Ground strap on head to firewall

Wait. CoilS? Plural? What year XJ are we talking about here?
 
On the 2000 XJ, that firewall to cylinder head bolt ground strap is to aid in containing radio frequency interference (ref section 8F of the FSM). It is not a primary ground path to the chassis. The primary ground path from the battery to the chassis in this vehicle is the AWG 8 cable that runs from the battery negative post connector to the right inner fender (designated G100), the primary ground path to the engine from the battery is the AW 6 cable from the battery negative post connector to one of the two ground studs on the right side of the engine near the generator (the old ignition coil mount bracket mount studs) (designated G101). G101 is also the home for the grounds for the PCM, TCM, and the O2S heaters.

The oil dipstick tube mount bracket stud is the ground point for the Data Link Connector ground wires (two each) and the Anti-Lock Brake Controller (If you have ABS) (designated G102). There are no primary engine or chassis grounds at G102)

There are two ground points (screws) on the left inner fender, near the PCM, that is designated G106. G106 provides chassis ground for alot of circuits, such as Cruise Control Servo, Transmission Range Sensor (NSS), Front wiper motor, window washer pumps, front lighting, etc.

Using a large cable between the firewall and the cylinder head bolt on this vehicle is an overkill. The OEM braided strap, if in good clean condition, would have sufficed. Edit: Jeep has no "G" ground designtor for this ground strap.
 
^^ Some good info!
I figured that ground couldnt be that important! ha
Why Jeep why are you doing this to me. No spark is no fun

New CrankPS, CamPS, plugs, coils are fine,

Where should I look next besides checking for 5v at the ign coil rail?
Could it be an ignition switch? Cranks but no spark
 
x91evo said:
^^ Some good info!
I figured that ground couldnt be that important! ha
Why Jeep why are you doing this to me. No spark is no fun

New CrankPS, CamPS, plugs, coils are fine,

Where should I look next besides checking for 5v at the ign coil rail?
Could it be an ignition switch? Cranks but no spark
Click to expand...

Why didn't you say you aren't getting spark. :rolleyes:

How do you know you're not getting spark?

Is it that the engine will crank over but not start running on its own?

Is it just spark or are you not getting fuel as well? Does your fuel pump operate for 1-2 seconds when placing the ignition key to RUN, before starting?

Your Automatic Shut Down relay plays a key/important roll for the engine to run. It activates the ignition system, fuel injectors, and oxygen sensor heaters. The ASD relay is activated by the PCM when it receives signals from the crank sensor that the engine is rotating.

The fuel pump relay is powered from a different circuit from the ASD but is activated by the PCM when similar conditions exist, as in the ASD being activated.

If you hear the fuel pump operate briefly when the key is turned to RUN, the fuel pump, its relay, the relay power circuits, and the PCM are okay.

Now, for a quick check, swap the ASD relay with the electric radiator fan relay (shown on the inside of the PDC cover) and see if the engine fires up.
 
While you're thinking about ASD relays, ignition system, etc....

Check these fuses in your PDC.

ASDIGNFI2000PDC_.jpg
 
Sidewinder CC said:
Why didn't you say you aren't getting spark. :rolleyes:

How do you know you're not getting spark?

Is it that the engine will crank over but not start running on its own?
Click to expand...

I used an inline spark tester between one of my coils and the plug.
Exactly the engine will crank but not run under its own power.

ASD relay is fine along with the fuse. I can hear the pump prime at key on, and I have 49psi pressure while cranking.


Sidewinder CC said:
While you're thinking about ASD relays, ignition system, etc....

Check these fuses in your PDC.
Click to expand...

Thats really funny you posted that picture, as I was coming here to post that exact diagram with questions.

pdcoc8.jpg

/


Obviously this diagram is wrong,
But at Key on I am getting little voltage across the terminals in F18 and F21 positions.

What voltages should these fuses be seeing?
 
Let me add to that, I had some feeling that my cam synchonizer was out of alignment making my timing off.
So I had a buddy crank it while I spun it around a little bit.
Heard a HUGE BOOM, I am assuming it was a back fire.

