4.3L V6)

I'm installing a tachometer on my 1991 GMC Sonoma which has the 4.3L V6 fuel injection.

There's no signal port or inductive pick-up option, so the only way I can see to connect the tach signal wire is to splice it into the (-) negitive ignition coil wire. However, the (-) negitive connection from the coil to the distributer on this engine is actually two wires, one white and one red. Both go into a single plug connector at each end.

Does anyone know which (white or red) would be the correct wire to splice into for the tachometer signal?

Should be a pink and a white wire to the coil. The pink should show battery voltage when the ignition is in the RUN position, engine off. The white wire should show a pulsing voltage while cranking, that is the negative wire.

That's where I'm confused.... see......

There are TWO wires for the negative (distributer) side, and TWO wires for the positive (battery) side. So EACH connection has TWO wires, one pink and one white.

I suppose I could just find out by trial and error which of the negative wires is the right one....... :eek7:

In the diagram in MOD it states that the tach is the white wire, the one that does not go to the ign module.

Sorry, I'm not exactly sure what you mean.

I don't know what a MOD is...... :confused: but is there a way I can view this diagram?

MOD is Mitchell On Demand. The only way I know of to view the diagram I have is to purchase the program. I can try to explain it to you though. On the coil shows 5 wires total. 2 white, 2 pink and one spark. There are 2 plugs , each has a pink and a white wire. One plug plugs into the ign module on the dist. The other enters a harness into the pass compartment. The tach should be the white wire that goes into the harness to the pass compartment, not the one that goes to the dist.

Hmmm, thats interesting.
My tach's instruction book just says to plug into the negitive side of the coil. :confused: The dist wire(s) are always the negative side right?
Although I'm more inclined to believe what MOD says over this fruity tach instruction book. :rolleyes:

I'm going to try tap splicing it, so if for some reason your way doesn't work I can still try the other one.

I've been working on this thing for weeks now, and its been a nightmare. I'll be glad when it's working!

For anyone who was wondering.........

Okay, I finally got it working! I called a GM dealer and managed to get a tech on the phone. He "believed" it was the negitive white wire; and it was! :iceslolan
So now my negitive wire is all butt-spliced to heck, (Tap-splices are the greatest fail ever) but it works good. :iceslolan





......now to install an A/C condenser....... :uhoh:

hello everybody, I am from tahiti and will need help to run my '91 chevy s10 4.3L V6 4WD. I was driving when suddenly the car did strange noise like if there wasn't gas anymore, the engine stop and I park near the road. I put some gasoline in the tank but nothing . My car cranks but don't start anymore, I have check many things on the engine, when i troubleshooted the ecm, any flashing "check engine" codes comes except "12"(diagnostic). I have change distributor shaft, ICM, cap&rotor, spark plugs wires, spark plugs, ignition coil (2 times for each piece), I have set my ignition timing (many times) correctly( i think).
I have gas from the injectors when cranking but I don't have spark from the ignition coil :banghead:, so here is my problem, even not any spark from the coil. I have 12V with ignition on (pink wire), and I got the signal from the icm( white wire) when cranking.NO SPARK FROM THE IGNITION COIL. I have checked all the wires from the coil and the ICM to the computer and there are good So I have do my best, I'm over. Does somebody here could help me resolving this no start problem. I think now with all the things I have done that the calculator(ECM/PCM) is bad but I need a confirmation before purchasing another one. All advises or question are welcome. Thank you everybody and sorry for my english, I'm a tahitian guy

hello everybody, I am from tahiti and will need help to run my '91 chevy s10 4.3L V6 4WD. I was driving when suddenly the car did strange noise like if there wasn't gas anymore, the engine stop and I park near the road. I put some gasoline in the tank but nothing . My car cranks but don't start anymore, I have check many things on the engine, when i troubleshooted the ecm, any flashing "check engine" codes comes except "12"(diagnostic). I have change distributor shaft, ICM, cap&rotor, spark plugs wires, spark plugs, ignition coil (2 times for each piece), I have set my ignition timing (many times) correctly( i think).
I have gas from the injectors when cranking but I don't have spark from the ignition coil :banghead:, so here is my problem, even not any spark from the coil. I have 12V with ignition on (pink wire), and I got the signal from the icm( white wire) when cranking.NO SPARK FROM THE IGNITION COIL. I have checked all the wires from the coil and the ICM to the computer and there are good So I have do my best, I'm over. Does somebody here could help me resolving this no start problem. I think now with all the things I have done that the calculator(ECM/PCM) is bad but I need a confirmation before purchasing another one. All advises or question are welcome. Thank you everybody and sorry for my english, I'm a tahitian guy

the ICM should be tested. over here the autozone part store has a wells tester to check these modules. the module will fail if the ignition spark voltage is with bad plug wires.also if the module is loose and you have no heat sink compound to keep this module cooler.

the other reason would be the crank sensor or the distributor does not rotate[timing chain or cam gear].

thanks for reply. I just come to buy a new ICM, and now I have gas from the injectors. Not before. But I don't have spark from coil. My crankshaft sensor is the ICM on this kind of pickup. I feel more about the distributor wich doesn't rotate. When I crank the engine with the key, the distributor rotates but when I handcrank the engine with a socket, the distributor doesn't rotate. Could you tell me the way to rectify the distributor. I have 2 marks on my harmonic balancer. how many degrees before does the second mark on the harmonic balancer must line with to set correct timing and find TDC without put a wire in cylinder #1.