ken72

I have seen some pressure kits and wanted to know how you tested the pressure from the rail? I have a 2001 XJ and I can not access the pump without dropping the tank. Can a guage be hooked up to the fuel rail to do this?

SeriousOffroad

Connect the gauge to port on the fuel rail.

tjwalker

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 you up.

The 2001 should have fuel pressure of 49 psi at idle, plus or minus 5 psi. Anything out of those numbers, replace the pump.

What symptoms are you seeing? Detail them for replies.

CJ7365

If you have an Auto Zone, you can "rent" a fuel pressure guage from them, when you get it they charge you for it, simply return for a FULL refund

ken72

thanks CJ7365 I might just do that instead of purchasing one. Although I understand you can use them to check alot of things.

TJWalker, Thanks for the info, I will give it a shot. My idle is acting up. It idles just below the middle mark betweek 0 and 1000. It surges or wiggles if that makes sense. Today it fell below the second hash mark or maybe the 250 mark. Before I spend money on O2 sensor or MAP sensor I want to rule out the fuel pump.

tjwalker

Good advice. Part stores are a great source to rent tools that you do not want to purchase.

tjwalker

A 250 rpm idle is too low. Should be around 750 rpm. Try the below before moving onto other possibilities. Never hurts to verify fuel pressure, but I do NOT think this is a fuel pressure issue.

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The Idle Air Control (IAC) is mounted on the back of the throttle body. The valve controls the idle speed of the engine by controlling the amount of air flowing through the air control passage. It consists of a stepper motor that moves a pintle shaped plunger in and out of the air control passage. When the valve plunger is moved in, the air control passage flows more air which raises the idle speed. When the valve plunger is moved out, the air control passage flows less air which lowers the idle speed. Over time and miles, the IAC can get carboned up which can have an adverse affect on idle quality. Cleaning the IAC may restore proper function and is an easy procedure to perform and good preventive maintenance so it is never a bad idea.

CLEANING THE JEEP 4.0 IDLE AIR CONTROL

Remove the air filter cover, associated hoses and the rubber boot that goes from the air filter cover to the throttle body. Remove the IAC with a torx driver (2 bolts; one can be kind of hard to get to)

“Gently” wiggle out the IAC from the throttle body. Gasket on the IAC can be re-used if it is not damaged

Clean the IAC with a spray can of throttle body cleaner; inexpensive and available at any place that sells auto parts. Throttle body cleaner is recommended rather than carburetor cleaner as it is less harsh, safe for throttle body coatings and is best for this task. Use cleaner, a rag and a toothbrush and or Q-Tips. Be gentle; don’t twist or pull on the pintle that protrudes from the IAC as it is fragile and you could damage it.

Thoroughly spray clean and flush where the IAC seats in the throttle body with the same spray cleaner

It is also a good idea to clean the entire throttle body itself, the butterfly valve inside of the throttle body and all associated linkage as long as you have things disassembled

Reinstall IAC and check idle quality

CJ7365

+1 for TJWalker on checking/cleaning the IAC, that costs no money

i believe its about $150.00 so unless you do a lot of testing then its not worth it, $150 bucks can buy you a lot of other things like, lets say a new fuel pump or sensors

ken72

Thanks, cleaned TB earlier this year and replaced the TPS and IAC. There is a chance that the IAC is bad though because I purchased it off ebay for pretty cheap. I hate to spend a lot of money on parts but I dont know how to narrow it down. I believe my problem lies in either the o2, MAP or IAC just like you are thinking. I just dont know how to tell which one is going bad.

tjwalker

ebay sensors can be cheap-charly. I have seen numerous examples of absolute junk coming from some of the vendors on there.

Therefore, the idle air control sensor itself is still clearly in play.

99KeeSport

Harbor Frieght has fuel pressure testing kits cheap. Mine has lasted for years. Get the compression tester and oil pressure tester too while you're there.

BotakBeng

nvm

B55Deppe

Hi,

Any luck with u low idle issue. i have a 96 with same problem and i've been fighting with this awhile now. We should talk

Thanks

michaelbgone

This is the one I bought or the jeep. $46