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4.0 TJ won't start and has no spark

-Lee-

New Member
Joined
May 23, 2020
Messages
3
Location
NC
I've been looking through a lot of posts, but I have one detail that is different than any other I have found. Full background so far:
1997 Wrangler Sport
4.0 Manual Trans

I had hit one of my light switches without knowing it and left my Jeep in my driveway with LED bar light on (daytime). That afternoon as the sun was going down, I noticed a light outside my window and found what I had done. Didn't fully kill the battery but it was close. Attempted to jump it, but it would only turn over and not start. Not having much time to work on it, I left it and tried to jump again the next day with the same result. With my luck, I figured the fuel pump had probably quit. The low battery part is what I have not seen anyone else have just prior to having this no start issue. Everything was running fine prior to that.

Got busy with work and didn't have time to diagnose the issue for a few months and we were going into winter. I replaced the battery about a month ago and it is still only turning over but not starting. Hit the bleeder valve on the fuel rail and found no pressure. Bypassed the fuel pump relay and the pump kicked on, having good flow (500ml in ~23secs). Attention got diverted to spark and found I had no spark on all cylinders. Checked from ignition coil and had nothing. Ignition coil was cracked in several places, so I replaced it (old one was still within spec when tested with ohm meter).

Am I missing something simple or is this leading to the ASD circuit? No codes are showing (although I failed to check codes prior to changing the battery :(). I did switch relays around and it did not fix the problem. All fuses are good in PDC and glove compartment. I don't have anyone else around right now to help with turning the key on while I stand over the relays for clicks or to test if the ECM is actually sending the ground to the ASD relay for the two seconds after key is turned, so I will have to run some temp wires on a meter or light probably today. I'm also looking closer at the circuit now to see which blades I need to run a jumper between to bypass the ASD to see if it will start. But I wanted to drop in and see if anyone knew something that I didn't that happens when the battery is almost killed and it sits for a while.

Side note: No aftermarket lighting is tied in with factory wiring. I installed them on their own circuits with their own relay box.
 

hear

TJ Addict
Supporting Member
Joined
Oct 18, 2020
Messages
1,170
Location
Prosper, TX
As a redneck workaround, could you pull the negative battery cable, then turn the key to ON, then with your finger on the relay re-introduce the negative battery cable? It's definitely hard to test some of these things w/o a 2nd person. BSK has a couple of videos that go over some basic PCM troubleshooting, I would check into the pins that provide ground & 12V for sure.
 
OP
-Lee-

-Lee-

New Member
Joined
May 23, 2020
Messages
3
Location
NC
Update:
Did not locate any damaged wiring under the hood or along the path of O2 sensors and fuel pump.

Re-tested all fuses with multimeter and confirmed all are good.

Disconnected and reconnected ECM connectors.

Made sure distributor was turning and cleaned the contacts (which were not really corroded much).

Paid closer attention to gauges on attempts to start, finding the tach does not move, fuel gauge stays pegged on E (yes it does have fuel in the tank) and volt gauge does not move. All other dash lights seem to operate normal and other gauges move slightly when key is turned on. Cluster test shows all are good.

Disconnected the crank shaft position sensor but no change in the way gauges act.

When key is turned on, fuel pump cannot be heard kicking on. Hit the bleeder valve on the fuel rail again and found no pressure.

Between the fuel pump not kicking on and still no spark, I started testing ASD at the PDC.
- Pin 30 = constant 12V power
- Pin 87 = Tested with multimeter off battery positive which gave a voltage reading showing it had a path to ground.
- Pin 85 = 12V when key is turned on / nothing when key is off
- Pin 86 = Used test light and found nothing with key on or off (supposed to be power for ~2 seconds when key is turned on initially correct?)
^Please feel free to correct me if I did that testing wrong^

I'm not the most mechanically inclined person... know just enough to usually get by.

@hear I hadn't thought of that but will have to try it... thanks. I will look into some of BSK's vids too.
 
Last edited:

hear

TJ Addict
Supporting Member
Joined
Oct 18, 2020
Messages
1,170
Location
Prosper, TX
No volts & no fuel gauge makes me wonder if you have a bus problem. Have you tried to read codes? Will a reader connect & communicate?

I know you said you checked all the fuses under hood and in the glove box, but it’s worth a double check. I had a similar problem, ended up being fuse 11 (which kept blowing due to a short elsewhere which I doubt is your problem but let’s make sure it’s not something easy).

The next easiest thing is possibly the ignition cylinder being broke’d. If the tumbler doesn’t make the right connection it could look like all sorts of broken stuffs. Relaxing that is pretty easy but it don’t know if there is an easy test routine. I also don’t know why a low battery would make that happen, unless something maybe burned up?