Datsun Roadster Forum-311s.org

My PL411 has symptoms that mimic a drained battery, but aren't. The car will run fine until I shut it down, at which point it may not start. The starter will barely engage if at all, and headlights may go dim to completely off just turning the key from OFF to ON (no attempt to start).

Battery low, right? A quick check shows it has 12.5v, so is OK. I thought maybe connections on the battery were dirty so I took the cables off, cleaned up everything, put it back together, same symptom returns. Simply removing the cables and reattaching them when this happens might allow the car to start.

I'd say bad starter but when this happens everything electrical goes dim or off, from the headlights to the dash lights to the engine compartment light to the electric fuel pump. If the starter wasn't engaging, I should have full power everywhere else, especially when I haven't even turned the key to START, but rather only to ON.

My thoughts are bad ground. I have two connections to the negative battery post. One is a big cable and goes to the alternator bracket bolt, which attaches to the head. The other is a smaller wire that goes to the alternator itself. I haven't disconnected the cable from the alternator bracket and cleaned that side, but it's tight. The positive connection to the starter is also tight.

Any other thoughts? Could it be a bad battery? Can a battery have 12+ volts but not put out enough amps? Or is there something else?

My suggestion would be to take the battery to AutoZone or Pep Boy, or somewhere similar, and have it checked uder load. It could appear OK until it's under load, then the voltage can drop to like 9-10 volts.

I had a car with a broken ring once, and when it got hot it would hardly even turn over, let alone start. A compression check should confirm that or prove it OK.

Keep us posted on what you've tried and we'll try to help.

Another thing to check is that you have a good ground connection from the engine to the frame/body.What you describe does sound like a grounding problem or as stated previously a bad cell in the battery.Easy way to check the ground would be to get some jumper cables and hook one end(either red or black,does not matter)to your alt. bracket and the other end to a clean spot on your frame/body.If the problem goes away, you need to fix/install an engine to body ground.

Yeah, I think it's time to attach a ground cable from the engine to the body (411 is unibody) and check the existing ground cable. That and replace the stupid battery frame bolt that disappeared. What the heck did I do with it? At least it's a standard AutoZone part...

I think redoing your grounds could not hurt. Most electrical gremlins on older cars are bad grounds unless some PO butchered the wiring harness. Bucky is right about the battery as well. I had a new--bad battery that read 12.5 to 13 volts but my car would not start. Under a load it dropped below 8 volts. Turned out to be a bad cell. Pretty frustrating but they replaced the battery because it was still under warranty.

Steve

You should have 4-6 grounding straps thoughout the body to the chassis and engine block. My friend had the same problem with his roadster and we attached an additional strap and the thing fires up like new.