NAXJA Forums -::- North American XJ Association  

Go Back   NAXJA Forums -::- North American XJ Association > NAXJA Unibody Jeep Technical Forums > Jeep Cherokee XJ (1984 - 2001) > OEM Tech Discussion
HOME Member FAQ Sponsor Info Rules Bylaws E-Mail

OEM Tech Discussion Forum for OEM (Original Equipment) or stock XJs and MJs.

Reply
 
Thread Tools Display Modes
  #1  
Old February 10th, 2018, 20:44
Ou2mame Ou2mame is offline
NAXJA Forum User
 
Join Date: Apr 2016
Location: Long island, ny
Posts: 157
Need some help.. Starting issue

I have a 99 xj and for the past few weeks it began having a starting issue. It would start but idle very rough. And then it went away 30 seconds later and ran great. Then one day it cranked but wouldn't start. Then it started again and rough idle again at startup. I changed the cps with an oem one and the idle air control valve as well. Rough idle at startup went away, everything was good. Now a couple days later it's cranking and not starting again! Fuel pressure seems to be around 45psi when cranking. Going to test for spark tomorrow morning... Anyone have any ideas though?


Sent from my iPhone using Tapatalk
Reply With Quote
  #2  
Old February 11th, 2018, 02:56
Jim Malcolm Jim Malcolm is offline
NAXJA Forum User
 
Join Date: Aug 2014
Location: PA
Posts: 46
Re: Need some help.. Starting issue

Camshaft position sensor
Reply With Quote
  #3  
Old February 11th, 2018, 06:22
CJR CJR is offline
NAXJA Forum User
 
Join Date: May 2005
Location: PA
Posts: 151
Re: Need some help.. Starting issue

Have you used Cruiser54's tip to see what the CKPS voltage of the new sensor is while you're cranking the engine? You may have a bad new CKPS sensor. It's got to be 0,5V or more.

Best regards,

CJR
Reply With Quote
  #4  
Old February 11th, 2018, 07:50
Tim_MN's Avatar
Tim_MN Tim_MN is offline
Freakish Hand Strength
 
Join Date: Mar 2003
Location: Minneapolis, MN
Posts: 6,215
Re: Need some help.. Starting issue

Combined starting idle issues are either a fuel delivery issue, or a battery voltage issue. Test the fuel pressure and test the check valve function. Consider that one or more fuel injectors are a bit leaky. Inspect/clean/test the battery, starter, and alternator connections. Load Test the battery and the alternator.

The CPS test is quick and simple, confirm the CPS is within specifications.


When a 1997 to 2001 Cherokee won’t start on the first try day after day, the first thing to suspect is a failed check valve on the fuel pump. The fuel pump check valve is supposed to hold pressure in the fuel line while the engine is off. The check valve is located on the fuel pump and located inside the gas tank. A failed check valve allows the fuel to drain back to the tank. This results in one or more of the following symptoms:

SYMPTOMS

• Longer than normal cranking times
• Never starts on first try, almost always starts on the second try
• Rough idle for a few moments of idling
• Rough running for first block of driving
• Little or no fuel pressure at the fuel rail test valve similar to this -

1- Key in on position; fuel pump primes for 2 seconds then stops. 0 PSI
2- Cranking over the engine. 2-3 PSI
3- Engine starts and idles for 20 seconds. < 5 PSI
4- Engine idles and fuel pressure creeps up to 45-50 PSI.

POSSIBLE CAUSES

• Failed check valve on the fuel pump in the gas tank.
• Leaky fuel injector(s) may be the true cause of your problem, but more likely they are simply contributing to the check valve issue.

Testing of the fuel injectors should show if any are faulty and are allowing fuel to drain into the cylinder. Either problem can allow heat soak to vaporize the remaining fuel in the fuel rail, and you may be dealing with a bit of vapor lock as well, especially in warmer weather.

1. Connect the gauge at the fuel rail and start the engine. The gage should read 49 psi plus or minus 5 psi.
2. Turn the engine off and immediately clamp the fuel line just ahead of the fuel tank. Watch the pressure gage and see how long it takes to loose pressure.
If the pressure remains at 49 psi for an extended period of time then the problem is in the tank - probably the check valve. If the pressure falls below 49 psi fairly rapidly then the problem is probably one or more leaky injectors.

