Have you considered the NSS as a possible suspect? (Assuming you have an Auto transmission... fill out your profile.)

 

I have. Putting it in neutral did no good and it starts when asd is jumpered.

 

Is there gas in the tank? lol

 

I recently got stranded in the mountains and had to get towed home. My 99 cherokee classic 4.0 was running fine. We stopped to check out a place to camp and the jeep wouldn't start. I assumed it was a dead battery because nothing happened when I tried to start it. I was able to ask someone for a jump. It just cranked over and over. The asd relay was clicking like mad. After a 2 hour wait and a 2 hour tow truck ride we made it home.

So today I was able to get it started by bypassing the asd relay. That still doesn't tell me what the actual problem is. I've switched relays around so I know the relay itself is good. Checked the batt terminals and ground and they seem ok. Now what???? Please help me. I'm going nuts.

There are several possibilities to consider..

The Crankshaft Position Sensor (CPS) activates the ASD relay through the PCM. When the PCM receives a signal from the CPS that the engine is turning the PCM will provide a ground to the ASD relay control coil which closes the power contacts (pins 87 to 30) of the rely (the contacts you jumped).

In that the engine runs when you jump the ASD relay may indicate that the CPS is working otherwise no other CPS controlled circuits would function.

The relay control coil circuit of the ASD relay may be open.

Power to the ASD relay control coil comes from fuse #11 in the Junction Block. It also powers the Fuel Pump Relay and provides power to the PCM, so I think this fuse is okay but the circuit to the ASD relay control coil (pin 86) may be open. Or, the circuit from the PCM to the ground side of the ASD relay control coil may be open.

To check these circuits you'll need a digital Voltmeter.

Refer to the ASD relay socket diagram below.

With the ignition switch OFF, touch pin socket 85 with the (+) probe and (-) probe to a good ground. You should see between .02 and .150 volts. This is the PCM idle voltage. Pin socket 85 is the coil ground circuit to the PCM. If you see this voltage it means the wire from 85 to the PCM is intact. If you don't see any voltage at all it may mean the wire is open or shorted to ground.

If you don't see voltage at pin socket 85, wiggle the wiring harnesses from the PCM connectors, along the firewall to the PDC.

Check for power from fuse #11 in the JB to pin socket 86.

Turn the ignition switch to RUN, without cranking the engine. Probe between pin socket 86 (+) and ground. You should see battery voltage. If not the circuit between fuse #11 and pin socket 86 is open. If you don't see battery voltage at 86 wiggle the wiring harnesses to see if the voltage recovers.

Do these checks and get back with the results.

 

I did what tests I could with my volt meter that only reads as low as one decimal place. Pin 85 to ground gave me nothing and wiggling the wire harness had no effect. Fuse 11 to pin 86 (assuming its the 25amp fuse because I have no chart that labels them) gave me 13.1 volts.
With the key on pin 86 to ground gave me nothing.
Also, as soon as I pull the jumper the cooling fan comes on.

 

I did what tests I could with my volt meter that only reads as low as one decimal place. Pin 85 to ground gave me nothing and wiggling the wire harness had no effect.

You'll need a better Voltmeter that will read at least two decimal places when set to 20 VDC. You may only be getting .02 volts at 85 and your meter isn't reading it. It's important to know if this circuit is intact. It is the relay control coil ground from the PCM.

Fuse 11 to pin 86 (assuming its the 25amp fuse because I have no chart that labels them) gave me 13.1 volts.

Where were you measuring to get 13.1 Volts? At the fuse holder? Fuse #11 in the JB is the 4th fuse up from the bottom, on the forward bank of mini fuses. Fuse #11 is a 20 Amp fuse. Check it before doing other tests.

With the key on pin 86 to ground gave me nothing. You should have had 13.1 Volts at pin socket 86 with the key to RUN. No volts at pin socket 86 with the key to RUN may mean the circuit wire to fuse #11 is open.

Try the same test for voltage at pin socket 86 for the fuel pump relay. It uses power from fuse #11 as well. The ASD relay and Fuel Pump relay pin 86 power wires are spliced together (S130), if you get power at the Fuel Pump relay pin socket 86 and not at the ASD relay pin socket 86 the splice may be bad. Splice C130 also brings in the TCM and the PCM.

Also, as soon as I pull the jumper the cooling fan comes on.

What jumper? Your not supposed to be using a jumper when doing these tests.

Get a good digital VOM and try again.

 

Another thing that might be useful to know is that with the jumper in place my a/c freezes up even though it is not turned on.

 

Ok, but I had the jumper out when I was doing the tests.

