Dolfinz

I did as you suggested. I pulled the plug and the piston is up. Not sure if it's all the way but I can see the piston head through the spark plug hole. Also, there's no damage to the spark plug electrode. Next steps?

So, the impression I get from Patcon is that there may be a way to reassemble this without pulling the head off. I understand that the valve may be bent but it would seem to make sense to try it before going to the trouble of tearing the engine apart. Any additional thoughts or suggestions? I've never personally worked on the head so I have no clue if this is possible.

I think I found the problem. See attached picture. Question now is how do I fix it?

I appreciate the support and anyone that might be here in Phoenix willing to assist me would be greatly appreciated. The main reason for my frustration is I just put out $3k to get this engine rebuilt. Unfortunately it didn't include a warranty. I'm going to pull the valve cover and see if there's anything obvious there. After that I could try checking compression on each of the cylinders but I'm afraid of doing any further damage by cranking the motor. I'm open to any other suggestions and will advise on what I find when I pull the valve cover. I really hate to give up my 44 year project but it will depend on what's it's going to take to get it fixed.

I think it was zed that suggested the starting fluid so I gave it a try and sure enough the engine fired. So I figured it was out of gas; since my gauges don't work, I figured it might need fuel. So I went and got 5 gallons. I can't figure how we drained the tank after the engine was rebuilt and 5 gallons overflowed the tank. Any ways, with plenty of fuel I pulled the choke full on and she started and ran for a couple of blocks. I was about to try to get her up to 40mph but it sounded like someone dropped a box of wrenches in the motor and she stalled and wouldn't run any more. So much for my engine rebuild. After 44 years I can't afford another rebuild. I'm 63 and I wanted to leave this car to my Grandson for it to be his first car as it was mine after I got out of the Navy. I'll do compression tests tomorrow but if it threw a rod I'm done. My wife has been begging me to get rid of this car for 40 years and my working on it has nearly ended in divorce multiple times. But, it's always been a love of mine. Oh well. fate will be what will be. I appreciate all the advice ya'll have given me. It always has given me hope. Unfortunately it appears this will be dust in the wind.

I'll inspect in the morning.

Yes it's a 74 260z and the smog shi* was removed years ago. Yes it has carbs and the mechanical fuel pump is going to provide fuel that I can smell as the air cleaner is off to facilitate the use of starting fluid should the engine fire. I go back to the fact that the motor was starting and running fine 2 months ago outside the charging of the battery. Now it won't fire. I did have the choke partially on as well to ensure fuel getting to the carbs. I have since shut it off. I will let the motor sit and let the battery charge until morning as it's seen a lot of cranking due to all of the testing. I will respond again after it has had time to rest. As for the spark on the number 1 cylinder it is timely and consistent but I'm unsure if it is strong enough due to the voltage at the coil during starting.

I'm certain about the fuel as I can smell it when I'm testing. The engine isn't firing at all so I doubt starting fluid would help. A video of the spark where? Coil wire to distributor or #1 cylinder plug wire? You don't think the drop in battery voltage when starting is significant? If it maintained 12+ it would raise the voltages everywhere. 7.5vdc at the coil is acceptable?

I checked one more thing. The wht/red wire at the ignition switch drops to 9.6 in the start position.

Ok, I cleaned the fusible link terminals, replaced the fusible links, replaced the white wire connection at the starter, replaced the positive battery cable and replaced the connections at the ballast resistor. The voltages changed as follows. Voltages under no load. Battery 13.07, wht wire at flink 13.06, wht/red wire at flink 13.06. Ignition switch on. Battery 12.95, wht wire flink 12.94, wht/red wire at flink 12.94, blk/blu at ballast 12.6. Ignition switch at start. Battery 11.25, wht wire at flink 10.9, wht/red wire at flink 10.4, blk/blu at ballast 9.1, coil+ terminal 7.5. Coil wire at distributor seems to have decent spark as well as spark at the #1 plug wire but it's still not firing. Keep in mind the engine was running without issue until we began troubleshooting the issue with the alternator not charging the battery when it was running. All that's really changed is the new voltage regulator and ignition switch other than cleaning/repairing connections. Looking for direction as to what to try next.

So here's what I'm getting. Battery voltage in static state is 12.75vdc. Voltage on white wires at fusible link when cranking 9.9vdc. Voltage at wht/red wires at fusible link when cranking 9.75vdc. Voltage on battery when cranking 11.4vdc. Is this indicative of a week battery? Definitely losing voltage elsewhere but what is considered acceptable? Clearly losing nearly 3vdc between battery and fusible link and another .25vdc at wht/red after shunt. Another 1.5vdc from fusible link to ignition switch. Please advise.

I got the replacement starter switch and installed it. I also disconnected the blk/blu wire at the ballast resistor. I checked voltage and now it's 8.5vdc at the connector to the resistor. I also checked the voltage on the wht/red wire at the ignition switch and when trying to start and it drops from 12vdc to the 8.5vdc. It appears that the supply voltage is dropping for some reason. Any ideas of what could be causing this? Can I just run a new wire to directly feed the ignition switch from battery power? I'm also uncertain how the transistor ignition unit is related to the starting function?

