No start symptoms, need advise..

[June]

Hi fella's

I had a case of Dejavu today as the identical no start symptoms occurred to me again. Only this time a little over a year later on my 96 XJ.
We'll I get out of work and attempt to start the XJ and all it would do was crank over. I let it sit for awhile, battery tested fine, fuel pump was kicking on, I disconnected the battery to reset the computer, dist cap appeared fine, getting plenty of spark, tried to start it in neutral to rule out the NSS. So after numerous cranks, I finally give in and call AAA. They said anywhere from 60-90 minutes they'd be there. So I say what the hell I'll go out there and try to start it again. I crank her over a couple of times and still no start. Finally I depress the gas pedal completely to the floor and after a couple of cranks it starts up but would not stay running unless I keep my foot on the gas. Soon as I let my foot of the gas it would die. And in order to start it again I had to depress the gas pedal completely to the floor. So I disconnect the battery again, reconnect it and the XJ starts up fine. Idles fine and drives normally. I drove all the way home and turned it off. Attempted to start it again and it started up on the first try.

I'm thinking it has definatley got to be a sensor. Where should I start. I'd hate for this to happen again. Bad enough I got to hear it from the wife because this is the second time it's happened. Last time it cost me a $90 tow charge.

Any advise would be great. Thanks.

June

[churky89]

Check ALL vacum hoses,could possibly be fuel filter is clogged,or fuel pump screen may be clogged.
Sediment in gas tank could be a problem,or condensation in gas line.
I try to keep mine as full as posible in the winter time,and ever once in a while
I dump in a bottle of gas line anti freeze.

[89xj]

sounds fuel related, but could be a sensor. CPS can give you a no start. sounds more like it is starving for fuel. if it happens again, you need to see if your getting a spark at the plugs. if you are getting a spark, that would eliminate the CPS. might want to check the fuel pressure on the fuel rail.

[Greg Smith]

Sounds like what happened on my 5.2 ZJ after I left on the inside light weakening the battery. It cranked but apparantly lost the computer setting for my idle etc. I noticed I also lost the settings on my vehicle info center and the cranking was a little slow. I had to do the same as you w. the gas pedal. Then I pulled off the metal no tamper plug on the idle set screw on the throttle stop and manually cranked up the idle. Drove home (1 hr trip) and computer had reset idle higher by then so I backed the set screw back to normal. No problems for the 1 yr since then. I have heard before that these newer cars w. computer can lose setting w. a weak battery. Greg

[Matthew Currie]

The fact that it seems to respond to flooring the accelerator before you crank leads to the uneducated guess of throttle position sensor. I'd at least start by checking and cleaning all connectors you can find. "Getting plenty of spark" sounds as if it rules out the CPS. One other thing that occurs to me is to ask if there was a lot of smoke when it finally did start. Flooding is pretty rare with fuel injection, but that's what comes to mind when an engine will only start with the pedal to the floor.

As far as I am aware, the computer on this model does not "learn" your driving habits or store user settings, and disconnecting the battery should have no ill effect, although Chrysler systems are known for running badly if the battery itself is very weak. But from the original post it doesn't sound as if this is a battery problem.

[Lou]

Here's my neophyte 0.01$

Power to the fuel pump is delivered in on of two ways;

1) via the ballast resistor

2) In WOT, the ballast resistor is bypassed.

Could your ballast resistor or connections to it be bad(or wonkie fuel pump -- checked fuel pressure?)?

[Matthew Currie]

Originally Posted by Lou

Here's my neophyte 0.01$

Power to the fuel pump is delivered in on of two ways;

1) via the ballast resistor

2) In WOT, the ballast resistor is bypassed.

Could your ballast resistor or connections to it be bad(or wonkie fuel pump -- checked fuel pressure?)?

That's a good point. I think the ballast resistor is also bypassed during the initial pressurizing, too, so hearing the fuel pump run before you crank wouldn't necessarily rule it out.

[aplatz]

I had a similar problem, but let me ask you something. How cold was it out? If it's frigid out (20 below at 10,000 ft.). I found the hard way-(bought a new battery took a day off from work), that a sensor that reads the outside temp. confuses it self in the extreme cold. It says, "hey it's cold, better richen the mixture" and floods itself. The AAA guy in Breckenridge showed me how to pull the fuel pump fuse inside the engine compartment while another guy cranks it. It will finally start, puff the black smoke of unburned fuel, replace the fuse quickly and WALLA!!! Done deal.

Hope this helps,

PLATZIE

[June]

Thanks for the feedback fellas. Just to answer and ask a few ?:

Does a 96 XJ have a ballast resistor? The last time this occurred I was pointed in that direction but was unable to locate the resistor anywhere. I presumed there was none.

The Fuel filter was replaced about a year ago when this occurred last.

I'd say it was about 30-40 degrees out last night and raining. Unk what elevation I was at.

No smoking at all once it started up so it doesn't appear to have been flooded.

Regarding fuel pressure, I did notice when I depressed the nozzle on the fuel rail that fuel came out but not at the pressure I would have anticipated. Just a small amount of the rag I was using.

The one thing I found strange, and still do. Is that fact that after I disconnected the battery and reconnected it. My XJ started up fine and ran normally. It's just wierd to me because when this same thing occurred a year ago I suspected a clogged fuel filter. So I changed the filter and it still would not start. Awhile later i decided to give it a couple more cranks and that's when I realized it would start when the gas pedal was at WOT. I did the identical thing then, just disconnected and reconnected the battery and it started up on the first try and ran fine after than. Giving me no problems until now. I just think there's a connection with it only starting at WOT and then running fine after disconnecting the battery. I'm presuming that by disconnecting the battery, I'm resetting something. Whether it's the TPS or CPS, I don't know.
Any idea's? How difficult is it to test the TPS and CPS? Thanks.

June