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How to check fuel pressure on a 03 and later 4.0

Mike_H

Rust Belt Heavyweight
Supporting Member
Feb 28, 2017
4,436
Grand Rapids, MI, United States
I'm having trouble starting my jeep, well, its been since I bought it. My suspicion has always been the fuel pump. I'm a cheap-skate though so I tried replacing the Filter thing at the top, because I heard that it was the anti-siphon valve. That didn't work so I've just been dealing with it. Lately however, its getting harder to start and its been running pretty rough when cold. I figured I had better deal with it.

First off...Whatever bean-counter at Chrysler decided to get rid of the Schrader Valve...eff you. I hope the $0.30 off each Fuel rail was worth it. I'm not bitter...

So...How did I do it?
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I started with a Fuel Pressure Gage Kit from Harbor Freight. 20 bucks, and it included that nifty "tee" fitting that makes the whole thing possible.
91S6oMKwL7wBSADFJWgMW9Lg41bjKZBirzX7XE7WamBGHhjBXyPyHY5cMhfIjfg1Wvx_zZZJIMbHv5pF4Z=w1129-h635-no.jpg


Then I bought some QD fittings at the local auto parts store. Dorman stuff in a blister pack...
20180701_101240.jpg


It actually came with two barbs and two sockets, so I can make another, if I wanted. Finally, I bought 3 feet of fuel line. I got the Fuel Injection Specified stuff...OUCH. 5 bucks a foot! Not sure I needed it, but they wouldn't take it back after it was cut.

Anyway, assemble the "tee" in the middle, press the socket side on one end of your adapter, and clamp appropriately. On the other side (the one with the barb), I cut about a 4" long piece of tubing, and used my flare kit to form a small barb on the cut end. Gave me something to clamp and prevent leaks.

Assemble the barb end to the Factory Socket and snap your new socket to the fuel rail. Viola!


As you can see, I have a MAJOR leakdown problem in my fuel system. As soon as that pump shuts off, the pressure drops, like NOW. New one is on order!
 

Chris

Administrator
Staff Member
Sep 28, 2015
38,127
Salem, Oregon
Awesome write-up! I was so disappointed on my 05 that I didn’t have the Schrader valve like TJ earlier TJs did. I decided to swap out my fuel rail for one from a 02 TJ that has the Schrader valve on it.

I figured it would make life easier going forward. Much like you said, I curse the guy whose decision it was to save an extra 30 cents by ditching the Schrader on the later models.
 
OP
Mike_H

Mike_H

Rust Belt Heavyweight
Supporting Member
Feb 28, 2017
4,436
Grand Rapids, MI, United States
Awesome write-up! I was so disappointed on my 05 that I didn’t have the Schrader valve like TJ earlier TJs did. I decided to swap out my fuel rail for one from a 02 TJ that has the Schrader valve on it.

I figured it would make life easier going forward. Much like you said, I curse the guy whose decision it was to save an extra 30 cents by ditching the Schrader on the later models.
I may still go down that route...I have a buddy parting a 94 YJ with a fuel injected 4.0L. I asked him to check if it has the Schrader. I'll just swap him at that point.
 

Chris

Administrator
Staff Member
Sep 28, 2015
38,127
Salem, Oregon
I may still go down that route...I have a buddy parting a 94 YJ with a fuel injected 4.0L. I asked him to check if it has the Schrader. I'll just swap him at that point.
What I found in my search was that even some of the 2002 models didn't have the Schrader valve. Some did, others didn't. It appears that they phased it out sometime in 2002, but likely used whatever NOS they had just to get rid of them.

That valve certainly makes things easier, that's for sure.
 

KDUB

New Member
Jun 12, 2019
1
Santa Cruz
I'm having trouble starting my jeep, well, its been since I bought it. My suspicion has always been the fuel pump. I'm a cheap-skate though so I tried replacing the Filter thing at the top, because I heard that it was the anti-siphon valve. That didn't work so I've just been dealing with it. Lately however, its getting harder to start and its been running pretty rough when cold. I figured I had better deal with it.

First off...Whatever bean-counter at Chrysler decided to get rid of the Schrader Valve...eff you. I hope the $0.30 off each Fuel rail was worth it. I'm not bitter...

So...How did I do it?View attachment 46103

I started with a Fuel Pressure Gage Kit from Harbor Freight. 20 bucks, and it included that nifty "tee" fitting that makes the whole thing possible.
View attachment 46104

Then I bought some QD fittings at the local auto parts store. Dorman stuff in a blister pack...
View attachment 46102

It actually came with two barbs and two sockets, so I can make another, if I wanted. Finally, I bought 3 feet of fuel line. I got the Fuel Injection Specified stuff...OUCH. 5 bucks a foot! Not sure I needed it, but they wouldn't take it back after it was cut.

Anyway, assemble the "tee" in the middle, press the socket side on one end of your adapter, and clamp appropriately. On the other side (the one with the barb), I cut about a 4" long piece of tubing, and used my flare kit to form a small barb on the cut end. Gave me something to clamp and prevent leaks.

Assemble the barb end to the Factory Socket and snap your new socket to the fuel rail. Viola!


As you can see, I have a MAJOR leakdown problem in my fuel system. As soon as that pump shuts off, the pressure drops, like NOW. New one is on order!
Sorry for the ignorance, but a new what is on order? A new fuel pump? Rail or? Did the pump fix your issue?
 

Chris

Administrator
Staff Member
Sep 28, 2015
38,127
Salem, Oregon
Somehow I missed this how-to guide, but it's a good one.

What I did on my 05 to make life easier was to get a fuel rail from an earlier 2000 TJ with the Schrader valve (you can even get one from a 4.0 equipped Grand Cherokee). It bolts right on, and then you have that wonderful Schrader valve again, which makes life so much easier when you need to do something like this.

All-in-all, it cost me round $40 for the fuel rail plus the time to install it, which wasn't much.