TJsWJnXJ

So I bought my XJ yesterday and have been driving it around for a day or so. I absolutely love it but it has a couple issues. One of which is a high pitched constant beep coming from the rear. Doesnt sound like gear whine or bearings and it only happens over 20 ish. Sorry for the poor description but any ideas in the right direction would be great.

mr white

If it changes with your throttle position it's the fuel pump.

TJsWJnXJ

It does have trouble starting sometimes too, I wonder if theyre related. Also when I first got it the gas cap wasnt venting at all. Ive replaced it since.

Dumajones

Test your fuel pressure,,with a gauge..

Dumajones

XRated

Maybe its your fuel pump
Maybe your fuel filter is clogged
Checking the fuel pressure at idle is useless unless all you do is let your rig run at idle in park.

OP Change your fuel pump and youll be fine, or wait till it starts missing and backfireing then change it. I bet its due for a pump anyway.

Also
Both those videos should be sucked back into the colon of the first vids kid with the funky glasses and lost forever.

Congrats on the XJ!!
Welcome to a world of hurt and fun.

Dumajones

I thought the two You Tube video's I put with that post would explain it.. OK her it go's I will give it a shot
There is a "schrader valve" on the fuel rail. Looks kind of like the valve you would see on a bike tire.The fuel gauge can be screwed directly to this valve. Fuel pressure gauges should include adapters which will hook up to the schrader valve. With the jeep running you should have fuel pressure of 49 psi at idle, plus or minus 5 psi. Anything out of those numbers, replace the pump. is that better

TJsWJnXJ

Lol I didn't expect to wake up, be informed and laugh all at the same time. Thanks guys!

XRated

The videos did explain what you are saying, my point is checking fuel pressure at idle is almost useless. What happens if the pressure is great at idle but the failing pump cant keep up with fuel demand while driving. According to the pressure check at idle theory the pump is fine so what do you do? Throw some other parts at it and hope for the best?

Dumajones

Oh so the videos did explain what I was saying, hmmmm. As for your ?'s. I don't know bud that's the way Ive always done it to check for a failing fuel pump. Because it works 60% of the time, every time...

XRated

Lol
Mr Burgundy

I almost lost some diesel injectors in my tow pig due to low fuel pressure. I had checked the psi at the fuel bowl and it was plenty good at idle but i got a bug up my a$$ and wanted to know what the fuel system was doing while driving. Put in a in cab fuel pressure gauge and found out that under wot runs the pressure was dropping from 60 to 20 which is suicide for the injectors in that truck. Shortly after that i was into a new fuel pump and was lucky i didnt loose some injectors.

XJmike0122

This makes me lol. In my last car fuel pressure under 1700 psi at WOT was suicidal. Sorry carry on.

Dumajones

I'm not sure what kind of vehicle that was your talking about. Maybe the Jeep has a different way of managing its fuel. I went out to my 2000 Cherokee, checked psi at the rail (50psi) revved it no change. turned off the motor, held fine at 48-49psi forever. Went out to my 96 Cherokee did the same thing(I know the fuel pump is bad on the 96 because I'm to lazy to fix it) Its psi at the rail is 39-40psi even if I rev the motor . The jeep has all the sings of a bad fuel pump tho, Like lack of power, cutting out, backfiring, etc. I always have to turn it on and wait for it to prime up then crank over 4 times before it starts. Like I said it holds 38-40psi did't change when I rev it.. I just Know that if the psi for a jeep Cherokee is under 49 +/- 5psi that its bad...

s346k

you can't check fuel psi at idle or with a park/neutral free rev. no load on the engine at that point. need to do what that other guy did and put a gauge in vehicle and go floor it on the highway.

Dumajones

hmm thank you good to know