Hard restart after sitting for a while 2000XJ

Seems to be a polpular thread over the last couple of days, but mine is a little different.

Turn the xj off and restart within the next 10 or 15 min's and it will run fine. Try to restart it after sitting for longer than that and it will crank for 30 +seconds and run like crap for the next minuet.

Background:
New XJ for me, I have a 90' for the last 7 years.

2000xj, 4.0, aw4. I just put in new plugs, air filter, and oil change.

Testing done so far.

Temp around here is about 50 so I left he hood up No help
Tried the turn the key on and off for a couple of cycles No help
When the condition exsists and I push the valve on the fuel rail just VAPOR comes out (i.e. no gas)
Fuel pressure gauge will be here tomorrow so I can post that then.

I was thinking that it is a problem between hot soak and or check valve in the fuel tank.

I have read about problems with the BMW check valve becasue I have no return line.

Well that is my story, I hope somebody can point me in the right direction.

Thanks

Sounds very similar to what I have going on, except that it only has the problem after shutting down and trying to restart after cooling for 3-10 minutes (Yes, i timed it). Does it make a difference if you open the hood after stopping? That seems to eliminate the problem on mine...sry I can't be of help, im chasing the same thing, maybe we can figure it out together! http://naxja.org/forum/showthread.php?t=1015645

90xj-65 said:

When the condition exsists and I push the valve on the fuel rail just VAPOR comes out (i.e. no gas)
Fuel pressure gauge will be here tomorrow so I can post that then

Click to expand...

The above statement pretty much tells the story. You have a fuel delivery problem. You are losing fuel pressure due to a fault somewhere within the fuel delivery system. Usual suspects include the check valve on the fuel pump assembly, or less likely, could be a seriously leaky fuel injector(s).

My gut feel is that it is probably the check valve which is a very common failure for your vintage XJ. It is best fixed by dropping the gas tank and replacing the entire fuel pump assembly (ie; go high quality OEM, stay away from el-cheapo if you have to replace this).

You are definitely on the right track to perform comprehensive fuel pressure testing so that you can isolate the problem properly. I think that there is a good chance that you will find your answer within that fuel pressure testing but nonetheless, you MUST start there.

When the 1997 to 2001 Cherokee won’t start on the first try day after day, the first thing to suspect is a failed check valve on the fuel pump. The fuel pump check valve is supposed to hold pressure in the fuel line while the engine is off. The check valve is located on the fuel pump and located in the gas tank. A failed check valve allows the fuel to drain back to the tank. This results in the following symptoms:

SYMPTOMS

· Longer than normal cranking times
· Never starts on first try, almost always starts on the second try
· Rough idle for a few moments of idling
· Rough running for first ½ block of driving
· Little or no fuel pressure at the fuel rail test valve similar to this -

1- Key in on position; fuel pump primes for 2 seconds then stops. 0 PSI
2- Cranking over the engine. 2-3 PSI
3- Engine starts and idles for 20 seconds. < 5 PSI
4- Engine idles and fuel pressure creeps up to 45 PSI.


POSSIBLE CAUSES

· Failed check valve on the fuel pump in the gas tank (1995 ½ to 2001 models ONLY)
· Leaky fuel injector(s) may be the true cause of your problem, but more likely they are simply contributing to the check valve issue.

Testing of the fuel injectors should show if any are faulty and are allowing fuel to drain into the cylinder. Either problem can allow heat soak to vaporize the remaining fuel in the fuel rail and you may be dealing with a bit of vapor lock as well, especially in warmer weather.

1. Connect the gage at the fuel rail and start the engine. The gage should read 49 psi plus or minus 2 psi.

2. Turn the engine off and immediately clamp the fuel line just ahead of the fuel tank. Watch the pressure gage and see how long it takes to loose pressure.

If the pressure remains at 49 psi for an extended period of time then the problem is in the tank - probably the check valve. If the pressure falls below 49 psi fairly rapidly then the problem is probably a leaky injector.

There are a few solutions to the problem –

1. Turn the key to ON for 5 seconds and let the fuel pump prime. Turn the key to OFF, turn the key back to ON for 5 seconds, start the engine.

2. Crank the engine for 3-5 seconds, pause, and crank the engine again. It will almost always start on the second try.

3. Replace the fuel pump assembly in the gas tank. The check valve is not a separate part and cannot be serviced. This is both expensive and time consuming because you have to remove any hitches and skid plates and then remove the gas tank from the vehicle.

You can use solutions 1 or 2 for as long as you want to, they do not harm anything and the fuel pump will continue to function for many more years.


The BMW check valve will cause problems on Cherokees that do not have a return line to the fuel tank.

What you need is a new fuel pressure regulator. My 99 did the exact same thing as your 2000. I tried an inline check valve but that didnt fix it. The fuel pump wasnt the problem because it ran fine after started. Replaced the pressure regulator and it starts right up in the morning with no more "priming the pump". The pressure regulator is located on top of the fuel pump, external of the tank. I got mine at HESCO, factory OEM for 80 bucks shipped...way cheaper than dealership.

Bstd_02_Wgn said:

Sounds very similar to what I have going on, except that it only has the problem after shutting down and trying to restart after cooling for 3-10 minutes (Yes, i timed it). Does it make a difference if you open the hood after stopping? That seems to eliminate the problem on mine...sry I can't be of help, im chasing the same thing, maybe we can figure it out together! http://naxja.org/forum/showthread.php?t=1015645

Click to expand...

Yea I was watching that thread. Only my problem is that it will restart fine with in the 1 to 3 min. window, after that is when I have the problem. Opening the hood in 40 degree weather has no effect on the condition at all.

It did throw a cylinder #2 misfire code twice.

Tim_MN

Thanks for the dianostic info. Work called me in today so I could not do the checks, but will tomorrow. I will post up some numbers and results.

I am hoping it is just a leaky injector, much easier than the pump.

Thanks for everybodys help so far, I am sure I will need more before this problem is solved.