 

Going to get a better meter now. Thanks for your patience.

 

Ok, so I got a new tester.
With the key off 85 to ground 0.00
And from the 85 pin on the fuel pump to ground is 0.00

With the key on
Asd pin 86 to ground 0.01
Pin 85 to ground 13.14

Fuel pump pin 86 to ground 0.04

 

It sounds like you have the pin sockets mixed up - easy to do.

I've included a different layout of the pin sockets so you can get organized,

Pin socket 86 on either relay pin socket should be 00.00 volts with key OFF, and battery voltage with key to RUN.

The .01-.04 volts are good voltages if read at pin socket 85 of either relay with the key OFF. The voltage will change a bit with the key to RUN.

Study the relay data below and get the relay pins and their pin sockets in the PDC straight in your mind then recheck the voltages.

I had a hard time getting it straight when intially doing these checks some years ago so I marked the socket numbers on the yellow base where next to the sockets using a pencil.

 

This is with the key on.

 

Pin socket 85.

This is not normal. It should be around .02 to .150 Volts with the key ON or OFF. It looks like there's a short from a power source from the Start/Run bus (key ON) to this circuit.

It is important to know what voltage is at pin socket 85 with the key OFF. What is it? If it's .02 to .150 Volts with the key OFF we know there may be a short in the harness somewhere. If it's still 11+ Volts with the key OFF there may be a problem in the PCM or its connector C3.

Disconnect PCM connector C3, which is the Gray connector closest to the firewall. Check the Voltage at pin socket 85 again with the key ON then with the key OFF. Do this and get back.

 

This is with the key off. Am I doing something wrong?

 

Pin socket 86.

This is normal. With the key ON it should turn to battery voltage.

 

Ok, I ran through all of the tests again this morning.
With the key off I get nothing on any pin.
With the key on I get 12.18 volts on pin 85 only.
Disconnecting the PCM had no effect. I got the exact same readings as stated above.

 

I really appreciate you taking the time and bearing with me.

 

On a side note, I get continuity from 85 to ground terminal on batt with key off, then it switches to battery voltage with the key on? Is that supposed to happen?

 

This is my PDC. With the pos. terminal disconnected from my batt and a volt meter put in between my PDC and the batt, fuse 17 (ignition off draw) shows voltage. I assume it should. When I pull that fuse the volt meter zeros out. Also the alternator shows voltage. When I unplug the small plug on the alternator it very slowly drops the voltage to zero.
Is any of this relevant?

 

The IOD fuse is F16. F17 powers the Data Link Connector and the headlamp switch.

Why are you dicking with this? None of it is relevant.

 

Just realized that I'm not getting power to either side of fuses 10 or 11. What does that indicate?

 

Boh of those fuses are fed from the Start/Run bus, i.e., the ignition switch has to be in the run position.

Most fuses in the JB are fed from the Start/Run bus.

 

Here's a diagram of the ASD circuit. Study it. Do the tests and post for every reading.

Do the tests on the Fuel Pump relay as well to get a comparison. Record and post the results as well.

Tips: Do not shove the meter probe in the relay pin sockets, it will enlarge the socket and the relat pin won't make good contact when installed. Use the battery negative post as the ground for your meter.

 

I'm just grasping at straws. But I have no power to fuses 10 and 11 with the key in the run position. Does that indicate anything?

 

In the JB - fuses F9, 10, 11, and 27 are powered from the ignition switch in the start and run position (Start/Run bus).

How are measuring the fuses for voltage? Describe how you are using your meter probes to do this. Are the fuses in or out of their holders?

 

With the key on, I set my volt meter to 20dc volts. I put one probe on the battery ground and the other one on the little contact that you can touch with the fuse in place. I did that on both sides of each fuse. Then I tried with the fuses out touching each contact while remaining grounded on the neg battery with the other probe.
Using that method I measure voltage every other fuse.

 

Are we talking about fuses in the PDC or the JB? Just curious because you said you put one probe on the battery ground. Just thought it would be a stretch to go from the JB to the battery with meter wires.

 

Reference the above diagram: Are you getting voltage at ASD relay pin socket 86 with the key to RUN? How about the Fuel Pump relay pin socket 86?

If you don't get voltage at the Fuel Pump relay 86 then there is a problem with the fuse 11 feed. If there is voltage at this relay and none at the ASD relay 86, the power interruption needs to be troubleshot.

 

With the key off ASD 85 = 0.00 v

 

With the key off ASD 86 = 0.00 v

 

Key off ASD 86= 0.00 v

 

With key off FP 85=0.00 v

 

Key off FP 86= 0.00v