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1969 Cutlass strange electrical/ignition problem in gear
Hi so I have a fully restored 69 Cutlass with a built 350 upgraded msd magnetic pickup distributor and streetfire ignition and new wire harness. So the car has been well gone through and I thought by doing all of this I would avoid electrical issues. However recently I have had some problems developing and I am somewhat at a loss as to what it could be. It started out as the stereo turning off and then immediately back on randomly during a drive. Thought maybe it was the alternator failing but it was still showing 14 volts solid on my gauge. This happened a handful of times but was not a huge issue and I figured there was just a loose connection on the stereo wiring. Then a day or two later driving along the car started to sputter and surge, the volt meter was slamming from zero to max back and forth. I pulled into a parking lot and put it in park and it returned to normal. I was able to drive home with no further issues. Next time I drove the stereo again was turning off and on and then again developed into the surging/dying. I pulled into a parking lot to try to diagnose the issue and what I found was that in park and neutral the car idles fine will rev up and there are no issues at all. As soon as it goes into gear either reverse or drive the electrical problems would arise, particularly when the gas was pressed. Most times it died if I put it back in park it started right back up, a few of the times I got no power at all, no lights came on at all and after a few minutes when I finally got power again the stereo had reset to demo mode so it was as if my battery was disconnected. When I finally tried to get home it was basically surging the entire way again with the voltage gauge going crazy but if I put it in neutral it would stop, I could rev it up and then pop it back in gear and that's how I limped it home. The battery in it probably isn't the exact size it should be as it was an extra from another car and there is a kill switch wired into the car to prevent theft which I initially investigated as a potential problem but after finding that it only happens in gear I doubt it is that switch. It is a 2 speed automatic I don't recall there being any electrical connections from the transmission that could be affecting the engine but I could be wrong on that one. It also appears to usually happen once the car is hot and warmed up. apologize for the long winded post just trying to fully explain the situation I appreciate any help or input that any of you have!
Thank you!
Last edited by Cutlass9691; August 21st, 2017 at 01:54 PM.
Reason: .
Would a loose connection in there happen only in gear? Loose connections were my initial thought but the fact it only happens in gear is what started confusing me.
Think about the problem, you load the engine on its mounts when it's in gear..right. This causes the engine to rock. I'd verify the integrity of both the positive battery cable at the starter and the negative cable on the driver side head (where the negative cable should be terminated). Both need to be clean and tight. Ohm the cables to see if there's an internal break somewhere along their length. Check the ends of both cables as that's a common stress point. Check all grounds. Check the bunk head too as Eric mentions. I'd actually pull it apart to see if there is any corrosion/Verdigris growing in between the halves. Check the connections at the horn relay on the drivers fender.
Close the loop when you find the problem.
I doubt its the cables as the car will run with the battery completely out of the car off the alternator. The battery technically is there primarily to start the engine, although it will also provide some backup during high load situations.
Does this system use a MSD control box? Is it mounted on the firewall? Check the ground between engine and firewall.
Yep good catch there too. The control module will fry in short order with a bad ground. Usually not an intermittent failure but who knows what transients will do.
I doubt its the cables as the car will run with the battery completely out of the car off the alternator. The battery technically is there primarily to start the engine, although it will also provide some backup during high load situations.
Not if the main ground source is intermittent and the secondaries are bad as well. My money is on a bad ground or a chafed positive open or going to ground. Get out the VOM and test light.
Is it column shift? If so maybe as Eric said the bulk head connector/s, if your back drive linkage is coming in contact with any harness? Just a thought. Have someone watch from under the hood and under the car as you shift through the gears, just moving the selector. Not running of course.
With the car running wiggle the wires on the ignition switch at the top of the column. Also wiggle them with the trans in neutral, in gear (have someone sit in the driver's seat with their foot on the brakes). Wiggle the bulkhead connector under the brake booster. It's going to take some detective work to figure out where the problem spot is.
I doubt its the cables as the car will run with the battery completely out of the car off the alternator. The battery technically is there primarily to start the engine, although it will also provide some backup during high load situations.
If you take the battery out of the system with an alternator, the alternator will self destruct, and blow out the diodes, and if internally regulated, it will also take out the internal regulator. Generators on the other hand, will keep the engine running without any damage. If you don't believe me, then try it with your car, by disconnecting the positive cable from the battery, and allow the engine to continue to run for 5 minutes. Then shut the engine off, and reconnect the battery. Take a reading of the alternator output, or just look a the alternator dash light. It will be glowing red, unless the bulb is burned out.
I had a battery explode back in the 70's, jumped the car off and drove the car 20 miles back home with no battery. Remember the field wire is connected to the electrical system and keeps the alternator from running wild. Initially there is a load dump that will spike the system for a brief moment in milliseconds. With these old cars it does not matter.
My money's on a short in the system that appears when the engine is under load (in gear and driving).
Voltage gauge being shorted to ground will make the needle jump to zero immediately, so a needle that bounces back and forth could be a short that comes and goes rapidly.
The ignition will run poorly if it gets less than 12+ volts, which a short will cause.
The radio typically turns off when ignition power is lost.
Does the voltage gauge get its 12+ from the ignition switch? If so, then start tracing wires that connect to ignition +; all three problems point towards a short in the ignition + circuit.
Focus on wires that run where they might have been burned or squeezed by the engine or exhaust. Look for wires going to the distributor, to the VG and to the radio.
Unrelated, but possibly the cause, might be the steering column. Is your car column-shift? Then the shifter mechanism might be rubbing a wire in the column. This would short out ignition + if it rubbed the wrong wire.
I have also seen steering columns where various wires were incorrectly routed and thus shorted out - particularly one where pushing down on the steering wheel would blow the brake light fuses. That was a fun problem to diagnose...
August 21st, 2017, 08:43 AM