There are a few solutions to the problem –

1. Turn the key to ON for 5 seconds and let the fuel pump prime. Turn the key to OFF, turn the key back to ON for 5 seconds, start the engine.
2. Crank the engine for 3-5 seconds, pause, and crank the engine again. It will almost always start on the second try.
3. Replace the fuel pump assembly in the gas tank. The check valve is not a separate part and cannot be serviced. This is both expensive and time consuming because you have to remove any hitches and skid plates and then remove the gas tank from the vehicle.

You can use solutions 1 or 2 for as long as you want to, they do not harm anything and the fuel pump will continue to function for many more years.

If you do replace the fuel pump assembly, purchase a high quality OEM style pump assembly such as Bosch or Carter. Some cheap aftermarket fuel pump assemblies, like Airtex, and Precision don’t hold up and will fail completely within 12-18 months.
__________________
.
.

Quote:
Originally Posted by bimmerjeeper

I'm starting to realize people on the Jeep forums are highly expert mechanics .....
Reply With Quote
  #5  
Old February 11th, 2018, 12:19
CJR CJR is offline
NAXJA Forum User
 
Join Date: May 2005
Location: PA
Posts: 151
Re: Need some help.. Starting issue

A couple of things to add to Tim Mn's excellent comments. I've lost the check valve in my in-tank fuel pump. Instead of pulling the fuel pump from the tank, I bought an all aluminium check for fuel systems and installed it in front of the fuel filter. Problem solved. Also, I found when an injector start dribbling a little I notice the RPM will jump high momentarily if I shut down a warm engine,wait a little, and then restart. Using some injector cleaner normally gets it back to normal.

Best regards,

CJR
Reply With Quote
  #6  
Old February 11th, 2018, 14:32
Ou2mame Ou2mame is offline
NAXJA Forum User
 
Join Date: Apr 2016
Location: Long island, ny
Posts: 157
Need some help.. Starting issue

The fuel pressure remains constant, and the injectors are only a year old as well. I can't get it started no matter how long or often I crank it. Luckily I have a 2nd car. My mechanic had the jeep for over a week and checked everything, and it was starting fine for him every day. Get it back with a new cps and it runs fine for a day and now it's not starting again. He thought it was the fuel pump but since he didn't observe a new start condition he couldn't test it. I have it in my driveway not starting now and fuel pressure is good.

I'll test the battery next.. But it won't start even with a jump pack, and the terminals are new and grounds are new as well.

It cranks and feels like it's about to start but never quite gets there. The plugs wires cap and rotor are about 2 years old.


Sent from my iPhone using Tapatalk
Reply With Quote
  #7  
Old February 11th, 2018, 14:37
Ou2mame Ou2mame is offline
NAXJA Forum User
 
Join Date: Apr 2016
Location: Long island, ny
Posts: 157
Need some help.. Starting issue

I'm on my phone and can't figure out how to edit my post.. "He thought it was the fuel pump but since he didn't observe a new start condition he couldn't test it." I meant no start not new.


Sent from my iPhone using Tapatalk
Reply With Quote
  #8  
Old February 11th, 2018, 15:41
Tim_MN's Avatar
Tim_MN Tim_MN is offline
Freakish Hand Strength
 
Join Date: Mar 2003
Location: Minneapolis, MN
Posts: 6,215
Re: Need some help.. Starting issue

Are you installing genuine Jeep OBD engine sensors ?

Most auto parts stores sell cheap crappy Chinese made parts, some that even come with a "Lifetime Warranty". These parts are poorly manufactured and/or made from inferior materials. They are often out of specification, or even failed, right out of the box. The ones that are not faulty many times will have a short service life before they fail. Always buy top quality replacement parts and genuine Jeep engine sensors. Numerous threads detail long and frustrating searches for a "problem" that ended up being cured simply with genuine Jeep repair parts.

Cheap parts are cheap for a reason.
__________________
.
.

Quote:
Originally Posted by bimmerjeeper

I'm starting to realize people on the Jeep forums are highly expert mechanics .....
Reply With Quote
  #9  
Old February 11th, 2018, 16:26
blakews2217 blakews2217 is offline
NAXJA Forum User
 
Join Date: Jun 2016
Location: Alton, Illinois
Posts: 243
Need some help.. Starting issue

Keep it simple at first. Check al fuses under the hood. When you turn the key on with the seatbelt clicked ( this stops the initial beeper so you can hear better) you should hear relays. If all they check out check for spark at the coil and at one of the plugs.


