What is the fuel pump pressure for a 91 dodge Cummins diesel?

Question edited for clarity.
Question moved to model category.

In the link, but you could test it with a multimeter or a test lamp.

all the wiring

https://www.justanswer.com/dodge/343b4-98-dodge-ram-2500-fuel-pump-had-12v-cranking-relay.html

More here

https://www.google.com/search?q=2000+Dodge+Ram+2500+fuel+pump+wiring

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Connect the fuel pump to direct 12 volt power. That checks the pump.

Then test the relay

https://www.google.com/search?q=2001+dodge+ram+2500+diesel+5.9+cummins+fuel+pump+relay+location

fuel pump. fuse is first, relay 2nd, and glow plug power .
fuse 42 diesel PCM
the 500 page glove box manual does no cover relays, I looked for you.
so that leaves 1 place, the SM the service manual

https://eautorepair.net/Marketing/Default.asp

i can not find the Cummis electrics wiring pages.
the fuel rail has pressure sensor
if you just SCAN the PCM it will show if that is good or bad.
check all fuse first
then SCAN the diesel PCM.
or buy the real books from DODGE< on this truck.

why do you need to be thinking outside of boxes? The Codes tell you exactly what the problem is.

P0088 - Fuel Rail Pressure Too High - Bank 1

https://mopar1973man.com > ... > OBDII Error Codes
Feb 18, 2019 - P0088 - Fuel Rail Pressure Too High - Bank 1 Theory of Operation The Powertrain Control Module (PCM) provides the Fuel Rail Pressure Sensor ...

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P0254 Injection Pump Fuel Metering Control A High - OBD ...

https://www.obd-codes.com > p0254
This generic powertrain/engine diagnostic trouble code can typically apply to all diesel fueled OBD-II equipped engines (e.g. Ford, Chevy, GMC, Ram, etc.) ...

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take it to a cummins diesel repair shop as it indicates a faulty non return valve

FIRST CHECK YOUR FUEL PUMP TO ENSURE IT IS WORKING PROPERLY, THEN DO A FUEL PRESSURE TEST. AN AVERAGE READING WILL READ BETWEEN 15 AND 30 LBS. THEN YOU NEED TO BE MORE SPECIFIC IS IT GAS OR DIESEL IF IT IS A DIESEL THEN YOU NEED TO LOOK INTO INJECTOR PRESSURE THE AVERAGE CUMMINS COMMON RAIL PRESSURE AVERAGES AROUND 5,000 TO 8,000 PSI ANYTHING LESS THAN 5,000 PSI THE TRUCK WILL NOT START OR WILL BE HARD TO START.

Someone has put the wrong lift pump on ( too high of pressure )

You said you have fuel flowing from the inlet line of the injection pump? But not at the injector lines?

14psi sounds low even for the sump.