IGN module thinks it's running at 2k when engine is off

[ntomsheck]

Hey guys. I've been working on piecing a 260z back together after it sat for who knows how many years. It's a couple days away from initial run, depending on how quick I can figure it's electrical gremlins out. The engine is in, only thing it needs is the alternator, and the cooling system hooked up. I hooked a battery charger up to it the other day (battery is dead) and when I turned the ign switch to 'run', the tach showed a constant 1800rpms or higher. The coil was making some angry noises, so I stuck a spark plug in the end of it and held it to the intake manifold. It made a constant spark across the gap.

The ammeter barely moves when the car is turned to run (even when the charger is set to 200amp START). I can't turn the car over yet, because the neutral safety switch is not connected (but I can hear the relay click). I can jump the starter solenoid with a screw driver, and the engine turns over, but it makes an unhappy noise as it turns over (metal grinding sound, I attribute it to a dry torque converter). The headlights and brake lights work (but no tail lights, yet). Anyone have any ideas?

[d240zx2]

You've likely got loose grounds out the wazoo and a few loose connections, maybe even a short or two, to boot.

Get yourself a FSM and start with one circuit at a time. Tedious, I know.

[alhbln]

The tacho just shows the ignition impulses received by the coil, those impulses also create the 'angry noises' which you normally won't hear because a running engine is louder than the coil. Question is why the coil receives ignition impulses at all. My wiring scheme for the '74 260Z indicates a point breaker setup, do you have a points setup or an ignition module/magnetic pickup fitted?

If you have a points setup, check out your contacts and the capacitor, the contacts might be touching each other and create a partial connection due to the high current flowing, a defective condenser could have similar effects (simple test, what happens if you disconnect the condenser?)

With an ignition module either the magnetic sensor/pickup is broken, or the ignition module is defective. Disconnect the pickup wire from the ignition module, do you still have the erratic ignition impulses? If so, the ignition module is most probably defective, otherwise the magnetic pickup might be the source of the problem.

Did you encounter the problem with a fully charged battery or with the charger still connected? An electronic charger connected to a dead battery can create similar symptoms when you put a load (ignition circuit) on the circuit.

[ntomsheck]

The 260 I'm working on has magnetic pick-ups instead of the points system. I don't know if it was aftermarket or not, because the pick-ups look as old as the rest of the components. However, the ignition module certainly looks new/aftermarket. It has what I can only guess is a temp sensor, and a pot. by the wires. I can't get close enough to read it, but my guess would be an internal rev-limiter. It also has the dual two-barrel (webber?) carb upgrade, so I don't know if there was a magnetic-pickup retrofit with that kit.

The battery, by the way, is completely dead. The charger reads zero current pull @ 35amps when it's connected. Didn't get a voltage reading on it though; left my multimeter at my house. I have to leave the charger connected if I want any power. That is, until the owner buys a new battery for it. The car isn't mine, it's a buddies, but he's paying me to work on it. I might be it's next owner if he doesn't want to pay my rates. I've fixed enough crap of his for free.

By the way, are there any grounding straps that connect the block to the chassis? My experience is in 1980+ vehicles and <1980 domestic vehicles and they all have block ---> chassis straps. The Z has what looks to be a 12 or 10 gauge wire that connects to the firewall, but is that enough?

Edited July 7, 2010 by ntomsheck

[alhbln]

I would recommend borrowing or purchasing a new battery first, the symptoms you have described could result from powering the car with the charger only.

Can you post some photos of the ignition module and magnetic trigger, that would help with the identification of the parts

Sorry, i don't know the 260Z wiring well enough to answer your question regarding the ground strap, but adding one is certainly a good idea.

[ntomsheck]

I 'borrowed' the battery out of a friends 72 charger (which fit surprisingly well), and once hooked up to it, everything worked properly. The tach no longer showed 2k, the underhood light came on. The electronic fuel pump even started working. It was pumping some orange/brown 20+ year old gas though , so I was surprised the pump wasn't clogged. Is there any kind of return system for the electronic pumps? There doesn't seem to be any kind of FP regulator, but there looks to be a return line.

We actually had the car pop to life for a few seconds, with a can of starting fluid. It backfired through the carb though, so I've gotta check my timing and plug wire orientation. Thank you for your help

[ntomsheck]

Double post