My Mountaineer is a V6 2WD with 117k on it. A couple weeks ago my wife left the key turned with the radio on and drained the battery. We were able to jump it just fine and the car started ok for a day or so. We had the battery and alternator tested, and they were good, so I cleaned the battery cables and checked to make sure solid connections were being made to the starter and alternator. Occasionally I will hear a click from the relay and other times the starter turns very slowly when trying to start the car. The only way we have been able to start the car is to pump the gas pedal a few times while turning the key and it will start, and run just fine. No engine lights or anything else that is strange while the car is running. I am going on a road trip next weekend and would rather not have to take it in and have the electrical diagnosed. I am thinking I have a short somewhere or a bad relay or fuse (which I have checked). Any suggestions or help would be appreciated! Thanks!
So if I understand correctly, the only symptom is slow or intermittently no cranking. A common Ford problem has been corroded battery cables near the starter and battery, but it's hidden under the insulation where you don't see it easily. You can prove that by measuring the battery voltage during cranking and measuring right at the starter terminal during cranking. It should be higher than 9.6 volts. If you find considerably less at the starter than at the battery, suspect the cables. This is so common there is even a foot note to that affect in the starter replacement guides.
June, 23, 2011 AT 11:06 PM
SOMETIMES THE SOLENOID,
INTERNALLY, THE LARGE CONTACTS WILL GET PITTED UP (FROM ARCING LIKE A WELDER EACH CRANK-UP), AND WILL NOT FULLY MAKE CONTACT AT EACH START---REMEDY IS REPLACEMENT
June, 24, 2011 AT 2:04 PM
Cardiodoc - I checked the cranking voltage myself at the battery and it had a cranking voltage was between 7-8 every time I checked it (3-4 times). The cranking voltage at the starter terminal was at 5.5 the first time I tried it and right at 7 the 2-3 additional times we tested. Because the battery was tested by 2 different people (Walmart, where I bought the battery and O'Reilly's where I get all my parts), is there a chance I have a bad cell and they just missed it? I am also considering just replacing the cable connected to the starter just as a precaution. Thanks for the help!
CJ MEDEVAC, I already suspected Solenoid, but I am trying the cheap alternatives first because it is attached to the Starter and I have to replace both to fix 1. Thanks for the tip!
June, 24, 2011 AT 8:21 PM
First of all, since you know how to take the measurements, let me go into more detail. 8 volts is too low, and 5.5 volts is not going to get the job done. Starters, and ignition systems during cranking, are designed to operate properly on no less than 9.6 volts. You have half of that.
I'm including a diagram I drew up for my students that might help. When you measure the battery voltage while a helper cranks the engine, put the voltmeter probes right on the battery posts, not the cable clamps. If you have 7-8 volts right there, the battery is either discharged or has a dead cell. If the battery is fully charged and good, it will read close to 12.6 volts when not cranking the engine. A good but discharged battery will read about 12.0 volts.
If the battery voltage stays above 9.6 volts during cranking, move one meter probe to the cable clamp and try again. You should get the same reading. If the reading is less, check that connection for corrosion and to be sure it's tight. Since the battery will be running down from the repeated cranking and voltage readings will too, there's a more effective way to make these measurements as shown in the drawing at the bottom left. Put one meter probe on the battery post and the other one on that cable clamp, then measure the "voltage drop" during cranking. Ideally there will be 0.0 volts but up to 0.2 volts is acceptable. If you find anything higher, that connection must be cleaned and tightened.
That 0.2 volts applies to any mechanical connection and the difference between any two points in that part of the circuit such as at both ends of a cable. Also, 0.4 volts is the maximum allowable drop in all of the negative circuit, (of which there are only two connections), and all of the positive circuit. So even if every mechanical connection in the positive circuit has 0.19 volts drop, and there's four or five of them, the total of all of those drops can't be more than 0.4 volts.
What this all boils down to is you gotta figure out where all that voltage is being lost in a connection or cable. When you get down to the starter, put the meter probe on the terminal that is crimped to the end of the cable, THEN on the stud that terminal is bolted to. That is both sides of another mechanical connection where the voltage drop could occur. You can't get inside the solenoid to measure the drop across each contact (5 and 6 in my drawing), but you can measure after those contacts on the braided wire that goes into the starter motor. Here again, measure on the stud first, then on the braided wire, or to measure the drop directly, put one meter probe on each one and take the reading during cranking. Taking readings across that connection can be pretty inconvenient and it's rare to find the problem way down there. Usually you'll find a bad connection in the positive circuit or in that cable.