73 240z stock ignition, intermittent problem

[djmartins]

Hi all,

As the subject says, 1973 240z stock ignition (well, a better

coil, but the rest looks OLD). The car has run fine for months,

no problems. Yesterday it cut out, and was hard to start.

Seemed that there was no spark, checked it and it didn't.

After a bunch of tries, it started, only to shut down suddenly.

After wating a bit it started. Now, even when cold, it will

sometimes run for a while, then immediately stop.

Unless I turn the key comepletely off, it won't start again.

Not every time will it start again right away. Runs from

10 seconds to 1 minute before stalling. I checked all the ignition

wires, ran a few tests from Chilton's, the only issue I see

is that the points are kinda crappy (pitted).

Thing is, when it is running it runs GREAT!

So, where to start? Replace the condensor and other cap near

the coil and the ballast resistor?

Anyone have a clue why this car acts this way?

thanks,

Doug

[2ManyZs]

Well, since you say the points are pitted the first thing I would suggest would be a complete ignition tune-up. Points, condensor, cap, rotor, plugs, ballast resistor, and possibly a set of wires. That should cover the obvious things that may be causing a problem. If after that it still does it I would say to go over the wiring to and from the coil, distributor, and ballast resistor to see if any are corroded or loose. If after all that you may want to try a different coil and perhaps even check your ignition switch. This should give you a pretty good start towards curing the problem. It could be something simple or it could be something that is hard to find and diagnose. The main thing I can say is start from what it most likely is and then work towards the less obvious.

I have seen some cars have a problem that took a long time to fix because it was something you would never expect. You could also check the ground wires on the wiring harness, check your alternator output and battery condition, there are actually too many things that could affect your ignition to diagnose the problem with any certainty. Sorry, you'll have to pick a starting point and go from there, hopefully it will be taken care of when you do the tune-up. If not, let us know and we'll get some more opinions to help you out.

[djmartins]

Hi!

I have all these things except the plug wires and

coil on order. Both appear next to new, though I

am worried that the coil is an aftermarket HiPo thing.

So I ordered the heavy duty ballast resistor for it.

I also ordered a bunch of other little things I needed,

like a fusible link, some brake parts, etc.

so a total of $80 to see what she does is not bad.

I wonder, the damn thing stalls so suddenly that it

MUST be electrical, even rev'ed up.

In the wiring I see two condensors, one near the coil,

one on the distributor. The car is a five speed the previous

owner put in. Seeing two condensor tells me that the car

was an automatic before, yes?

Can I disconnect the condensor near the coil w/o problems?

It would be one less component to worry about if I could.

I was just hoping there aren't any Z particular gotchas I may

not know, like something to do with relays or the link on the

back of the tach getting too hot....

I am off to Thailand for a week, so the car will have to wait until

I get back!

Doug

[2ManyZs]

Not sure about the second condensor, it is possible the previous owner put a distributor from an automatic in. If you are running dual points you will need the second one, if you are only running a single point set you should be able to do without it. It definately sounds like it is electrical, something you said about the car not re-starting until you turn off the key has me wondering if it might not be in the ignition switch or relay. I guess when you get back and put the parts in, if the problem persists we'll have to get some more people on this to get their input. Let us know what happens and we'll go from there.

[Daniel]

The condensor on the coil was a 70's trick to try and stop motor hum in the radio.It won't make any difference on or off.Check the wire going into your distributor and most important the ground wire inside your dist.Clean them up good.They oxidize.look good but are poor conductors.Sometime when a coil goes bad you can pull the main coil to dist wire out and it will have oil on it.Look for hairline cracks in the dist cap. Have fun!! Daniel

[EScanlon]

A common problem with the Z distributor, whether point or electronic.

The Vacuum Advance Plate which is plastic and houses a few ball bearings, is the plate on which the internal portion of the dizzy rides on. When the vacuum advance pot actuates and pulls on the rod, this is what allows the dizzy to advance timing. These things do go dry and brittle over time and eventually break, releasing ball bearings all over the inside of your dizzy.

Depending on where the dizzy plate ends up when it busts, you could be right on, slightly advanced or .... And then it depends on whether or not you have enough vacuum to move the plate. When it went out on mine, my car went from peppy to DOG, and it would cough and sputter and backfire and geez....all sorts of crud. I was thinking I had blown the engine. Took it to a mechanic, figuring the worst. He did a complete tune-up, wires, timing, changed the advance plate, adjusted valves and presto zesto......zoooooooooom!

2¢

[Dave Sommers]

From your description of the failure it is an ignition issue without question. All previous posts are good info and directions to go. Just a couple of areas to check before you throw a lot of $ at the problem. A couple of areas that have acted this way for me over the years:

Check all the spade lug connectors at the coil/ballast resistor to make sure the wires are still firmly attached and the lug is got a good grip on the spade. I had to strip one of these wires and wrap it around a lug to get home once.

Check the two small wires in the dist are still intact and have continuity. One feeds the breaker points; the other grounds the breaker plate. I have had both fail due to fatigue and they will also cause this problem.

I have also had ballast resister have intermittent short after it runs a few minutes and cause the same response - engine quits only to restart and run a few more minutes.

Remember always start with the simple and work up to the complex (and expensive).

Advice worth everything you paid for it - nothing.

good luck

[73240z]

I had a similar problem three years ago on my 73. It ended up being a bad condenser.

[AxtellZ]

yep, sounds like condensor. as far as 2 cond on the auto, both are screwed to the dizzy- the third deal by the coil is for radio hum.

[Z-Priv]

i was gonna say condenser but it looks like i was beat to it. I just finished replacing my whole ignition system, points,rotor,condenser,cap,coil,resistor,plugs and plug wires,battery, battery cables, and ignition switch. all easy fixes. My car starts and runs a lot better i'm guessing everything cost me around 300$,i think. I dont like to keep exact cost numbers..valve adjustment is next..

[djmartins]

Hi!

Thanks for all the good answers!

Have replaced the ballst resistor, point and condensor.

ALL the electrical connections were ugly, cleaned them

up a LOT! For a few day now, no more problems.

I believe it was the condensor considering how

badly pitted the points were!

Thanks!

Doug

[rzkas]

hello and how ya all doing? i need help. i bought a 76 datsun 280 from a friend. he told me all i need to change is the feul pump and the car will start up. i changed the pump and put in a battery. i tried to the start the car but not cranking or sing of trying to start. but all headlight and taillight turns on and off. pls help me solve this problem. any idea will help. i am also looking for a wiring diagram on how to installa an aftermarket stereo and installating racing on this car. thanks for your help.