fuel pump???

i have been having a starting problem with my 1998 cherokee 100xxx miles, no CEL. it takes two cranks to start from cold. if hot, it starts fine. I performed a fuel pressure test. when key was turned to on position, pressure read 8psi. when cranked the first time, it was at 45psi, but did not start. the second time the car started, the pressure stays at around 45psi while running, but when the car is turned off, the pressure reading falls costantly untl it hits 0. shouldnt it stay at 45psi? Does anydody have any ideas what could cause this? I think the fuel pump could be the culprit. any insight is appreciated. thanks

I think they have an inline check valve built into the fuel pump. Its probably leaking somewhat. Its a problem but won't bother normal operation.

the jeep also runs a little rough at idle, could this be due to this check valve? Can the check valce be replaced or can it obly be changed with the whole fuel pump assembly? I was thinking of changing the whole fuel pump assembly, as I thought that the long crank times would put wear and tear on some of the starting components, and it is a little embarrassing when your car doesnt start first time, and you are in public.

Could be a fuel issue, but at KOEO you should read about 32-35 psi, with engine running about the same. It sounds like your regulator might have gone bad, when the engine is running, disconnect the vac line to the regulator, fuel pressure should go up to about 40-45 psi. I'm would suspect your regulator first though. As far as the long crank, there are a couple things that could cause this. I have a similar problem on my 89 XJ using a niod light I found that I am not getting any signal to fire the injectors right away, as soon as they fire, it starts. Could be a CPS but not sure yet.

Fuel pressure spec is 47 to 51. It is a returnless system and has no regulator at the fuel rail. It has a combo filter/regulator mounted on top of the pump. Next time at start-up turn the key to run position and the back to off 2 to 3 time and it will probably fire up when you try to start it.

I'm having somewhat of a similar issue, though not as drastic, and hope you all could help. 96 Cherokee Sport, 4.0 V6 104,000.

If it sits overnight and I start it the next day it seems like it struggles slightly to fire up, and then the first 30 seconds or so while idling it seems as if its missing a little bit... once I pull out it runs fine. (possibly loosing fuel pressure when cold?)

However, if I make a short trip after its been running and start it back up, it starts with no issue at all. Also in this case (after running) it will occasionally lose power for a brief moment after traveling a few hundred feet, but then runs smoothly after that. I've also though fuel pump, or a component of it, so I thought I would post here.

Doesn't seem to be a huge concern.... yet, but I'd like to figure it out before it gets worse!

Thanks!

P.S. I tried the Lucas Fuel Additive to lube the fuel system, and it seems to help some... also helps mileage. For about 10 bucks for the big bottle (several tank treatments) I recommend everyone try it!

If you're losing pressure at key off, thats your problem. You will get air in the line that needs to clear as fuel pressure builds. There is a check valve in the pump, as well as a pulsator or hose connection in the tank, fuel regulators can leak into the vac port, or into the return line. You should have 47 psi either key on eng off, or at idle with vac disconnected. It should drop about 9psi when vac is reapplied. You can even have injector seeping when off. You'll have to block first the return line then the feed line to see where its going.

If this is the case (air in the line) and it seems to be... what are the possible solutions? Cost? Difficulty?

Also, how urgent is this issue?