Fuel Pressure Still Leaking Down

[Klaatu55]

On my 1999 Cherokee, the fuel pressure drops from 50 to 20 immediately upon key off,then zeros out very soon after. Has Permanent fuel pressure gauge. Pressure fine when engine is running. Pump has been changed twice. What would be the next part that might leak. I'm thinking I only have to be concerned with the components between the pump outlet and the fuel injectors.Has anyone had this problem. there is a short piece of hose with two female quick connects on top of the gas tank. Has anyone had any problem with that. Do fuel injectors leak pressure?
2. As an aside when i changed the fuel pump something has happen to slow up fill ups at gas station. pressure relief vent appears to be blocked. lever on gas station pump keeps shutting down. Any thoughts would be appreciated.

[OldFaurt]

On my 1999 Cherokee, the fuel pressure drops from 50 to 20 immediately upon key off,then zeros out very soon after. Has Permanent fuel pressure gauge. Pressure fine when engine is running. Pump has been changed twice. What would be the next part that might leak. I'm thinking I only have to be concerned with the components between the pump outlet and the fuel injectors.Has anyone had this problem. there is a short piece of hose with two female quick connects on top of the gas tank. Has anyone had any problem with that. Do fuel injectors leak pressure?
2. As an aside when i changed the fuel pump something has happen to slow up fill ups at gas station. pressure relief vent appears to be blocked. lever on gas station pump keeps shutting down. Any thoughts would be appreciated.

I had some issues with leak-down and it was my injectors.
I made an adapter wit vacuum fitting and used a can of
spray sea foam to back flush them.
I used a 9 volt battery to energise them.
at first they pissed in just about every direction possible,
after a few blasts, after you energized, they all shot straight.
Also clean the input side filter on the injectors.
use a toothpick so you don't damage them.
Most Auto parts stores carry the o-rings CHEEP,
DO NOT reinstall old ones unless you're desperate.

My 92 started and ran much better after the refresh and I gained 2-3 MPG.

Hope that helps!

[Klaatu55]

Changed injectors today, http://www.xjtalk.com/images/icons/icon9.png no joy pressure still drops immediately after shutdown. new fuel pump ,Guess i need to check the line near the gas tank. I have the permanent fuel pressure gauge mod on test port. any new suggestions will be appreciated.

[Mudderoy]

Changed injectors today, http://www.xjtalk.com/images/icons/icon9.png no joy pressure still drops immediately after shutdown. new fuel pump ,Guess i need to check the line near the gas tank. I have the permanent fuel pressure gauge mod on test port. any new suggestions will be appreciated.

Did you replace the entire assembly in the tank? Pickup, fuel pump, and pressure regulator?

https://www.amazon.com/Bosch-67658-Original-Equipment-Replacement/dp/B001C6023G/ref=sr_1_3?s=automotive&ie=UTF8&qid=1465629298&vehicle=1999-42-347-141----8-3330-242-8-2--14-2-0&sr=1-3&ymm=1999%3Ajeep%3Acherokee&keywords=fuel+pump

[Klaatu55]

Yes, fuel pump Bosch all one unit. after i changed, gas fill ups got sketchy, keep shutting pump off.
Today first use after injector change. 1 hour into use, car starts trying to stall and there are fine bubbles in the permanent fuel pressure gauge. Parking it to check, after rain.Maybe there is air in the line, gonna check and see what code got thrown.

[Klaatu55]

Uninstalled permanent fuel pressure gauge. stalling problem stopped. Think Teflon tape was problem. Will try again when i get the leak down problem solved.

