Starter Problem Troubleshooting
One of our customers is having problems with intermittent operation of his starter. I thought that this might be of interest to others:.
Troubleshooting a problem involves:
1) Understanding the system.
2) Trying to logically determine what failures in the system could cause the problem.
3) Performing tests that split the system so as to find the fault as quickly and as positively as possible.
The starter system on the 928 functions as follows:
1) Power (12 vdc) constantly is available from the battery to the power panel, then to the ignition switch, as well as to the starter solenoid.
2) When the ignition switch is turned to the start position, power is available for the ignition circuits, including the ignition and injection computers (if equipped - depends on the MY), and to the starter relay in the power panel.
3) The starter relay passes the power to the starter solenoid, a heavy-duty solenoid switch mounted on the starter, operating the solenoid.
4) The starter solenoid closes a set of heavy switch contacts, connecting the starter motor to the heavy battery cable. The starter should spin the engine.
If the starter doesn't spin, we can split the system by assuming either:
1) Sufficient power isn't getting to the starter solenoid; or,
2) Power is getting to the solenoid, but sufficient power is not getting to the starter motor.
Turn on the interior lights and hit the starter switch. If the interior lights do not dim at all when you hit the starter switch, but the starter doesn't operate, you probably aren't energizing the starter solenoid. Suspect the ignition switch, starter relay, transmission safety switch (auto only - provides a ground for the starter relay), starter solenoid, or wiring between these devices. If the interior light go very dim or go out when you hit the starter, you are probably energizing the starter solenoid, but there is not sufficient power to operate the starter motor. Suspect the battery cables or the battery.
If you are not energizing the starter solenoid, test for 12 vdc on terminal Q13 at the bottom of the power panel when the ignition switch is in the start position. If there is power, the problem is the starter solenoid, the starter motor, or the wiring/connections feeding them. Go to the next paragraph. If there is no power, remove the starter relay (XIV on MY86), and check for 12 vdc on terminal 86 of the starter relay socket when the ignition switch is in the start position. If there is power, the problem is probably the starter relay or the transmission switch.
If you have power at terminal Q13, but the starter solenoid doesn't click, either the solenoid is bad, or you are not getting enough power to pull the solenoid in. Make CERTAIN that the car is out of gear, and that there will be no problem if the engine starts. Get under the car, and touch a jumper wire to the heavy battery cable and the smaller terminal on the solenoid. If the starter doesn't operate, go to the next paragraph. If the starter operates, you have a problem in the wiring between terminal Q13 and the solenoid. Disconnect the smaller wire and test for 12 vdc on the wire when the ignition switch is in the start position. If you have 12 vdc, but the solenoid won't pull in, one "fix" is to mount a Ford starter solenoid nearby, and use the small wire to pull the Ford solenoid in. A heavy wire from the battery cable to the input side of the Ford solenoid, and from the output side to the small terminal on the starter solenoid will operate the starter solenoid, and usually cure the problem. If you don't have 12 vdc at the smaller wire, you have a wiring problem between there and terminal Q13.
If the starter doesn't operate with a jumper touching the battery cable and the smaller terminal on the starter solenoid, but the solenoid clicks, the problem is probably starter motor brushes or bad contacts in the solenoid. Any automotive electrical shop should be able to rebuild the starter (brushes and bushings) for a reasonable cost, and probably can clean the contacts in the solenoid. If the solenoid doesn't click, the solenoid is bad.
If the problem is intermittent failure of the starter to operate, and the quick check with the lights doesn't help, you can make a 12 vdc test light to help isolate the problem. Get four feet of lamp cord (sometimes called zip cord), and solder a small 12 vdc lamp bulb to one end of the wires, insulate the connections and bulb base, and put small alligator clips on the other end of the wires. Clip one alligator clip to the small terminal on the starter solenoid, and the other clip to a nearby ground. Route the wire up through the engine compartment, avoiding moving parts and hot parts. Put the bulb outside the hood so you can see it from the driver seat. Every time that you hit the starter, the bulb should light. If it doesn't light, the problem is between the small terminal and the ignition switch. If the light illuminates, but the starter doesn't work, the problem is in the solenoid or starter. If the light doesn't illuminate when you hit the starter, move the alligator clips to terminal Q13 and a nearby ground - you will have to use a probe to connect to the terminal. If the light illuminates, but the starter doesn't work, the problem is between Q13 and the solenoid. If the light doesn't illuminate when you hit the starter, move the connection from Q13 to A23. If the light doesn't illuminate when you hit the starter switch, the problem is the ignition switch. If the bulb illuminates, but the starter doesn't work, the problem is either the starter relay or the transmission switch (auto only).
Let us know if we can help you.
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