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97 4.0 Engine cranks but has trouble starting

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Old Aug 15, 2012 | 02:59 PM
  #1  
zkruse92's Avatar
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Default 97 4.0 Engine cranks but has trouble starting

This started a couple days ago. When the engine is cold it will have trouble starting. It sits there and cranks for a few seconds before it starts. Starts fine when engine is warm. Also, just for ****s and giggles, I turned the key to on then off a couple times. Heard the fuel pump kick on each time but if I do that and build up the pressure in the fuel lines it seems to start right up just fine. This leads me to believe that my fuel pump is on its last leg. Although, I could be wrong. Where should I start with checking everything to make sure it's not something else?

Not sure if this makes a difference, but I installed a new stereo and speakers about a week before this started. My timing always seems to be great with cars though. Used to have a POS Alero and threw new spark plugs in it. Two days later two of my ignition coils burned out. -_-

Any pointers before I start tearing my fuel pump apart would be great. Hopefully it's just something ridiculously stupid.
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Old Aug 15, 2012 | 03:01 PM
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ZINGGG's Avatar
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From: Seal Beach, CA
Year: 1996
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Engine: 4.0 HO Straight Six
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Sounds like a bad fuel pump to me.

There's a valve on the fuel rail that you can hook up a fuel pressure gauge to to make sure that the fuel pump is in fact your problem.
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Old Aug 15, 2012 | 06:54 PM
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Year: 1997 (RHD)
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Engine: 4.0 ltr
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Originally Posted by 1996sportXJ
Sounds like a bad fuel pump to me.

There's a valve on the fuel rail that you can hook up a fuel pressure gauge to to make sure that the fuel pump is in fact your problem.
x2.
What you could check on cold start up is the what I believe TJWalker calls the 'poor man's prime'. Before starting, turn the key to on (but not start), you will hear the fuel pump prime. Turn key to off position again, and do this a few times. If your engine fires up a lot quicker than without this procedure, than its likely your fuel pump being the issue.
Doing this 'prime' doesnt hurt anything, been doing it for months now, and at some point, yes, the fuel pump needs replacement.
See how you go with this and let us know.
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Old Aug 15, 2012 | 08:35 PM
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From: Colorado
Year: 1997
Model: Cherokee
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Originally Posted by Roler
x2.
What you could check on cold start up is the what I believe TJWalker calls the 'poor man's prime'. Before starting, turn the key to on (but not start), you will hear the fuel pump prime. Turn key to off position again, and do this a few times. If your engine fires up a lot quicker than without this procedure, than its likely your fuel pump being the issue.
Doing this 'prime' doesnt hurt anything, been doing it for months now, and at some point, yes, the fuel pump needs replacement.
See how you go with this and let us know.
Thanks for that explanation. I'll try your prime test if I can remember next time. Seems I have the same symptoms as the OP.
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Old Aug 15, 2012 | 11:05 PM
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Yeah, it fires right up if I prime the pump about five times. I just wasn't sure if it could be something else or not and thought I'd ask the experts. =P
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Old Aug 18, 2012 | 07:05 AM
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From: Colorado
Year: 1997
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Originally Posted by Roler
What you could check on cold start up is the what I believe TJWalker calls the 'poor man's prime'. Before starting, turn the key to on (but not start), you will hear the fuel pump prime. Turn key to off position again, and do this a few times. If your engine fires up a lot quicker than without this procedure, than its likely your fuel pump being the issue.
Doing this 'prime' doesnt hurt anything, been doing it for months now, and at some point, yes, the fuel pump needs replacement.
So I tried the "Poor Mans Prime" and got the predicted results. However it doesn't suggest a defective fuel pump, rather a missing/defective check valve that allows the fuel to drain back into the tank. The fact that it starts and runs fine indicates a working fuel pump.

Your take???
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