With that being said still could not get the motor to run under its own power. And I reajusted the cam sensor in its previous position.


This makes me wonder, how would the car be able to back fire if it has no spark?
Also installed the new ignition coils for the time being just as a precaution.

Was getting upwards of 7V at the connector for the ignition coil rail.
But reguardless I checked the fuse terminals in position F18 and F21 with those questionable results?
 
Last edited:
x91evo said:
I used an inline spark tester between one of my coils and the plug.
Exactly the engine will crank but not run under its own power.

ASD relay is fine along with the fuse. I can hear the pump prime at key on, and I have 49psi pressure while cranking.




Thats really funny you posted that picture, as I was coming here to post that exact diagram with questions.

pdcoc8.jpg

/


Obviously this diagram is wrong,
But at Key on I am getting little voltage across the terminals in F18 and F21 positions.

What voltages should these fuses be seeing?
Click to expand...

F18 (Ignition rail/Injectors) and F21 (O2S heaters/PCM) will have no voltage until the ASD relay pulls in.

How little voltage are you seeing, .02 volts?

How do you know the ASD relay is fine? Did you try swaping it or something.

The ASD relay control coil power comes from fuse F11 in the JB but it also feeds the control coil for the fuel pump relay, so if your fuel pump is working, as you say, F11 should be okay.

Using your digital voltmeter, there's a test you can perform to see if the ASD ground circuit to the PCM is okay and if the PCM ASD relay driver exists.

Here's a pic of the ASD relay socket in the PDC. Each pin cavity is number like the pins on the bottom of the relay.

Copy2ofimg301.jpg


With the ASD relay removed, and the key OFF, probe pin socket 86 with the (+) meter probe and the negative probe to the battery negative post. You should see zero volts. Turn key to RUN, you should see battery voltage.

Turn key OFF. Probe pin socket 85. You should see around .02 volts. Key to RUN, you should see around .02-.03 volts.

This .02 volts is the PCM idle voltage. It is the differential between the CCD Bus (-) and (+) circuits. If you see the .02 volts that's very good; it means the ASD ground circuit PCM driver is intact and ready to go. Bad part is, if you don't see the .02 volts, either the PCM driver is inop or the circuit is open between the PCM and the ASD relay (pin socket 85).

Do the tests and get back with your results.

Cheers
 
Tried swapping a relay again, no go. Car doesnt even sputter.
#86 everything was normal. 0V key off, and battery voltage key on.

#85 key off was seeing 0.00-0.03V
at key on 0.125-0.129V

So what would this indicate?
 
x91evo said:
Tried swapping a relay again, no go. Car doesnt even sputter.
#86 everything was normal. 0V key off, and battery voltage key on.

#85 key off was seeing 0.00-0.03V
at key on 0.125-0.129V

So what would this indicate?
Click to expand...

You look okay on pin socket 85. Max you should see is .150.

Just wondering about the split with key ON vs. key OFF voltages at 85.

Try doing this test (pin 85/86) in the fuel pump relay socket to compare results. You should see the same results.
 
Sidewinder CC said:
How did this happen all of a sudden without the engine runnng/
Click to expand...

I had codes stored before when the car was operational about 4 days ago. The TPS code must be new since there wasnt a problem with it before.

Sidewinder CC said:
Just wondering about the split with key ON vs. key OFF voltages at 85.

Try doing this test (pin 85/86) in the fuel pump relay socket to compare results. You should see the same results.
Click to expand...

Would it really matter though?
I have 49psi while cranking?
 
Sidewinder CC said:
We know the fuel pump circuit is okay that's why I'd like to see what pin 85 is doing on a known good circuit, in terms of voltage difference between key on and key off.

If you don't want to do it, that's up to you.
Click to expand...

Oh no, that makes perfect sense.
Just wasnt sure as to why, you sir are a genius!

I just went to check the pins on the fuel pump relay, and they arent layed out exactly the same?
How do I know which pins to check?
 
Let me add to that, I have been using a battery charger on and off because the battery is always draining itself from constant cranking.
Wont that vary the results?
 
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