How to test a starter relay switch - 1998 Jeep Grand Cherokee

GM anti theft doesn't cause a no crank. Bad ign switch is far more likely

Do you know how to test automotive electrical circuits ? Do you know what a electrical wiring diagram is. Have a DVOM - digital volt ohm meter ? How about a automotive relay , do you know what it is an how it works ? Free wiring diagrams here http://www.bbbind.com/free_tsb.html Enter vehicle info. year , make , model ,engine . Under system click on engine , then under subsystem click on starting. Click the search button ,then the blue link . You will see all the componets involved in starting the vehicle. ignition switch , starter range switch , starter relay , PCM -powertrain control module . When you turn the ignition switch to the start position it sends a voltage signal to the PCM , this tells the PCM start is requested , in turn the PCM energize's the starter relay . This will close contacts inside the relay allowing B+ voltage at pin 30 of the relay to go to the starter solenoid . engaging the starter . Checking fuse's an power an ground , testing relay control . . Videos on youtube for electrical testing.
Electric Testing Techniques You Need to Know
Relays Understanding Diagnosis and Testing Relayed Circuits Pt1

You need to test the electrical circuit , starter relay in the engine compartment . Is there B+ voltage at the smaller gage wire on the starter solenoid when cranking ( or trying to crank the engine ) ? Videos on you tube , testing from relay base ( where the relay plugs into ) Find the start relay in the fuse / relay box an pull it out . Look on the bottom of the relay , you should see four sets of numbers ! 30 , 87 an 85 , 86 . > 30 an 87 are the power side of the relay . 30 should have B+ voltage ,if not ignition #2 30amp fuse is blown . If there is B+ voltage you can take a jumper wirer ,an jump 30 to 87 > 87 goes to the starter solenoid . Jumping 30 to 87 will engage the starter .Checking for B+ voltage at pin 85 while trying to crank the engine, if there is b+ voltage you know the ignition switch is good an so is the transaxle range switch (neutral safety switch ) ! Does yours have a burglar alarm ? If so then there is an other part burglar alarm relay ! By testing at the relay you can tell which part of the circuit is bad ! Plus testing the heavier battery positive cable also needs to be done . Voltage drop testing the cables Starter Voltage Drop VEHICLE RELAYS Operation Diagnosis VEHICLE RELAYS Testing from the relay base This would cost you $86.00 to have this diagnosed at most auto repair shops. 1 hr .

At the starter relay, you have two red or purple wires, one goes to the starter and the other comes from a 30amp fuseable link. Is that fuseable link circuit hot ?
From the key switch, power goes thru the alarm relay, then the clutch safety switch or automatic selector switch, then to the starter relay. The fourth wire on the starter relay is a ground.
You should be able to put power to the starter relay on the white or yellow wire coming from the safety switch to make the relay engage.
My guess is something wrong with the alarm system.

I will try to help, powell. Your start circuit from battery to ignition switch to starter-and back to battery. You may need to check every thing here, including the grounds, for a loose connection, or just possibly a failing part.
If only complaint is intermittent starter action, and no other problems with ignition switch, let's assume switch is good, so battery to ignition switch is good. Now from the switch, a yellow start wire goes to the instrument panel fuse block, to "crank" fuse #8 (10 amp), from there a purple wire goes to the safety switch. If manual it is a clutch pedal position switch (simple on/off switch-when clutch down switch is on). If automatic, purple wire goes to Transmission Range Switch on the transm.-in park or neutral the purple wire has continuity in and out of switch.
From that switch, the purple wire goes to the starter relay (under hood fuse-relay center). Now the relay: purple wire in start will energize the relay- wire goes to coil side of relay, and then coil side goes to ground. On relay power side, the power feed is a red wire-and it is the same red wire that initially sends power to the ignition switch. A 40 amp fuse in fuse-relay center sends power to ignition switch, and a splice goes to the starter relay as the power feed for relay. When relay is energized, contacts close, and power is sent from relay to the starter solenoid, again on a purple wire. When solenoid contacts close, starter motor is connected to the big battery cable on the starter.

There is your start circuit. try a new or different relay, try a new or test the clutch switch (or transm. range switch). Buy a $5 test light and use it to check where power is lost when starter won't operate. Hold key in start and check if fuse #8 is getting power. Check the safety switch, with key held in start, the purple wire should be hot. Check if relay has a power feed (pull relay out and check terminals) and if relay coil has a power signal in start. Check the relay's coil side ground. If that ground is intermittent, relay won't work.
When it won't start, use a test light, you should be able to find it.
Good luck.

