2000 4.0 not getting fire to coil - JeepForum.com
 
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post #1 of 8 Old 04-04-2019, 02:48 PM Thread Starter
do_ob
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2000 4.0 not getting fire to coil

Hey all. I just bought a 2000 XJ which ran fine when I went to pick it up, but now is not getting fire to the coil (I think).

Long story, but here goes.

I went to look at this thing after a guy posted it for sale online - said he couldn’t get a good brake pedal. So I go check it out, and it starts and runs good. He has hard wired the starter to the battery with a switch inside because he couldn’t turn the ignition cylinder all the way over. It also has dual electric fans, one of which is broke and the other is also hardwired to the battery with a switch inside. And, like he said, the brake pedal was going all the way down to the floor.
He said when he bought this thing, he had driven it back to his house from where he bought it (about a 45 minute drive) and the brakes were pulling hard to the right. When he got home, he put new calipers and pads on the front but couldn’t get a pedal after bleeding them. He gave up and put it up for sale.
So I buy this thing and bring it home on a trailer after looking it over. There was a busted brake line on the rear end and he had put the calipers on the wrong sides. During the course of bleeding the brakes, I had this Jeep running several times throughout the afternoon (I always like to have a vehicle running when bleeding the brakes...don’t know if it’s necessary but yeah). My point is, it started up and ran decent. There were some vacuum lines unhooked. Someone in the past has also replaced the exhaust from the manifold back and did not install any 02 sensors or a catalytic converter (rednexxx). But it started and ran. Surprisingly well, considering.
After getting done with the brakes, I put the tires back on and dropper her back down on the ground. Now she won’t start. It cranks over fine, and I am getting fuel to the fuel rail. I dont have a gauge to check the pressure, but it squirts out when the needle is pressed so I assume it’s not a fuel issue.
Next I went through and checked all the fuses. Every one in the junction block (inside the passenger floor area) was good EXCEPT the 20 A fuse that’s connected to those 2 red wires. I’m not sure what this one is for (couldn’t find it on any diagram) but I went ahead and replaced it. Under the hood, fuse 10 (starter relay) was blown so I replaced it. All the other fuses were good. The relays are all clicking when the ignition is turned on, so I think they are good.
Note: when I replaced fuse 10, the ignition cylinder started working normally and will crank the engine over now. So now I can engage the starter with the regular ignition OR with the switch mentioned before.
My next thought was the crank position sensor. I went ahead and bought a new one and put it on, thinking surely that was the problem. Nope. No change at all. I watched BleepinJeep’s video on testing the CPS’s ohms/resistance and did so. My ohmmeter/voltmeter did not go to zero so that told me the new CPS wasn’t bad if I understood correctly.
Next, I attempted to check the spark to the coil using the old screwdriver-in-the-plug-boot method and got no spark when someone cranked it over. So ****, no spark, maybe the coil’s bad? Before spending more money, I tried to read some tutorials and threads on how to check the coil on these for resistance (this Jeep has the coil rail, no distributor/plug wires). I found a couple informative posts here and there, but my multimeter is a cheapie and I’m not an electrician. I also read one post where someone said you can’t check this type of coil one-boot-at-a-time...something about wiring different plugs together that fire from the same coil pack... I ended up just buying a new coil rail to see what happens, which I was told I could return if it didn’t help my problem. Put it on, and still nothing. It’s still on there.
Next I’m thinking maybe the pigtail to the coil isn’t supplying any juice. Again, I’m not an electrician. I pulled the pigtail off the new coil and checked the voltage (multimeter set on 20V) and got ~0.6V on each of the 4 female terminals when someone was cranking the engine. Someone later told me that that number should have been damn near 12, but I’m not sure.
After this, I figured I could check the resistance of the new coil and compare those numbers to the old one. They were different (old was ~6 and new was ~18 IIRC). I don’t know if that’s good or bad, or if those numbers matter in terms of the coil providing fire to the plugs..

So at this point, I’ve changed and checked the crank position sensor, fuses (inside and outside), and changed the coil rail.

My other Jeep is a 98, so next I pulled the PCM/ICM/computer out of it and put in the ‘00. Took 2 minutes, so why not try it. This didn’t help anything either. After reinstalling the original computer, I did that test where you hold the odometer pin in and let the gauges cycle...all the gauges and lights did their thing like they should.
At this point, I’m starting to grasp at strings. I bought a new camshaft position sensor and ignition switch and installed both of those - old cam sensor’s internals were very dirty, so I cleaned it and reinstalled to no avail...and the key was hard to get out of the ignition cylinder so... - no change at all in the cranking. I ended up returning the new cam sensor and reinstalling the old one. Kept the ignition switch.

