Misses on start-up some times

sam53

TJ Enthusiast
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Nov 8, 2019
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sioux falls sd
I know this has been discussed before but cant find it. I have a 2001 with 4.0 auto. total off the frame restoration. When I did this (frame was totally rusted away to the point it nearly folded in two) anyway, to make a long story short, i replace the fuel pump at that time and has been about 3 years ago. here is the issue. sometimes when i start it it starts but seems like it is not getting enough fuel. If i depress the gas pedal, it always dies. So I turn the key back and forth to get the pump to reprime, most of the time it sarts and runs great. the other day, i had to restart 5 or 6 times to make it run. It does this maybe only every 1 in 10 times of starting and doesnt matter if it is hot or cold. any ideas folks. Thanks for reading this
 
Pressure regulator?
 
I had an issue with a leaky fuel injector that caused similar symptoms.
 
I know this has been discussed before but cant find it. I have a 2001 with 4.0 auto. total off the frame restoration. When I did this (frame was totally rusted away to the point it nearly folded in two) anyway, to make a long story short, i replace the fuel pump at that time and has been about 3 years ago. here is the issue. sometimes when i start it it starts but seems like it is not getting enough fuel. If i depress the gas pedal, it always dies. So I turn the key back and forth to get the pump to reprime, most of the time it sarts and runs great. the other day, i had to restart 5 or 6 times to make it run. It does this maybe only every 1 in 10 times of starting and doesnt matter if it is hot or cold. any ideas folks. Thanks for reading this
If this only happens after the Jeep has sat for a while it's likely the check valve inside the fuel pump. And no, not all fuel pumps last 3 years... especially store brand or cheap online brand fuel pumps. If it happens even after the engine has only been off a few minutes like for filling the gas tank it's likely to be a leaky check valve inside the fuel pressure regulator.
 
I'm sorry to say i can not remember what brand it was. It was not a five and dime piece of trash as i went into this restoration not giving two hoots about what it cost
 
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Thanks all for the replies!!!! The other day it happened at a fast food joint. The engine had been off for manybe 10 minutes. I tried to restart it several times. It then, maybe on the 6 try it started and ran fine, Since then it has not acted up. If it was you guys would you just replace the regulator to begin with?
 
I had an issue with a leaky fuel injector that caused similar symptoms.

wouldnt a leaky injector make it run poorly all the time. This engine runs very very well. I also have a 2003 Rubicon and this engine makes that look like trash
 
Thanks all for the replies!!!! The other day it happened at a fast food joint. The engine had been off for manybe 10 minutes. I tried to restart it several times. It then, maybe on the 6 try it started and ran fine, Since then it has not acted up. If it was you guys would you just replace the regulator to begin with?
That does sounds like a bad fuel pressure regulator. The good news is it's easily replaced once you get the gas tank dropped. The bad news is dropping the gas tank can be a PITA. Make sure it's near empty before starting the job too.

This is from when I replaced my FPR years ago...

FuelPressureRegulator1.jpg
 
Does the brand name make any difference in quality, if it does, please name the best one as that is what i will buy, again, THANKS ALL!!!!
 
wouldnt a leaky injector make it run poorly all the time. This engine runs very very well. I also have a 2003 Rubicon and this engine makes that look like trash

It was undetectable when running, but would drip and leak down after shutoff flooding that cylinder. After starting it would chug and miss until the flood condition cleared out. Replacing the faulty injector fixed it for me.