I'm back, Gary-like that commercial on tv where mechanics chase cars down the road on creepers! You have a failing connection somewhere. If you rock it and it works, don't sound like a relay-don't sound like the neutral safety switch-it really sounds like a failing starter or starter solenoid. To check, wait till it won't start, then check for power at solenoid wire when key is held in crank. If power then, suspect a bad starter or solenoid-have tested. If no power, try a new relay-starter relay. Another relay in your car may be same as the starter relay (same part number) so try swapping a different relay. Again, doesn't sound like relay, but you never know until tested. Good luck.

PNP park neutral safety switch . Try moving gear selector to neutral . If it starts the switch is bad .
Voltage drop test starter circuit .
fusible relay ??? Now thats funny ! It's just a relay , not fusible relay ! A fusible link is a kind of fuse ,will melt with a short circuit. TEST ,TEST DON'T GUESS and if you can't test ,take it to a qualified repair shop. How to voltage drop test starter motor circuit
Starter Voltage Drop
The computer has nothing to do with it .

http://www.bbbind.com/free_tsb.html Free wiring diagrams ! Suggest you view a wiring diagram to see what all is involved in the starter circuit . NO starter relay ! Enter vehicle info. under system click engine, then under subsystem click starting . You will when you turn the key to start it send's B+ voltage to the PNP switch ,from there it goes to the S terminal on the starter solenoid . Very simple . Get a volt meter an test B+ voltage .

Hi, the most likely cause is the range switch on the transmission, but it could also be the relay or the ignition switch. You can diagnose by interrogating the socket under the starter relay using a 12 volt test light. The starter relay is probably in the box under the hood by the air filter box. Just pull the relay out, connect your test light clip to ground, and probe the socket while someone holds the key to start. If the ignition switch is good, there will be 2 hot terminals in the relay socket. Next, move the test light clip to battery positive and probe the socket again. Assuming the transmission is in park, there should be one terminal that lights the test light brightly and one that lights it dimly. If there is no bright light, the range switch is bad. If there is no dim light, the wire from the relay to the starter is bad. Finally, if all of the tests are good, the relay is bad. Please let me know the results of your tests for repair advice.

Hello, You need to check the Starter Relay. The Starter Relay connects the Battery to the Starter when you turn the Key to Start. There are 1 or 2 small wires that connect on the Starter Relay.

The idea is the Key sends power to the small wire to make the Starter Relay work. You need to test the Starter Relay. Have your car in Neutral and out of gear. You can use a jumper cable and bypass the Starter Relay by connecting one end of the Single jumper cable to the terminal connector from the Battery where it mounts on the Starter Relay. The other end will be live, hot, and full of power so watch where you lay it.

Then there will be sparks when you touch the end of the jumper cable to the mounting connector coming from the Starter where it bolts onto the Starter Relay. The Starter should crank. This will mean the new Starter is good. You can use any metal tool to bypass the Starter Relay if you do not have a jumper cable. Be Careful, the tool can melt and burn you.

One final test is needed. The small wires I mentioned earlier are important to making the Starter Relay work. You need to see if the small wire is getting power when the Ignition Key is turned to Start. You need a test light or Voltmeter to show if the small wire is providing power. If the small wire is providing power, then you need to replace the Starter Relay and you are good to go.

If you are not getting power through the small wire, then you must trace down the problem. There is a Safety switch on the clutch linkage or Brake linkage which must be pressed before it lets the Starter work. This is called an Interlock switch. There can also be a safety switch in the shift linkage which must be in Neutral before allowing the Starter to work. These get power from the Ignition switch which may also be bad.

You most likely fixed the problem just by replacing the Starter Relay. If you do not want to test, just buy a Starter Relay. I gave you extra information for bad switches and how to pinpoint the problem and this time you might not need to know this stuff.

I hope my solution is very helpful to you.

there is an interrupt switch, called neutral safety switch. When it fails or goes out of adjustment, no start, and essentially no protest or indication. Try foot on brake, shift to neutral, turn key to start and slowly move shifter out of nuetral in each direction. If starter actuates, look into switch adjustment.