My 91 4.0 Cherokee had been running fine,however because I haden't replaced the starter relay ,(intermittent problem)it finally wouldn't work.I got stuck,was alone,and got the bright idea to turn the ignition on ,on and crawl under the jeep and jump the starter bendix relay terminal to the hot lead on the starter with a screw driver while gently tapping the starter case with a hammer.After a few tries the starter engaged,turned the engine over but now the engine would not fire.I removed and fixed the starter but now had a new problem,the fuel pump stopped working.I checked the fuel pump with a 12v dc power supply by attaching it to the connector at the gas tank end and the pump runs .I re -connect the pump connector and the engine started for a few seconds then died this was due to the fact that I had re pressurized the fuel rail by running the fuel pump off of my 12v dc power supply doing my testing. When I turn the key to the on position,for a split second the fuel pump relay clicks on then shuts off.I switched both the auto shut down & the fuel pump relay and checked the ballast resistor.The engine gets spark but no fuel.Do you think I burnt out the fuel pump timing circuit in the computer by jumping the starter w/screwdriver ? After analyzing the wiring schematic my thoughts are the computer.I would greatly appreciate any thoughts...

My 91 4.0 Cherokee had been running fine,however because I haden't replaced the starter relay ,(intermittent problem)it finally wouldn't work.I got stuck,was alone,and got the bright idea to turn the ignition on ,on and crawl under the jeep and jump the starter bendix relay terminal to the hot lead on the starter with a screw driver while gently tapping the starter case with a hammer.After a few tries the starter engaged,turned the engine over but now the engine would not fire.I removed and fixed the starter but now had a new problem,the fuel pump stopped working.I checked the fuel pump with a 12v dc power supply by attaching it to the connector at the gas tank end and the pump runs .I re -connect the pump connector and the engine started for a few seconds then died this was due to the fact that I had re pressurized the fuel rail by running the fuel pump off of my 12v dc power supply doing my testing. When I turn the key to the on position,for a split second the fuel pump relay clicks on then shuts off.I switched both the auto shut down & the fuel pump relay and checked the ballast resistor.The engine gets spark but no fuel.Do you think I burnt out the fuel pump timing circuit in the computer by jumping the starter w/screwdriver ? After analyzing the wiring schematic my thoughts are the computer.I would greatly appreciate any thoughts...


THE FUEL PUMP ONLY RUNS FOR 2-3 SECONDS WHEN YOU TURN KEY ON JUST TO PRIME FUEL RAIL. THE WHITE CERAMIC BLOCK ON THE INSIDE OF DRIVERS FENDER DID YOU TRY JUMPING THE TERMINALS. TRY JUMPING THE TERMINALS . DALE jeepman600@sbcglobal.net

THE FUEL PUMP ONLY RUNS FOR 2-3 SECONDS WHEN YOU TURN KEY ON JUST TO PRIME FUEL RAIL. THE WHITE CERAMIC BLOCK ON THE INSIDE OF DRIVERS FENDER DID YOU TRY JUMPING THE TERMINALS. TRY JUMPING THE TERMINALS . DALE jeepman600@sbcglobal.net
Hi Dale.Thanks so much for your response.Yes ,I did jump the terminals and nothing,I ohmed out the ceramic resistor also and it checked out OK.I checked the fuel pump relay while another person turned the key on and the relay clicked on and off within a fraction of a second.I also can feel and hear the auto shut down relay click.I probed the output terminals of the fuel pump relay with a VOM and confirmed a 12 DC output voltage for a fraction of a second,more like a milisecond and then back to zero volts.I was told by the dealer and read in the shop manual that the relay is controlled by the main computer .By me jumping the starter selonoid post to the starter hot lead post w/a screwdriver I fed 12vdc thru the wire that runs to the selonoid and by the ignition being in the run position and not the start position do you think that this could of damaged the computer? It seems like too much of a coincidence that after I did this that the fuel system stopped working.I'm wracking my brains on this one.Any other input would be appreciated. Kevin

Hi Dale.Thanks so much for your response.Yes ,I did jump the terminals and nothing,I ohmed out the ceramic resistor also and it checked out OK.I checked the fuel pump relay while another person turned the key on and the relay clicked on and off within a fraction of a second.I also can feel and hear the auto shut down relay click.I probed the output terminals of the fuel pump relay with a VOM and confirmed a 12 DC output voltage for a fraction of a second,more like a milisecond and then back to zero volts.I was told by the dealer and read in the shop manual that the relay is controlled by the main computer .By me jumping the starter selonoid post to the starter hot lead post w/a screwdriver I fed 12vdc thru the wire that runs to the selonoid and by the ignition being in the run position and not the start position do you think that this could of damaged the computer? It seems like too much of a coincidence that after I did this that the fuel system stopped working.I'm wracking my brains on this one.Any other input would be appreciated. Kevin

I SUPPOSE THAT YOU COULD HAVE DAMAGED THE COMPUTER. THERE ARE A LOT OF CHANGES WITH THE COMPUTER SYSTEM. CAN YOU EMAIL ME AT jeepman600@sbcglobal.net I'VE GOT A COUPLE SHEET THAT MIGHT HELP YOU BUT I CAN'T SEND THRU FORUM DALE