No Fuel

96 4.0 AW4. Where I'm at: Ran fine, parked it and then the next day no start. Has no pressure on the fuel rail. I swapped some relays around still no pressure. Checked for power at the fuel pump plug, had no juice. Made a jumper and jumped the relay, power in, to pump power pins (spades) and got fuel to the rail. Still no start.
Checked the activation power to the relay and the ground through the PCM, both tested good, the activation current for the relay was around 10.5 volts and there was a ground there (through the PCM). The newer style relays are quiet and it's hard to tell when they activate.
I tested for spark and didn't get any, though the ground I used was questionable.
A couple of funny things. The female spade connectors in the relay socket seem really loose (could be my problem). They may have overheated, I may have a partial short someplace. Not enough to blow the fuse, but enough to heat things up.
It started snowing, so I knocked off. Today I plan on a pressure test and to check for spark again (with a better ground).
The wifes 96 is kind of a bastard, it's some different than other 96's I've seen, but not exactly the same as a 95. I was getting a strange ground path, the relay power out to the pump (with the pump plug disconnected) had some type of ground path, that according to my schematics shouldn't be there.
Another oddity, I'm not having any luck retrieving the codes by the key methode. Question, does the check engine light normally come on when the key is in the run position? I can't really remember (mine doesn't), the 96 is the wifes XJ and I don't often drive it. I'm hoping the problems don't go deeper than the fuel pump relay/power circuit. I've had little trouble in the past retrieving the codes, other than having to repeat several times, to get the rythem right.
Any suggestions or anything that sounds familiar?
If anybody has a full page schematic (private message) for the 96 (relay and fuel system), it could be helpfull (or maybe a 95, I'm thinking what I have is a combination of both). What I have doesn't match either All Data 96 or the OBD 1 schematics I have on hand exactly. The layout of the actuall relay box and what my owners manual specifies is even rather different.
Any help or suggestions that my shorten my time out in the cold and may help to avoid a towing charge will be appreciated (I don't really know if the auto club will tow from the house to the dealer for free?). I may have to bite the bullet and put it on the machine at the dealer, the wife wants her Jeep now!

Both times my pump failed it was the same as yours-running fine when parked-no start next time.Try hitting the tank near the pump with a block of wood or No-spark hammer that may loosen the pump enough to run to somewhere to get it fixed.
On my 96 the key on-off-on off -on method will bring up the codes.The check engine light should come on when key is turned to start-like all other lights then go out when the engine is running unless there is a problem.
Wayne

Got some help today, it's nice to have someone to turn the key on and off when your trying to troubleshoot.
First thing I noticed was the fuel pump relay would activate for a second then shut down. I'm guessing because some reference signal was out of spec.
Tested the cam position sensor, because I was on that side of the motor anyway. Noticed it had only 2 volts of supply voltage (my book says it should have 5 volts).
Moved over to the CPS and did an ohm test between the ground and output pin on the CPS and it was infinit ohm, just like it should be. My daughter noticed that the Check Engine light came on when I unpluged the CPS? It didn't seem to be working at all yesterday, no matter what posiiton the key was in and/or when trying to retrieve the MIL codes.
Just on a whim I tested the supply voltage for the cam position sensor with the CPS unplugged and the 5 volt supply voltage was there. Hook up the CPS sensor and the supply volts dropped to 2 volts. I'm guessing the CPS and Cam position sensor share a power supply, that is shorting at the CPS and drawing the voltage down.
Tested the supply voltage pin and the ground pin at the CPS (side) connector and found like 0.2 ohms of resisitance. Seems kind of low, I'm guessing there is a near short between the supply voltage in and the ground out, in the sensor or maybe in the wire lead (I'm gonna have to look closer and see if it has been burnt or cooked). I tested the ground to the PCM (at the CPS) and it had like 0.4 ohms of resistance (sounds like typical connector resisitance).
I didin't find any resistance values (in what reference material I have) for the CPS in the 96. It may be in the DRB scan tool tables, which I don't have.
Anybody have a clue as to what the resistance between the "A" and "B" pins should be at the CPS for the 96? "B" and "C" pins should be open (infinit ohms), by my book.
I'm going to order and try changing the CPS on a hunch, it should be here in a couple of days, but any additional info would be appreciated. My problems may go deeper than the CPS.
I already found some loose connectors for the fuel pump circuit, that appear to have gotten hot, that I'm gonna have to deal with and probably some other stuff that will turn up.
I want to get as much as possible right, before I turn it over to the dealer, if I must.

First thing I noticed was the fuel pump relay would activate for a second then shut down.

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Thats normal it should do that.

