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Unread 01-31-2005, 10:29 PM   #1
1GreenTJ
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Dead TJ...Fuel Pump or CPS?

Hey Everyone,
To make a long story short I was out wheeling for the first time this past weekend and on the second day my 97 TJ 4.0 with 152k started acting up on me. It started hard, and choked bucked whenever a little extra gas was needed. Up hills, over rocks, and even around corners were only possible at idle in 4Low. I limped it out of the park and my buddies and I checked the ignition system. Plugs, cap and rotor all looked a little fouled even though I just changed them in October. I left and again limped it down the road to the Autozone where I proceeded to change plugs, cap and rotor and even did an oil change. I began the 140 mile trip home, made it about 25 miles never getting over 2500 rpm and 45 mph and there she sat. I was going up a hill and she quit and wouldn't start up again. Thanks to AAA I was able to get a tow home. We thought it might be the o2 sensor so I changed that but it didn't help. We then checked the spark and it is definitely firing. Next we tried starter fluid in the air tube and turned right over but would not idle or run on it's own. Thinking at this point it must be a a fuel issue I disconnected the gas line at the intake manifold and turned the ignition and nothing at all came out.

At this point I think that it must be the fuel pump but before I drop $434 at the stealership I thought I would just run this by the forum to see if my thoughts are accurate. I can't think of anything else but I have read where people had problems with the Crank position sensor. I'm not really sure exactly what this sensor does but does anyone think it more likely to be the CPS then the pump? I ran it for codes but only got a "system running lean" code.

If it is the pump does anyone know where I can buy it cheaper than the dealership? The local Autozone doesn't sell it and says I have to buy from the dealer.

Thanks in advance,
Nick

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Unread 01-31-2005, 11:07 PM   #2
The_'ster
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Yea, if you are not getting any fuel pressure at the fuel rail it sounds like a weak fuel pump or stuck fuel pressure regulator. Check the fuel pump fuse? I had similar problems last year. Wouldnt start but after several key on/off/on it would instantly build pressure and fire right up. Hasnt acted up at all this year so I havent gotten around to changing the pump and regulator, so I dont know what prices are anywhere.

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Unread 02-01-2005, 12:15 AM   #3
Jerry Bransford
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What diagnostic code is stored in your computer? Turn the ignition key on-off-on (but not to Start) three times within five seconds and then after leaving the key in the On position, wait 3-10 seconds for the diagnostic codes to begin displaying in your odomter. When the '55' code displays, that indicates no more codes follow with the codes preceding the 55 code being the ones you should write down and post back here.

From those codes, a possible diagnosis might be possible.

To eliminate the CPS as a possible culprit, see if you're getting spark to one of the plugs as someone cranks the engine. If you see spark, it's not the CPS. If you don't see spark, it could be the CPS but the diagnostic codes will further help to diagnose the problem.

To see if your fuel injectors are getting fuel from the fuel pump, see if fuel squirts out of the Schraeder valve (like a big tire stem valve) that is located on the fuel rail between two of the forward-most injectors. It has a black plastic cap on top that is unscrewed to reveal the valve push -pin that you depress to see if fuel pressure is present. No fuel means the pump is not being energized or, rarely, the pump is bad.
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Unread 02-01-2005, 05:18 PM   #4
1GreenTJ
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Thanks for the responses guys. There is a spark so I think its safe to rule out the CPS. And, there is no fuel pressure at all in the lines or at the valve. It was towed to a friends ( house with a garage so I can't check right now but the only code it was reading on a code reader was something to the effect of, "system running lean".

I will try to get back over to it tomorrow to double check the codes and I'll post them on here as soon as possible.

I also will check the relay and the fuse but if those are both working I think the only thing left is the pump or the regulator.

Thanks again,
Nick
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Unread 02-01-2005, 05:24 PM   #5
joeyt17
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after my first off-road trip i had a similar diagnosis. first i did a tune up and that did not solve it. it would buck on turns and sometimes just while driving on the highway, and would stutter at idle at times. it turned out to be the CPS, no problems since replacing it. my jeep first had a code for misfire in a cylinder....after i did the tune up a code eventually came on (3 days after tuneup) that was for teh CPS
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Unread 02-01-2005, 05:43 PM   #6
DigDug
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Sounds like fuel pump to me... Can you hear it running? It's right smack dab in the middle of the tank. Turn your key to RUN (without starting the engine) and either listen (I can hear mine from inside the jeep) or have someone stick their ear down there. You should hear a buzzing that stops after a few seconds. I replaced the fuel pump in my 97 TJ a few months ago and bought the pump from PepBoys for (if my memory serves) $98. You can also buy the whole assembly (comes with the gauge sending unit and everything) for like $300, but it would only save you maybe 15-30 minutes of repair time. (The one I bought has a lifetime warranty too).

It's a fairly easy process to change (it took me like 3 hours to do it slowly and with distraction) but you do have to drop the tank. There used to be a link around here somewhere that had pretty good directions (I did mine with just a Haynes manual and the instructions that came with the pump).

Also, when mine went, I got NO codes on the computer.

Good Luck
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Unread 02-01-2005, 07:42 PM   #7
doorocks
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Quote:
Originally Posted by 1GreenTJ
Thanks for the responses guys. There is a spark so I think its safe to rule out the CPS. And, there is no fuel pressure at all in the lines or at the valve. It was towed to a friends ( house with a garage so I can't check right now but the only code it was reading on a code reader was something to the effect of, "system running lean".

I will try to get back over to it tomorrow to double check the codes and I'll post them on here as soon as possible.

I also will check the relay and the fuse but if those are both working I think the only thing left is the pump or the regulator.

Thanks again,
Nick

Nick, don't tell me I froze my *** off sitting on 81 with you( in my warm jeep) , and we still don't know what the problem is?

I think what you're leaving out here is, after you did a full tune up, nothing changed and the use of Heet in your tank.....Also if the fuse is/was defective, it would be dead.....fuses are like circuits....open or closed. I just happen to have a fuse for you in my glove box. (my spare).

Im sticking with my fuel pump theory.
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Unread 02-02-2005, 09:03 PM   #8
kgillard
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Hi 1greenTJ,

I had almost identical problems....a nightmare! I finally changed the fuel pump assembly and have not had a problem since.

Karl
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Unread 02-02-2005, 09:19 PM   #9
nwjeepguy
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When was the last time the spark plug wires were changed? If they are bad you'd still have a spark but it would be a bit weak.
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Unread 02-02-2005, 09:23 PM   #10
1GreenTJ
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Thanks for responding, I just installed Jacobs wires last October so I don't think they would be bad yet. And, like I said, there isn't any fuel in the fuel line so I think we've ruled out the ignition system.

Nick
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Unread 02-07-2005, 10:33 PM   #11
1GreenTJ
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It's alive!

Just an update, I replaced the fuel pump and she's running again. Still starts kind of hard but other then that just like normal.

Thanks to everyone for your help.
Nick
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