Fuel pressure/regulator question
06-06-2015, 05:03 PM
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Year: 1994
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Engine: I6
Fuel pressure/regulator question
Hey guys! I've got a 94 xj with the 4.0. Recently, I was doing some general diagnostics and tested my fuel pressure. At the rail at idle speed I had a steady 29 psi. According to my manual it should be 31 at idle. Would being 2 psi low cause any issues like lack of hp or low mpg?
Also, I noticed that all the replacement regulators in the stores are specified as having a 39 psi operating pressure. What's the deal with that? Thanks you in advance for your answers!
Also, I noticed that all the replacement regulators in the stores are specified as having a 39 psi operating pressure. What's the deal with that? Thanks you in advance for your answers!
06-06-2015, 08:12 PM
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My .02 is you are fine. The"39 psi operating pressure" is with the vacuum line off the regulator, then you look for about 10 less with it on. 
http://www.jeep4.0performance.4mg.com/tech_specs.html
http://www.jeep4.0performance.4mg.com/tech_specs.html
Last edited by DFlintstone; 06-06-2015 at 08:15 PM.
06-06-2015, 08:33 PM
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My .02 is you are fine. The"39 psi operating pressure" is with the vacuum line off the regulator, then you look for about 10 less with it on.
http://www.jeep4.0performance.4mg.com/tech_specs.html
http://www.jeep4.0performance.4mg.com/tech_specs.html
Oh, well that makes a lot of sense. Thanks for the great info!
06-07-2015, 05:12 PM
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No prob Doug, happy trails. Adam...I'm a bit "old school". I'd feel better about a regulator from the JY then a new one. That's just me though. (don't loose the spacers between the O rings on the connection!)
If your pressure is low you can crimp/squeese the rubber return line closed and see it the pressure spikes. If it doesn't, the low pressure is from something else.
If your pressure is low you can crimp/squeese the rubber return line closed and see it the pressure spikes. If it doesn't, the low pressure is from something else.
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