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Discussion Starter #1
Hello all, I'm a newbie on this site. I just bought my first jeep, a 94 YJ 2.5 manual trans. It was running like crap and got the following codes 12, 17(low coolant temp), 33( A/C clutch), 51(running lean), 55. I don't have A/C. I changed the O2 sensor, no change. So I replaced the fuel filter..no change. So I replaced the fuel pump and saw parts of an old gasket in the tank that was sucked up to the fuel strainer. Removed the pieces and replaced the pump. Runs much better but is getting horrible mpg...like 10mpg maybe. I did a fuel pressure test and pressure was good (31psi) at idle for about 45 seconds. Then it started climbing up to 70psi. I now get the 52 code (Rich running condition). So it went from lean to rich after changing the fuel pump. I haven't changed the thermostat yet. Could that be making the engine use more fuel to try to get engine up to operating temp? It normally runs at 155 degrees which I know is too cold. I have also heard about pinched fuel lines above the tank, and blocked fuel return line causing rich running conditions. What about the regulator? Just not sure where to start and I don't want throw parts at it anymore. Please help!!! Thank you.
 

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Check your return line. It may have got pinched when you reinstalled the tank. Especially since you said you changed the pump.
 

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Yeah I have a lean condition, code 51, just replaced the fuel filter and oxygen sensor with no change. I need to go buy a fuel pressure test guage, I think my fuel pump might be going out. Spark plugs I changed also, old ones were white in color (too hot).
 

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Discussion Starter #4
As it turns out, it WAS a clogged fuel return line. There was a piece of rubber lodged in the bottom of the return line on the fuel pump. So I picked it out and ran some wire through it and sprayed carb cleaner through it to make sure. I also cut the the end of the return line at an angle so it wasn't flat on bottom, just in case the tank were to get distorted it wouldn't push against the bottom of the line and restrict fuel flow. All is well now. Runs good, no check engine light, and great mileage again!! I'm learning!! Thanks to all for the help. Fyi- I have become an expert at dropping tanks and replacing fuel pumps!!!:)
 
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