Starter gets no juice

I have a 01 Taurus that has an intermittent starting problem. After the car sits overnight, sometimes it will not start. No juice to starter, no crank, no noise, nothing. Battery is good, lights don't dim while switch is engaged. It's like the connection to the starter is off. Come back in an hour or two and it works just fine. It continues to work fine for a week or more and then does it again. Indie shop AND dealer have found nothing wrong. It acts like the old neutral safety switches use to act when failing. All wires to battery and starter are tight, not corroded. ECM and air compressor were replaced a short time ago, not sure if related. Any ideas appreciated.

Have you checked the relay / solenoid?

The dealer and shop told me the starting system all checked out fine. ????
I cannot get to the starter solenoid without jacking up the car. Maybe this weekend? Where is the relay, on the firewall or somewhere else?

I'm not sure where the relay is. On my 88 thunderbird it was located neer the fuse box on the drivers side in the passenger compartment.

If the dealer checked the strarter while the car was starting I think the solenoid and relay would check out as good. You would need to test them while the car is refusing to start. I think the relay/ solenoid are cheap parts. It may be easiest to just replace them and see if the problem goes away.

Are you saying no juice is getting to the starter based solely upon that the engine doesn't turn over, or did someone actually put a test light or meter on the starter motor and solenoid leads to verify there is not power at the starter?

-Rod

I don't know if the starter is getting juice when it won't start, but I'm assuming it is not because the car will start 24 out of 25 tries. This tells me the starter and solenoid work when they have voltage. Of course the shops cannot find anything wrong. It will not act up for them. It only does it in my garage every other week or so. I can't realistically leave the car at the dealer for two weeks and tell them to try it every morning until it doesn't start. So I'm hoping to narrow down any parts that could be responsible and start testing/changing them. My assumption is a starter doesn't usually function intermittantly when it's failing under similar situations. A relay may, however, I don't know. A sensor definitely can function intermittantly when it's failing. Do you concur?

Pretty much any electrical component can function intermittantly when it's failing, be it a relay, sensor, electric motor, etc. As the component heats up, solder joints can expand and "cold solder" joints can go open circuit, crimp connections for the armature windings of an electric motor can expand and go open circuit, and a relay is a mix of windings and sometimes solder joints.

There really are no sensors that would prevent the starter from getting power. So when it won't start, there's not even a momentary "tink" noise?

Do you know if your car has the Passive Anti-Theft System (PATS)?

I think your next step should be to pick up a test light or multi-meter and check for voltage at the starter when the car won't start. This will most likely take at least two people to do.

-Rod

Yes the car has PATS. I think the light on the dash is supposed to blink if it is engaged - which it doesn't. ??? You are correct however, there is no sound or "tink" when the key is turned to start. Isn't there a sensor that tells the computer the car is not in park (used to be nuetral safety switch) , the car acts like something is telling it not to start. It only does it under these two circumstances: overnight sitting, engine dead cold. The car has never stranded me anywhere because it doesn't sit that long anywhere else. Even though it is intermittant, it still needs those circumstances in place to act up. Then without any jiggling, banging, or fidgeting it will start in a few hours after periodic attempts.

If you have a second key for the car, keep it handy. Sometime when the car won't start, try the second key.

There is a Transmission Range Sensor (TRS) that has been a known trouble part on the Taurus, as well as the ignition switch (not the key cylinder switch).

However, before shotgunning parts that may not fix the issue, get a test light and multimeter and make sure power is or is not making it to the starter when the car won't start. To me, that should be the next step.

-Rod

I tried the second key, no go. But I will test if juice is getting to the starter next time it happens, and my wife is home, and I'm not late, and I'm not in a suit, and.... well, you know.

I have heard about the TR sensor. Maybe...

Thanks again Rod

You could wire up a couple of LEDs or lights to the starter (one for the solenoid power and one for the starter motor) and run them up the base of the windshield so that they are in plain sight. Then, everytime you start the car, you should see both indicators illuminate and know if you are getting power without needing to get under the car and having a second person handy. :)

-Rod

Just a thought.
Starter may have a bad armature. It may be stopping on the bad one occasionally, but that wouldnt explain starts after a bit too well.

Good luck

Under the hood is a power distribution box that has a starter relay that powers the starter solenoid on the starter the starts the starter. It is a $10.00 part. It may or may not be the problem but for a few bucks I'd buy on and try it. If you look close, there are a few more relays in that box that may be the same. You may be able to swap them.

Jim