Sent from my iPhone using Tapatalk
Reply With Quote
  #10  
Old February 11th, 2018, 16:44
blakews2217 blakews2217 is offline
NAXJA Forum User
 
Join Date: Jun 2016
Location: Alton, Illinois
Posts: 243
Need some help.. Starting issue

Another thing that comes to mind is to check the wiring harness near the fuel rail and all over the engine bay. The fuel rail bites into the harness over time and can break/short wores


Sent from my iPhone using Tapatalk
Reply With Quote
  #11  
Old February 12th, 2018, 22:02
Ou2mame Ou2mame is offline
NAXJA Forum User
 
Join Date: Apr 2016
Location: Long island, ny
Posts: 157
Need some help.. Starting issue

The cps is oem. The idle control isn't though. Changing them made no difference.

I remembered that the coolant temp sensor had been funky this summer reporting the wrong temps once in a blue moon so I replaced that and it started but idles very rough still. Doesn't sound like a misfire though.. Sounds like it's about to die unless I give it gas. Once warm it's fine. Voltage on the battery is 14 when idling, and it doesn't drop past 11.5 when starting. So I'm going to assume the battery and charging system are intact.

I pulled some plugs and noticed that they were discolored slightly. I decided to just do everything so I have the coil plugs wires cap etc coming and I'll do that and eliminate that issue. I do have spark but it seemed weak to me.

Once it was running I checked the fuel pressure again. It holds at 45psi, and stays around there while idling, even roughly. I have the old injectors and while they did work, 2 were cracked. I could replace my current ones with those and see if the idle issue changes to eliminate the injectors. Not really sure where else to go with it. It runs great if it'll start and I let it warm up.


Sent from my iPhone using Tapatalk
Reply With Quote
  #12  
Old February 13th, 2018, 03:54
Tim_MN's Avatar
Tim_MN Tim_MN is offline
Freakish Hand Strength
 
Join Date: Mar 2003
Location: Minneapolis, MN
Posts: 6,215
Re: Need some help.. Starting issue

What are the results of the battery and alternator load testing ? When cleaning and tightening all the ground connections, did you find any worn out, loose, damaged or corroded wires/cables/connectors ?
__________________
.
.

Quote:
Originally Posted by bimmerjeeper

I'm starting to realize people on the Jeep forums are highly expert mechanics .....
Reply With Quote
  #13  
Old February 13th, 2018, 09:19
Ou2mame Ou2mame is offline
NAXJA Forum User
 
Join Date: Apr 2016
Location: Long island, ny
Posts: 157
Need some help.. Starting issue

My mechanic did a load test and said that everything checked out. All the grounds and power wires are new, I did them last year. Sanded the rust and paint off every ground point, even used a dremel brush on the bolts. New ground strap even.


Sent from my iPhone using Tapatalk
Reply With Quote
  #14  
Old February 13th, 2018, 11:13
Motod6's Avatar
Motod6 Motod6 is offline
NAXJA Member
 
Join Date: Mar 2016
Location: Yorba Linda Ca
Posts: 112
Re: Need some help.. Starting issue

TPS sensor can cause idle and start issues as well. Doesn't take much for them to fail. Especially the cheap ones. Sneezing on it is enough moisture to make it fail.
Reply With Quote
  #15  
Old February 13th, 2018, 17:58
in_motion in_motion is offline
NAXJA Forum User
 
Join Date: Aug 2016
Location: Indianapolis
Posts: 9
Re: Need some help.. Starting issue

Sorry to threadjack, but by "genuine Jeep" sensors do you mean Mopar brand only? Or are there other bands that will work? Thanks!
Reply With Quote
Reply


Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)
 
Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump

Similar Threads
Thread Thread Starter Forum Replies Last Post
Cherokee multiple cranks, starting issue. Very unusual starting / fuel issue. Intellect OEM Tech Discussion 6 November 17th, 2017 09:48
'93 XJ STARTING ISSUE MEEMERS Modified Tech Discussion 14 February 14th, 2014 17:25
94 XJ starting issue MIKE.94XJ OEM Tech Discussion 7 July 20th, 2011 13:43
Random non starting issue to not starting at all XJ project Arizona Chapter 11 April 20th, 2009 08:37
Starting issue Jeff-97XJ OEM Tech Discussion 1 July 16th, 2008 17:38


All times are GMT -7. The time now is 14:13.


Powered by vBulletin® Version 3.8.9
Copyright ©2000 - 2018, vBulletin Solutions, Inc.
NAXJA and NAXJA logo's Copyright NAXJA. All content/images Copyright NAXJA 1999-2014