Car only starting sometimes

Question

I have a 2002 Mercury Sable. Just had the heater core replaced and since getting it back, it has only been starting sometimes. At first it would start right away, but not every time, especially if you shut it off and turned it back on soon after. If I waited five minutes or so, it would start, but now it's not starting at all. Lights and radio come on, fuel pump comes on, but no other click or sound when you turn the key. I tried a jump in case the battery was dead, but it didn't help.

I have to rely on this vehicles to drive my sick dad back and forth to appointments, so I'm in trouble right now, and for the same reason I don't have much money to be bringing it in to a shop so any help would be appreciated.

Does anyone have any idea what the issue could be?

Answer 1

I am only going to answer the Sable question here.

I am assuming the Sable does not crank at all when it is not working.

As for the Sable, there could be a loose wire. To check this, find the starter relay. It should be in your fuse box. The pic below is a 2002 Ford Taurus, which I think is simply a re-skinned Sable.

You will need to look at a wiring diagram to see which pin is which. You will need a voltmeter or a test light. With someone sitting in the driver's seat and the ground lead on the tester grounded, remove the relay. One of the pin slots will go hot only when the key is turned. There should also be 2 grounds and one that is always hot. You may find a schematic with the pinout on the side of the relay.

If you get ignition power here, then we need to test if the relay works. Ground out the low amp ground and give the low amp positive pin some power. Test the resistance across the high amp pin. The reading should be 0 ohms, if it is anything else replace the relay. Keep in mind it starts sometimes, which may be a sign of a sticky relay.

If the relay checks out, then the problem may be the starter and you may want someone to hold the key to crank and listen for the starter solenoid to click into place. If it does not, then tap the starter solenoid with a hammer and see if it springs to life. If it does click into place, then tap the back of the starter to help the brushes make contact with the commutator. Be careful not to cross the positive lead with the casing, it shouldn't do damage but it's not good sucking that many amps from the battery.

Back to the top. If you do not get voltage on the low amp positive pin slot for the starter relay while turning the key, then you need to trace this into the dash. I suggest using a tone generator and probe.