jeep wont start, no fuel pressure, changed fuel pump, still no pressure

[Rick Jefferson]

Good Evening All. Im a newbee to this forum looking for technical help. heres the scoop. My baby (1997 Jeep Wrangler Sport) decided to stop running on me.
The symptoms started a couple weeks ago. Jeep would not start up after sitting for about 10 min. Finally started up (dont know why). Then same thing happend about 5 starts later. just turned over but wouldnt fire. I suspected it could be a fuel pump so i rapped on the gas tank a few times and it fired up.
well it started up on for the next 15 to 20 starts. Cool i figured i must be out of the woods and mabey it was water in the gas.. just then... it died but this time while i was driving it. just acted like it ran out of gas. Well i towed my baby home and prepared for one of the repair jobs i just love..dropping the tank and replacing the fuel pump. Fast forward to tonight. I got a new fuel pump from NAPA, installed it. The only glitch i ran into was that the electric connector on the new unit did not fit. I had to drop the tank again and splice the connector from the old pump onto the new pump. Got everything back in place. Added 5 gallons of fresh gas and tried to start her up ... Nothing.. Turns over like a champ but wont fire. The sending guage shows gas in the tank but there does not seem to be more then a dripple of gas from the pressure release valve on the fuel injection rail. That puppy should be shooting out. soooo im not getting fuel to the rail.

Any ideas from this forum would be appreciated. im stumped. My next step is to check the voltage to the pump. im assuming it should be a straight 12 V when the ignition is turned on.

Thanks!
Rick.

 

[Ghost Rider]

Rick,
my daughter had issues with her 1998 TJ wanting to die while driving. Originally, I was thinking it was the fuel pump or the filter but someone here suggested that it was the Crankshaft Position Sensor. Since it was the cheapest and easiest thing to fix ($71.00) we went with that and it did the trick for us. I am not sure if your car has one of these things or that it is what causes your problem but it is something o think about. The thing is located on top of the bel housing and you are going to need some long extensions to get to it. I also decided that if I was going to change the fuel pump, I was going to make a cutout on the tub for feature access in case I might need to do it again and not to have to drop the fuel thank..... It is kinda of dumb that they never did that. Hope everything goes well and you get it fixed. Please let us know what you find out.

 

[dnr421]

You can use a test light to check for power going to the pump. Unplug the connector and touch the light to the green/black wire. Have someone turn the key on, at that time you should see it light up for a couple of seconds. Then have them attempt to crank the motor, it should stay lite while they are spinning it over. But remember there is only power while the motor is spinning over

 

[Rick Jefferson]

Thanks guys, the problem is in the power. now im stumped. Im not very good at reading skematics. i alredy swapped the relays around and its not the realy. i did have a bown fuse on the fuel pump circutt but i changed that and it did not blow agan. I dont know if the power runs through the computer or direct from the relay to the pump. im about ready th throw in the towel and take it to the garage. but ill keep trying to find alternatives.
Thanks. Rick.

 

[Brent H]

I know its been awhile since this thread was active but I am having the same problem with my 1998 TJ, the symptoms all seem to be the same. I was wondering if you were able to figure out what the problem was?

 

[k-2]

ideally you want a fuel pressure gauge to do checks.

Always scan for code even if light is off.

I will guess a 4.0L - let us know if you can trouble shoot elecs. use a wiring diagram and a test lamp.

 

[JPNinPA]

I know its been awhile since this thread was active but I am having the same problem with my 1998 TJ, the symptoms all seem to be the same. I was wondering if you were able to figure out what the problem was?

It would be great if everyone posted their fix. Out of the suggestions made in the post to just before you posted what ones did you try and did anything change?
If you swap new sensors use only oem parts. Others have been found bad right out of the box.


Regards,
JPNinPA

Sent using TapTalk

 

[Brent H]

It would be great if everyone posted their fix. Out of the suggestions made in the post to just before you posted what ones did you try and did anything change?

I've switched the relays and found that wasn't the problem. Also I put in a new fuel pump. The pump doesnt start up. I'm thinking it's an electrical problem. Engine starts fine when I pour fuel in through the intake. Also CPS is ok.

Regards

Brent

 

[k-2]

Again I ask - can you use a test light and a wiring diagram? We can post the diagram

Other wise chek fuses, pump only runs @2seconds* if engine does not start.

*makes chcking 12v a 2 person job

Remote starter lt us know

 

[JPNinPA]

When you turn the key to on you should hear the fuel pump. You should get a fuel pressure reading.


Sounds goofy but do you have gas in the tank? Had an old vehicle the gage stuck just below 1/4 tank and ran out of gas 1-2 times.

CKP is the sensor in question. That is on the bell housing?


JPNinPA
Using Jeepz.com app

 

[k-2]

I see the term CKP and have seen poster mention CPS as being OK -

I am thinking that CPS is referance to Crank sensor?

Maybe a little anal, the trade uses CKP for crank position sensor...

The fuel pump only enegizes @2 secods without a CKP signal SO checking 12v is easier as a 2 man job

 

[JPNinPA]

I see the term CKP and have seen poster mention CPS as being OK -

I am thinking that CPS is referance to Crank sensor?

Maybe a little anal, the trade uses CKP for crank position sensor...

The fuel pump only enegizes @2 secods without a CKP signal SO checking 12v is easier as a 2 man job

I'm not taking offense to the anal comment. If that's what it takes to get things fixed, it's not a bad thing. We just need to be sure we speak the same language and not guess what the other is saying. Both are position sensors one for the cam and one for the crank. What they are used for is different.


JPNinPA
Using Jeepz.com app

 

[Brent H]

Figured out the problem. The green/white wire which brings power to the fuel pump module was broken. Runs fine after fixing that.

 

[Ignis]

Did you check the fuel filter

 

[SteveMann]

My jeep did the same thing a couple of years ago. And it was driving me nuts because it would just stop running. And not restart for a few minutes. The independent dealer who sold me the Jeep was also at a loss to explain it. After one day when my wife got stranded on her way to work, I borrowed a neighbors car to take her to work. When I got to the Jeep, of course, it started right up. On my way home, it died again. This time I decided to let the Chrysler/Jeep dealer look at it.

A few hours later and a new Crankshaft Position Sensor, and the problem was solved. Total cost was $151, parts and labor. According to the service manager, the sensor failure was apparent on his factory-supplied OBD, but no home or independent shop OBD would have seen it.