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  #1  
Old September 23rd, 2009, 15:25
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mflueras mflueras is offline
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No start, no fuel pressure/bad fuel pump?

Never had any starting problem until today. Jeep has always started on the first few cranks. Today I finished mounting Rusty's air tube, cleaned the tb with some carb cleaner and tried to start her. I got nothing but cranking and no start. Cycled the key on and off but cannot hear the fuel pump priming. Maybe it's my ears so I check the valve on the fuel rail and get no fuel coming out--bone dry. Swap the starter and fuel pump relays, still nothing. Jeep just turns over but won't start. I tried spraying some carb cleaner down the tb to see if she starts but still nothing. Am I crazy but shouldn't she start or try to start with the carb cleaner if I had fire? Does this mean that my fuel pump and some other unrelated ignition issue are happening at the same time? What do guys think it can be? The jeep was fine like a couple of hours ago, ran great, started right up and now she's down...
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  #2  
Old September 23rd, 2009, 15:30
joe_peters joe_peters is offline
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Re: No start, no fuel pressure/bad fuel pump?

Sounds like the ASD relay may be bad/not energized.

If it is out you won't get power to the coil or fuel pump.
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  #3  
Old September 23rd, 2009, 15:32
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winterbeater winterbeater is offline
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Re: No start, no fuel pressure/bad fuel pump?

Try spray start, not choke cleaner.
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  #4  
Old September 23rd, 2009, 16:16
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mflueras mflueras is offline
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Re: No start, no fuel pressure/bad fuel pump?

Where is the ASD Relay?

I know I should try the starting fluid but choke cleaner should still ignite, right?
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  #5  
Old September 23rd, 2009, 16:36
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mflueras mflueras is offline
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Re: No start, no fuel pressure/bad fuel pump?

Never mind, I'm a dufus. Checked the ADS relay. Swapped it with the starter relay and it's good. Pulled it out and checked to see if power is getting to it. It does. Plugged up an OBD II and getting no codes stored and none pending. It is still cranking but no start, cannot hear fuel pump priming and getting no fuel out of the valve on the fuel rail. While cranking the tach is also not registering any rpms. Does this indicate a faulty CPS? Is the fuel pump out?
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  #6  
Old September 23rd, 2009, 17:12
joe_peters joe_peters is offline
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Re: No start, no fuel pressure/bad fuel pump?

Do you still have the ballast resistor to the fuel pump on the driver's side fenderwell? If so, try bypassing it.
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  #7  
Old September 23rd, 2009, 18:14
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mflueras mflueras is offline
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Re: No start, no fuel pressure/bad fuel pump?

No resistor on mine. I disconnected the harness to the pump and tested it. It's good. At this point I'm all but certain the pump is bad. I can't believe it can just go out without warning. What am I missing.
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  #8  
Old September 23rd, 2009, 20:45
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Re: No start, no fuel pressure/bad fuel pump?

I'm confused, could a bad CPS cause this problem? Could it cause the pump not to come on?
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  #9  
Old September 23rd, 2009, 23:05
JJacobs JJacobs is offline
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Re: No start, no fuel pressure/bad fuel pump?

Absolutely. The rpm signal starts the party, so to speak. No cps, no nothing. Newer vehicles will throw a code from CMP detected with no CKP (cps) but I don't think xj's ever did.
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  #10  
Old September 23rd, 2009, 23:09
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mflueras mflueras is offline
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Re: No start, no fuel pressure/bad fuel pump?

Well, I jumped the relay from 30 to 87 pins and could not get the fuel pump to come on. Can someone confirm this is the correct procedure to jump the relay to force the pump on? I guess I'll start with the crank sensor first. I have never replaced mine so I guess this will be good to learn to do in the garage. If it's not the problem at least I'll have a spare. If it doesn't fix the problem I guess it will have to be the fuel pump.
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  #11  
Old September 23rd, 2009, 23:28
JJacobs JJacobs is offline
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Re: No start, no fuel pressure/bad fuel pump?

Wait- you're going two different directions. Normally the pump runs for a couple of seconds when the key is first turned, and then again when rpm signal is detected from the cps while cranking.

Testing the fuel pump relay socket of course bypasses all that. If you're putting 12 volts on the output pin of the fuel pump relay and the pump doesn't run there is a circuit or pump problem. If the pump runs but builds no pressure suspect the hose in the tank that connects the pump to the hardline.
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  #12  
Old September 23rd, 2009, 23:32
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mflueras mflueras is offline
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Re: No start, no fuel pressure/bad fuel pump?

Yes, I know. Two different directions. First, the pump. I cannot get it to come on. That's why I was jumping the pump relay. I figured I can try to force it on. The other problem I seem to be having is I have no spark. I did not pull a plug tonight but when trying to spray carb cleaner in the tb it will not even try to start.
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  #13  
Old September 23rd, 2009, 23:41
JJacobs JJacobs is offline
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Re: No start, no fuel pressure/bad fuel pump?

Just read your first post again. Did you remove any ground wires while doing the air tube swap?
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  #14  
Old September 24th, 2009, 02:53
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Tim_MN Tim_MN is offline
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Re: No start, no fuel pressure/bad fuel pump?

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 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 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 gauges 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 OBDII 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, 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. 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.


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.

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  #15  
Old September 24th, 2009, 08:38
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242_cherokee 242_cherokee is offline
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Re: No start, no fuel pressure/bad fuel pump?

Bad CPS. Had he same problem a few weeks ago. Its like 70 bucks for a new one.
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