transistor ignition module maybe?

[77280zcar]

hello all, my 77 280z recently developed a problem.. i can start it and it runs for about 5 minutes then it shuts off, then i have to wait for 30 minutes or better for it to actually run again. i have been reading online and on the fsm about a transistor ignition module, most of the symptoms of other failed modules match mine to some extent, i have singled it out to a definite spark problem, and the fact that when the car dies i can take a light meter with the car on and try and crank with no signal from the junction box right there on the drivers inner fender by the ign. coil that holds the 2 wires to the distributor, is my theory along the right lines? or am i missing a step somewhere in my testing? im trying to diagnose this as best i can without asking for help but i feel i would make better time of that if i had some expert advice, any information given is deeply appreciated! thanks, Jordan.

[FastWoman]

Jordan, you're trying to measure the signal of the distributor's reluctor. You can of course do that, but you probably have to use either an oscilloscope or a needle-movement volt meter, and your results won't tell you anything about whether the ignition module is failing. (It will tell you only whether the signal to the ignition module has gone bad.)

Here's a quick fuel/spark test: Buy a can of starter fluid. Run the engine until it dies. Then pull off one of the vacuum hoses from the intake manifold, spray some starter fluid inside the manifold, replace the hose, and try firing the engine up. If it runs (but only very briefly), you have spark and no fuel. If it doesn't run, you probably have bad ignition.

FAIW, if it's the ignition module, it will die faster if your engine is running faster (because it's working harder to create sparks at a higher rate). If it's something like the fuel pump, which is under the same load regardless of engine speed, it will tend to die in a more consistent time. So you might try running your engine at a faster idle to see if it dies faster. That will give you another clue.

[zKars]

Jordan:

You're doing a pretty good job so far but there is more to do. You won't see much of a signal with a volt meter at that junction box. Its not a 12v on or off signal there, its a very low voltage waveform from the magnetic pickup in the distributor. I'de just pull the coil to dizzy spark plug wire from the center of the dizzy cap and put it near a ground (1/4 in) and crank to see if you have spark or not. Does the car die instantly (ignition loss) or does it run worse and worse and finally die (running out of fuel, though happens quick with an FI car).

You can check for +12 at the coil + terminal when running, and not there when you're in the "dead" condition with the key "On". This will tell you if power supply from the key switch is staying on or not.

There are five components in your system that might be heat failure related.

In order of likely hood they are :

-Bad dirty/hot connections that work when cool, but lose connection when heated. Clean every connection to the coil, ballast resistor, dizzy and ign module.

-Ignition Coil internal failure. Needs replacing.

-Transistor ignition module. passenger side kick panel up above right foot on the right side. Not in the engine bay, so less likely to heat affected as much.

-ECM module that runs the Fuel injection. By drivers left foot on the side. It controls the fuel though, not the spark. If you are losing spark, its likely not this.

-Distributor pickup coil.

There's some leads, now go out and start methodical testing.

[77280zcar]

Jordan:

You're doing a pretty good job so far but there is more to do. You won't see much of a signal with a volt meter at that junction box. Its not a 12v on or off signal there, its a very low voltage waveform from the magnetic pickup in the distributor. I'de just pull the coil to dizzy spark plug wire from the center of the dizzy cap and put it near a ground (1/4 in) and crank to see if you have spark or not.

cool, i have done this in fact, and there wasn't any spark. im going to try tonight to do some testing as you recommended, hopefully ill find a culprit soon! its stranded at work so i can only work on it an hour or so a day, but i do work at a ford dealership so i have techs who can help me if i really need it =)

Edited July 16, 2013 by 77280zcar

[77280zcar]

On a side note, if it ends up being the module, ive heard of people using a gm HEI module in place of the stock one? also would one from a 79 zx differ any from my module?

[FastWoman]

Since your car is at a dealership, consider the following to CONFIRM the ignition failure:

1. Borrow a can of starter fluid from the service dept and try what I suggested above.

2. Borrow a timing light, and see if it flashes when you crank.

Sometimes a spark is hard to see in the daylight, especially if you don't have an appropriate gap. You might also have a weak ignition but a failure point that lies elsewhere. Most old cars have multiple problems. Only rare ones are completely straight.

FAIW, fuel pumps also fail when overheating. Or at least mine did.

[PastorMike]

Get some freeze mist (compressed can) or bagged ice, and cool down the different suspect parts one at a time, making sure that the part is cool prior to moving on to the next part; this will isolate the part. After cooling each part, try to start your car. The problem sounds heat related to the part, this should find it.

[EuroDat]

Im with PasterMike. Buy a can of electrical contact cleaner and spray each unit. Make sure the liquid evaporates on the part your spraying to cool it quickly.

Then try to repeat what you did to confirm it.

[PastorMike]

Freeze mist is actually a refrigerant in a can (possibly not available in all countries of the World because of the local politicians concern for the ozone layer). This product will cool below zero F so be careful. The concern in the humid South is the condensation on the part when you are finished. So, let the condensation evaporate prior to closing up a compartment.

Edited July 16, 2013 by PastorMike

[Wade Nelson]

A can of Spray-Freeze will quickly determine if it is an ignition module overheating problem.

A can of brake-cleaner or starting fluid will quickly determine if you have a fuel problem.

Try also taking the gas cap off; if the vent is clogged, it will pull a vacuum until the pump can't suck any more fuel out of the tank. And a lot of spiders and bugs decide to build nests in those vent tubes.

[77280zcar]

ok update, i found the problem... on the right side of the ballast resistor there is the rubber hood covering a wire around a nut, well somehow this wire was touching just by a hair and any movement would break the contact, and i guess with me fooling around in the engine compartment near it would set it back, so i started it up and tested this theory by thumping/tugging the wire and every time it would cut the engine off, so i set it back in place and i ran it tonight around for about 30 minutes and it never died once i set it back.. tomorrow night im going to bring some wire strippers with me to cut back on the wire some to run it under that nut, it also probably helped i used some CRC electrical cleaner on every connection i could find! thanks for everyone and their advice!

[Virto]

Glad you found the problem. Those single-wire issues can be a real bear to track down.