I replaced the voltage regulator as previously suggested because the alternator wasn't charging the battery when the engine was running. I then went to test the charging circuit with the car running and it wouldn't start. I determined there was no spark and the voltage at the coil was around 5vdc. We've narrowed it down to possibly a faulty ignition switch so I ordered a new one. Once I receive it I will follow all the testing mentioned to determine why all of a sudden I have no spark. I started at the resistor and worked my way back to the switch and once replaced I will work my way back from the switch to the resistor. I have no issues yet, at least, with the battery draining when the ignition is off. Only when the engine is running. The engine was starting and running fine prior to the 2 weeks it sat waiting for the new voltage regulator other than the charging circuit. As for the firewall connections, et al C-5, I don't trust any of them as my gauges don't work and I had to completely rewire my headlights, horn, running lights and turn signals. Once I get the engine running again I will remove the dashboard once again and deal with the remaining issues at the firewall connections. I've never heard of Vintage connections and I'd prefer to replace the connector if possible. I will google it.

I ordered just the module on the back of the switch. Once I receive it I will install it and if the voltage drop still exists then I will try eliminating the molex connector on the ignition switch and individually connect the wires via spade lug connector to eliminate the connector. Then, if the voltage drop still exists I will tape up the blk/blu wire and check again with it disconnected. If there is still a drop then I will run a new wire from the ignition switch to the ballast to eliminate a partial short to ground somewhere between the ignition switch and the ballast. After that, ????

The 7.2v was at both the resistor and the ignition switch terminal connector. I didn't see any corrosion at this connection.

This is excellent information, thanks. I checked the voltage at the ballast resistor blk/blu wire and it was 7.2vdc with the ignition switch on start. I checked the wht/red wire at the ignition switch and it was 12.2vdc. When I turned the switch to start, the wht/red was constant but the voltage at the blk/blu was 7.2vdc. I removed the ignition switch assembly and checked the contacts resistance at less than 1 ohm. While I wouldn't think this is indicative of a bad switch I am ordering one anyways due to the voltage drop. I also checked the resistance between the wht/blk and blk/blu on the ballast resistor and got about .1 ohms. Is this correct? I will follow up once I receive the new switch.

The battery is also fairly new. I checked the voltage while cranking and it was 12.3vdc. The motor is turning over just fine but there's no spark from the distributor at the plugs. Not surprising since there's only 5vdc at the coil. What could be causing the voltage at the coil to be so low?

New problem. When I first tried to start it it was firing but wouldn't stay running. I had to turn it over several times which was hard on the battery so I let it sit for a bit and put the charger on the battery. After it had recharged I tried again and now I have no spark at all. I measured the voltage on the coil and in the start/on keyswitch position I'm only getting 5 vdc. I assume this is insufficient and I'm baffled as to what could have happened. It was starting just fine prior to troubleshooting the alternator issue and replacing the voltage regulator, neither of which should affect it's ability to start. Any ideas as to what could have gone wrong and how to troubleshoot this new problem?

Now that I know what you're talking about I disconnected that thing years ago. I assume that's all it takes to bypass it? As for my problem, the voltage regulator and alternator are new. I haven't tried restarting it since I replaced the voltage regulator as it already had a new alternator. I'll attempt to start it again this weekend and advise if I need further troubleshooting tips. Hopefully it was an issue with the 47 year old regulator.

This is great info but I have a few questions. You mentioned that the WB wire goes hot when the appropriate contacts are closed. A prior post said the the WB wire should be hot when the ignition switch is in the ON position. Does this wire not go hot until the engine is running and if so what activates the relay that closes the contact to make this happen? My problem is that when the engine is running it uses the battery and the alternator doesn't charge the battery. I assume that this relay must activate to excite the windings in the alternator so it charges? Regarding the Ignition interlock unit you don't seem to like. It can't have been bypassed as I would have had to have done it and I don't even know where it is located. Is this something you would recommend that I do? If so, please advise on how to do it and why you think it's a good idea.

I know it's been a while but I had to wait on a new voltage regulator; which I received and installed, and I've been working on getting turn signals, headlights, horn etc. operational. This required having all my steering column switches rebuilt. These are all completed and I'm back to addressing the alternator issue. I have verified continuity of the F wire from the regulator to the alternator( this is a white/blk wire). What I haven't been able to determine is the color of the wire at the regulator plug that is supposed to go hot when the ignition is in the on position. The white wire is constant +12, the black wire wire is ground and the yellow wire goes to the alternator N terminal. Can you advise as to the color of the wire from the harness that is supposed to be the IG connection? The blk/ylw goes hot with the ignition switch on but if that's it why doesn't the wht/blk F wire get voltage? I'd appreciate some further assistance.

Zed, It finally cooled down enough for me to work on the car. So, as you suspected there's no +12 at the F terminal to the alternator, white/black wire. I traced the wiring via the vehicle schematic and this wire goes through the voltage regulator and the electric fuel pump relays. Any reason I can't just run a new wire from the ignition switch ON wire to the alternator? It would save a lot of troubleshooting of the wiring in between if I can. Let me know.

Been too hot and humid here in Phoenix to work on the car. I'm hoping to get some time this weekend.

Thanks for the advice. I will check it. I know it has a good ground as the black ground wire is connected. It is possible that the F wire isn't a good con nection as the molded plug broke due to age and only the spade lugs are left.

The engine is drawing on the battery not the alternator. There is no draw when the key is off only when it is running. This is a second alternator and the engine has done the same thing with both. The first one was only a couple years old and I had it tested and it was good but got a new one because the plastic cover on the back got lost. I had the same problem with it before I replaced it so the alternator doesn't seem to be the problem. Like I said previously, I'm going to pull all the fuses and see if that helps. But now I'm thinking the engine won't run then because the electric fuel pump won't get power. I'll try the measurements above but expect that if something is draining the alternator it's still going to look like a bad alternator. I'll try it with white/red wire disconnected from alternator output. As for the current draw, what would be the normal current draw to charge the battery while the engine is running and everything else is off?