Zed Head

If you want to match the Nissan system specs. then about 08. - 1.0 is the range. You want to match the coil's resistance with the module's. Lower resistance might give a stronger spark but it will put more heat in to the ignition system since total resistance will be lower. Hotter coil and hotter module. There's probably room in the Nissan engineer's design safety margin for lower resistance. Your dice. Copied a picture from the 1981 FSM.

I'm with Blue, check your basics before getting too far. Timing is easy to check and very important. Check static timing and mechanical as suggested, and disconnect the vacuum advance and check its operation if you're using it. While you're there make sure that the new parts you installed didn't come loose and the points aren't pitted. Recheck all of your settings. If something bad happens within a short time of doing some work I always look at the recent stuff first.

Sent you a message. I'd just post the info here but with all of the trolling and phishing and nefarious stuff that goes on, I don't want to add to anyone's problems. Good luck.

Who is feeling reasonable and considerate? I found Lenny's phone number on the internet. I can send a message to whoever feels like making a call, but I don't want to facilitate any overt aggression. It's a business number so whoever calls won't be getting too personal. Worth a shot, he might just be very busy.

He probably won't be back. One post, just for his CL ad. Without siteunseen's fix, there wouldn't be any interest.

Just curious - do you drive it without air filters or are they off just for display?

Start at zero and work up. The pot is actually a good theft-prevention device. Just crank it up and you'll flood the engine. I have a 5K from Radio Shack and I barely use 5 degrees of knob rotation.

The atlanticz page shows the coolant sensor with both bullet ends disconnected, for demonstration, so is a little confusing. But you only need to break open one connection, and insert the potentiometer in-line. It can be before or after the sensor. All you're doing is adding resistance to the wire that starts at Pin 13 on the ECU and goes to ground. The ECU will think that the engine is colder than it is and add fuel. The sensor's resistance increases as temperature drops. It won't take much, I hope that you got a taper style potentiometer, they have a finer touch on the ends of their adjustment. I ran a few feet of wire from the connection on the engine harness and mounted the pot under the driver's side dash. In the engine bay is fine if you don't plan to mess with it much. Make sure it doesn't get too hot, it's probably not designed for engine bay temperatures. I added a picture from the Fuel Injection Book, illustrating the circuit and the bullet connections.

Many of us have had better luck with a potentiometer on the coolant temperature circuit to add resistance, to fix a lean problem. Messing with the AFM spring changes the slope of the enrichment curve, richer at the bottom not so much at the top, adding potentiometer resistance just moves the whole thing up. Richer everywhere. Plus, if you mount it in the cabin, you can tune on the fly.

I had the same issue for a little while. Leakage around the radiator cap. You solved yours faster than I solved mine. The hole in the cap of the overflow bottle is tiny, much smaller than it would seem necessary. I reamed mine out a little with a drill bit. Later (recently) I bought one of those pressure-releasing radiator caps so that I can test the system with a short pressure blow-off, along with being ready for any quick repair work. Bubbles in the overflow bottle means everything works. One way at least.

This is a sign that the regulator is not regulating correctly, but the pump is okay. Pull the vacuum hose from the bottom of the regulator and see if it smells strongly of gasoline. It might smell faintly of gas but if there's any mositure in there or it reeks of gas you probably have a blown FPR. Also, when you get a chance, warm the engine up again and remove the vacuum hose. If pressure does not rise to 36 psi or better then you have a bad regulator. Should have added this step before to save you time. I've seen on another forum that a blown diaphragm can cause a cold spot on the intake manifold at the point where the FPR vacuum hose nipple on the manifold points. The cold fuel cools it off. Just another sign. It might be that you have a hole or crack in the FPR diaphragm or the seal around the diaphragm, that gets worse when it warms up. This will give conflicting behavior, the intake will suck in extra fuel causing rich running, but the fuel pressure might read low, which would normally cause a lean mixture. The smoke from the exhaust might be signs of too much fuel. I had a bad FPR that showed correct pressure but was dumping way too much fuel. My gas mileage dropped to 15 mpg from 19, and the people driving behind me were angry. I got screwed up even more because I had a gauge on the fuel rail that read high when it got warm.

The battery gauge wouldn't really indicate a slight overcharge. It's not very accurate. And the older external voltage regulators can put out up to 15.75 volts, which is high by today's normal range of 13.8 - 14.3 for an internally regulated alternator (pulled these from a rebuilt alt. install sheet). Do you have any numbers? Your mechanic may not be familiar with the older regulators. The temp. gauge is also not very accurate and shares its voltage supply with the oil pressure gauge. The high number might just be an artifact. Is your mechanic suggesting an internally regulated alternator with solid-sate regulator or an external solid-state regulator? You can still get the external regulators. Might be the easiest fix, if you do have a regulation problem. But you need the voltage numbers first.

Send a message to superlen, he's been deep in to the ECU functions. He's building a standalone engine management system to replace the Z EFI. And the ECU is really easy to take apart. Maybe you'll find a shorted or corroded circuit. I've seen some crusty ECU internals, they live in a spot that gets moist if there's a windshield leak.

