New battery, fine alternator, car won't turn over without jumpbox

I have a 2009 Ford Focus with ~95000 miles on it. Today at the grocery store, when I put my key in the ignition, the car wouldn’t turn over. Lights were on, radio worked, etc, but the car didn’t turn over. I pulled out my jumper box I keep in my trunk, and I was able to turn the car over with it attached. I then drove around for ~30 minutes without any issues. The battery was ~4-5 years old, so I took it to Autozone where they put in a brand new battery.

I went to start the car right after the battery was replaced and the same thing happened again. Lights on, radio on, etc., but it wouldn’t turn over. I again had to use my jumper box to start the car and it turned over with it attached. They checked and said the alternator is charging just fine. The cables didn’t appear to have any corrosion either.

I had the ignition switch system replaced about a year ago, and the spark plugs replaced 6 months ago. I will take it in to a mechanic in a few days, but any ideas as to what might cause this? Could the battery cables be bad? Did a fuse blow? Why would the car not start with a brand new battery/good alternator, but would with a jumper box? I hope it isn’t some random electrical wire…

It is most likely “some random electrical wire” that shorted to ground and has created a “parasitic draw”. You’ll need a mechanic with good electrical troubleshooting skills and plenty of patience to properly diagnose this.

The contacts in the starter solenoid are worn. The jumper box helps maintain a higher voltage for a better “pull” in the solenoid or may not have had any effect, usually after a dozen start attempts the failing solenoid makes contact.


there may be corrosion inside one of the battery cables. Corrosion provides high resistance to your electrical circuit, preventing sufficient current flow to start the vehicle. when you put the jumper box on you are giving it a little more power to get it started.


My guess is the same as Nevada’s above, the starter motor likely needs replacement. One test you or your mechanic should do before starter motor replacement however is to measure the voltage at the start terminal on the starter motor when the key is in start. It should measure at least 10 volts. Measure directly from the S-terminal to the starter case. If it measure 10 volts or more pretty good chance replacing the starter motor will fix this. Batteries tend to last 5-6 years, so you needed a new battery anyway, so no harm done on that purchase.

If you know how to use a volt meter, here’s a quick check of the battery and charging system: Before first start of the day the battery (measured at the battery terminals) should measure about 12.6 volts. Then immediately after starting the engine 13.5 - 15.5 volts.

I don’t recall many Ford starter motor problems posted about here. Toyotas seems to have the more problematic starter motors. You could use the forum search feature here to see what sorts of Ford Focus starter motor problems have been discussed here before. I have a 50 year old Ford truck still with the original starter motor. My 30 year old Corolla has had 3 or 4 starter motors. Search link above/right on this page.

If you do replace the part, don’t cheap out on the replacement starter motor. Either buy an oem version from a Ford dealership, or if from a parts store buy a reputable brand.

Or there is an issue with the neutral safety switch (a.k.a. range selector) and the starts are entirely coincidental. That switch is what allows the starter motor to operate in park or neutral but not in reverse or forward gears.

Next time it acts up shift into neutral and see what happens.


Or take it to a local auto electric shop. They can test, diagnose, and fix it, then test it again before returning it to you. Much cheaper than a new one from the automaker; likely more reliable than a “rebuilt” from a parts store.

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Note to OP: This vehicle – being a Ford – may use a separate starter relay, rather than the relay being part of the starter motor ass’y. If so, that’s good news, the starter relay component is the more likely culprit, rather than the starter motor itself. That’s the way my Ford truck is configured, and while the starter motor has never had to be replaced, the starter relay has. On my truck that relay is in the engine compartment, easily accessed, attached near the firewall. The attachment to the firewall is part of the electrical circuit ground. I had one failure mode where it wasn’t making good electrical contact due to corroded metal/loose fasteners, something also to check.


Typically, the starter relay is in the fuse and relay center.
The starter solenoid is mounted on the starter motor and part of the starter drive. Very old Fords used a moveable pole shoe to actuate the starter drive.

If the starter solenoid has failed, replace the starter assembly.

It could be as simple as a bad battery ground connection. Follow the ground cable,to where it grounds to the car. Remove the mounting nolt and sand or wire brush the cable end, bolt and where ir makes contact with the are. See if that makes a difference.


Thanks all for your help. I went to a mechanic and there were two issues. First, as oldtimer-11 suggested, I needed to sand down the connection where the negative battery terminal was grounded to the frame of the car. Also, as weekend-warrior sort of suggested, there was a loose connection in the wire that was attached to the positive battery terminal connector as it was slightly corroded. They simply cut out the loose wire, stripped it down a bit more and reconnected. Car tuned over like a charm after that.

Thanks all for your help!


You were right. Thanks so much for the advice!

You were right. Thanks so much for the advice and your assistance!

I hope they did a good job when reconnecting it

That would be properly crimpling AND soldering, in my opinionn