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autodoc_2000
autodoc_2000, Auto Technician
Category: Ford
Satisfied Customers: 2563
Experience:  ASE Master Tech W/Advanced Engine Performance, Ford Senior Master Certification
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95 FORD F150: INJECTOR PULSE..FROM COMPUTER SWAPPED..KNOWN GOOD

Customer Question

95 FORD F150 5.8
LOSSING INJECTOR PULSE ON 2,3,6,7. FROM COMPUTER
SWAPPED WITH KNOWN GOOD COMPUTER
Submitted: 10 years ago.
Category: Ford
Expert:  autodoc_2000 replied 10 years ago.

You may have a failing camshaft position sensor which is internal to the distributor. You will need to disassemble the distributor to replace it if this is the concern. Here is the explanation of how the Camshaft Position Sensor works. If the sensor is shorted it may only fire some injectors.

PURPOSE
The Camshaft Position (CMP ) sensor utilizes a hall effect sensor to provide crankshaft position, base timing and engine speed information to the Ignition Control Module (ICM ). The ICM supplies this information to the Powertrain Control Module (PCM ) as the Profile Ignition Pickup (PIP ) signal. The PCM uses this information for fuel injector timing and calculating ignition timing advance and dwell.

CONSTRUCTION
The CMP sensor is located within the distributor and is comprised of a hall effect switch and a camshaft driven 8 bladed shutter plate.

OPERATION
Each blade on the shutter plate corresponds to a separate position on the crankshaft. As the shutter plate passes through the hall effect switch the output of the sensor alternates from 0.0 to 12.0 volts in a square wave pattern. This output is sent to the ICM where it is converted to the PIP signal.

Customer: replied 10 years ago.
ALREADY REPLACED CMP IN DISTRIBUTER, THIS ONE HAS ME STUCK, ALSO REPLACED ICM, EXACT SAME PROBLEM AFTER REPLACING BOTH PIECES
Expert:  autodoc_2000 replied 10 years ago.
Are you loosing the power side of the injectors or the ground side?
Customer: replied 10 years ago.
Reply to autodoc_2000's Post: the ground side of the injectors 2,3,6,7. it is a white wire . it starts off with a ground then as you acellerate is loes the ground signal. and the computer has been replaced with a known good unit. i have taken the wiring harness that connects the injector our and searched all the cables, but the problem is coming out of the computer. i isolated the white wire, or disconnected from the injectors and it still does the same thing, its like what ever tells the pcm for numbers 2,3,6,7 is not sending the signal at accelleration.