My 2000 XJ...well my sons XJ now. He says that sometime when leaving work it takes it a while to crank. He said motor spins but does not fire up . Strange thing is he said its ONLY when he leaves work but I think that's just coincidental. I haven't had time to look at it but figure either fuel pump as most likely its the original or coil rail also original. I know a couple weeks back I scanned it for codes and had one pending for misfire cylinder 3. I got viper coil kit coming anyway as it was ordered before he told me this. I thought when the coils acts up usually its when its running...hot. I know his tank is full and wondering can our tanks be siphoned in case it is the pump? Motor has 140k, 12 hole rebuilt injectors, plugs was replaced about 7k miles ago.

 

It sounds like a bad fuel pump check valve. Fuel pressure is slowly leaking out while it sits, making it harder to start as there no fuel in the rail ready to go - hence why it does it when he leaves work - it's been sitting for hours.

You can test this by priming the fuel pump the next time it's cold. Just turn the key to the RUN position (don't start it), listen for the pump, repeat. Do this about 3-5 times and see if it fires much faster when cold. If so - it's probably the check valve. The best way to fix that is to replace the pump module.

You can drive the Jeep around with the gas in it to lessen the load when you drop the tank - there's no real easy way to siphon the late model ones.

I left my Jeep idle on jack stands for a year with gas that was at the time of the "hibernation," already a year old. I just got some help to drop the tank with that much gas in it (about 10 gallons) and pumped it out from the fuel pump module opening.

 

Just checked the pressure looks good when running 46-48 psi (think I read somewhere as long as over 42 its good) If I just go to run it goes up to 48 and settles around 44. loses about 1 psi a minute until it gets around 10 psi...So looks like its check valve but doesn't appear to be that bad. Guess I'll drive it myself to get it low in the tank so kind of a win for me!. Strange thing is it sat for 10 hours and cranked right up with me...always has.

oops! I see Pressure should not fall below 30 psi for five minutes...guess I'll go back and time it for 5 mins to be sure. NOW I'm wondering since I had a pending miss fire on cylinder 3 if that injector could also be leaking? But today I scanned it and no stored or pending codes.

 

Actually the first couple of times pressure dropped a little faster but still not down to 30 psi in 5 minutes. Last 2 times took 20 mins to go to 30 psi. Think I'll let it be for a while and see if it gets worse.

 

Crank sensor starting to get weak?

 

Wouldn't that be acting up say when vehicle had ran for a while and turned off and would also loose all power?...worse when hot? I thought about just replacing it anyway as it never has been.

 

Maybe. Just wondering if the sensor is still a bit warm when he goes to leave work. When they start to get weak, they have trouble picking up the signal at low cranking rpm but are okay once started. Versus the other failure mode where they stop working once they get hot. What happens if he shuts down and immediately tries to restart once he's at work?

 

I think since he is now driving 40 mins to work ( thank God he finally got a job!) I'm just going to replace all the sensors one at a time as they all are original...except for the IAC. Would it give a code if it was weak enough to cause a issue even a small intermittent one?

 

What if one or more of those injectors wasn't closing completely, allowing the engine to flood after turned off?

 

Thought about that since I also had a pending misfire code for cylinder 3 (cleared and a week later never came back). Figured since I have the viper coil and wires coning in Ill remove them then should be seeing a rich burn on one of them or possible fuel when I remove them...maybe. The injectors are rebuilt ones from a place the rebuilds and tests them and has maybe 8k miles on them.

 

The crank sensor often does NOT throw a code. I always cringe when someone starts blindly replacing sensors without testing or troubleshooting - colloquially known as "Firing the parts cannon". The quality of aftermarket parts is often worse than the original oem part You might create another problem while thinking "That can't be it, I just replaced it". There are plenty of posts here about non-mopar crank sensors being bad out of the box or having very short lives. Cheap aftermarket wheel hubs and bearings are pretty bad too. Anything "rebuilt" by Cardone...

That said, I don't think it's a bad idea to replace the crank sensor and see if it changes the symptoms. Just don't throw the old one out just yet.

 

If it spins, it cranks. "Crank" does not mean START. It means the engine turns over.

 

 

True but lets see.....20 years old and only 1 sensor has been replaced. THe coil and wires was order before all this so they don't count . I tested and found loosing fuel pressure when it sits so either fuel pump check valve leaking (common issue) or possibly a leaky fuel injector (they were replaced couple years ago but were rebuilt one but not by a Joe Blow down the road) So I'm going wit fuel pump. Rest I may replace just for piece of mind and his safety driving at night and not for THIS issue. Guess I should of made this clear in my post above about replacing therm.

 

ONLY thing I'm replacing so far for THIS issue is the fuel pump due to loosing fuel pressure and injectors were replace 2 years ago. I Tested fuel pump and it lost pressure the first couple of tests was about 2 psi a minute and those after were better. So I figured check valve leaking by, working OK but not great and its the original one. The comment I made above about replacing all the sensors eventually was just for piece of mind since he is driving late at night not for this issue. The coil pack and wires were ordered prior to this....So not firing a parts cannon for this issue. I may replace them all overtime just for his safety as he is driving late at night as I don't mind spending money for that as to me its being pro-active and I don't buy cheap parts unless that's all there is and I need it ASAP.