caballogris

Hi. My 1993 XJ 4.0 make me crazy... I start engine normally, good feeling... 25 seconds after, RPM going down with a heavy aspiration noise (with filter hose apart) then stops. Its repeats every time when you start, no matter how much time you wait to do it. I checked fuel pump and filter, MAP sensor too... The first time that it fails I was runnning normaly and suddenly has no gas response...

SirCyber

Curious, how did you check your pump and filter? I would see if you are getting a good pressure. When I had a similar issue I disconnected my gas line from the pump side of my filter then had someone turn the key to the on position. Pump turned on, spit gas out. I took off filter and replaced with new. I was uncertain on if the pump was working properly at this point because it wasn't a lot of gas. Also, old filter didn't seem blocked up to me. But once I installed new filter, voila! Couple cranks and it fired right up.

caballogris

Mmmm... Pump its a new good unit, and I checked it. The filter looks to me good... I took it appart and blow through without dificulty... But its good to know that someone was the same symptom and the filter looks good too... I will buy one and change it tomorrow... Thank you very much!!!

SirCyber

Yup same blew threw it with no apparent difficulty but the new filter fixed the issue

caballogris

OK, after a saturday of tests and search, my XJs fail is growing up in place of dissapear..
I bypass the fuel filter, test the car: 25 seconds running, then stops. OK, I think that the fuel pump could be stucked and gave me a good fuel pressure only when starts... I test it again and surprise!! No fuel pressure after start, but its OK ONLY at start moment...????
I check the feeding of fuel pump and noticed that only have it AT THE MOMENT TO START THE ENGINE. Engine running= no current at fuel pump!!! Also, I noticed that when engine stop after 25 seconds running, fuel pump works 1,5 seconds, then off again....
I know that all cars actually have a device to stop fuel pump current feeding when engine its not running or RPM are below 200 or so (depending of model and/or brand). We were looking and testing for every relay and any other device that could control this behavior and didn't find it. Then, I took a wire directly from IGN fuse box (inside the car, beside brake pedal) and hook up to pump positive and voila!! Its running perfectly.
OK, I know that is not a so safe procedure, because any accident that causes an engine stall, will let the pump running and feeding fuel... But I need the car and had to get out from my friend's garaje... So, the question is: where is that device?? Its like some kind of relay, or would be ECM who control that functioning?? have somebody this answer???

caballogris