So now I’ve done this:

checked and replaced fuses
eyeballed over wiring
replaced and tested new crank position sensor
replaced coil...attempted to check, not sure what I’m doing
checked voltage of coil pigtail...got numbers but not sure if they’re good or bad
swapped ECM with good one, swapped back
Replaced ignition switch
Replaced camshaft position sensor, then put old one back on

At this point, I’m at a loss. I know my 02 sensors are gone, but this thing went from starting and running fine to not starting at all in a matter of an hour. I haven’t found any broken/burn wires, loose connections/grounds anywhere. I have a buddy who is supposed to bring his OBDII over Saturday, but I’d really like to get this thing drivable before the weekend. If anybody has any ideas, please let me know.

—————
TLDR: changed brakes now won’t start. Got fuel, no spark. Changed crank sensor, cam sensor, coil rail, computer, ignition switch, fuses...not in that order.

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post #2 of 8 Old 04-04-2019, 03:08 PM
jtec
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2014 JK Wrangler 
 
Join Date: Oct 2017
Posts: 5,346
lets start with BASICS -

with KOEO - Key On Eng OFF.-

the coil rail is 4 wires - what is the voltage on DG (dark green) wire?
>> source is ASD and then fuse 18 PDC.
What is the voltage on the injectors? again DG wire

At the TPS what is voltage terminal ##3 - see attachment

Did you try to get codes?
Attached Images
 

When I see the price of OEM I think aftermarket.
When I see the quality of aftermarket I think OEM.
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post #3 of 8 Old 04-04-2019, 03:33 PM Thread Starter
do_ob
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Quote:
Originally Posted by jtec View Post
lets start with BASICS -

with KOEO - Key On Eng OFF.-

the coil rail is 4 wires - what is the voltage on DG (dark green) wire?
>> source is ASD and then fuse 18 PDC.
What is the voltage on the injectors? again DG wire

At the TPS what is voltage terminal ##3 - see attachment

Did you try to get codes?
Thanks for the reply

4 wires on the pigtail to the coil are white, green (with orange stripe), blue (with pink stripe), and red (with yellow stripe).

Voltage at the green wire is 0.03 V

Voltage at green wire on injector is also 0.03 V

Voltage at T3 on TPS is 5.20 V

I donít have a code reader and canít get it started to drive it to the parts store to have them check it.
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post #4 of 8 Old 04-04-2019, 03:47 PM
jtec
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I did not addd the tracer wire color everything gets faded and confusing...

OK the Coil and inj should have 12v - did you check fuse?

unplug coil and then check the DG wire on coil connector for voltage -
Also see if injector Volts came up. IF not back up to 12v.
Unplug injectors 1x1 and see if 12v returns,
trying to determine what may be pulling the Volts down.

When I see the price of OEM I think aftermarket.
When I see the quality of aftermarket I think OEM.
jtec is offline  
post #5 of 8 Old 04-04-2019, 03:57 PM Thread Starter
do_ob
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Quote:
Originally Posted by jtec View Post
I did not addd the tracer wire color everything gets faded and confusing...

OK the Coil and inj should have 12v - did you check fuse?

unplug coil and then check the DG wire on coil connector for voltage -
Also see if injector Volts came up. IF not back up to 12v.
Unplug injectors 1x1 and see if 12v returns,
trying to determine what may be pulling the Volts down.
I checked all the fuses pretty much after each thing I did. Iíll run to the store and get a test light real quick, though, and retest them all.
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post #6 of 8 Old 04-04-2019, 04:13 PM
jtec
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2014 JK Wrangler 
 
Join Date: Oct 2017
Posts: 5,346
I will ck back tomorrow.

When I see the price of OEM I think aftermarket.
When I see the quality of aftermarket I think OEM.
jtec is offline  
post #7 of 8 Old 04-05-2019, 09:07 AM Thread Starter
do_ob
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Quote:
Originally Posted by jtec View Post
I will ck back tomorrow.
Hey! The good news is I got it running thanks to you, I appreciate it. Turns out my ASD fuse under the hood was testing good but was actually bad...not sure how that happens, but I replaced the 30A fuse with a new one and it started.

For some reason, though, most of my fuses in the interior junction block are not lighting up my test light, although everything seems to be working...only fuses 1,2,13,15,20, and 21 test good...

Iím happy itís running again, just a little confused.
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post #8 of 8 Old 04-05-2019, 10:53 AM
jtec
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Join Date: Oct 2017
Posts: 5,346
might help - let me know
Attached Files
File Type: pdf 00XJ fuse box.pdf (390.7 KB, 3 views)

When I see the price of OEM I think aftermarket.
When I see the quality of aftermarket I think OEM.
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