SteveJ

Between 2 & 3 - Coat the area to be soldered with a good flux. That will help the solder adhere to the wire.

Where exactly is this in the wiring harness? I can't make it out with the close-in shot. By the way, great job on the perseverance. You're representing your generation well. Edit: Wait, I'm taking that it's at the fusible link. So that branch wasn't getting full current due to the corrosion. When it got the extra load, the voltage would drop.

These numbers seem high to me. The resistance across wire runs should be very low. You may want to validate your readings. Keep in mind that the quality of the probe with the wire being measure can greatly affect your readings. Make sure you have very firm contact on each side of the circuit.

I got 6AN to 1/8 NPT fittings to replace the barb fittings on the TBI adapters. I could not put the back throttle body fitting at the angle I wanted because it was hitting on the base of the adapter before it was to the point I wanted, so I compromised. It looks a little kludged, but it doesn't leak. (If it looks stupid but it works, it's not stupid.) I also purchased a Walbro GSL395 fuel pump. This fuel pump is rated up to 20 PSI and is targeted for GM TBI systems. In other words, it's a good application. In addition, it takes male 10mmx1 fittings, so I got it with 6AN to 10mm fittings. After that I put 90 degree elbows on the inlet and outlet and 5/16 to 6AN fittings on the elbows to go to the fuel lines. I was able to orient the pump so the inlet is on the bottom, like it should be. I got the fuel pressure set, and I got a smooth idle, though it is at 1200 RPM. Now I have to test. That might have to wait until Tuesday, though.

@Usain_Boat- This is the thread @wal280zis referring to

Please note that ZCON 2020 runs MONDAY through Saturday. The past several ZCONs were Tuesday through Saturday.

When my friend (and long time Z mechanic) worked on my wheel bearings, he left the nut on enough to protect the threads and used an air hammer on the back side. That worked well for the left. The right did not budge. He attached a slide hammer to the right, and it still did not budge. Then I used the slide hammer while he used the air hammer. That worked. The threads were protected, too. Mind you, this was done with the parts attached to the car.

Make sure the resistor is connected between the ignition and the tachometer.

Upper and lower voltage limits are important for some components. For instance, don't run a standard sealed beam headlight at 17 volts. It won't last long, and the fuse won't blow.

FYI to the reading public, @Usain_Boat and I have talked on the phone. He is going to examine the body wiring harness for signs of damage. The cutting off may be happening with the left turn signal, too. The common path is through the body wiring harness. Fortunately, the interior panels are off so he can trace it more thoroughly.

Oh, since we would expect the flasher fuse to blow, check the rating on the fuse to make sure it is only 10A.

Okay, here is an explanation of the fuel pump control relay and fuel pump relay 78 Fuel Pump Relay Notes There are two relays 1. Fuel Pump Control Relay 2. Fuel Pump Relay Fuel Pump Control Relay: Positive coil voltage comes from the white/black wire (Origin is the Ignition Relay) One coil is grounded through Alternator (blue wire). The other coil is grounded through the oil pressure switch (yellow/black). The relay has form C contacts. A contact puts wiper (white/black) in contact with power from ignition relay. B contact puts wiper in contact with power from engine cranking (black/yellow wire). (Note: This is opposite of how it is drawn in the factory wiring diagram, but how it is drawn does not make sense.) The wiper provides coil power to the Fuel Pump Relay. Fuel Pump Relay: Positive coil voltage comes from the white/black wire from the Fuel Pump Control Relay wiper. Form A contacts connect two green/blue wires. One side comes from a fusible link. The other side goes to the fuel pump. Theory of operation: When cranking the engine, within the Fuel Pump Control Relay, the second white/black wire mentioned above is connected to the start position on the ignition switch. This energizes the Fuel Pump Relay and powers the fuel pump. If the engine starts, the key is released to the ON position, and the first white/black wire is energized from the ignition relay. The blue wire is grounded through the alternator and the coil is energized within the Fuel Pump Control Relay. This closes a set of contacts within the Fuel Pump Control Relay that allows the second coil to energize, provided there is sufficient oil pressure. With the second coil energized, the power from the ignition relay is providing power to energize the coil on the fuel pump relay. How this applies to your problem: The odds are that the voltage is dropping on the white/black wire coming off the ignition relay. List of components fed from the white/black wire from the ignition relay: Fuel Pump Control Relay Electronic Fuel Injection Main Relay Flasher fuse (Green wire) Fuel Gauge fuse (Blue wire) The loads off the Flasher fuse: Brake Warning Lamp Check Relay Turn signals Seat Belt Warning Timer Unit Fuel Level Warning Lamp Reverse Lights The loads off the Fuel Gauge fuse: Fuel Gauge Water Temp/Oil Pressure Gauge Tachometer Process of Elimination: There are several components here that we can definitely cross off as problematic: Fuel Pump Control Relay, EFI Main Relay, Seat Belt Warning Timer Unit, Fuel Level Warning Lamp, Fuel Gauge, Water Temp/Oil Pressure Gauge, Tachometer. So IIRC, you said that the car would die when using turn signals or putting the car into reverse. Those are BOTH powered off the flasher fuse in the fusebox, and the flasher fuse gets its power via the white/black wire from the ignition relay. There is even a common point for these two circuits that initiate the problem: the right rear taillight assembly. Here is a simple test. Disconnect the wiring harness going to the right rear taillight assembly. Start the car and try to put it into reverse. If it does not die, try turning on the right turn signal. If it does not die, you have confirmed that the issue is at the right rear taillight assembly. You may have to take off the plastic panel to access the connector.

