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Category: Heavy Equipment
Satisfied Customers: 3653
Experience:  16 Years working on Cummins Diesel engines,
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1999 freightliner with cummins isc 8.3 engine.

Resolved Question:

I have a 1999 freightliner with cummins ISC 8.3 engine. The problem I have with the truck is that it's losing half of the power. I would like to know what could be wrong with it. I changed old filters and it didn't do nothing. Thank you I'll be waiting for your response.
Submitted: 5 years ago.
Category: Heavy Equipment
Expert:  DR.Cummins replied 5 years ago.
Hello and welcome to Just Answer! I would be more than happy to assist you today.may i have the engine serial number? Is there a specific condition when you are running that you notice the loss of power? any check engine lights? if so do you know the codes
Customer: replied 5 years ago.
it has a check ingene light with code 94
Expert:  DR.Cummins replied 5 years ago.

The fuel pressure sensor contains supply, signal, and return pins. The electronic control module (ECM) provides 5 VDC to the fuel pressure sensor for a supply voltage. The ECM supplies a shared ground from the fuel pressure sensor circuit. The signal voltage is variable depending on the pressure that is being generated inside the fuel pump accumulator.

This 5 VDC power supply is a shared supply. Other sensors on this circuit include the engine speed sensor, engine position sensor, oil pressure sensor, intake manifold pressure sensor, and ambient air pressure sensor.

The shared ground for the fuel pressure sensor also connects to the injection control valve identifier, temperature sensor, intake manifold air temperature sensor, engine position sensor, oil pressure sensor, intake manifold pressure sensor, and ambient air pressure sensor.

location of sensor

The fuel pressure sensor is located on the top rear of the fuel pump. The pressure sensor can be identified by its mounting location, rear center of the CAPS accumulator module

This fault can be set due to:

  • Faulty fuel pressure sensor wiring (pig tail harness), sensor connections (pin fretting), or engine harness issues (shorts) which can cause the pressure signal to erratically spike up or down
  • Excessive fuel inlet restriction
  • Internal sensor failures.
Fault Code: 456
PID: P094
SPN: 94
FMI: 10
LAMP: Yellow

Fuel pressure sensor stuck in range while engine is operating or fuel pressure sensor reading erratic in range.

Engine power derate; engine can run rough or die

Customer: replied 5 years ago.
how do i check if the sensor is good or bad
Expert:  DR.Cummins replied 5 years ago.
You need special tools to check the sensor, Cummins insite program will also help alot. Unless you replace the sensor you will be unable to check and confirm
DR.Cummins and 3 other Heavy Equipment Specialists are ready to help you
Customer: replied 5 years ago.
what other things should i check since the truck start fine and there is no smock. do you think changing the sensor will solve the problem
Expert:  DR.Cummins replied 5 years ago.
if that is what the fault is for you must follow the fault cods. You have changed the filter's check the harness ends, worst case scenario is the fuel pump is under or over pressurizing and starting to fail. all needs to be checked with special tools and Cummins insite
Customer: replied 5 years ago.
thanks for your help