2003 Jeep TJ turning over but no ignition

TheCanadianSahara

TheCanadianSahara

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Joined
Apr 2, 2022
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Location
Ontario, Canada
This morning I drove my 03 TJ to and from my school (about 30 km’s) with zero issues, fired up right away as usual. However not even an hour later I went back out to run errands and despite turning over, she wouldn’t start. I’ve had this Tj for about a year now without any ignition issues once or ever.

This is my first vehicle so any advice or potential causes would be greatly appreciated. I’ve included a video showing what happens upon key turn.

Oil level looks ok, changed it about 8 months / 5,000 kilometres ago. I did notice slight corrosion buildup on the positive battery terminal, as well as some oil on the bottom of my front differential. Fuses look ok. Has anyone encountered and solved this issue? Thank you very much. Potentially important to note the previous 3 days have been roughly -25c while today is 3c.
 

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Do you here your fuel pump priming when you turn your key forward 1 click?
Probably not your issue, but I ran into this same thing a couple months ago, my plug on top of the fuel tank had come undone, guess we didnt get it clicked back in last time the tank was dropped.
 
It's a good idea to check for codes, this sort of thing is often a crank or cam position sensor. Assuming you have no codes, fuel relay is pretty much always my first actual check. Put your finger on the relay, have somebody turn the key ON (don't try to start it) and feel for the click. It always a good idea to check fuses after that, and then check for fuel pressure (rent a gauge from the parts store) & spark (google for how to test your spark, I don't have a preferred method).

It takes 3 things: fuel, air, and spark. Air is probably not the problem, and fuel is easy to test for, and the possible causes are relatively few. Spark is the hard one, because while testing it isn't that hard, the computer controls it from about 15 different places. But lets zero in on which pillar is the problem.
 
hear said:
It's a good idea to check for codes, this sort of thing is often a crank or cam position sensor. Assuming you have no codes, fuel relay is pretty much always my first actual check. Put your finger on the relay, have somebody turn the key ON (don't try to start it) and feel for the click. It always a good idea to check fuses after that, and then check for fuel pressure (rent a gauge from the parts store) & spark (google for how to test your spark, I don't have a preferred method).

It takes 3 things: fuel, air, and spark. Air is probably not the problem, and fuel is easy to test for, and the possible causes are relatively few. Spark is the hard one, because while testing it isn't that hard, the computer controls it from about 15 different places. But lets zero in on which pillar is the problem.
Click to expand...

I don't think its the fuel pump, I can hear the pump priming when I turn the key 1 click and when giving it some gas while cranking can smell the fuel outside the vehicle. When it was running this morning I had a check engine for small evap however when trying to turn over the check engine light flashes for a second and then stays off. The key turn trick to get the onboard computer to throw a code also does not display the evap code but I know the problem is still there. Later today I am going to attempt to remove and clean my throttle body / IAC and will update from there.
 
TheCanadianSahara said:
I don't think its the fuel pump, I can hear the pump priming when I turn the key 1 click and when giving it some gas while cranking can smell the fuel outside the vehicle. When it was running this morning I had a check engine for small evap however when trying to turn over the check engine light flashes for a second and then stays off. The key turn trick to get the onboard computer to throw a code also does not display the evap code but I know the problem is still there. Later today I am going to attempt to remove and clean my throttle body / IAC and will update from there.
Click to expand...

If you hear the fuel pump kick on then you've definitely narrowed things down. It's still worth it to check the pressure but odds are it's on the spark side of the equation. I don't have a good process for what to check or how to check it, but I think starting from the end and working backward makes sense. Determine if you even have spark.

In my experience the IAC being dirty will just cause it to stumble at idle especially at startup. If the IAC is faulty in just the right way, it can probably affect the computer.
 
Just a small update for anyone who may stumble across this thread with a similar problem, a bottle of fuel injector cleaner in the gas tank and a thorough cleaning of the throttle body + IAC fixed my issue for about a month. My IAC was caked black! definitely had never been cleaned before. After about a month of being fine I tried it again this morning and back to step 1, where the engine will run solid while I give it gas but the second my foot comes off it dies. I'm honestly at a loss of what to do next. Gonna order new spark plugs and see if that helps. If anyone has been in a similar situation id appreciate it
 
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Your IAC is sticking closed, so that when you give it some gas it finally gets some air and will run.

It's either dirty again, or could be a bad IAC.
 
JKP said:
Your IAC is sticking closed, so that when you give it some gas it finally gets some air and will run.

It's either dirty again, or could be a bad IAC.
Click to expand...

Interesting, I'll pick up a can of throttle body cleaner and see how that does. Interestingly, both times I've had this issue it's been after heavy snow or, in todays case, heavy rain. Do you think moisture along the ignition wires or something along those lines could be exacerbating the issue? Thanks a lot!
 
The cold is probably making the crud on the IAC stickier.

As long as it runs fine other than it won't idle without cracking the throttle blade open, it's the IAC not opening up to let enough air through.
 
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