1996 XJ Fuel Pump Fuse Issues?

Hey Ya'll,

After repeated blown 30 amp fuses (often after only 10 to 20 miles of travel) in the Auxiliary Under Hood Fuse Panel in my 1996 XJ, I have installed a brand spanking new fuel pump. While this seemed to have corrected the problem with no blown fuses since installing the pump (about two weeks ago), yesterday this same fuse popped yet again. Replacing the fuse allowed me to get home without further problems (about 25 miles or so) and everything seems to be working fine this morning. This Cherokee has been used extensively on some pretty rugged roads since fuel pump replacement (at least 350 miles driven) without incident until yesterday's glitch as well. Obviously, I would definitely like to get this issue completely resolved but both the Chilton's and the Haynes manuals have provided little additional info to go on. Anybody have any idea what might be going on here? For example, is/are there additional component(s) serviced by this 30 amp fuse that may be contributing to my problem? Any help would definitely be much appreciated, particularly since I cannot figure out the manuals' wiring diagrams to save my a**!  

I'll take a stab at it.

Fuses blow because of high amp draw. The cause of the high amp draw can be difficult to determine. An instantanius blow would be expected for a short. But shorts caused by vibrations in the form of chafed wires take vibrations in order to solve.

Another cause of high amp draw is heat. As an electric motor gets hot, it will draw more amps. As an electric motor wears out, it generates more heat and draws more amps. If the duty cyle of an electric motor is exceeded, then the motor will run hot and draw more amps. If the work load is heavy, the motor will get hot and draw more amps.

So, if you don't find chafed wires, or loose connectors, look into things that cause additional work load. Bent steel or kinked rubber fuel lines, dirty fuel filters, or leaky or clogged fuel injectors. Also don't rule out a bad fuel pump relay or ASD relay.

Also notice that for '97 it's a 15a fuse, not 30a. Are you sure the '96 should have a 30a fuse?

Here's the fuel system wiring for a '97 XJ from the factory service manual. Sorry I don't have '96.



 

ftgiles... Thanks much for the reply.

In my mind, at least, I have a basically ruled out a short associated with chafed wiring, as latest fuse blow occurred while driving on comparatively smooth pavement whereas no problem in over a week's worth of off-road activities. Hard to see how a bump associated short could be the culprit with this in mind. Suppose the next logical step is to test the two relays mentioned. Anuy idea as to whether or not any fan motors, etc. are governed by this circuit?  

Oh yeah, I almost forgot this... 30 amp fuse clearly indicated on fuse box cover, so definitely assume this is correct. Been trying to find a 96 service manual too, but no luck on that thus far either.  

What is the fuse position number for the fuse that you are replacing inside the power distribution center (PDC)? I'll see what other sheets from the wiring diagrams would be helpful.  

you may want to make a tester with a self reseting circuit breaker from a power window, i went to auto zone and spent 5 bucks making mine (15 amp), just put some wires in the ends of it and stick them in the fuse spot, if it blows it will automatically reset so it makes finding a short a lot easyer than replaceing the fuse a 100 times, i used this to find ouy why i am blowing my reverse lite fuse,,ended up being the switch on the tranny  
"WHEN IN DOUBT TACH IT OUT!"

Where exactly does one find the fuse position number? Nothing listed on the box cover, etc., etc. The fuse in question is in the center position of 3 small fuses on the left side (9th of the possible fuse placements including larger critters from front of box) when viewed from the front of the vehicle.  

Does your PDC look like this?

 

Not exactly, here's what I got (hand created since my scanner and/or digital camera won't take an adequate shot of the fuse box cover). The 30 amp fuse in the left hand row of 3 fuses in the center of the image (above the SEE OWNER/SERVICE MANUAL deal) is my frequent blower.

 

Nada on this critter?  

Can't believe this one, just bought a 95 XJ and guess what... yet another version of the auxillary under hood fuse box! That now makes 3, one each for 95, 96, 97. Anybody out there have schematic for the 1996?