frantic29

I've been having a starting issue after abut 4 hours or so. Won't start first crank then good on the second. It's good after that until it sits again.

I have rented a pressure gauge and during running its right on 49. It bleeds down to 22 in about 30 minutes then slows but still bleeds into I'm assuming it gets down to teens or lower over a period of time. My question is what is acceptable limit of bleed down. I know it's not going to hold 49 at all times and I have read that a bleed down to 24lb is normal after about 5 although I'm not sure I believe that.

I'm letting it sit for 4 hours with the pressure gauge on now to see how low it gets. That way I have hard number. Next I guess I'd figure out whether I'm losing pressure at the pump or injectors.

frantic29

I went out after 1.5 hours and it was at 8lb. Pretty confident it gets to zero eventually.

holycaveman

You can bleed it completely out and one turn of the key switch and It should start.

holycaveman

Providing of course that your fuel pump is good.

s346k

mine does this. ever heard of the poor mans prime? I have to do it if the jeep sits over 20 minutes. it will start otherwise after raping the starter.

frantic29

Yes. Thats kind of what got me started down this road. It helps but I want to fix the issue. Definitely draining back to the tank. I put a clamp on the line between the tank and filter and that slowed the bleed down a ton. After an all night sit it only bled down to 25lb. Then when you turn the key it builds back to 40 immediately then starts right up.

I guess I need a new fuel pump because the drain back valve is bad. I have a 1996 is it just the pump that has the valve or do I need an entire assembly? I know I saw a post a while back where someone pulled and serviced the pump but now I can't find it and don't remember exactly what they did.

cruiser54

You have narrowed it down to your injectors not being the culprit at least.

Isn't 96 a "bastard" year as far as fuel systems?

holycaveman

If it's leaking through the injectors you will most likely run into a minor hydro lock situation or at least some smoking or rich acting when it fires up. You can also measure the pressure before the filter (in line test) to check the pump.

One injector stuck wide open and your motor will still immediately start up. So it would take a few to lose enough prime to make starting a concern. And again you would see signs of it.

Unfortunately compression would cause the same thing.

frantic29

Unfortunately yes it is a "bastard" year. I am really confused as to what I need. I know I have seen a detailed post about what to do from this point with a 96 but can't seem to currently find it. Not sure if it was here or on Jeepforum.com. it's been a few months and it was an accidental find anyway. I'll keep searching and see what I can come with.

cruiser54

IIRC, up to 96 had a return fuel line and later ones didn't.

Do you have a fuel return line?

cruiser54

Nah. The pressure leaks off slowly and evaporates while sitting.

Long crank time to build enough pressure for the injectors to squirt when triggered.

Ever read the FSM?

frantic29

Going to show my ignorance. I am honestly not sure. Still learning the system and I don't have/can't find a 96 fsm. Need to look up a diagram to see what's what. I know the regulator is in the tank as there is nothing in the line from the pump to the motor except the filter. I'm not exactly sure how the other years are set up but I'm hoping that maybe since mine was a very early 96 build that it got a 95 fuel pump. Not holding my breath but stranger things have happened. When I get home from work I'll figure it out and let you know.

cruiser54

Post up your vehicle's production date.

holycaveman

Not my experience. I can bleed off everything including filter and still fire up first crank.

The fuel pump if working correctly should prime any dry area.

Cycle the ignition switch if you have any doubts prior to cranking.

A bad cam sensor can cause the injectors to not fire up immediately.

cruiser54

Let's see a video of that. No ignition cycling first though.

Makes ya wonder why they use check valves if that's the case, and why there's the "poor man's prime". Your magic powers must make the difference I suppose. In all my years of working on XJs, only 30 years, I've never experienced an instant start on a system with no pressure.