About fuel not going into tank without shutting off pump. When I installed new fuel pump I rinsed gas tank out,

1. Is there a valve or something inside of tank that could have gotten jammed shut.
2. Where does that other large hose running from tank in the direction of gas filler go.( It would appear to be a pressure release hose.)
3. From drivers side to passenger side where do those three small lines from the eva. cannister go. I've found some references to all of these questions but they appear to be for other year cars or maybe I'm just not visualizing them correctly. Any thoughts would be appreciated. Thanks

[4.3LXJ]

I am getting confused here on your lines. You should have only one line to the fuel rail. The pressure, backflow valve, pressure bypass are all part of the fuel tank sending unit. If you have another line, that would be for earlier fuel rails

[Klaatu55]

These hoses come from the gas tank.These lines (hoses) are concerning question #2. I thought one of these is the gas filler hose and one is the vent hose?

[4.3LXJ]

That is correct

[Klaatu55]

Thank You,Now my understanding is: The gasoline comes in one hose and the displaced air exits through the other hose. When I changed my fuel pump I also rinsed out my gas tank, by sloshing gas back and forth and dumping it. out several times. Is there a valve or something inside the tank that may have gotten stuck or damaged by this action. Iim also not understanding why or how the evac system affects filling the tank,if the displaced air comes out of the big hose. Exhaust hose seems too be almost the same size as the fuel inlet hose.Unless the hose has some type of anti backflow valve that is stuck closed?

[4.3LXJ]

That breather hose is designed to have fuel come up it when you are filling it and activate the automatic shut off on the pump nozzle when the tank is full, but not so full that there is no air in the top to allow for expansion etc.

[Klaatu55]

Well,ts shutting off pump nozzle,several times per gallon. Ive read articles that say the emmison vapor recovery system. also has some impact on intermittent fueling. The articles make it sound like the only vent is one of the smaller lines from the gas tank to the vapor holding cannister. But tI dont fully understand that system yet.

[4.3LXJ]

Have you checked both hoses for kinks etc?

[Klaatu55]

If it's not raining this morning I'm going to drop the gas tank again,Maybe a piece of gasket or something got lodged into one of the small lines.

[Klaatu55]

I need something like this for my "99 sport. I'm not sure which jeep this is from.

[Klaatu55]

Good Information:http://ka3tfh.com/JeepInfo/XJ/3503856-Jeep-XJ-2000-25-Emission-Control-Systems.pdf

[Klaatu55]

Good Information: Thanks to NiteDog -Cherokee Talk
http://ka3tfh.com/JeepInfo/XJ/3503856-Jeep-XJ-2000-25-Emission-Control-Systems.pdf

[Klaatu55]

Are there any components between the fuel pressure regulator (part of the fuel pump) and the fuel injectors, other then the continuous fuel line, that could provide an immediate pressure leak. Injectors and gaskets,fuel pump new.I had the permanent pressure gauge mod connected to the test port on the fuel rail but have removed it. Must long crank after only 1 minute off. Jeep runs good otherwise. It is throwing a code for large evap leak, but my understanding is that' that is an unrelated system. on the other side of the pressure regulator/check valve. For that to cause the fuel pressure to drop so fast wouldn't the new fuel check valve have to be defective too. When pressure gauge was connected fuel pressure went up to 50 with key on ,engine off . once engine started pressure gauge needle gyrated wildly but car never missed a beat. I will test evap system but first wanted to correct pressure problem in fuel system. or could they be related.

[4.3LXJ]

You say you replaced the check valve, but did you do it piecemeal or did you replace the whole sending unit?

[Klaatu55]

I replaced the entire pump assembly.(pump,regulator,check valve,float,potentiometer) First with an Airtex, than later a Bosch. I thought the Airtex was defective,apparently it was not.

[4.3LXJ]

If you are not smelling gas anywhere, then I really don't know. I think this is one of those where I would need to be there to make the call

[Klaatu55]

Thanks, When I figure it out i will report back.

[Klaatu55]

I took the gas tank down, and with a funnel I poured gas down the gas line,(the one with the click fitting) The gas went into the gas tank ,Isn't the anti-back flow suppose to prevent this. Is it possible this is why I'm getting the long start.This pump is the new one.