99 cranks but won't start

I did some searching but didn't find any concrete answers.

I bought a '99 XJ about 30 days ago. 135,000 miles, 4.0L Automatic, 4WD.

It ran good when I bought it. I drove it over 90 miles to get it home with no problems. Out of habit I wanted to do a tune up, change fluids, etc...
I changed the plugs, cap, rotor, wires and coil and when done it ran great except for it wanting to die right off idle when cold.

I went on vacation (Jeep Jamboree in TN with WJ) last week and so the XJ sat in the garage for a week and was not started.

Now it will not start. It cranks over good and strong, but will not fire. Im guessing maybe fuel pump, maybe fuel drained down after sitting for awhile?

Not sure exactly were to start.

Is there a Schrader valve to connect a fuel pressure guage to check fuel pressure? if so where?

Any other suggestions on how I can get her running again?

If you have one, the Schrader Valve is on the fuel rail.

The most likely cause of it cranks and cranks but won't start up is the Crankshaft Position Sensor (CPS) located on the transmission bell housing. Often this part is also referred to as the CranKshaft Position Sensor (CKP) CPS/CKP failure is very common. The CPS/CKP can stop working with no warning or symptoms and the engine will not run or the engine may randomly stall for no apparent reason.

Crank Position Sensors can have intermittent “thermal failure”. This means that the CPS/CKP fails when the engine gets hot, but works again (and will test as “good”) when it cools back down.

Begin with basic trouble shooting of the start and charge systems. Remove, clean, and firmly reconnect all the wires and cables to the battery, starter, and alternator. Look for corroded or damaged cables or connectors and replace as needed. Do the same for the grounding wires from the starter to engine block, and from the battery and engine to the Jeep's frame/body. Jeeps do not tolerate low voltage or poor grounds and the ECM/ECU may behave oddly until you remedy this.



Symptoms –
- Starter cranks and cranks but engine won't start up and run.
- Fuel gauge and voltage gauge may not work or display properly.
- You sometimes will have No Bus on the odometer after 30-60 seconds.
- A failed CPS/CKP may or may not throw a CEL trouble code.
- No spark at the spark plugs.
- Fuel pump should run and prime for 3-5 seconds.

If the CPS/CKP is failed sometimes the OBD-II trouble code reader cannot make a connection to the ECU/computer or cannot read Check Engine Light/MIL codes because the CPS/CKP has failed. Disconnect the code reader, disconnect the CPS/CKP wire connector, and reconnect the code reader. If the code reader establishes contact with the ECU and scans, your CPS/CKP is failed and needs to be replaced.


Diagnostic steps to confirm the CPS is the cause of your no-start


You should be able to verify a bad cps, by unplugging it, and turning the ignition key to on. If the voltage gauge and/or the fuel gauge now displays correctly and/or the No-Bus is gone, replace the CPS.

Unplugging and reconnecting the CPS sensor where it connect to the main harness near the back of the intake manifold usually resets the ECU and if the jeep fires right up after doing this you can bet that the CPS is faulty and needs to be replaced.

Exchange the fuel pump relay and the ASD relay with one of the other similar ones in the PDC to eliminate the relays as the cause of the no-start. Check the ASD relay fuse.

Confirm that the fuel pump to runs for 3-5 seconds when you turn the ignition key to ON.

Eliminate the NSS as a cause of no start. Wiggle the shift lever at the same time you try to start. Put the transmission in Neutral and do the same. Do the reverse lights come on when the shifter is in Reverse?

Inspect the wires and wire connectors at the O2 sensors on the exhausts pipe. A short circuit from melted insulation or from broken O2 sensor wires can blow a fuse and the ECU/ECM will loose communication. Don’t get tunnel vision and assume the sensor is bad (unless it tests bad with a meter). Damaged wiring or a dirty connector can inhibit the signal from making it to the computer. Inspect/test/clean/repair wiring or connectors as necessary.


CPS Testing


Crankshaft Position Sensor Connector (CPS/CKP)



.



TESTING PROCEDURE 1991 – 2001 4.0L H.O. engines

1. Near the rear of intake manifold, disconnect sensor pigtail harness connector from main wiring harness.
2. Place an ohmmeter across terminals B and C (See Image). Ohmmeter should be set to 1K-to-1OK scale for this test.
3. The meter reading should be open (infinite resistance). Replace sensor if a low resistance is indicated.

