TJ cranks but won't start

N

Nate 2002 TJ

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Joined
Nov 30, 2022
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Location
Nebraksa, USA
I have looked around a few times now and haven't found a thread on this but if there is one please point me to it. I have a 2002 TJ Sport with 4.0L engine and automatic transmission.

I went out to start my Jeep this morning as usual. It was cold (15 degrees) so I pumped the gas pedal 3 times before turning the key. Normally it takes a few seconds of it just cranking before it fires up and runs. If I turn the key back and try again it starts up right away usually or if I leave it turned it starts after a few seconds. However if I turn the key back at the same time it is going to start up the engine dies and when I try to start it again it only cranks and doesn't start. This is the 3rd time this has happened to me.

The first I checked the spark plugs and cleaned them a little even though they were pretty clean and it started after that.

The 2nd time I tried replacing the ignition coils after getting a bad reading from them but the new ones gave the same reading (I forget exactly what the reading was but I got it from the Hayne's Jeep Manual). It started up with the new coils but I put the old ones back in to test them and it also started with those (i ended up putting the new ones back in after that). It happened again and I am stumped as to what it can be.

I have tested my fuel pressure and that is fine and made sure my choke is working. Like I said this only happens when it is both cold and I turn the key back when it is about to start. I know that if I just leave the key turned it will start but the sound of it cranking and not starting at first still causes me to pull the key back sometimes and try again. If anyone has any suggestions as to what could be causing this I would greatly appreciate them.
 
First, the TJ is fuel injected and thus has no choke. Pumping the gas pedal in a fuel injected vehicle does not pump gas, it only opens the butterfly valve to let more air into the throttle body. Like opening and closing a window. Your problem is a leaky check valve inside the fuel pump which is not separately replaceable.

The check valve is there to prevent fuel from draining out of the fuel rail and fuel injectors and back into the gas tank. When it leaks and let all the fuel drain out to the gas tank, it takes several seconds of cranking to give the fuel pump more time to get fuel back up to the fuel injectors via their fuel rail.

The fix it to replace the fuel pump since its check valve is not separately replaceable. There aren't many good brands of aftermarket fuel pumps, most are pure junk. Especially store brands like Duralast from Autozone or online brands like Spectre and Airtex. Bosch is the OEM brand but they are not pretty much impossible to find, I'd probably go for a Carter or US Motor works from a site like https://www.rockauto.com/en/catalog...fuel+&+air,fuel+pump+&+housing+assembly,10147

In the mean time turn your key on-off-on (not Start) 5-8 times, pausing in the On position for 2 seconds each time. That will give the fuel pump extra time to refill the fuel line and fuel injectors, THEN start the engine.
 
Thank you for the correction about the choke. The butterfly valve is what I had previously checked*. I tried the on-off-on with no luck and tried it again just to make sure and still with no luck. I will look into the fuel pump however and let you know
 
Jerry Bransford said:
First, the TJ is fuel injected and thus has no choke. Pumping the gas pedal in a fuel injected vehicle does not pump gas, it only opens the butterfly valve to let more air into the throttle body. Like opening and closing a window. Your problem is a leaky check valve inside the fuel pump which is not separately replaceable.

The check valve is there to prevent fuel from draining out of the fuel rail and fuel injectors and back into the gas tank. When it leaks and let all the fuel drain out to the gas tank, it takes several seconds of cranking to give the fuel pump more time to get fuel back up to the fuel injectors via their fuel rail.

The fix it to replace the fuel pump since its check valve is not separately replaceable. There aren't many good brands of aftermarket fuel pumps, most are pure junk. Especially store brands like Duralast from Autozone or online brands like Spectre and Airtex. Bosch is the OEM brand but they are not pretty much impossible to find, I'd probably go for a Carter or US Motor works from a site like https://www.rockauto.com/en/catalog...fuel+&+air,fuel+pump+&+housing+assembly,10147

In the mean time turn your key on-off-on (not Start) 5-8 times, pausing in the On position for 2 seconds each time. That will give the fuel pump extra time to refill the fuel line and fuel injectors, THEN start the engine.
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Question. I previously tested the fuel pressure via the fuel line. Would these readings reflect whether or not the sensor has gone bad? If not is there a way to test the sensor other than buying a new fuel pump and seeing if the new one works?
 
When you tested the fuel pressure what reading did you get? I’m assuming you mean regulator and not sensor? The regulator has a check valve that keeps the pressure in the line after you shut the motor off. Cycling the key builds the pressure back up.
 
Update. I went out today to start it and had the same trouble as before. It would crank but not start. I pressed on the accelerator while the engine was cranking to give it fuel which would cause it to rev up an increase RPM's but when I would let off it would choke down and die. I did it again but depressed the accelerator for longer until the engine had warmed up some then tried starting it again. It worked this time with no problem. Not for sure what exactly it was because it has started on much colder days, but it seems I have a fix now and just wanted to put this out here for anybody else who may run into this problem. Thank you guys again for your advice and help.
 
That sounds like the IAC to me. There’s a process here for how to clean it. My 97 will very rarely do the same thing. I have to feather the gas to get it started & stay running, but after a minute or so it’s fine again.
 
hear said:
That sounds like the IAC to me. There’s a process here for how to clean it. My 97 will very rarely do the same thing. I have to feather the gas to get it started & stay running, but after a minute or so it’s fine again.
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could be I have had the same trouble on my 04
 
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