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Discussion Starter · #1 ·
97 tj 4.0

Here are the symptoms

:Takes 5 seconds of turning to get it to fire.
:If I push it hard in 1st and 2nd it starts to die
:If before I start it and turn the key to on them off then on then off it will start right up

I suspect its not keeping fuel pressure. I have no experience with jeeps so any input would help.
Maybe fuel pump is crapping out? I just want to be sure before I start to fix it.

I am capable of doing this kind of work. Just never tried it on a jeep.
 

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What you are describing is a problem with what I blieve is called the fuel anti-drainback valve. This is supposed to keep the pressure in the fuel system when the pump is off. You engine starts if you let the key sit for a few seconds because the pump turns on and resupplies the pressure to the engine. This is located on the top of the tank if I remember correctly, so you need to drop the tank to replace.
 

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What you are describing is a problem with what I blieve is called the fuel anti-drainback valve.
The fuel pump check valves rarely cause a problem. Leaking fuel pressure regulators are usually the cause of the hard start condition.

Solution: replace the fuel pressure regulator.
 

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yea mine does the same thing.. if i dont prime it 3-4 times before start it takes forever to start, and sputters a bit once i start moving, the FPR is on my to do list that never seems to end on my jeep
 

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where is the Fuel Pressure Regulator on a 97 2.5 TJ and is it hard to change
 

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The FPR is located on top of the gas tank, it physically sits on top of the fuel pump... you only need to drop the gas tank to change it. Once the tank is dropped, it only takes 2-3 minutes to swap the FPR itself which just snaps into place.

I'm holding a replacement FPR in the below pic, you can see the old one on the tank below.
 

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Discussion Starter · #8 ·
Alright thanks for the replies! So before I get a new regulator is there a way to do a pressure check to confirm it?
 

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Yes, your '97 4.0L has a Schraeder pressure test port on the fuel rail that the injectors are seated in. It's like an oversize tire stem valve with a big black plastic screw-off cap that covers it. After it has set overnight, unscrew the cap and after placing a towel underneath to catch any gasoline that may spray out, press the center pin like you'd let air out of a tire. If there is any remaining pressure, fuel will spray out. I doubt you'll see much more than a dribble. Once you get it started and running, stop the engine and try it again where it will squirt out from the 49 psi of pressure that is supposed to be maintained in the fuel rail for fast starts.
 

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tangofox007 said:
The fuel pump check valves rarely cause a problem. Leaking fuel pressure regulators are usually the cause of the hard start condition.

Solution: replace the fuel pressure regulator.
Oops sorry for the misleading info everyone! Still learning myself :) :hide:
 

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I had the slow start issue with my 1997 2.5. First I changed the screens in the fuel pump assembly. That fixed the cut-out around turns. Still had the slow start. Changed the fuel pressure regulator and that fixed the slow start. Seems to pull 5th a little better too.

I paid a little more for the Mahle regulator and got a part marked "made in USA". Lotsa luck on that one.
 

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I have the same issue on the same year 4.0, so the FPR it is! Does it make sense to replace the fuel pump while the tank is dropped, or do they rarely fail?
 

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glad I found this thread, thought I was going to have to replace my fuel pump. in fact, I already purchased one. I'll just file it back and get a FPR. got good fuel pressure, just have to prime the pump 2 or 3 times before start.
 

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glad I found this thread, thought I was going to have to replace my fuel pump. in fact, I already purchased one. I'll just file it back and get a FPR. got good fuel pressure, just have to prime the pump 2 or 3 times before start.
Because of the trouble to drop the tank, many do replace the entire fuel sending unit if their vehicle has high miles.
 

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Run the Jeep as low on gas as you dare. Carry a gallon in a gas can in case you run out. Use tie down straps to lower the tank. Unscrew the filler neck at the body and lower it all together.

The regulator change is easy. The screens are not easy, not at all. If you buy a pump assembly, buy the original Bosch.
 
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