• NAXJA is having its 18th annual March Membership Drive!!!
    Everyone who joins or renews during March will be entered into a drawing!
    More Information - Join/Renew
  • Welcome to the new NAXJA Forum! If your password does not work, please use "Forgot your password?" link on the log-in page. Please feel free to reach out to [email protected] if we can provide any assistance.

Starts Hard. Long Crank Time.

Ugly's2000XJ

NAXJA Forum User
Location
Fair Haven, MI
First time thread. I have a 2000 XJ and it has a longer than normal crank time for a 4.0L. Its followed by rough running for a few seconds, usually if I put my foot in the throttle and rev it up, it clears out and will be fine. I have owner many 4.0L and familiar with crank times with thses motors. What gets me is that the engine has been tuned up, new plugs. Throttle body cleaned, new air filter. I own my own DRBII and there are no codes and everything apears good on the state displays. I have not run a snapshot as I no longer work in the dealer and have access to download and look at all the volt lines comming in and out fo the ECU.
This drives me nuts as it will not allow mw to use my remote start, yeah I am a wuss..! I have 3" lift with 31" tires and am still getting 15-6mpg, so I am assuming that I am still running pretty good. The jeep used to get near 20mpg before the lift and tires...
I remember therebeing an issue with valve being to tight on certain 4.0L? but cannot locate old tech bulletin or anything with Chrysler.. If anyone can help with this issue I would appreciate it more than you know.. Otherwise its up for sale and on to my next XJ....

Thanks..
 
The clue to focus on here is that when it starts, it runs rough for a few seconds and then clears out. That makes me think that excess fuel is getting into one or more cylinders, probably through a leaky fuel injector.

If the injector is leaking fuel, what that does is reduce fuel pressure at the rail which could be the cause of the longer crank times.

I'd really suspect an injector here. How many miles on the engine?
 
Thanx.. I never thought about the injectors once because they motor ran good after was started. There is 112,000 miles on the jeep now. Do you think I can put a pressure guage on the rail and observe a drop after shut off? The Jeep has the coil on plug so I am trying to think how I can isolate the cylinder without just replacing all the injectors??
Do you have an idea what the pressure should be?? and what it might be at over time?? how long?
I wonder if I pull the plugs would one leaking indicate a different color than the rest??

thanks..
 
I don't have the fuel pressure specs off hand for a 2000 ( I want to say 49 psi running but not sure; someone else please chime in) but as long as you're getting good performance when it is running, I would be more concerned in just watching for a fuel pressure drop during the first say 30 minutes or so after turning the engine off.

Question...if you turn the car off and wait only say 5- 10 minutes, does it start cleanly? What time period with the engine off is required before it stumble starts? If there is enough fuel leaking into the cylinder, the plug for that suspect cylinder may be wet with fuel. Would be worth pulling plugs one by one and inspecting/smelling for gas after of course waiting the requisite time that it takes to create the stumble/start.

Does anybody else know of a good way of isolating a leaky injector with injectors on vehicle? I'd sure be interested to learn about it.
 
Last edited:
The other potential problem is a failed check valve on the fuel pump assembly. A failed check valve will let the pressure drop, slowly at first and then more quickly. With low pressure in the fuel rail you are now going to get some potential vapor lock, even in the winter time.


Test: Turn key to on, let fuel pump prime. Turn key to off. Turn key to on, pause, start.
 
The vehicle had sat all night and was nice and cold, hooked up a guage and with key on had 43-45psi.. Upon start up went to 49psi... Long crank time and stumble was present. Reved up engine and cleared it out. Left guage on after shutting vehicle off and pressure dropped, was @ 23psi after 20-25 minutes or so.... I cant remember spec but do not believe drops that fast. I have a friend with an XJ with no problems and I am going to compare the drop. The more I get into this the more I think you guys are right on with an injector or so leaking down. Once I compare the specs with the good test vehicle, I will pull the rail, energize the fule pressure and then let sit. I will observe the injectors and see if any of them actually leak! Will try this over the upcoming weekend and get back with my test results... I thank you guys for all the input.. I have years upon years of wrench time under my belt but always awesome to compare notes with other Jeep guys..! Thanks and will get back with my findings asap.... awesome site..

Mark
 
My 01 XJ FSM says that it should hold pressure above 30 PSI for at least 5 minutes to pass the leak down test. I tested mine two days ago...it took about 7 mins to drop below 30 the first time I tested it...I never started the motor, just turned the key to build up pressure and then I timed it to see how long it took to leak down below 30 PSI.
Second time I tested it, I ran the motor for about a minute. This time it took about 20 minutes to leak down below 30 PSI. By the way, I am not having any long crank times, power problems or driveability problems ...my city mileage is about 15-16 mpg. I was just testing my jeep so I would have a baseline to work from if it starts to have a problem in the future. My fuel pressure while running oscillates rapidly from 48-51 PSI.
 
Going off your specs, leaky injector might not be it...! My test this afternoon was very similar to yours!! :( Now I am thinking, I will pull the rail and energize and look for any leaking. Should not be to bad to pull the rail....

My MPG is same as yours..what are you running for gear? tires etc???
 
cambosoup99 said:
yes, t-stat sensor is for ecu and sensor in the back of the head is for gauge.

Hm - half marks, I think. IIRC, there is only one ECT sensor in OBD-II - it drives the ECU; which, in turn, drives the fan (through a relay) and the IP gage (via the CAN bus.)

The 0331 head (COP/DIS) doesn't have provision for the in-head temperature sensor, as I recall. That was deleted.
 
cambosoup99 said:
bad coolant tempurature sensor in the thermostat housing causes this also.

X2. Do you have a scanner that can pull the readings from this sensor, so you can see what it thinks the temperature is?
 
Tim_MN said:
The other potential problem is a failed check valve on the fuel pump assembly. A failed check valve will let the pressure drop, slowly at first and then more quickly. With low pressure in the fuel rail you are now going to get some potential vapor lock, even in the winter time.


Test: Turn key to on, let fuel pump prime. Turn key to off. Turn key to on, pause, start.

I agree w/Tim_MN about the check valve. You could always try the $6.00 inline BMW check valve... On my '94 XJ it ended up being the FPR(fuel pressure regulator).
 
I hooked up my DRBII and the coolant temps (as inputs) are right on the money... Still have to pull the fuel rail and see if is leaking. The rough running on stat up after sitting really has me puzzled. If the injector doesnt leak I will be really stumped.

Has anyone heard of any issues with the valves? I worked tech assistance for Chrysler years ago and remember an issue bvut cant find my notes or anyone that remembers.. I believe it was a mis-fire issue, so I am definetly thinking fuel, but trying to remember. Getting old sucks.. LOL
 
Did you ever come to a conclusion? I have the same issue on my '97 XJ. When doing the fuel pressure check on the rail it reads 45 PSI running and drops down to 5 in less than a minute after shutdown. Im sure this is probably a leaking injector or bad check valve. Experiencing long crank times, dying after starting, and rough idling. Anyone???
 
Back
Top