How to check fuel pressure on a 2003 and later 4.0

Mike_H

autos are better - WRWD508
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Location
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.

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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!
 
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.
 
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.
 
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.
 
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?
 
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.
 
I have a 2003 TJ 4.0. I replaced my original fuel pump (Mopar) with one made by Precision. I wasn't having the long crank starting problem with the old pump. The starting problem began approximately 2-3 months after the Precision fuel pump assembly was installed. Since I had a new fuel pump assembly, I assumed that the long crank starting issue couldn't be related to the pump/fuel pressure regulator. So...I have installed new fuel injectors, spark plugs (Champion), and a crankshaft position sensor. However, the long crank starting problem still exists. This morning I bought a Delphi fuel pump assembly (based on recommendations I've read on the forum). I'm assuming that the Precision fuel pump assembly is just poor quality and not providing the proper fuel pressure. Yes...the fuel rail on my TJ doesn't have the Schraeder valve either, and I would also like to strangle the guy who made that silly decision!!!

Have any of you had problems with a Precision fuel pump assembly? If the Delphi fuel pump assembly doesn't resolve the problem, I'm guessing it's the computer. What else could it be?!?! This is driving me insane!!!
 
Hi Mike,
Great idea! I purchased the materials and must be having another senior moment. Would you happen to have a photo of the gauge connection to the fuel line (incoming) and the fuel rail?

A picture is worth many words as we all know but I’ll be more than happy to take the words on you don’t have a pic.
 
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!
 
Hi Mike,
Great idea! I purchased the materials and must be having another senior moment. Would you happen to have a photo of the gauge connection to the fuel line (incoming) and the fuel rail?

A picture is worth many words as we all know but I’ll be more than happy to take the words on you don’t have a pic.
Not sure I follow what you're looking for? Are you looking for how I connected the gage to the fuel line, or the fuel line to the dorman fittings?
 
Not sure I follow what you're looking for? Are you looking for how I connected the gage to the fuel line, or the fuel line to the dorman fittings?
Thanks for the reply. I can see what I need in at the bottom of the picture with the gauge.
Did you have any problem with the metal fuel line piece leaking at the stock connector?