mudallday

it wil start right up everytime but will start sputtering and die after like 20-30 seconds. i need to know what it is its sitting in a parking lot and i would like to get it home so any advice is useful. befor i replaced the fuel filter it would run for a little bit then die and i would have to wait 10 minutes to get it to run for any period of time. not its starts and runs everytime but like i said dies after about 30 seconds.

fox128

I'll give you a bump....hopefully someone can give you more help than I can. Might help to know the year of your xj. Does it idle and rev up fine before it dies?

mudallday

yeah it idles fine and when its about to die it just slowly dies and if i give it gas it doesnt do anything just keeps dying. its an 88

BowtieGuy3

I have no clue about the Renix jobs.... I think Blue is the guy you want for this one... I'm clueless...

UNCC_99XJ

I'm thinking a dead CPS (Crankshaft Position Sensor)......normally they will run when the motor is cold, but once it gets warmed up they stop working and the motor peacefully shuts off, but I have heard of them only running for a few seconds regardless of the temperature of the motor before.

The last one I put on a renix ran about $35 from Advance Auto.

zjrog

I sound like a broken record, but check youre fuel pressure with a gauge...

nick_n_ii

I'd say more like the throttle Position Censor. Just replace one on my brothers, XJ for the same reason you described..

mudallday

ok so you think its its the tps? how much do those cost cuase im running low on money trying to guess what it is. i did check the fuel pressure an its good.

BuckB91XJ

Ditto on the fuel pump. Plug a test fuel pressure gauge into the test port on the fuel rail. Start your XJ up and watch the pressure.

1.) If it never reaches 31 PSI your fuel pump is definitely bad.

2.) If thr pressure drops off as it starts to die at the 30 second point. I would say your fuel pump is bad.

mudallday

i will try that but it doesnt seem like it would be that it starts right up and never had problems pulling hills or anything. ill check though

BuckB91XJ

Sometimes when the fuel pump starts to die you will get an intermittent problem for a long time before it dies all the way....and that usually happens at the worst possible moment. It's better to catch it before it dies completely.

mudallday

i wish i would have thought about it being the pump before i filled the tank haha...... i really whanna get to the bottom of this its lame

BuckB91XJ

I dropped the tank when I replaced the FP in my son's 87 but, I didn't drop the tank when I replaced the FP in my 91. It can be done without dropping the tank but, I would recommend having a half tank of gas or less before opening up the tank to get your pump out.

mudallday

yeah thats what i figured i knew you could do it without dropping it just that i have a full tank of gas haha. so if i pruessre test it and it doesnt drop when it starts to die its not the fp?

BuckB91XJ

That is correct. The fuel pressure should never drop so long as the key is turned on and power is going to your fuel pump, even after the motor dies. That is why this is a valid test to hopefully rule out your fuel pump.