2001 4.0 fuel no-start issue

[crazyaj12345]

Good afternoon everyone. I have a curveball that even I cannot wrap my head around. Im a certified powersport mechanic and ive been battling this issue for about 3 months now and im sick of it. Its killing my passion for driving the jeep. Anyways, Ive replaced my fuel pump assembly from delphi almost a dozen times the past 3 years. I was sick of the check valve going out, so i installed a Boche pump into the assembly, and replaced all of the shit nylon fuel lines with braided and upgraded lines. (Pump to hard line, and hard line to the rail). Reason for this is because i installed an in line check valve between the pump and the hardline in the rear. My stock fuel rail started to leak gas from the fuel damper due to pressure, so i replaced the rail with an aluminum billet aftermarket rail. It drove fine and when i would leave it over night i would have a blown injector O ring waiting for me when i leave for work in the morning. To solve this, i put 2 sets of O rings where the injector would seat in the fuel rail. My reasoning for this is the injector would slide back and fourth in and out from the rail and the intake. In total there are 18 O rings ONLY where the injectors meet the rail. This solved my problem for O rings blowing out, for now. With just my luck, i still have hard starts in the morning sometimes, and always if i turn it off when hot if i get gas, or whatnot. Here's the kicker, if i ever have a problem with the no start even after cycling the key, all I have to do it press the Schrader valve on the rail for not even a split second, turn the key, and it fires straight up. I have rail and injector reflective material, and i have COMPLETLY ruled out a fuel leak. Pressure is where it should be, but im on my last leg with crossing my fingers to hope it starts in the morning to go to work. Im most confused about how pressing the Schrader valve for not even a split second could make that big of a difference. Thanks for everyones input and hopefully i can get to the bottom of this POS.

 

[macleanflood]

Sounds like you have too much fuel pressure. How confident are you of the accuracy of your gauge? Are you monitoring fuel pressure through startup and shutdown?

I added a Racetronix 5/16" QD to 1/8" adapter to the side of my oem fuel rail so I'd retain my 97 shraeder valve and have an on rail gauge.

I'd also suspect the quality of that aftermarket fuel rail...might want to check the inner diameter of the injector hole.

For what it's worth I rebuilt my pump assembly with a Bosch pump from Amazon via Brazil and it lasted two weeks.

I hear most of the Delphi issues are bad connectors and wiring.

I put a Rock Auto sourced Brute Power fuel pump assembly on my 97 almost 3 years ago. It's been on road trips to Canada, down to Moab and on the Rubicon Trail twice (all places I didn't do kind things to it... smashing the bottom of the fuel tank skid.)

Also consider a DEI fuel rail heat shield kit.

-Mac

 

[crazyaj12345]

Thanks for the reply Mac. Used a buddy’s gauge. Same type as mine and reading the exact same. While driving, under a good amount of gas will drop to low 30s. Sure as hell, when shut off pressure drops near instantly. Even with a check valve. This is so frustrating. Even with 3 o rings. I’m lost here.

 

[crazyaj12345]

The inner diameter of the new rail is significantly smaller than the OEM one, but I got the aftermarket to stay clear of the fuel damper as i mentioned before.