The car is a 51 chevy with an 86 350 in it. It has less than 70k on the motor and less than 500 miles since I installed it. It has NEW: Alternator, HEI, cap, rotor, wires, plugs, etc. Until last week I could drive it at 85 all day with no real issues. Last week I was driving home on the freeway and about 10 miles into my drive the motor started cutting out. It would be fine, and then it would act like I let off the gas, even though I didnt. And it was SUPER eratic. On off on off on off, sometimes 10 times in 5 seconds. To me its acting like a loose wire somewhere, but I coulndt find it. A buddy was having similar problems with his car and it ended up being a bad alternator. Is there anything else I should check before I replace a nearly new alternator?
Doesn't sound like an alternator problem to me....sounds like an ignition problem, or wiring. I've seen ignition switches do things like that
Im with Squirrel on this .It sounds like a bad key switch or possibly the plug on the HEI dist is loose or bad or the wire between the 2.Its an ignition problem from what your describing .The Alternator has nothing to do with cutting the ignition on and off ...
Bypass everything .... run a single wire from your battery to the HEI. If the car runs fine, the issue IS somewhere in the ignition circuit. Something else just popped into my head ... where did I leave my pants? If it still runs like crap, start looking somewhere other than the ignition circuit for the cause. How are your grounds? Damn, wonder if that donut I left in the car (last week) is still good.
Check the small white and yellow wires IN the distributor. They will get loose or break due to constant vacuum advance movement and cause intermittent shut down or loss of power.
you did not have to "clock " your alternator when you installed it? have seen them with the brushes droped out and not charging car misfired and i was driving it to shop and converter caught fire on that one and almost had to buy a 1976 invicta years ago
Ricks Garage Re: Bad Alternator? Strange Electrical Problem <hr style="color:#e5e5e5; background-color:#e5e5e5" size="1"> Check the small white and yellow wires IN the distributor Those two things are what I would check. If you don't have the plug with the clip to hold it in place on the ign wire to the distributor get one. I fought that one on my daily driver for way too long. The regular female wire ends will come just loose enough on the plug to break connecton either part of the time or all of the time. The two wires that Rick's Garage is talking about are on the pickup coil and they tend to go bad right where they connect to the pickup coil due to the vacuum advance moving the plate they sit on all the time and causing them to flex. It could be the switch or something else but I would check those two things first and if they are good do the wire from the battery to the distributor thing That Borntoloze suggested to eliminate the rest of the system from the equation.
I have two alternator running during failure experiences. The first was in the truck that hauled my Model A home as the regulator failed and started to charge at above 15 volts and cooked the battery at the same time. Before that happened, the radio didn't shut off when you turned off the ignition like it is supposed to happen. Keyswitch off annomolies became the norm with accesories. And then on the latter Model A that was hauled by the previous truck had another alternator failure or not good. The alternator didn't want to charge unless RPMs were above 1500 or so, and wouldn't charge more than 25 amps at speed. You will run into many experiences and problems if you like rust and fixing stuff.
Thanks for the replys. I do not have the correct locking plug on my HEI, so that will be the first thing I change. Also, I dont know if it is a coincidence or not, but if I turn the car off and then back on the problem will go away for a while. And so far it has not done it driving around town, only on the freeway. Also, my HEI is one of the big ones with the coil built in (not sure if that matters). My grounds are good, the problem actually didnt start until I fixed a ground issue. Now I have an 8aug from one head to the body, another 8aug from the stater to the frame, and a battery cable from the other head to the battery. The problem never actually caused the car to die, but I was forced to about 20mph on the freeway. Thats a scary thing on the 405 at 2 in the afternoon!
once i had a bad battery when the motor got hot, it would go to a dead short and pull all the electric out of the alternator and the motor would quit. when the battery cooled off the engine would resart.
Did your dash lights and all power flicker or go out while this was happening? It sounds an awful lot like a bad ground from the battery to the block.
I've had more headaches from bad grounds than any other electrical problem. It seems idiot level, but it is common and troublesome.
Gotta agree with the ignition module wiring as the first place to look. What is your charging voltage? Also connect a multimeter and check for AC voltage at the alternator terminal. If the diode trio or a rectifier diode are bad, it can send an AC signal which might fool the ignition module. You say it acts like you let off the gas, could it be a fuel problem?
I had this problem with a Buick Regal that I put a small block in. Drove fine for a month then it would cut in and out. The problem ended up being a loose connection to the HEI. Gremlins, they always come out of nowhere.
Thanks for the replys guys. I have somewhere to start now. I just need to get some time to get out there...
To me it sounds like the module and magnetic pick up in the distributor ,Replace both ,I experianced shut down and wouldnt restart in my old elcamino.....
You are running a "big cap" HEI. They require a full twelve volts to run. Make sure you aren't running through a resistor (or a resistor wire). As mentioned earlier, you can run a single wire from a twelve volt power source (directly from the positive battery cable would be nice, either at the battery or from the starter) ... if this solves the problem, you have an issue somewhere between the distributor connection and the power source (ignition switch, etc) ... if this does not solve your problem, then chances are the issue is inside the distribtor itself (where you have the coil, ignition control module etc). Again, this is assuming all grounds are good.
When you relaced that HEI cap and coil, did you remember to transfer the gound terminal from the old cap? Without it, it could backfeed for a ground(or not start at all). With new grounds on the engine, it could have aggrevated the condition by overheating the coil, and causing it to cut out. Shut it off...coil cools down slightly, and it runs good for a while.
I just bought a complete drop in distributor, so the cap and rotor and module were already installed on it. And when I shut it off and restarted it, I did it right away. Like less than a minute later.
DING! DING! DING! We have a winner. I had this same problem on the HEI in an OT car. The locking tab had broken off the power connector to the HEI and it would periodically vibrate loose. When the car died, I would have to push the connector back on to get it to run again. A junk yard replacement connector body fixed the problem.
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