I guess I read it the way I thought showed that the TPS would be the culprit. Sorry about that, looking back I did read it wrong. Bummer then, problem not solved. It's odd though, that disconnecting the TPS removes the problem. That doesn't fit with the ECU being bad. Going back to what FastWoman suggested, when you say open, do you mean infinite resistance? Do you have a high quality meter that shows infiinty, or are you using a test probe with a beep? It might be that there's enough conductivity to trip the ECU's idle circuit, bit not enough to show on your probe.

30 psi at idle when cold is in the right range. Since your problem happens when warm you need to do the same thing when it's warm and you have 20 psi, which is not in the right range, it's too low. The cold test just shows that everything is working right when cold.

I guess I'll keep harping on the TPS. This is not right - open when accelerator is depressed all the way to full throttle I don't know if you can see the picture I attached in my last post, or if you haven't seen that page in the FSM. Pin 2 should show continuity at idle then OPEN when the throttle is just off-idle - 4 degrees is barely cracked open. Basically, when you crack the throttle, Pin 2 shows NO MORE IDLE. What you're writing is that the ECU sees IDLE all the way up to full throttle. That's what I've been proposing. Plus the fact that you don't see the cut with the TPS unplugged supports that it's the IDLE circuit continuity (Pin 2) causing the fuel cut. There appears to be something wrong with the TPS signal to the ECU, not the ECU itself.

The power break-up is because the fuel mix is lean. You should be at ~28 with the hose connected and 36 without. Did you get an adjustable regulator? It may have slipped adjustment or was never set right. If you have the stock regulator, pinch the return hose when the pressure is at 20 and see if it rises to 36 or greater. this will tell you if the pump can supply the pressure. Be careful, the aftermarket pumps will hit 90 psi and can cause leakage. If you think it might be the pump, you can prop the AFM door open with the key On, as Blue suggests in another thread, and just let the pump run while watching the gauge. Several people have had pumps that fail when warm. If the pump is bad, eventually it will start making funny noises and pressure will drop. I had one of those.

I was just looking at a used car, and the guy had just bought so knew little about it. It was in bad shape though, with an off-year AFM zip-tied in place and general poor maintenance. Someone had messed with it. The hole seemed to fit the general condition of the car.

Oddly, that picture shows up on a Ukraine web site also. Is there more to Blue than we know? The page translates to "How to Draw a Hut".

Interesting clue. But that's not supposed to happen either. The pump should only run when either the alternator is spinning or the oil pressure switch is activated, with the key On. That's what the pump control relay is doing. You're getting closer though. On looking at the relays - I think it might be easiest to just unbolt the complete relay bracket to get to the relays. I seem to recall trying to get to them form underneath and it's a pain. Don't forget to disconnect the battery first in case you have exposed wires. There might also be a fuse on the pump circuit that could have blown if you have a shorted relay or wires.

I saw a similar hole in the side of the engine of a Z I looked at last year. The guy said he din't notice anything odd, he was just driving down the freeway and the engine stopped. Are you going to pull the head? I'm curious about valve damage if a piston got pushed back up the cylinder after its cap came off.

A common noise for the Nissan transmissions is the countershaft bearing. When you disengage the engine from the transmission by pressing the clutch pedal, the bearing stops spinning. The banging could be a bearing with some balls missing. You might want to get in there before it fails completely. It's under the transmission front cover so you'll be able to get to it easily once the transmission is out.

Have you checked for power at the injector connections? You should have 12 volts on each pin in the connector. That's the first thing you should do. No power, no injector open.

Expanding on FastWoman's point - you're not reporting "no continuity" or open circuit at 4 degrees + off idle. You should see the idle circuit go open when the throttle blade is moved (looks like Pins 2 and 18). You might need a good meter to be sure that there is not some slight conductivity that would "trip the logic" as she suggests. In the same vein, I assume that the ECU TPS idle circuit monitoring itself could be bad. But I've never seen anyone report that. Still, the observations at 2800 and 3200 RPM should tell if any of this is even worth following up on.

That was probably my relay. Could you separate out the problems that are there when it was running, and the problems that are there now? Looks like you have everything blended together. The odd one is that the starter will turn the engine,which means the solenoid wire is getting power, but the fuel pump does not have power (this should be confirmed). That could be the fuel pump control relay or the pump relay itself. Try unplugging the small yellow wire from the starter then turn the key to Start and make sure that the fuel pump does not run. You can see in the attached diagram that the Fuel Pump Control relay gets power from the Start circuit first and powers up the Fuel Pump relay itself. If the pump is not getting power, make sure that your car actually has these two relays. Some of the 1978 cars still have the combined EFI and Fuel Pump relay, but may still also have the Fuel Pump Control relay to power it. I had a 78 with the combined relay. I think, that a failed Fuel Pump Control relay might explain some of your symptoms, like the back feed through the alternator charge light, since the L wire runs through it. There are others with better electrical knowledge on the forum. Yeah, it's complicated. Unplug that yellow wire at the starter solenoid and make sure the pump does not get power. That's what I would do first.