Crank But No Start

[Sputter]

Hey All

New member here. I am not a Jeep expert or a mechanic but I recently rebuilt a 2004 Land Rover Discovery including the engine so I know a bit about troubleshooting and the different systems in this type of vehicles. I was looking for a new project and so picked up a 2003 TJ with a 2.4L engine which was a perfect project jeep for my daughter and I to work on. This thing has been frankenstein'd over the years and so I am dealing with a mess. Need some help with a few things before I shoot the parts cannon at it.

History

1. Jeep did run but not anymore.
2. It used to crank but not start unless I first disconnected the battery and join the black and red leads for a minute or two. Then it will start but runs rough at idle.
3. Worked on troubleshooting this for a bit - also replaced MAP sensor - no change.
4. I had an unrelated code for the transmission solenoid. I have replaced that and the code went away.
5. Had some other weird electrical issues and rough idle so I finally bit the bullet and sent off the PCM.
6. PCM was tested - no issues.
7. After putting the PCM back on, it cranks but now does not start - even if I disconnect the battery leads and bleed the caps.
8. I am not getting any codes.
9. PO said he replaced the CPS. It looks new.

What I Have Done

1. Replaced MAP sensor
2. Checked/replaced fuses in PDC
3. Verified no spark with inline
4. Verified with noid that fuel injectors are not getting power
5. Verified power to the CPS and continuity of the CPS with multimeter
6. ASD relay has been tested with multimeter and is good.
7. 5v reference power coming to ASD and key on power have been verified.

I don't want to shoot the parts cannon at this and would prefer to troubleshoot but if its a no-brainer, I will replace a part. Feedback I have gotten from others is ignition switch or faulty CPS but I am skeptical. Thoughts on approach?

 

[Daryl]

Download a copy of the FSM and go to the ignition system wiring diagrams to diagnose why no spark. Section 8I explains how the ignition system works and 8W will have the diagrams and pin outs for the connectors.
https://wranglertjforum.com/threads...ice-manuals-fsm-technical-documentation.4618/

 

[Sputter]

Got a copy of that already but have not checked out that section. I will take a look and see what I can find out. Thank you.

 

[Daryl]

Got a copy of that already but have not checked out that section. I will take a look and see what I can find out. Thank you.

The ASD relay will not be energized until it “sees” the engine turning over and that is done via the crankshaft position sensor.

 

[Sputter]

The ASD relay will not be energized until it “sees” the engine turning over and that is done via the crankshaft position sensor.

When I key on the Jeep, I can feel the ASD relay click. Doesn’t that mean it is energized?

 

[Daryl]

When I key on the Jeep, I can feel the ASD relay click. Doesn’t that mean it is energized?

Yes, but after 1.8 seconds if it doesn’t see the engine turning over it de-energizes.

 

[Sputter]

Ok so what your suggesting is this is a CPS issue?

 

[Daryl]

Ok so what your suggesting is this is a CPS issue?

No, I’m trying to teach, lol. It could be, but we’re not there yet.

 

[Daryl]

@Sputter here’s a paragraph out of the FSM that needs to be read and understood in order to diagnose whether you have a component or wiring issue.

OPERATION - PCM OUTPUT
The ASD relay supplies battery voltage (12+ volts) to the fuel injectors and ignition coil(s). With certain emissions packages it also supplies 12–volts to the oxygen sensor heating elements.
The ground circuit for the coil within the ASD relay is controlled by the Powertrain Control Module (PCM). The PCM operates the ASD relay by switch- ing its ground circuit on and off.
The ASD relay will be shut–down, meaning the 12–volt power supply to the ASD relay will be de-ac- tivated by the PCM if:
• the ignition key is left in the ON position. This is if the engine has not been running for approxi- mately 1.8 seconds.
• there is a crankshaft position sensor signal to the PCM that is lower than pre-determined values.

 

[Sputter]

Teach me, Sensei!

Not ready to throw a CPS in there just yet. Here is my plan for the weekend.

1. Double-check ASD relay ground tomorrow and a few other wiring issues. My understanding is that when the ground is applied, the relay is energized, and voltage is allowed to flow to fuel pump, fuel injectors, ignition coil, and O2 sensor heating element. This would possibly explain the issue.
2. Check voltage from PCM to injectors and coil.

Make sense?

 

[Sputter]

@Sputter here’s a paragraph out of the FSM that needs to be read and understood in order to diagnose whether you have a component or wiring issue.

OPERATION - PCM OUTPUT
The ASD relay supplies battery voltage (12+ volts) to the fuel injectors and ignition coil(s). With certain emissions packages it also supplies 12–volts to the oxygen sensor heating elements.
The ground circuit for the coil within the ASD relay is controlled by the Powertrain Control Module (PCM). The PCM operates the ASD relay by switch- ing its ground circuit on and off.
The ASD relay will be shut–down, meaning the 12–volt power supply to the ASD relay will be de-ac- tivated by the PCM if:
• the ignition key is left in the ON position. This is if the engine has not been running for approxi- mately 1.8 seconds.
• there is a crankshaft position sensor signal to the PCM that is lower than pre-determined values.

Ok I will add check for "crankshaft position sensor signal to the PCM" to the list. Thanks!

 

[Daryl]

Ok I will add check for "crankshaft position sensor signal to the PCM" to the list. Thanks!

Here’s another bone I’ll throw out there for you.

 

[Sputter]

Here’s another bone I’ll throw out there for you.
View attachment 183826

Thanks! I have been working off these pages for the past couple of days. Actually have the whole wiring section printed out! Im a bit new to reading and interpreting wiring diagrams but slowly getting the hang of it. I’ll continue to focus in this area.

 

[Daryl]

Thanks! I have been working off these pages for the past couple of days. Actually have the whole wiring section printed out! Im a bit new to reading and interpreting wiring diagrams but slowly getting the hang of it. I’ll continue to focus in this area.

View attachment 183833

You’re on it! Read these two pages as they explain how to interpret a wiring diagram.

 

[Sputter]

Ok - here is what I found so far:

1. Getting 12 volts battery power and 12 volts key on power at the ASD
2. Pinout A22 - (Fused B+) checks out with 12v
3. Jumpered 87 & 30 on the relay - still no start but Pinout C12 (ASD relay output) - reads 12V

How do I check for ground signal?

 

[Jerry Bransford]

With a helper holding the ignition switch in the Start position, measure for +12v on the 12 gauge brown wire at the starter motor itself. The brown wire comes from the starter relay in the power distribution center, it energizes the starter solenoid at the starter itself. If you're getting 12 volts on that brown wire at the starter motor itself while the ignition switch is in the Start position, the starter is bad.

The bigger 6 gauge red wire at the starter is connected directly to the battery's + post.

 

[Sputter]

It's cranking but not providing spark or power to the fuel injectors. If its cranking, wouldnt that mean the starter is good?

 

[Daryl]

Ok - here is what I found so far:

1. Getting 12 volts battery power and 12 volts key on power at the ASD
2. Pinout A22 - (Fused B+) checks out with 12v
3. Jumpered 87 & 30 on the relay - still no start but Pinout C12 (ASD relay output) - reads 12V

How do I check for ground signal?

When you installed a jumper wire between relay terminals 87 & 30 you did that with the relay removed correct? And those would be pin-outs A14 & A15 correct?

 

[Sputter]

Yes. See picture.

 

[Daryl]

Yes. See picture.

View attachment 184078

Do you have a way to back probe connectors? I would like to test the crankshaft position sensor.