The wire that goes to the bulbs is not continuous to ground. The bulbs are the load (resistance). You should be reading about 3 Ohms resistance from the wire at the switch to ground. Only the negative side of the bulb socket should have continuity to ground.

Okay, this is a good start. If you have not already done so, download a copy of the FSM from this site. (If you are on a computer, the link is in my signature.) Also, look at Blue's tech tips for a copy of the full wiring diagram. I think there is even a color copy of the wiring diagram floating around this site somewhere. On page BE-14 of the FSM, you'll find the reverse light circuit. The diagram shows that one side of the switch gets power from the fuse box, and the other goes to the taillights. Neither side should be grounded. Since you say one side of the switch is grounded, let's assume that is the side with the bulb sockets. Unplug both of your taillights at the taillight panel. Check the wire that had continuity with ground to see if it is still grounded. If it is not, the problem is at a taillight. That might also correspond to the dying problem happening with the turn signal. If the wire is still grounded after that test, break the connection at connector C-4. Test again. If it is grounded, the problem exists between the switch and connector C-4. If it is not grounded, there is a chance the body wiring harness is damaged, probably by a screw and is grounding out. To trace the path of the body harness, look at the BE section of the FSM. If my instructions don't make sense, send me a PM with your phone number. Sometimes I can explain this over the phone more easily than I can type it up.

You're not posting too much. You are providing detailed observations. From this I can look at the wiring diagram and try to find some things for you to look at. Did you strip off the wrapping around the wiring harness, or was that the work of a previous owner? From picture 1, I can't tell if those are factory splices in the background. From picture 3, is that the end of a wire that has been cut? From my previous comment, it sounds like someone was trying to fix something and may have introduced a short. Just wild speculation, but it may be that the power for the second fuel pump relay coil or the fuel pump itself gets shorted out with the reverse switch. The car dies (and the damaged circuit loses power) before a fuse or fusible link is blown. If you can get under the car easily and access the reverse switch on the transmission, take it out and see if that resolves the car dying when going into reverse. Also while you're under the car, see if either side of the reverse switch has continuity to ground.

I also don't like how the fuel lines ended up at the TBI adapters. Look at the bend in the line at the front throttle body. (I almost typed "carb".) Rick confirmed the fittings are 1/8 NPT, so I ordered 1/8 NPT to 6AN 90 degree elbows. Then I'll put another 90 on to point to the fuel rail. Hell, I have plenty of braided hose, still.

First verify the battery is good. A bad battery or charging system with the accompanying voltage drop could account for some of the issues. Get the battery load tested. Don't try running the car with a low battery. You can damage things that way. By the way, what is the battery voltage right now? Check with a meter, not the voltage gauge on the dash. I'll trust a 40 year old Simpson meter. I'm not sure I would completely rely on the 40 year old voltage gauge. Verify the presence/absence of spark with an inline spark tester (https://www.harborfreight.com/90-in-line-spark-checker-63593.html). Have someone crank the ignition while you watch for spark. Do this in a relatively dark setting. Again, look for wiring modifications from a previous owner. Search on this site. I know I have provided diagnostics for the 78 fuel pump relay and even described how to bypass the relay for testing.

It's a late 80's/early 90's GM EFI system, so I would any self learning is limited. I don't recall anything about self learning on the website, either. The fact that I could back off slightly (under load) and get the car to respond leads me to believe there is some kind of lack of fuel for a brief period...that and the bucking.

Let me be frank here... You'll need to supply a LOT more information to get decent responses (and not have someone posting pictures from The Naked Gun). You found a splice you didn't like, but you don't say what wire was spliced (the colors are important), how it was spliced, or where the foreign wire went to. That splice may have been one of those "fixes" a previous owner did to work around a problem instead of diagnosing it properly. It is challenging to track the history of the issues. When did each issue start? You added things about the dash light and fuel pump. When did you remove the splice? We cannot see your car, so you have to paint a picture with words (and post photos). If you have a half decent camera on your cell phone, there's no excuse for posting without photos.

You have text message exchanges like this:

With the behavior you described, it's likely one of two scenarios. There is a problem, possibly with the ignition switch, and what you perceive as triggering events are just coincidence. A previous owner has hacked into the wiring to "fix" problems. You might want to pull off the steering column cover and start looking for splices.

Well, I took it for the first test drive. It ran, but it did not run well. At times it seemed like it was fuel starved. I'm going to re-orient the fuel pump to see if that helps some. The plugs were fouled, so I replaced them. The car does not like to idle. I opted to add an Idle Air Control Valve in case I added AC later. I just ordered all of the parts I believe I need to install the IAC valve. I let Rick Patton know the results. I haven't tried to datalog anything, yet. That might happen tomorrow depending upon how well the fuel pump repositioning goes.

The cables are going to the same place they went to on the SUs. They still move the butterflies. I don't know enough about how the GM system works in actual GM cars to know how the throttle body/fuel injection accounted for cold start conditions.

It doesn't matter how big and strong you are if you don't have a way to get leverage. Fortunately I know 50 ways to love my lever.