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Unread 08-27-2014, 10:27 AM   #1
rsadler
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91 yj bogging

Hi, newbie to the forum and jeep world here! I just bought a 91 yj 2.5, got it cheap and po could not keep it running, I found out the fuel pump relay had a loose wire so I fixed it and it stays running. It's take awhile of turning over to get it started and runs rough for 2 or 3 seconds after it fires then it smooths out. While driving around my neighbor hood it will bog down when and not gain any speed then I can change gears and pick back up speed and then do it again! I just changed the regulator, fixed vacuum leaks put injector cleaner in tank. I don't wanna start throwing money I don't have at it, maybe you guys could help me out with what would be the best to start with now. Thanks in advance for your help

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Unread 08-27-2014, 11:04 AM   #2
mike134
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change your fuel filter and air filter, should cost $15 or so and take 20 minutes.

You'll want to test your fuel pressure. Borrow the fuel pressure gauge from autozone (its free, you just have to leave a deposit). You just plug it into your shrader valve on the fuel rail. Let us know what the fuel pressure is with the key in the ON position. Then tell us fuel pressure at idle. Then turn the engine off and wait 30 minutes, tell us what the fuel pressure is. Next try running the vehicle and have someone watch the fuel pressure under load (high rpm) let us know what the pressure is.

Next Tap on the catalytic converter with a screw driver. Does it sound like its rusted out and destroyed? If so, it could be clogged.

It is likely that your fuel pump is on its way out, usually because of inadequate fuel filter changes and because its over 20 years old. The above fuel pressure test will confirm that.

There are other possible causes, could be you need to change your spark plugs, cap, wires. Do the above tests first since it is free. You should be changing your fuel filter and air filter anyway, so that doesn't cost extra.
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Unread 08-27-2014, 11:21 AM   #3
rsadler
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I changed fuel filter yesterday..plugs wires and cap are new. I'll get the pressure gauge later today or tomorrow and let you know
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Unread 08-27-2014, 11:23 AM   #4
rsadler
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Oh and no cat.
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Unread 08-27-2014, 11:24 AM   #5
Luuca
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Originally Posted by rsadler View Post
I changed fuel filter yesterday..plugs wires and cap are new. I'll get the pressure gauge later today or tomorrow and let you know
Any change with the new fuel filter?
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Unread 08-27-2014, 11:32 AM   #6
rsadler
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No
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Unread 08-27-2014, 11:36 AM   #7
mike134
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ah, not a good sign. Usually if the fuel pump is struggling, changing the fuel filter can reduce the symptoms by at least a little bit since you are removing a large pressure loss in the fuel line. Its possible that the fuel pump is damaged beyond that stage though, we'll have to wait for the pressure test results.
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Unread 08-27-2014, 11:38 AM   #8
rsadler
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I don't hear the fuel pump running in the tank but if it wasn't working it wouldn't run at all, right?
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Unread 08-27-2014, 12:12 PM   #9
Luuca
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Originally Posted by rsadler View Post
I don't hear the fuel pump running in the tank but if it wasn't working it wouldn't run at all, right?
When you first turn the key on, you should hear the fuel pump prime the lines, i.e. add pressure and fuel to the rail. The reason your jeep isn't starting on the first key turn is that your fuel pump is not priming the system. It eventually builds up enough pressure when you are cranking it to run the jeep, and consequently, maintains enough pressure in the system for you to shut it off and start it right back up first try; however, once the fuel system is void of pressure, i.e. all the fuel leaves the rail and enters the tank again, your pump needs to slowly build up the pressure again, i.e. long cranking starts.

My 2 - replace your fuel pump with a Bosch unit. Do not get an AutoZone brand pump... ask me how I know..
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Unread 08-27-2014, 12:50 PM   #10
rsadler
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I got the pressure gauge and it stays around 24psi idling and giving it throttle. I unhooked the vacuum line also and stays same pressure. I understand your view on auto zone brand pumps, I've been thru that also
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Unread 08-27-2014, 01:15 PM   #11
mike134
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24 is low at idle. 24 is very low when you unplug the vacuum line. One thing you want to try before going ahead and changing the pump is pinching the fuel return line to make sure it is not your pressure regulator. If your FPR is returning fuel to the tank at 24 psi then it is broken. If it is not returning fuel to the tank then you have either a leak or a bad fuel pump.
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Unread 08-27-2014, 01:24 PM   #12
rsadler
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I changed the fpr this morning
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Unread 08-27-2014, 01:24 PM   #13
rsadler
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I changed fpr this morning
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Unread 08-27-2014, 01:29 PM   #14
mike134
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oh thats right, you did say that. I'd go after the pump next then. I think there is a strainer just upstream of it as well, make sure to clean that out.

be sure to come back and let us know if it worked!
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Unread 08-27-2014, 01:32 PM   #15
rsadler
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Yeah I'll change the strainer. It will probably be sat. Before I can get to changing that
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