My 1997 XJ 4.0 starts losing fuel pressure slowly after its been turned off. What can cause this? Overall it starts fine and runs but it idles low.

 

The fuel pressure falling is normal.

 

Your oil pressure will lower when hot you have mechanical fuel pump that runs by engine so more throttle more pressure less throttle less pressure
Hello from a 4th gen Alaskan and jeep driver my great gramps drove a old military jeep up hear in 1940's.

 

First off he has an electric fuel pump, as far as I know all Cherokee's have electric pumps.

 

Engine at idle 49.2 ±5 psi
Fuel Pressure Drop (pump not engaged) Not fall below 30 psi for 5 minutes

 

My xj has a mechanical fuel pump found out when friend left on steep hill in third rolled down hill and flooded it

 

I honestly don't think you know what you are talking about.

 

If you take a look at jeep Cherokee haynes repair manual you will see some Cherokees do have an mechanical pump believe me it sounds like you dont know as much as you think you do

 

Well the pressure is in spec at idle but after 5 minutes it gradually goes down to nearly no pressure

 

I would say you have a bad regulator/filter. Replace the fuel pump assembly.

 

Go buy a jeep Cherokee haynes repair manual has it all

 

Well, you need to learn to read.

He has a 97 xj it has an electric fuel pump

 

It says on the V6 models, the 4.0 is not a V6. Jeep used a Chevy 2.8 V6 back in the 80s for a year or 2 that did have a mechanical pump. The 4.0 never did. Before you read your book could you take a picture of your mechanical fuel pump and post it.

 

Easy buddy I just happen to be a certified mechanic what are you a
librarian

 

Enough is enough you might be rite but I will tell you my jeep has a mechanical fuel pump