2002 TJ 4.0 auto, crank no start

[Chopperbuilder]

Original issue was a bad fuel pump, barely any pressure when checked at the rail. R/R'd the pump, fuel pressure is great now, cranks no start. Looked online and checked the ASD circuit troubleshooting in several videos on the tube of yous. I have power where I need it, when I need it (key on/off) and the ground is good from the relay to pin 3 on the gray (outboard) ECM plug. I've swapped relays with known good relays and issue still persists. ASD fuse is good. I do not have power at the O2 sensor fuse nor the fuel injector fuse, both fuses are good. The Jeep has no codes present. From what I understand from the videos, something is telling the computer not to fire up. The Jeep ran fine before and did have worn plugs that was causing a misfire issue. That issue has been resolved. Where should I look next?

 

[GregBelleville]

If I understand what you're saying, your Jeep stopped starting due to a bad fuel pump, which is now replaced? But now, you still have a crank no start? was the Jeep running fine prior to the fuel pump?

I had a crank no start on my 99 that ended up being caused by a poor connection between the ignition coil and the PCM. I disconnected and reconnected that plug at the coil and it resolved my issue.

The crank position sensor is another common cause of a crank no start.

 

[Jerry Bransford]

Is the tach needle rising up while the engine is being cranked? If not that's a pretty good sign the crankshaft position sensor has gone bad. No store brand replacements!

 

[Chopperbuilder]

Is the tach needle rising up while the engine is being cranked? If not that's a pretty good sign the crankshaft position sensor has gone bad. No store brand replacements!

Jerry,
Thanks for that, it’s one thing I wasn’t even looking at while trying to start it. So if that is faulty, the ECM doesn’t send signals out to the ASD system causing the no start. Got it.

 

[macleanflood]

And you've put a gauge on the fuel rail and confirmed pressure? Can hear the pump running for a few seconds.

Wouldn't be the first time new parts were junk out of the box.

-Mac

 

[williambmac]

Did you plug the fuel pump connector in?

 

[Chopperbuilder]

And you've put a gauge on the fuel rail and confirmed pressure? Can hear the pump running for a few seconds.

Wouldn't be the first time new parts were junk out of the box.

-Mac

Fuel pressure was verified good after the pump was replaced.

 

[Chopperbuilder]

Did you plug the fuel pump connector in?

Well…..yes. There were no “atmospheric impedance “ issues related to the fuel pump wiring during replacement.

 

[Jerry Bransford]

Jerry,
Thanks for that, it’s one thing I wasn’t even looking at while trying to start it. So if that is faulty, the ECM doesn’t send signals out to the ASD system causing the no start. Got it.

The crankshaft position sensor both drives the tachometer and provides the engine's master timing signal required by the ECM/PCM. Without it the engine won't start or run.

 

[Chopperbuilder]

The crankshaft position sensor both drives the tachometer and provides the engine's master timing signal required by the ECM/PCM. Without it the engine won't start or run.

Thanks again Jerry.

 

[williambmac]

Well…..yes. There were no “atmospheric impedance “ issues related to the fuel pump wiring during replacement.

Just a suggestion. It would not be the first time I have seen it happen.

 

[Chopperbuilder]

Just a suggestion. It would not be the first time I have seen it happen.

Re-read the first line in my original post.

 

[Chopperbuilder]

Hey all, went out today and tried to start it looking for tach movement and there was none. Per Jerry's advice, I got a new crank sensor and a cam sensor (in case). Installed the crank sensor and tried it again. It fired right up like something kicked it hard! it's fastest start I've seen in a while. Thanks for everyone's help on this, much appreciated!!

 

[TJonfire]

What CPS did you get?

 

[Chopperbuilder]

Local sourced from NAPA. Works great!