no fire in the hole

[deadflo]

Ive finally been able to determine my no run condition has a alot more to do with weak spark than the carb situation (see rust in gas now bad running thread) I had spark at the plugs, but realized it is very weak.

My mechanic loaned me a little tool that will show spark from a spark plug wire and how far of a gap it will jump and its real tiny for the spark plugs.

I did replace the coil.

I can get spark from the coil wire to ground, but comparing it with the spark from my 280Zx shows it to be weak, as in not very bright.

I also used a 12 V test probe to confirm I do have power to the coil, and that the switcheing mechanism in the dizzy is working (tester on neg side of coil blinks on and off when engine turns over).

A trouble shooting guide i have says it could be cap and rotor, at least if you have spark from the coil, and I havent checked that out yet. They are not all that old, but NOTE I did put a rebuilt dizzzy in last fall. Think it could be bad????

[beandip]

Is the ignition that you are having trouble with on your 280 ZX ?

[deadflo]

Oops no, it's the 71 Z. Stock dizzy with points. I seem to be getting spark at points, but again I beleive it to be weak, given the previous description.

[Curtis240Z]

What is the dwell setting? It should be about 37 degrees.

[deadflo]

When i got the car to run, whcih was for only a minute or so before she died, I checked the dwell and it was in the ballpark. I have not been able to restart since, and thats when I noticed the weak spark.

[=Enigma=]

Could be as simple as a bad cap, rotor, corroded connections at the cap, or bad plug wires? My old plug wires were leaking all over the place and the car wouldn't rev past a certain RPM. New plug wires fixed that problem. However, these sorts of problems normally don't exhibit at low RPMs, or under no load conditions.

As for the dizzy cap, check if you can see any noticable carbon tracking in the inside of the cap. Ionized particles carbon will build up inside the cap and create a track for electricity to follow. The track can lead from one secondary terminal to another or to the body of the dizzy and ground. This occurs more frequently where there is crack in the cap but if there is enough carbon build up a crack is not needed.

[Curtis240Z]

The spark from a stock 240Z points system will be weaker than the electronic 280ZX system, but the goal at this point is not optimization but to get the car running and if you are getting spark from the 240Z system at the spark plugs then you have completed your task.

Try remove the spark plugs from the head, attach the spark plug wire on the spark plugs and clamp the spark plug bodies to ground. Crank the engine over and you should see the spark plugs firing if everything is working correctly. If you get the sparks then concentrate on the gas system.

[deadflo]

Again I am getting spark, but too weak to realy get car running for very long...i.e the plugs will foul with gas.

I am basing this on spark that will not jump across a KV meter. It reads how much spark you have and if there is enough to jump the.30 or so gap of your spark plug. Right now it will only jump about .005

It's a deal you connect to plug wires and ground, and then it has two points that mimic a plug gap.

Wires, cap and rotor are all nearly new, but I am wondering if the rebuilt dizzy is more the culprit.

Also wondering if the ballast starter would be playing a role?

[=Enigma=]

The ballast resistor would certainly reduce the voltage to the points. That's it's job. If it is bad it could potentially redice the voltage by more than it should, or possible not reduce it at all. Should be easy enough to check.

[deadflo]

OK, I wonder if it's a difficult part to get?

[deadflo]

Well I guess I should ask for opinions on how to test the ballast resistor???

[deadflo]

If I got this correctly, my mechanic says I should take voltage readings from the positive side of the coil , with the key in start and run. Check for a voltage difference there, and then see what kind of voltage reading I get with a wire bypassing the resistor.