1996 XJ Fuel Pump Fuse Issue Still Unresolved?

Howdy All,

Still in need of major help with this one, as the 30 amp fuel pump fuse in the underhood Aux Fuse/Relay box in my 1996 XJ Sport still sporadically blows for no readily apparent reason (at least not to me, anyway). Initially, the problem was believed to be (and probably was) related to a failing fuel pump, as a maximum of 10 to 15 miles driving distance was all that could be expected from newly replaced fuses. Replacing the fuel pump (approximately 3 months ago) appeared to resolve the issue, as in most instances the vehicle performs without problem. Unfortunately, however, the fuse will still sporadically blow and, worse yet, invariably while my wife is driving it alone. I drive it for weeks at a time in all types of on and off road situations without problem, while she continually experiences blown fuses and is never off the pavement. In other words, I have not been able to duplicate what ever it is she does differently that produces this condition.

In light of this I am actively seeking opinions regarding full resolution of this issue and have a couple of questions that may help spark additional discussion.

1) Could the Fuel Pump and/or ASD relay(s) malfunction sporadically or would they simply be either good or bad?

2) Connie (my wife) associates accleration to Interstate speeds with blown fuses (hasn't happened with me thus far, however). Could that be a possible factor via  partially clogged injectors, other faulty fuel delivery components, etc., etc? ...or

3) Could said wife be inadvertently propagating blown fuses via a bare wire/faulty connection by having her feet (vehicle is equipped with AT) positioned differently than mine?

Any help at all would be greatly appreciated, as I'm puzzled almost beyond belief. Heck, I'll even gladly buy you all a couple of beers at a jeep meet somewhere sometime. Thanks much in advance and I look forward to any and all replies.

Most sincerely, John the XJ Freak currently lost in South Dakota  

Assuming my 1992 XJ fuel pump wiring is similar in design, you said one thing that sparked a thought concerning your wife experiencing the problem more frequently.  Wide open throtle uses a different power path then standard throtle.  It bypasses the big fender mounted resister on the '92s and goes straight to battery power to make sure you maintain full pressure during the hard acceleration.  Now, a '92 is OBDI and I belive the '96 is OBD II so there may be some differences, but probably not much.

A blown fuse means a positive 12v wire is touching ground under a certain condition (like a heavier foot then yours).   I'd suggest you chase all the wiring for the fuel pump resistor bypass circuits to the fuse first.  These shorts are rarely inside the split loom harness that is totally taped up and covered (unless you've opened it up recently).  Check all the end connections and check the resistor, it's ceramic and can break in half causing it to short to the fender.

In total desperation, run all new wire and let the factory stuff stay in place.  

why not have a look at the wiring diagram...

http://repairguide.autozone.com/znetrgs/repair_guide_content/en_us/images/0900c152/80/0a/9e/12/large/0900c152800a9e12.gif

fuse #6 powers the fuel pump through the relay

and the power train control module...  the red wire..   look at the upper right corner of the diagram... but .. i only see one wire powering the powertrain control module... on circuit A22...   there are dozens of things that have their power run through that module...  everything on the bottom of the page with a black and light blue wire... and a few things up on the side of the page...

cruise control, speed sensor in the side of the transmission, battery temp sensor,  both o2 sensors, the cam and crank sensors, teh map sensor. throttle position sensor and the transmission control module... i may have missed one.. or two.. everything along the bottom of the page...

print the page large....      or get one from alldatadiy.com or eautorepair.net...  

being a 96... does it set any codes????/     if so.. i would go directly to that code first...   almost everything on those circuits have several codes possible for them...

post what codes you find...

hope this helps...

wayne  

If you're not getting any codes, start tracing the wire from the 30 amp fues through the fuel pump relay and all the way through to the end.  Don't bother with the PCM wires connected to the relay, they have a separate source from a different fuse.  

Had the same problem with my TJ.  Had a chaffed wire back by the tank that would short to the frame every now and again.  Look at the wire all the way down as best you can.  If you can't find anything, run a new one back to the pump from the fuse box.  
99tj/ 4.6 stroker / 4.88 / '06 rubicon axles / 7"rockkrawler l/a / steering upgrade / agr pump psc box and hydro assist / mm 10.5k hyd. winch / 35" Trxus MT / comp cams xtreme 4X4 cam