No Spark on 73 GTV

[mainline]

I am new to the BB. I joined after previwing some threads and was very impressed with the knowledge of the participants. I have recently purchased a 73 GTV and I'm thinking I'll be here often, hopefully contributing.

I am having a problem where I have very low voltage in the primary ignition circuit at the coil. Reading I get is just under 4 volts. I am not sure what I should be getting, but I know that I don't get any spark at the Plugs and I traced the issue to this.

When the ignition is on, I hear the fuel pump operating, so I know juice is flowing from th ignition switch. Does anyone know if there is any device between the coil and ignition switch that, in a faulty state, be causing this low voltage? Or am I barking up the wrong tree?

Thanks in advance ....

[papajam]

Welcome to the BB, mainline!

Looking at the wiring diagram that's located here the green/black stripe wire that powers the coil with battery voltage should run uninterrupted from the top of fuse #6 to the coil + terminal. First thing to do is to check/clean the wire connection at the top of fuse #6. If it's OK, then either the wrong wire is on the coil, the wire is broken somewhere or perhaps the PO installed an alarm with an ignition interrupt.

[Roadtrip]

Does your car have a ballast resistor on top of the coil? If so:

1. Gr/Bk wire goes to the ballast resistor (from start key switch)
2. Green wire goes to the + coil (from fuseblock)
3. Black wire goes to - coil (from the distributor)
4. Short Red wire connects ballast resistor to + coil

TEST:

A. Test your coil as follows:

1. Between + and - terminals .75 to .81 ohms
2. Between + or - terminals and center (coil to distr) 10,000-11,000 ohms.

B. Test the green wire disconnected from the coil and ignition key switch on. Should read 10-12 volts. If not, remove the fuel supply pump fuse to disable the supply pump (high current load). Does the voltage improve significantly?

C. If your supply pump is getting old and drawing a high current, it may be robbing current from the rest of the car. If it is drawing abnormally high current, it's probably a short time until it fails altogether.

D. Check the female spade termainals in good shape. Old ones can loosen up and the side crimps break altogether. Check the black wire from the - coil terminal to the distributor. It connects with a spade terminal to the underside of the distributor base. I'll bet you'll find that connection very corroded, dirty, and probably loose.


PAPAJAM: Did pre-74s have ballast resistors? I note in the wire diagrams that it isn't there.

[mainline]

Thanks guys.

Wiring diagram is great! Funny thing is .. I don't have a green and Black going to the coil. I have a heavy gauge (10?) black wire to the + side, a ballast resistor, and also a condensor attached to the positive terminal.

I will try the tests you propose and let you know how I make out.

Thanks again,

Jeff G

[Roadtrip]

Condenser? Do you mean a ballast resistor? Is it a ceramic looking square thing with two screw terminals?

It sounds as if the PO did some "customization" (to put it politely).

You can determin which wire comes from where by doing a little logical analysis.

Disconnect the wires. Do not allow any to ground themselves.

Turn the ignition key to "on." check which wires are hot. The only one that should be hot is the wire coming from the fuseblock and should go to the + terminal of the coil.

Next go to the other wire coming from the firewall that wasn't hot. Crank the engine and see if it goes "hot" while cranking the starter motor. That wire should go to the ballast resistor.

Next check the (what should be) the black wire from the - terminal of the coil to the bottom of the distributor. Make sure it's got good ends, good connections and is clean and does not have damaged insulation.

Did you check the coil resistance yet?

[papajam]

Quote:

Originally posted by Roadtrip ...PAPAJAM: Did pre-74s have ballast resistors? I note in the wire diagrams that it isn't there. [/b]

[Roadtrip]

Jim -
My 74 Alfa Owner's Manual has its wiring diagram depicted with a "Resistance (off for starting)", but no condenser . . . . (and, of course, the infamous POS electronic interlock module). The 2000 GT Veloce page in the manual has it too.

Jim, check your PMs.

[papajam]

You're absolutly right, RT. Just checked the '74 US version diagrams WITH resistors. Should have checked first before putting my fingers in gear.

[Roadtrip]

Mainline - If you have a ballast resistor on your 73, then either it's been added by the PO or Alfa switched production standard in the middle of the model year (could it be???). In any case, go with what I've already written, which is WITH ballast resistor.

Test the coil with the ohm meter. After you disable the fuel suppy pump and re-test voltage at the coil +, you could also try just running a hot lead direct from the battery positive post to the + on the coil and see if it starts. That would eliminate the coil onward as a cause. From there, you're going to have to chase wires back and see where the voltage thief is.

[emr5503]

My 2 owner '71 GTV (34,000 mi.) has a ballast resistor - same color as the coil. Don't have the owners manual here, but my '73 manual doesn't show it either. The
'73 car has it - also 2 owner, but it's a doner/ parts car now.
Ed

[mainline]

Sorry for replying so late .... yes it has a ballast resistor and a condensor. There are a few other differences I've noticed as well. For instance, I don't have a SeatBealt Warning sign or a Key Buzzer. Maybe this car is an early 1973.

Anyways, you mentioned that a Green resistor bypass should be present. Ain't got like that. From what I've researched elsewhere, this is probably not a good thing.

I did perform some tests with a Multimeter and although I can't remember the values for resistance, I can tell you that differed from the ranges you noted. Also, a voltage test with the condensor and resistor disconnected yields something I don't understand.

The Green/Black wire from the fusebox shows 12V only when disconnected from the coil. If I reattach, reading drops to around 7V.

Does this mean that the coil is shot?

Any help appreciated.

Jeff G

[papajam]

Quote:

Originally posted by mainline The Green/Black wire from the fusebox shows 12V only when disconnected from the coil. If I reattach, reading drops to around 7V. Does this mean that the coil is shot?