TESTING PROCECURE for 1987 – 1990 4.0 L engines

Test # 1 - Get a volt/ohm meter and set it to read 0 - 500 ohms. Unplug the CPS and measure across the CPS connector's A & B leads. Your meter should show a CPS resistance of between 125 – 275 Ohms. . If the CPS is out of that range by much, replace it.

Test # 2 - You'll need a helper for this one. Set the volt/ohm meter to read 0 - 5 AC volts or the closest AC Volts scale your meter has to this range. Measure across the CPS leads for voltage generated as your helper cranks the engine. (The engine can't fire up without the CPS connected but watch for moving parts just the same!) The meter should show .5 - .8 VAC when cranking. (That's between 1/2 and 1 volt AC.) If it's below .5vac, replace it.


The 2000 and 2001 will have the CPS in the same location on the bell housing, but the wire connector may be on the passenger side, not as shown in the diagram below. Simply follow the wire from the sensor to the connector.

.

The ground wires by the coils were covered in oil when I was changing the coil. Could it be as simple as a bad connection at that ground point?

Begin with basic trouble shooting of the start and charge systems. Remove, clean, and firmly reconnect all the wires and cables to the battery, starter, and alternator. Look for corroded or damaged cables or connectors and replace as needed. Do the same for the grounding wires from the starter to engine block, and from the battery and engine to the Jeep's frame/body. Jeeps do not tolerate low voltage or poor grounds.

Grounds can be the root cause of many electrical gremlins. Refreshing grounds is NEVER a bad idea!

You can't just check or look at these grounds. You must remove, scrape, clean until shiny the cable/wire ends and whatever they bolt to. The one on the back corner of the head, and where it attaches to the firewall. Scrape the paint from the firewall. Best to replace that woven cable with a #4 or #2 gauge cable. You can attach the one end to the intake manifold if you would like.

Next go over to the engine dipstick tube stud. Remove the nut and clean the wire ends and scrape the block until shiny at the stud. Reattach tightly.

If you are so inclined, add at least a #6 cable from the negative terminal of your battery to one of the bolts on your radiator support. Scrape the paint off first.

If it still won't start after freshening grounds, you need to figure out if you are missing spark or fuel. Remove a spark plug, keep it attached to the plug wire, place the plug electrode near a good engine ground, have a buddy crank the engine while you watch. You are looking for a strong, BLUE, snapping spark. Yellow/orange/white indicates a weak spark, which may not be strong enough to start the engine. As Tim mentioned, the #1 cause of no spark is the crankshaft position sensor. Any particular reason why you changed the coil? They usually last a long, long time. If you have a spark issue, I would try installing your old one back on. It is not impossible that you got a bad coil out of the box. It happens.

If spark is good, then try small shot of starting fluid into the intake, or a small splash of gas into the intake. If it runs with this technique, you have confirmed a FUEL DELIVERY problem.

Once you know the results of the above, check back with us! Good luck.

Just now getting back to a computer.

Thanks for the replies. As it turns out apparently I was just impatient with the ignition key. I tried again later that day, ruen the ignition on and sat there for a few secs, at least until the fuel pump shut off, and then tried to crank it and it started right up.
Guess the fuel drained down the the first time I just wasn't giving the fuel pump time to build pressure in the fuel rail.

Thanks again for the tips.

rshackleford said:

. I tried again later that day, ruen the ignition on and sat there for a few secs, at least until the fuel pump shut off, and then tried to crank it and it started right up.

Guess the fuel drained down the the first time I just wasn't giving the fuel pump time to build pressure in the fuel rail.

Click to expand...

The check valve is located on top of the gas tank and is part of the fuel pump assembly on 95.5-2001 vintage 4.0 XJs. When the check valve starts to fail, it reduces fuel pressure to a point where an extended crank is needed to start the engine. It is a very common failure. I experienced it on my 99 at around 75K.

A good (and simple) way to troubleshoot this problem is called “the poor mans prime”

1. Turn key to ON position (do not crank the engine!)
2. The fuel pump will energize and run for a couple of seconds
3. Turn key to OFF position
4. Repeat above a two more times
5. NOW crank the engine over

If the engine starts quickly and cleanly after performing this procedure, you may have the check valve issue. If it starts and runs poorly for a few seconds, it could also be a leaky fuel injector resulting in the bleed down and the stumble upon startup is the engine clearing the excess fuel that has leaked into the cylinder because of the faulty injector.

Also be aware that a bad battery can give you this symptom. Sounds strange but it definitely does happen. Have battery load tested if you have any questions; your XJ does NOT like low available battery voltage. Be sure battery connections and posts are CLEAN.

