Working with a 1980 SA -

First, I have some experience with 12v dc systems. Most recently on a 35' sailboat. Let me tell you, you don't know what fun is until you are wrist deep looking for a bad ground in bilge water from a questionable choice or hanging 40' in the air at the top of the mast to rewire an anchor light which has broken in the conduit 2/3 of the way up...

1980 SA - car starts, runs, drives reasonably well. The ACV was removed when I bought the car and did not come with it. I removed the air pump and the remainder of the anti after burn system since it was doing exactly nothing. I have replaced the alternator. The previous one was on its last legs. This problem was going on before and after the alternator replacement. I do not think it is the alternator itself unless T3 sent me a bad one. I know of a vacuum leak in the exhaust as there is a 3/4 inch hole through the heat exchanger and the thermal unit is questionable. Water pump, thermostat, along with gaskets have been replaced. Oil change and oil pan gasket replaced. As far as I know, everything else stock is still there.

Here is the problem -
When starting the choke does not remain out under any condition.
While idling or driving if I use any accessory - radio, antenna, lights up or down, turn signals, brake lights, head lights!, or even parking lights, heater or A/C fan the engine loses serious power and rpms. To the extent that use of the headlights will actually stall the engine.
Here is where it gets weird -
While idling or driving if I pull the choke out and hold the choke out when turning on any of the aforementioned accessories (or multiple ones) there is no issue and the car runs fine until I want to turn something else on or off. The higher the electrical draw, the more disruptive it is to the engine.

I am semi-retired. I have the time and patience to track every wire and check every circuit. I would love to not do that if possible. If anyone can give me a starting point, it would be greatly appreciated.

Thanks

 

To answer the first simple question, is it something in the harness or is it purely additional electrical draw tipping it over, you could get it idling, and then take an external load like headlight and connect it directly to the battery terminals. If it stays idling, you know it's not falling over from just a slight increase in load.

I would also disconnect the battery and check that you get a good solid 12.6 volts. And while the car is running, measure the voltage coming off the charge line from the alternator to the battery and see that you have 14.5 volts. I'm not sure if your car has an external voltage regulator on the alternator or not, so consider my suggestion in light of that.

Edit: I just read that the T3 mini alt is internally regulated, so if you did have an external regulator before, then you should have removed it. Just spit balling.

Also, you can find manuals here, including electrical
foxed.ca/index.php?page=rx7manual

Good luck!

 

Thank you for your input and suggestions. The previous alternator did not have an external regulator so that was already gone. Tomorrow I'll try jumpering the headlights directly to the battery as well as get out the volt meter for the return line to the battery. Last time I checked (3 or 4 weeks ago) battery was fine at 12.6. Thanks for the links to the manuals. I've been through them many times already and still can't figure this one out. I think I am also going to get under the dash and see if the choke cable is somehow brushing up against something else and completing a bad ground or circuit. My other thought is the choke magnet is somehow involved since it is an electromagnet.

 

Have you checked the sensor on the back of the water pump housing to ensure a wire didn't break off? It controls the automatic choke.

Like said by Toruki, my first guess was that the external voltage regular on the rear driver side fender well is still connected. I'd also check to ensure the alternator is actually charging the battery while the car is running. This will also test if the voltage regulator is working.

To test if a voltage regulator is working, use a multimeter to measure the battery voltage while the engine is running; a healthy regulator should show a steady 13.5 to 14.8 volts at ~2,000 RPM. Readings above 15V indicate overcharging (faulty regulator), while readings below 13V indicate undercharging.

 

Along with checking the charging circuit make sure the fuel pump is working to spec. Putting the choke on makes it run richer, even with a bad pump. Without the choke it may be leaning out.

An 80 SA never had an external regulator just so you all know.

 

Thank you - Especially on the external regulator. I thought that was the case but was unsure.

 

Small update. The voltage on the battery is fine. The water temp. sensor on the back of the water pump is bad. I suppose I didn't look at it close enough when I took it off to do the gasket back there. Now I need to source a part. I wonder if the 81-85 part will fit it. I can find 84-85 12a online for about $25. I can get an authentic one from one of the reputable scrap resellers but it will be 6 times the cost and likely just as brittle. The wires came apart in my hand just after this photo.

I did not get to test the charging circuit or fuel pump today. Possibility of that on Sat. Definity will have time next week. I'll update again after that.

If anyone has a source for a replacement for the water temp. sensor I'd love to learn of them.

 

That can be fixed. Take that white insulation off with a razor blade and carefully remove some of the hard, I think red, epoxy to the stud underneath and then solder the wire to it. Put some heat shrink on the wire and move it away from the end before soldering. Those wires are really easy to break when putting the sensor back in, even on good ones. You could even have a helper or an alligator clip to hold the wire to test before soldering.

 

Ha! I just left amazon where I picked up a new solder gun. Been forever since I used one. The cover came off in my hand and I found the metal stud inside of it all. I'll be practicing on something unimportant first. If it works, refill the epoxy? I have to think it helps protect it.

 

You can use some epoxy. I like JBWeld in general. When I repair mine, I only use a few layers of heat shrink that span the stud and good portion of the wire insulation. It's the flexing of the wire itself that breaks then.

 

Just a thought, but repairing older wires that are brittle you may just want to just use multiple layers of heat-shrink. Adding a hard epoxy added might lead to the older brittle wire you repairing to break again if the wiring is impacted by something/someone.