# Testing fuel pressure



## jblakeslee (Nov 30, 2005)

1992 D21 KA24E w/fuel injection. What is the best way to check fuel pressure? There is no fitting on the fuel rail. 

Thanks in advance.


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## rogoman (Dec 16, 2004)

Remove the hose on the output side of the fuel filter and install a short piece of fuel hose with a tee for the fuel pressure gauge. Now reconnect the original hose to the tee and you're all set to go.


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## jblakeslee (Nov 30, 2005)

*Fuel Pressure testing*

Thanks...now all I need to check is if the fuel pressure gauge I have reads high enough......

The Haynes manual said it something about it should be 33 with vacuum and 43 without? What is that all about?

What should the pressue be at the output of the filter?


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## rogoman (Dec 16, 2004)

The pressure at the output of the filter will vary as dictated by the pressure regulator. The pressure regulator has a vacuum line connector which is what the Haynes manual refers to. With the engine idling or part-throttle operation, there is full vacuum at the regulator, thus 33 psi. At full throttle, no vacuum and 43 psi to provide more fuel flow that the engine needs.


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## cwilliamrose (Jul 11, 2010)

My V6 D21 runs 75-80psi unregulated.............Bill


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## jblakeslee (Nov 30, 2005)

thanks......common sense would tell me that if the pressure is low at the output of the filter, then I need to either just change the filter, and check again, or check the pressure before the filter.....the eliminate it as part of the problem.......


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