Help needed for a new Jeeper: TJ won’t start!

Mayojeep

New Member
Supporting Member
Jan 18, 2019
9
Toledo, Ohio
I’m glad to be a new part to this community and the jeep community all together but my Jeep is giving me a huge headache. Any help would be greatly appreciated.

I have a 97 TJ 4.0 5 speed manual. 197,000 miles.
In the last 5 months I have replaced.
Both O2 sensors
Crank sensor
Cam sensor
Throttle position sensor
ECM
Battery
Plugs, wires, cap, rotor and coil.
Exhaust from head back.

It’s in the shop now because it cranks but won’t start. No spark. The ECM will not communicate with the OBD2. I’m lost and
could use any kind of advice.

Thank you.
Mike.

8D1402FA-48A9-40AF-85CE-59C98D32C9BC.jpeg
 
Last edited:
Reactions: JMT

AndyG

TJ Addict
Supporting Member
Jul 30, 2018
1,539
Alabama
Hang tight brother , some guys will chime in ..this forum is all about helping each other.

Beautiful TJ, is that paint factory?

Toledo ,Ohio-oughta be a wealth of knowledge in that area too.

I bet it will he something simple ...like the switch.
 

Chris

Administrator
Staff Member
Sep 28, 2015
34,467
Salem, Oregon
If the ECM won’t communicate with an OBDII scanner, the first thing I would have the shop doing is testing the ECM. There are testing procedures for it in the FSM I believe.
 
Reactions: Mayojeep
OP
Mayojeep

Mayojeep

New Member
Supporting Member
Jan 18, 2019
9
Toledo, Ohio
Thank you Andy. Yeah I’ve been beating my head over it for a few weeks now. And I’m sure there is plenty of knowledge out here.
It is not the original color. It was already painted that color when I bought it this summer. I do like the color although the original color is metallic blue and may some day become metallic blue again.
 
OP
Mayojeep

Mayojeep

New Member
Supporting Member
Jan 18, 2019
9
Toledo, Ohio
If the ECM won’t communicate with an OBDII scanner, the first thing I would have the shop doing is testing the ECM. There are testing procedures for it in the FSM I believe.
Thanks Chris. I’ll check with them on that. They’ve already said it’s rhe same with both the old and new ECM. They tried running a new ground to the ECM and still no luck.
 

AndyG

TJ Addict
Supporting Member
Jul 30, 2018
1,539
Alabama
Cool, you will see the names Chris, Jerry Bransford, Blaine and many others on here. Take note . They have a lot of experience and common sense.
 
Reactions: Mayojeep

ac_

zombicon
Supporting Member
Jun 15, 2017
3,729
AZ, United States
Ok can you give more details? Even if your ECM is bad it should still run or try. I don't really understand what you mean by the ECM won't communicate with the OBD2. I mean I do understand what you are saying, but I don't know what you mean.

Is there a check engine light?
Is the OBD2 connected to anything?

My suggestion would be to start with the basics.
Do you have spark?
Do you have fuel?
Do you have compression?

You need all three or it wont start.
I am betting that your obd2 might have a broken wire somewhere but you ECU actually works.

It should have a limp in mode if it fails. I cannot think of a scenario where if you ECM was bad that the TJ wouldn't try and start.

I am betting you have wiring problems somewhere, but you need to check those 3 things first.
If you have all three of those, it should run. May not run great that is where your computer kicks in, but it should run.

Also, If you mechanic couldn't figure out what the problem is, but tried grounding your ECM. I don't have much faith in his knowledge of diagnosing new cars. Let us know what he finds since he still has it, but do not spend money unless he is sure that is the problem. I am scared he is going to change parts and try and get lucky at your expense. Hold him accountable.

Don't be afraid to come here and ask questions.

Please if he does happen to fix it, come follow up with the results.
Keep us posted either way.
 
OP
Mayojeep

Mayojeep

New Member
Supporting Member
Jan 18, 2019
9
Toledo, Ohio
Thank you AC.
First it’s a reputable shop that I go to for a lot of my work. With this being a toy and not a daily driver it’s not an urgent repair as I told them. So they haven’t had a lot of time to dig into it yet. I’m just stumped as to what happened where. My hope was they could just hook it up and see what was wrong.

This started a few months ago with random stalls while driving, only the engine would shut off but would always re start. And slowly progressed to a no start situation with no check engine lights.

A few further notes. When the key is turned to ignition the fuel pump turns on and there is fuel pressure in the rail. There is no gauge movement when the key is turned to ignition, the odometer reads miles, and the check engine light is on. When the key is turned to start it will crank and all sounds fine.
I’m told there is no signal going from the ECU to any point in the vehicle and is the same with both the old and the new ECU. There is no spark from the coil to the distributor. I’ve checked all fuses, and the AMS relay under the hood was switched out. Compression is good.

