Long crank time 96 XJ, confused?

[awinterstale]

Hey everyone, I'm new here!
Got a 96 XJ with 4.0L I just bought about a month ago.

It has a long crank time if it has been sitting for more than about 30 minutes or so. If I prime the pump about 6-8 times it will start a little quicker. It seems to run fine once started and running.

I have already replaced the fuel pump and the O-rings on the injectors, but have the same issue. Fuel pressure seems to drop quickly after engine shut off, probably drops to 5psi or less in about 20 minutes.

Any ideas?

thanks!

 

[831_xj]

Check valve on the fuel pump assembly

 

[awinterstale]

If I replaced the fuel pump wouldn't it have had a new check valve?

 

[Anak]

Did you replace the fuel pressure regulator while you were taking care of the pump?

The fuel has two directions it can go; either back into the tank courtesy of a defective fuel pump/pressure regulator (I am not sure which one contains the check valve) or forward through one or more leaky injectors.

I have not done it, but I believe you can test the injector side by clamping off the fuel line at the filter (someplace where it is not a hard line) and then waiting an hour or so (or even overnight, depending on how your vehicle is behaving) and checking pressure at the rail. Of course this requires that you clamp it off right after shutting down the engine. If it will hold pressure while the line is clamped off then you know your problem is in the tank.

The fuel pressure regulator can indeed be replaced. I got mine from Morris 4x4. It is the same regulator as the earlier H.O. years but yields a 10 psi higher pressure because it is not hooked up to a vacuum line.

 

[awinterstale]

did not replace regulator, probably should have. i'll get into the jeep a little more this weekend and see how it goes

 

[Lowrange2]

Did you replace just the pump or the entire pump/sender assembly?

 

[Anak]

If he didn't replace the regulator it would have to have been pump only. The pump is about the only thing that is likely to be readily available. The complete assembly is slightly easier to come by than a spotted unicorn, but you will probably have to special order it and most likely wait a couple of weeks. Someone did manage to get one recently, so it can be done.

 

[awinterstale]

yeah, it was just the pump. sending unit works fine. getting into it tomorrow (hopefully, have to go to the gun show first!)

 

[XJ_Rudolph]

sounds like the check valve!

 

[RoyalXJ]

A lot of guys use an inline check valve from a BMW. I'm sure there's a thread on one of the forums about it.

 

[awinterstale]

finally got around to it. replaced pressure regulator and all is good, thanks for the replies