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Old 02-07-2011, 04:31 PM   #1 (permalink)
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YJ 6cyl starting issues

Hey all,
I have been a lurker for quite sometime absorbing all that this forum has to offer. Even back before I could even drive! About time I posted!

I have a 94 jeep YJ with 230,000 km's (138,000 miles) on it. ~7" lift, 35's, cv, SYE, regular synthetic oil changes etc, etc.

I'm pretty gentle on it as it is my daily driver (about 70 miles a day at 60mph) The last few days when I have gone to start it it cranks for a while like it isn't going to start, and then kinda starts to cough to life (feels like it needs the help of the starter to keep running at first (for about 1-3 seconds), like starting big diesel equipment) then it revs up to about 1200rpm and runs fairly rough for 10-15 seconds, then smooth's out and the idle slows and it idles normally. Driving on the highway it's the same as normal, runs well.

At first I thought it might be a fuel pressure regulator or filter (i plan on changing the fuel filter anyways) but it runs so well after it is started. Same with an injector, if that was the case wouldn't it run rough at highway speeds? It doesn't even sputter when I apply a bit of skinny peddle to merge.

It starts a lot easier once warm (nearly no hesitation)

I would usually jump into it, but being that my funds from working all last summer are almost gone, and I am a full time student I don't have money to throw at it right now.

Thanks for any help!
- Navis
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Old 02-09-2011, 11:44 PM   #2 (permalink)
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A picture of my rig/bump

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Old 02-19-2011, 05:55 PM   #3 (permalink)
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I have a 95 4.0 that does the same thing. I have to touch the gas to get it to run. Starts and runs fine when warmed up. Maybe some body knows whats wrong.
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Old 02-20-2011, 10:59 AM   #4 (permalink)
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My guess: Sounds like classic dying fuel pump symptoms.

When starting cold, all pressure has bled out of the fuel system and it takes your weak fuel pump a little while to re-pressurize the rail. Reason it starts fine when warm has nothing to do with temperature...rather it just hasn't had a chance to lose all pressure at the rail yet.

Try this: With the Jeep cold, turn the key on for 5 seconds (but not cranking), then off, then on for another 5 seconds and then turn it the rest of the way to crank the engine to start it. If it fires right up after doing that, it's your fuel pump (EDIT - Genetic Disposition is right...could also be you're fuel pressure regulator). The reason being your pump is automatically cycled for five seconds every time you turn the key on.


Especially at 230k miles,
Jake
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Last edited by Jakesteramalamajama; 02-20-2011 at 05:51 PM.
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Old 02-20-2011, 11:42 AM   #5 (permalink)
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Other possibility's TPS, O2, and fuel pressure thing on fuel rail.
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Old 02-21-2011, 06:01 PM   #6 (permalink)
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I just tried the 5sec on off 5 sec on and crank. Didn't start till i bumped the gas . I'll try fuel pres next. Thanks Mike.
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Old 03-10-2011, 08:05 AM   #7 (permalink)
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Had fuel pres checked . Over 60 psi . reg has fuel leaking on vac side . Going to put new reg on .
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