The fuel rail builds a little pressure, but not enough. The fuel pump relay just clicks once and then opens. It may be less than a second. On my Renix I can hear the pump run for a few seconds, in the 96 it is a lot quieter (I haven't really noticed how long it primes when the key is turned on normally).
Something I failed to mention is I'm not getting any spark either.
I'm guessing the CPS. Though I don't really know if a faulty CPS, will turn off the fuel pump relay. It seems plausible.
If I had another CPS to test the resistance between the ground (black with a light brown stripe) and the 5 volt supply voltage (violet with a white stripe), I'd likely know for sure. Mine tests almost dead short between the two and I don't really know if it should be that way or not. Some kind of resistance internal in the CPS between the 5 volt supply voltage in and the ground out seems likely (0.2 ohms seems kind of low).
The sensor signal wire (grey with a black stripe) and the ground wire (black with a light brown stripe) is supposed to be open (infinit ohms). But I haven't found any ohm values (or tests) for the supply voltage wire and the ground wire (CPS) in my literature?
Not being able to retrieve the (MIL) codes from my Check Engine light is making me nervous. A PCM is really expensive.

CPS test from 96 FSM
Place ohmmeter across term B and C ,meter should be set to 1K-to 10K scale.The meter readind should be open no resistance Replace sensor if low resistance is indicated.
Wayne

Wayne Sihler said:

CPS test from 96 FSM
Place ohmmeter across term B and C ,meter should be set to 1K-to 10K scale.The meter readind should be open no resistance Replace sensor if low resistance is indicated.
Wayne

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I did that and it tested good. But everytime I plug the CPS in, the Check Engine light goes out and refuses to come back on for any reason, no matter what position the key is in. The fuel pump relay and the ASD relay also pop open.:confused1
The cam position sensor and the crank position sensor share a 5 volt power supply (it may be the same wire with a splice). Everytime I plug in the CPS, the cam position sensor supply voltage drops to 2 volts (and the Check Engine light goes out and refuses to come back on again among other things).
I'm thinking the problem may be between the "A" and "B" pin on the CPS. I vaugely remember a warning about about testing the CPS (Hall sensor), with an ohm meter, I may be mistaken or am thinking of another year (model run).
I'll have another look in the DRB testing procedures and see if they have an ohm specification between the "A" and "B" pin. I know they do for the pre 96 (the 91-95 model run). Our 96 hasn't messed up much in the past, other than normal maintenance stuff, this model (transition) run is pretty new to me.
Thanx for the help, we are having thunder storms today and the troubleshooting is on hold.

The solution was the CPS.
It tested "OK" by the book; Test for ohms between pins "B" and "C", with ohm meter set to 1 ohm scale, circuit should be open (or infinite resistance).
I had a short between "A" and "B" (which the test procedures in the book didn't mention). My new CPS tested open between "A" and "B", my old one tested short between "A" and "B" (removed from the XJ). I did get an ohm reading, with it installed of .2 ohms once, which may have been a faulty test or maybe the metal from the flywheel, affected the reading. But out of the XJ it tested dead short between "A" and "B".
Symptoms were, no fuel at the fuel rail, the fuel pump relay would click on then off, so quick that that the fuel rail would't build much, if any pressure.
The CHECK ENGINE light wouldn't come on with the key in the run position and I couldn't pull any codes by the key methode.
I tested the cam position sensor and had only 2 volts of index voltage, there should be 5. When I unplugged the CPS, the index voltage for the Cam position sensor went up to 5.16 volts.
I also wasn't getting any spark.
If you have a 96, file this away someplace, it's likely it wasn't a one time occurance and will happen again in somebody elses 94-96 XJ.
One note, check the out voltage on your ohm meter before testing, some of the analoge types, put out quit a few volts (9 or so), over 7 volts can damage the CPS ( I read a warning about that someplace once, that stuck in the grey matter).

great info - i have a '96 with no cargo area carpet - i can hear the fuel pump "buzzing" now all the time - could it be starting to get tired?

does the tank have to come out to replace the unit?

bacelaw said:

great info - i have a '96 with no cargo area carpet - i can hear the fuel pump "buzzing" now all the time - could it be starting to get tired?

does the tank have to come out to replace the unit?

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On the 96 it does not have to come out(tank) but it is a cramped work area.
Wayne

bacelaw said:

great info - i have a '96 with no cargo area carpet - i can hear the fuel pump "buzzing" now all the time - could it be starting to get tired?

does the tank have to come out to replace the unit?

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My new one is louder than the old one.

Wayne Sihler said:

On the 96 it does not have to come out(tank) but it is a cramped work area.
Wayne

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Is it a complete unit? is there any danger of dropping anything backwards into the tank? any special tools required to get it out?

http://autozone.com/servlet/UiBroke..._us/0900823d/80/15/28/b9/0900823d801528b9.jsp
That should take you to Autozone's vehicle repair site. it's like an online haynes manual with pictures.
You'll need a brass punch of some sort to take the flange off, don't use anything steel. Sparks are bad.

bacelaw said:

Is it a complete unit? is there any danger of dropping anything backwards into the tank? any special tools required to get it out?

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I just replaced mine yesterday. I was easy. No special tools except the brass punch to spin the retaining ring off. I bought the screen and Bosch pump from Autozone. The 96 does show two pumps at NAPA. My XJ was built in late 95 so it still used the old style pump.

Check out this thread.
http://www.naxja.org/forum/showthread.php?p=757479#post757479