All leads me to believe there is corrosion or a break in a harness somewhere but I’m just not sure.
 
Reactions: ac_

ac_

zombicon
Supporting Member
Jun 15, 2017
3,729
AZ, United States
Thank you AC.
First it’s a reputable shop that I go to for a lot of my work. With this being a toy and not a daily driver it’s not an urgent repair as I told them. So they haven’t had a lot of time to dig into it yet. I’m just stumped as to what happened where. My hope was they could just hook it up and see what was wrong.

This started a few months ago with random stalls while driving, only the engine would shut off but would always re start. And slowly progressed to a no start situation with no check engine lights.

A few further notes. When the key is turned to ignition the fuel pump turns on and there is fuel pressure in the rail. There is no gauge movement when the key is turned to ignition, the odometer reads miles, and the check engine light is on. When the key is turned to start it will crank and all sounds fine.
I’m told there is no signal going from the ECU to any point in the vehicle and is the same with both the old and the new ECU. There is no spark from the coil to the distributor. I’ve checked all fuses, and the AMS relay under the hood was switched out. Compression is good.

All leads me to believe there is corrosion or a break in a harness somewhere but I’m just not sure.
That seems like a solid diagnosis. Now the tough part is to chase down wires.

So if I read this right, you do have a check engine light but nothing at the OBD2. That seems more like a wiring issue than a ECM issue. Not to say the ECM is not the problem, I cannot confirm or deny without actually looking at it, but that would be the last thing I would change. You have more work to do first.

You did good, You have fuel and you have compression. You just eliminated 2 problems already.

Now as I was reading your follow up, my Jeep had the same exact problem last summer and it turned out being my distributor rotor.

On mine it would randomly died too and just started, then one time it never started back up. It ended being the end of the distributor rotor that spins in the cap. The little metal piece broke off. I replaced the rotor and never had an issue since. Only proving that you can be bit by the basics.

It sounds like you may have some wiring issues, but I would focus on why you don't have spark first. Make sure you have power going to your coil. Maybe add a power wire to the coil to see if you can get it to spark. Also pull the cap and make sure there are no issues in there. It sounds like even if you get it running you may have a little wiring to diagnose, but find your spark issue first.
 
Reactions: Mayojeep

Bastman Boys

Didn't I tell you, the phone in the limo is busted
Supporting Member
Jan 26, 2019
1
Phoenix, AZ
Just had almost the exact same symptoms on my 99. I replaced the fuel pump and relay and still it would die while driving, this time wouldn't start back up and at my waits end I towed it to the shop.
They replaced the crank position sensor and cleaned up the wiring about 12" from the fuel pump. Still, would run for a few minutes and die. They said the ECU was bad, luckily I had found this forum and had some info/questions to ask, they couldn't answer and so I took it home and started from scratch, literally. I sanded down every ground location I could get to, put things back together and have been fly-n-hi for a few days now.
Cant over emphasis the importance of clean ground even if your test lite says they are good.
 
Reactions: Mayojeep and ac_
OP
Mayojeep

Mayojeep

New Member
Supporting Member
Jan 18, 2019
9
Toledo, Ohio
Thank you for this info. It is still in my shop and being seen to as they can bring it’s not my primary car, hopefully I’ll hear something soon. What you said all sounds very familiar!
 
Reactions: Chris

TJ4X4HORTON

New Member
Feb 6, 2019
2
north carolina
I’m glad to be a new part to this community and the jeep community all together but my Jeep is giving me a huge headache. Any help would be greatly appreciated.

I have a 97 TJ 4.0 5 speed manual. 197,000 miles.
In the last 5 months I have replaced.
Both O2 sensors
Crank sensor
Cam sensor
Throttle position sensor
ECM
Battery
Plugs, wires, cap, rotor and coil.
Exhaust from head back.

It’s in the shop now because it cranks but won’t start. No spark. The ECM will not communicate with the OBD2. I’m lost and
could use any kind of advice.

Thank you.
Mike.

View attachment 72970
Hi, If the ECU will not communicate with the OBD port , from my experience the ECU is bad..
 
Reactions: Mayojeep
OP
Mayojeep

Mayojeep

New Member
Supporting Member
Jan 18, 2019
9
Toledo, Ohio
Thanks for the info. It’s the same with the original ECU and the new ECU so I’m in the process of swapping out the new ECU under its warranty. I’ll keep you posted on the outcome.
 
Reactions: KCsTJ

JJsTJ

New Member
Feb 6, 2019
5
Kitchener,Ontario
I’m having the same issue with my 2003 TJ,it won’t start unless I spray a little quick start into the air intake.It stays running(nicely)until I shut it off then same thing.