Bad fuel pressure? - JeepForum.com
 
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post #1 of 8 Old 07-14-2017, 10:26 AM Thread Starter
Tjkarl169
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Bad fuel pressure?

I have a 2000 cherokee sport that cranks but won't run. Acts like it has spark because it will catch on with carb cleaner. Fuel pump comes on and pressurizes for a second I know because I have a little pressure at fuel rail but the pressure goes away as soon as I crank the motor. Please help!

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post #2 of 8 Old 07-14-2017, 11:33 AM
CJ7-Tim
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More likely, there is a Crankshaft Position Sensor issue, but test the fuel pressure first.

Check the fuel pressure at the fuel rail with rented gauge from the auto parts store. Jumper the fuel pump relay. It should have 39 psi +/- 5 psi.

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post #3 of 8 Old 07-14-2017, 01:59 PM
bluejunior
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I don't do this often but...I disagree with Tim. Sounds like fuel pressure. Get a gauge (parts stores rent them and harbor freight has them for like $20) to confirm, and consider replacing the pump if there's not a locatable kink in the line or something to explain it. Bosch fuel pump only, airtex, parts store store brands (which are usually crap) and whatnot are crap.

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post #4 of 8 Old 07-14-2017, 08:22 PM
07tjt07
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Sorry to hijack your thread but I'm having the same issues, except mine are intermittent. Last night coming home from work my 2000 xj started surging and sputtering while on the throttle, and when slowing down the rpms dropped to 200. At one stop sign, the Jeep stalled out, but then started right back up and ran fine for about 30 seconds before it started sputtering and surging again. The next morning, I drove it for a few minutes with no issues, then it started lightly sputtering and surging again for a few minutes, then it started running perfectly fine again. Drove it again around the block a few hours later and everything was perfectly normal the entire trip. Is it possible that the fuel pump is just weak and only works when it wants to? Also, last night while it was running rough I put it in neutral and tried to rev it up to keep it alive, but it wouldn't go past 1200 rpms. I am running a pressure test tomorrow morning, but I don't think that will be helpful because it's running fine right now. Any ideas?
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post #5 of 8 Old 07-14-2017, 08:26 PM Thread Starter
Tjkarl169
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So I got the voltmeter out and tested the power wire at the plug just before the fuel pump. So what it does is when I turn the key to idle the power wire energizes for 2 seconds then goes away. It seems that there is something wrong with the power for the pump. The relay seems to work and I haven't found a broken fuse yet...
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post #6 of 8 Old 07-15-2017, 05:29 AM Thread Starter
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So lots of youtube videos later I am going to try replacing the crank position sensor. Seems to be a popular problem with not powering up the fuel pump in these cherokees. I'll let yall know how it goes.
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post #7 of 8 Old 07-15-2017, 09:18 AM
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Quote:
Originally Posted by 07tjt07 View Post
... 2000 xj started surging and sputtering while on the throttle, and when slowing down the rpms dropped to 200. At one stop sign, the Jeep stalled out, but then started right back up and ran fine for about 30 seconds before it started sputtering and surging again. The next morning, I drove it for a few minutes with no issues, then it started lightly sputtering and surging again for a few minutes, then it started running perfectly fine again.
It is best to start your own thread.

The symptoms you describe are different, and should make one suspect a faulty Throttle Position Sensor, low battery voltage, or faulty O2 Sensors.

Is the Check Engine Light ON ? Have attempted to download any trouble codes with a Trouble Code Reader ?

Begin diagnostic testing the of suspects.

.

A recent Gallup public opinion poll shows the NRA, at 58% approval, has a higher approval rating than either Hillary Clinton or Barack Obama.

Progressive Liberalism: Bringing you new Healthcare ideas so wonderful, they have to include mandatory participation ...

Originally Posted by Ronald W. Reagan: Government is not the solution to our problems; Government is the problem.
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post #8 of 8 Old 07-16-2017, 08:17 AM Thread Starter
Tjkarl169
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So 99$ later I was holding a new. Crank position sensor. It was a bear to get in to place. I had it on the hoist and took the drivers side tire off, then I put it in place then my wife reached in from the drivers side wheel well and I guided her fingers to it to hold it. Once she held it in place I started the 7/16 bolts back into it. Then I could back myself up to under the transfer case and send a socket with a universal with 2 20" extentions over the cross member under the transfer case and tighten the bolts down. (Just like I did to get the old one out). Note that there was no physical damage or different looking between the old one and the new one. Like I mentioned the only way I found out that the old crank position sensor was bad was by putting a test light on the power wire in the fuel pump plug and cycling the key. The test light showed the power wire prime for a second and shut off. Thanks for all the help on the forum. I'm probably sure I will be on here asking more questions in the future lol.
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