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Scot How many wires hook up to a starter search guy for pleasures

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If the starter does not turn the engine although the car battery is in good condition, the fault may be a simple mechanical one or it may be an electrical one in the starter-motor circuit. The starter system is simple, and the checks on it are straightforward.

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First question: Why would you want to do this? Perhaps the car has had an electrical fire.

Starter motor, starting system: how it works, problems, testing

In my case, I was given a free BMW fauxtii a into which someone had transplanted a fuel-injected tii engine. But when I looked at the wiring, I found that someone had begun moving the battery from the engine compartment to the trunk and had abandoned the job part way through, leaving wires hanging, insulation frayed, and the fuse box unsecured. It was enough to make me want to play it safe and bypass the entire mess. First, let me be clear that this method applies only to vintage cars, by which I mean cars that are primitive enough that there are no electronic control units, sensors, or ancillary devices that need power.

That being said, this should work on just about any non-smog-laden carbureted car with a mechanical fuel pump. It needs the starter motor to spin the engine, the spinning of the engine to create a vacuum that draws mixed air and fuel into the cylinders, and the ignition to send correctly-timed spark to the plugs as the distributor spins around.

Like any electrical device, the starter motor requires a positive and a negative connection to the battery. On nearly all cars, the starter has an integrated solenoid, which is just a relay that turns the starter on and off. The electrical connections are to the relay, not to the body of the starter. The positive connection is a thick, red wire that runs from the positive battery terminal to the big threaded post on the solenoid.

But there is a third connection—a thin wire connected to a small terminal on the solenoid via either a spade or a ring connector. It is imperative that, before you do this you first make sure the car is in neutral, because when you do this, you are bypassing the neutral safety switch and can cause the car to lurch forward if it is in gear.

Battery cables

Because the wire is just powering the solenoid and not actually carrying current to spin the starter, it can be a thin wire, not a thick one like the battery cables. Instead of touching a wire to battery positive, you can buy a remote start switch that has a small alligator clamp at both ends. That makes it easier, as you can connect both ends and then squeeze the switch. I prefer to cut off one of the alligators and crimp on a spade connector instead, as it makes the connection to the solenoid more secure and less likely to short against the body of the starter.

So, now that you know how the connections to the starter work, if the battery cables are a mess—or, as was the case with my tii parts car, the wiring is so messed up that you wish to bypass all of it—you can simply connect the battery to the starter with jumper cables as follows. Note that clamp-on jumper-cable connections like this are extremely insecure and can fall off easily.

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Every standard ignition coil has two connections. It also usually runs the tachometer. This eliminates the possibility that something in the path to the tachometer has fried and is grounding out the ignition.

To start and run a vintage car, you need only four wires—three for the starter and one for the coil. To recap:.

Note that I did not say there needs to be a wire from the battery to the chassis of the car. In my case, because I was starting a fuel-injected car, I also had to power the electric fuel pump. And, because the injection has a cold-start valve that I needed to fire temporarily, I had to momentarily touch its wire to the positive terminal too. Thus, there were two extra wires that needed to be run to the positive battery terminal.

All you need is two wires:. Provided the fuel and ignition systems are functional, this is all you need to get the car rolling: put it into second gear and let out the clutch, which spins the engine just like the starter motor would, and fire the coil.

First, as I said, having wires temporarily secured with alligator clips is flimsy and potentially dangerous. Third, it bypasses important indicators like the oil pressure sensor and light and the temperature and gas gauges.

Checking the starter pinion

Lastly, it bypasses the fuse box, so if any of your jury-rigged positive wires touch to ground, things are going to burn. But if you simply need to spin and start a long-dead engine in a car with booged-up wiring or get a car that just fried its wiring harness a few miles down the road to a safe location, this technique can be helpful.

All of his books are available on Amazon. You can also order personally inscribed copies here. Maintenance and Tech. How to start a vintage car using only 4 wires Rob Siegel. A Story About.

Checking a starter circuit

Hagerty covers all kinds of collector cars, trucks and modified vehicles. Get an insurance quote. More on this topic.

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