Some troubleshooting tips for extended crank times:

Hook up fuel pressure gauge on the schrader valve on the fuel rail

Start engine and bring to normal operating temperature.

Observe test gauge. Normal operating pressure should be 49.2 psi (plus or minus 5 psi)

Shut engine off.

Pressure should not fall below 30 psi for five minutes.

If pressure falls below 30 psi, it must be determined if a fuel injector, the check valve within the
fuel pump module, or a fuel tube/line is leaking. An adaptor tool/hose included with the fuel pressure gauge can help you with this. Consult gauge manual for more information on this but here is basically how it works:

*Turn the engine off and immediately clamp the fuel line at the adaptor hose. Watch the pressure gauge and see how long it takes to lose pressure.

*If the pressure remains at 49 psi for an extended period of time then the problem is in the tank - possibly the check valve. If the pressure falls below 49 psi fairly rapidly then the problem is probably a leaky fuel injector.

You can limp a check valve problem along indefinitely if you wish as it doesn't mean the fuel pump itself is going bad. Normally, the check valve is replaced as an entire assembly as you have to drop the gas tank to access the assembly. Fuel pump assembly consists of fuel pump, regulator, check valve, filter. If you do replace the fuel pump assembly, purchase a high quality OEM style unit. Some cheap aftermarket assemblies don’t hold up and fail prematurely. I specifically seek out Bosch fuel pumps as they are the best in the business. Stay away from Airtex, as IMHO, they have a bigtime reliability problem.

I think it is the check valve. Im going to just run with it for awhile and see if it gets worse.

Thanks for all the info. Part of the reason I like Jeeps is because of the great websites and info on the net to troubleshoot and repair them. And of course, the websites are no better then the people who post their knowledge and help.

I know it's been awhile, but if I can add to this thread, I just went thru this with my 99 XJ-

After doing maintenance on the Tcase and reinstalling it, I started her up and she ran, then after about 20 min just quit. Started once after that, ran rough, and quit again, Could not get to start again.

Switching the fuses around in the PDC had no effect. I could hear the fuel pump and the engine would crank, but still no start.

After reading through several forums, I concluded it must be the CPS.

I replaced that, as well as the fuses in the PDC since they were the originals. For good measure, I also replaced the coil (not original, but still old).

Once all was replaced, she started right up like nothing ever happened. I am convinced it was definitely the CPS, but again the other items were quite old as well.

Hope this helps anyone.

Hi all,
I've not been contributing on here, but regularly check out the site...:wave1:

Had a similar problem with my '99 (it's a UK 'Orvis' with 36k miles)

Symptoms: initially wouldn't idle all the time (really had to tickle the gas pedal..., then the fuel pump failed (replaced with a Bosch unit).
This seemed to fix things, but it ran for 5 miles then died completely..!

-On UK market Jeep there is an immobilizer fitted when they arrive. -For a long time I thought this had died -Which is a real problem, because the PCM is locked to it, so you can't by-pass it...

After checking on here, and seeing Tim_MN's post, I finally diagnosed the crank sensor. -As Tim says: no temp or voltage gauge, no OBD connection, no spark.

New crank sensor fitted and all is well again!

So I wanted to say a big thank you Tim_MN for an excellent post.

And also say thanks to everyone on here for making an excellent site.
Keep up the good work guys atriot:

/Andrew

Hi there.



Just solved a similar problem. Not trying to hijack your post, but to help others.



Here's what happened to me. After parking the car. The next day was unable to start the engine, "check engine" blinking. Cranking the engine was working, but wouldn't start.
After connecting several OBDII readers, no luck on getting the error codes.

Finally got the tip. The process to retrieve the code from key is as follow:
Turn ignition on /off five times, do not crank the engine.
At the last time you will see the check engine blinking. Count the blinks. This is your error code. For me the first code was 15.
It will pause for a moment and the give you the next code.

But beware the code it is not digit by digit as it was stated on other post i read. For code 15 i counted 15 blinks.



After that, you need to check the error codes on the table.

https://sites.google.com/site/thezjpage/zj-diagnostic-trouble-codes-dtc-shttp://


On my case, after checking the fuses and asking for help on several shops. Finally one guy with magic touch, just readjusted the plugs next to the engine and voilá. One bad conector.


Back to the road, for now. :roflmao:

Not sure why, couldn't edit the post.



I drive a Grand Cherokee Limited 2.5 TD from 1998. My first JEEP.


Note: remove the http:// at the end of the link for the error codes.