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Jeep Wont start on first crank???

2K views 11 replies 9 participants last post by  Bayou 
#1 ·
i have a 01 TJ and haven't been having any issues with it starting until about 4 days ago here is what its doing
Put the key in go to start it and it just cranks over i dont just keep cranking it i just do it for about half a second then wait about 3 seconds and crank it again and it fires right up and once its running if i turn the jeep off and start it back up within 15 min or so it starts right back up but if left setting for about 30 min or longer i haft to crank it and re crank it and fires up any ideas what it could be? Fule pump, o2 sensor, bad starter, plugs i dont want to just start replacing parts when it could be just about anything
 
#2 ·
Sounds like you are losing fuel pressure in the rail as it sits.

The most likely cause is the fuel pump anti-drain back valve has failed. If that is it, replace the pump with a quality unit.

It's also possibly (although less likely and less common) that you have an injector leaking fuel slowly into the cylinder as it sits. But you would most likely notice it being rich and coughing a small puff of black smoke upon start up if that were it.

Try turning the key to run for 5 seconds or so and then all the way back off five times or so before you try to start it after the next time it sits for a while. If you are losing pressure in the line while sitting, this will build pressure back up by priming the pump several times (which automatically happens for a few seconds each time you turn the key from off to run) before you try to start it.
 
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#4 ·
I agree 100% with noturmailman. An O2 sensor wouldn't keep the Jeep from starting, the starter is more than likely fine if it's still turning over, and plugs nowadays almost never fail. Even if one or even 2 plugs failed (or a coil), your engine could probably still start (assuming you have the 4.0), but would run rough. It definitely sounds like you're having trouble with initial fuel pressure because it sounds like it's running fine once it's started and you're having no problem cranking.
 
#5 ·
You can get a fuel pressure test kit from places like Autozone to verify your pressure. The spec is 49 +/- 2 psi.
 
#7 ·
If you decide to test the fuel pressure there is a very good diagnostics section in the FSM that walks you through the procedure. A few things to look for...

1 - The fuel system should charge to spec pressure after turning the key to the on position (without starting).
2 - The fuel system should remain charged, not leak back, for an extended period of time.
3 - The fuel system should remain at spec pressure after the engine is started, regardless of what RPM the engine is at, and not fluctuate beyond spec range. Check both at idle and upwards of 2200 or so RPM.

Volume should also be checked, especially if you see no issue with pressure. If pressure is good volume could still be an issue. The FSM specifies how much fuel should be pumped for a given period of time.

Good luck. :cheers2:
 
#8 ·
My sister and Bro-in-Law just bought a 2002 TJ with the 2.5 this past weekend. The exact same thing as the OP described is happening to them when they try and start it. Thanks for the advice guys. Any leads on what a good replacement fuel pump would be? The Mopar unit is over 500 bucks. There are Crown and OMIX-ADA units for about half that. Is this what one should expect to pay for a decent fuel pump?
 
#9 ·
The only one I and most everyone else here will recommend is Bosch. Store brands like from Autozone and online brands like Airtex and Spectre are crap. The Bosch holds up and is what I installed years ago. Most believe Bosch was the OE manufacturer of the factory fuel pump.

For their 2002 SE, I'd go for the Bosch which includes a new fuel pressure regulator & fuel filter at https://en.wikipedia.org/wiki/Magnuson–Moss_Warranty_Act
 
#11 ·
Does it start right back up if you turn it off and it only sits for a few minutes?

Does priming it like outlined above in post #2 alleviate the issue?

If so, it is likely the drain back valve in the pump, which means you need a new pump.

Best way to verify that is with a pressure tester and see if it loses pressure when sitting. If so, it's a pretty good bet you need a pump. Although it could still be a leaky injector, but that is less likely as that will usually cause drive-ability issues.
 
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