Ignition/distributor - no spark to plugs. Help!

[ron32966]

The distributor ('77 280z) has no spark to some of the plugs. If only 3 wires are used, there is a spark; if 6 wires are used, there is no spark to any of them. If one wire goes to ground, it fires. The pick-up coil seems to be working. I've changed the coil and balast resistor, and changed the module and the distributor; no luck - still cannot get all 6 wires to fire, but when 3 wires fire, it's weak.

I've changed the (regular) coil, distributor cap, rotor and pick-up coil. Also, I've added another ground wire to the block from the battery.

This all does not make sense and I'm at a loss to know why or what needs attention next. It was running good one day, then the next day, no spark to the plugs.

Thanks for your help. Ron

[JimmyZ]

It might be a bad coil wire. (HT) You have checked that proper voltage is getting to the coil right?

Assuming the plugs are all good then that leaves you with the coil wire. Try using a regular plug wire for the coil wire if you don't have a spare. AT least this will tell you if it's the coil wire.

Very odd.

Jim

[ron32966]

I have a spare coil wire, but it not that. The wire that's on the car tests ok. Yes this is odd. Any other suggestions? Ron

[JimmyZ]

You did try new plugs right?

[JimmyZ]

I'll be in Vero tomorrow morning around 7:30AM. If you like I could swing by. I'll actually be in Orchid which is down by Disney's VB resort.

PM sent

Jim

[JimmyZ]

Is it an automatic??

The following applies to dual pickup units...

Water pump switch or relay then. Haynes manual pg 79 section 12.

There is an advance control relay that uses the WT & relay change ignition advance.

You did check for proper voltage at the coil too right?

[ron32966]

Automatic - yes.

There seems to be spark at the coil, but doesn't come out of the distributor.

[ron32966]

The pickup coil from another 280z is magnetized. The new I bought from a parts store is not. Would this make a difference?

[JimmyZ]

Is it a single or dual pickup dizzy? According to the Haynes book it should be dual unless it's been switched.

You have the air gap set @.012-.016 on the new coil. (Gap between projection and P/U)

[JimmyZ]

I'm a 240/breaker points guy and know very little about the specifics of the 280's system. I do know a little about electronics and understand the various triggering systems.

From the Haynes manual... pg233

If it is a single pickup unit there is a warning about not removing HT leads while the engine is running. It may damage IGN system components.

Not knowing which pickup style/system the 77Z uses...

The star wheel on the dizzy is magnetized right?? If so, then the pickup shouldn't be magnetized or might have very slight magnetism from exposure. This would be a non-magnetic pickup.

If the start wheel is just plain iron and not magnetized then the pickup is a variable reluctor and has a magnet in it... A magnetic pickup.

It's funny you should ask about this because I just hooked my oscilloscope up the other night to play with a magnet and a nail wrapped in magnet wire. Nice little sine waves... A homemade pickup.

[ron32966]

If I ground out one of the plug wires on the battery with a spark plug in it, it shows that the pickup coil is working.

Thank for your help. Talk to you tomorrow. Ron

[JimmyZ]

The pickup coil from another 280z is magnetized. The new I bought from a parts store is not. Would this make a difference?

I imagine that all Z's used only one style of pickup but I could be wrong. (see message above) It would make a difference what style of pickup was being used if the "brain" was designed to accept a particular signal. Depending on the design of the brain's internals it might kill it if the wrong signal was introduced. One would think that the brain should have been made to handle such abuse but the signal in question is extremely faint during starting. (especially on non-magnetic P/U system)

Hopefully a knowlegable 280Z person will chime in. Someone who knows all of the later style dizzys ins/outs.