Engine Prob

[92DripCherokee]

your fuel pressure should rise with higher RPM (as the vacuum lowers)
probably not a bad pump, they tend to go intermittent, or just quit
it may the pressure regulator completely pooped out

your 99 has the in-tank, returnless fuel pressure regulator?

 

[XBoBJ]

interest, your fuel pressure should rise with higher RPM (as the vacuum lowers)

that 99 has the in-tank returnless pressure regulator?

i have no idea? maybe some one else could tell me, but it definetly dropped

 

[92DripCherokee]

easy to tell...you have just one line going to the fuel rail?

if so, the fuel pump and regulator are serviced as a unit. Along with the fuel filter/screen.
not a small job on that design, have to drop the fuel tank.

 

[XBoBJ]

correct one line going in, should i replace the fuel pump assembly?

 

[92DripCherokee]

the fuel pump assy is all one unit, the only parts you can swap out are the filter screens.

 

[XBoBJ]

yeah i know that. should i replace the whole assy.. could this be causing these problems?

 

[92DripCherokee]

if you've eliminated the other causes of running extremely lean, it's entirely your call. An OEM pump is $$$. With a critical electrical part, go OEM. Too many threads here with aftermarket fuel pumps going kaput.

Collision Catalog Item Number MSRP Core Price Price 5012953AC $417.00 $0.00 $291.90 Fuel system - Fuel system components - Fuel pump assy
Fuel pump assy 1997 - 2001
Add to Cart Contact Us

 

[XBoBJ]

ouch im going to wait to see whats going on maybe i can eliminate something else

 

[4wheelnfun]

Put a vacuum gauge on the intake manifold and do the tests listed in the attached article. It will give you some clues on what may be causing you issue.
http://autospeed.com/cms/A_2393/article.html

I'm not sure if your year XJ has an external fuel filter, by my '96 had the original filter on it (previous owner neglect = 12 year old filter). A clogged filter can give poor pressure that will drop with engine load as you mentioned. When I changed the filter, brown sludge poured out of the input side.

A overheated header can be caused by very late ignition timing, or very lean A/F mixture.

Have you torqued the manifold bolts? (the ones that hold the intake to the head)

 

[XBoBJ]

thats at idle, it drops when revved. i got a deal on a tank and fuel assy im picking up tomorrow, i hope its that...

 

[lilredxj99]

I'm not a Chrysler Tech, but that seems too low. IMHO But, I would go fuel filter first.

 

[Dundy]

The fuel filter is inside the fuel tank. Keep chuggin' Bob, you'll figure it out.

 

[XBoBJ]

yeah im chugging, going to pick up a new used tank with a new used fuel assy in it, im just going to plug it in with out droping my tank and if the fuel pressure is up then illl throw it in and see what happens

 

[billyjp2]

any progress Bob?

 

[XBoBJ]

just fixed it, it was the fuel pump all along. who would of thought? im happier than a pig in shit thanks naxja:yelclap:

 

[92DripCherokee]

awesome

your pistons will thank you!

 

[97Jeepers]

Its good to hear you got things sorted out. At the same time you posted that it was the fuel pump, I immediately started to get the same problems. Mine's a ax-15 as well, but sometimes when i push the clutch in or pop it in neutral coming to a stop light, my idle goes down to like 250 rpm. I definitely believe its a fuel pump, will be doing it this weekend. Ive already replaced all of the sensors, so I hope its not from one going bad.

Good luck

 

[89xj]

Its good to hear you got things sorted out. At the same time you posted that it was the fuel pump, I immediately started to get the same problems. Mine's a ax-15 as well, but sometimes when i push the clutch in or pop it in neutral coming to a stop light, my idle goes down to like 250 rpm. I definitely believe its a fuel pump, will be doing it this weekend. Ive already replaced all of the sensors, so I hope its not from one going bad.

Good luck

instead of just throwing parts at it, test the fuel pressure with a gauge.

 

[97Jeepers]

I didn't just throw parts at it, about a month ago I had to replace the Tps, and came across a new throttle body with all new sensors on it for cheap, so I replaced them for safety's sake. I checked it with a gauge and it reads low, but to be sure I'm asking to see what would make it be intermittent, the parameters are the same, about the same load, engine speed, gear, and sometimes the rpm drops to 200 and sometimes it stays at a level 750. Whenever it drops to 200 or so, I just blip the throttle and it goes back to normal. Just checking if anyone has had these similar symptoms before.