Did You Know...? (Truck Nuggets)
#32
12-20-2018, 10:27 AM
What the Truck?!? It Won't Start.
Our trucks are old and mostly mechanical. Compared to the newer software process where the cars boot up more than they start up, our start sequence is fairly straight-forward - turn key, wait for WTS light to go out, start the truck.
There are plenty of troubleshooting threads (posted or updated almost daily) on this but, for some reason, it's hard to find what actually needs to happen to start the truck. That being said there are some specific parameters that the PCM is looking for before it gives the green light to the IDM to fire the injectors and bring the big block to life (these are all minimums while cranking):
1. Engine RPM - 100
2. Injection Control Pressure (ICP) - 500 psi
3. Injection Pulse Width (PW) - 0.6 ms
4. Volts - 7-10 VDC
There are nuiances between years but these are the four basic things your truck PCM needs to see while cranking before the IDM gets the go ahead to start injecting fuel.
Note: The 0.6ms pulse width requirement indicates that the PCM and IDM are talking and not an indication of actual pulse width. If the PW was 0.0ms then the IDM did not answer when the PCM called so it left a voicemail telling the IDM there will be no injection action this round.
I'm not sure if the Ford shop manual has this listed anywhere (I've never looked) but I've pieced this together over the years from forum posts here (and other places) and the handy-dandy diagnostics PDF from Oregon Fuel Injection (page 3)...
There are plenty of troubleshooting threads (posted or updated almost daily) on this but, for some reason, it's hard to find what actually needs to happen to start the truck. That being said there are some specific parameters that the PCM is looking for before it gives the green light to the IDM to fire the injectors and bring the big block to life (these are all minimums while cranking):
1. Engine RPM - 100
2. Injection Control Pressure (ICP) - 500 psi
3. Injection Pulse Width (PW) - 0.6 ms
4. Volts - 7-10 VDC
There are nuiances between years but these are the four basic things your truck PCM needs to see while cranking before the IDM gets the go ahead to start injecting fuel.
Note: The 0.6ms pulse width requirement indicates that the PCM and IDM are talking and not an indication of actual pulse width. If the PW was 0.0ms then the IDM did not answer when the PCM called so it left a voicemail telling the IDM there will be no injection action this round.
I'm not sure if the Ford shop manual has this listed anywhere (I've never looked) but I've pieced this together over the years from forum posts here (and other places) and the handy-dandy diagnostics PDF from Oregon Fuel Injection (page 3)...
#33
12-20-2018, 10:51 AM
Fleet Owner
Brian, in addition some "standards" of what to look for while the truck is running, but may not be doing well. This was originally posted by @pirschwagon on 10 Dec 2018 here.
Delta for comparison table:
AP: 5 Volt Reference Circuit, 0.5-0.7 vdc at idle, 4.5 vdc at WOT.
BARO: 5 Volt Reference Circuit, @ 4.6 volts / 14.7 psig at sea level, decreasing as altitude increases.
CMP: high = 12 vdc, low = 1.5 volts.
EBP: 5.0 volts Reference Circuit, 0.8-1.0 vdc / 14.7 psig
EOT: 5 Volt Reference Circuit, 4.37 vdc @ 32°F, 1.37volts @ 176°F, 0.96volts @ 205°F.
IAT: 5 Volt Reference Circuit, 3.897 vdc @ 32°F, 3.09 @ 68°F, 1.72 @ 122°F.
ICP: 5 Volt Reference Circuit, 1.0 vdc @ 580 psig, and 3.22volts @ 2520 psig.
ICP Vdc
0 0.2
200 0.4
400 0.73
600 0.96
800 1.2
1000 1.4
1200 1.6
1400 1.9
1600 2.1
1800 2.3
2000 2.6
2200 2.8
2400 3.0
2600 3.3
2800 3.5
3000 3.8
EXBP 10-15 psig w/ EBPV closed and not exceed 45 psig at WOT
*Note: EXBP showing low (3-5psi) that barley rises with acceleration indicates bad sensor or plugged tube.
IDM: 110 volt signal to the injectors. Grounds each injector as fuel is required for that cylinder. Fuel Pulse width is increased to deliver more fuel. The IDM sends a feedback signal to the PCM for fault detection.
IVS: 0 vdc at idle, 12 volts off idle. (off/on)
MAP: Frequency output; 111Hz / 14.7 psi, 130Hz / 20psi, 167Hz / 30psi.
IPR: Idle Warm: 8% - 14%, Idle Cold 10% - 15%, Electromagnetic Coil Test: OHMS = 10.2 - 10.6, Range: 0% - 65% (Not more than 20% Starting).
EPR: Exhaust Back Pressure Regulator, also EBP regulator Output: For quicker engine warm-up at cold temperatures. If the IAT is below 37°F (50°F some models) and the EOT is below 140°F (168° some models) the PCM sends a duty cycle signal to a solenoid which controls oil flow from the turbo pedestal. This causes a servo to close a valve at the turbo exhaust outlet. The PCM monitors the EBP input to determine if the EPR needs to be disabled to provide power for increased load, then reapplies the EPR as load demand decreases until EOT or IAT rises.
The Exhaust Back-Pressure sensor is a variable capacitor sensor that is supplied a 5-volt reference signal by the PCM and returns a linear analog voltage signal that indicates pressure. The Exhaust Back-Pressure sensor measures the pressure in the RH exhaust manifold. This sensor is used in conjunction with the exhaust back-pressure regulator to form a closed loop exhaust back-pressure control system.
The exhaust back-pressure is controlled by the PCM to provide more heat to the coolant for cab heating when ambient air temperature is below 7°C (45°F) and engine oil temperature is below 75°C (167°F) during low load, low speed operating conditions.
An open or short in the Exhaust Back-Pressure sensor wiring will result in a low out of range voltage at the PCM, and the PCM will disable Exhaust Back-Pressure control.
** NOTE: The Exhaust Back-Pressure sensor is not present on F-650 and F-750 models. **
Delta for comparison table:
AP: 5 Volt Reference Circuit, 0.5-0.7 vdc at idle, 4.5 vdc at WOT.
BARO: 5 Volt Reference Circuit, @ 4.6 volts / 14.7 psig at sea level, decreasing as altitude increases.
CMP: high = 12 vdc, low = 1.5 volts.
EBP: 5.0 volts Reference Circuit, 0.8-1.0 vdc / 14.7 psig
EOT: 5 Volt Reference Circuit, 4.37 vdc @ 32°F, 1.37volts @ 176°F, 0.96volts @ 205°F.
IAT: 5 Volt Reference Circuit, 3.897 vdc @ 32°F, 3.09 @ 68°F, 1.72 @ 122°F.
ICP: 5 Volt Reference Circuit, 1.0 vdc @ 580 psig, and 3.22volts @ 2520 psig.
ICP Vdc
0 0.2
200 0.4
400 0.73
600 0.96
800 1.2
1000 1.4
1200 1.6
1400 1.9
1600 2.1
1800 2.3
2000 2.6
2200 2.8
2400 3.0
2600 3.3
2800 3.5
3000 3.8
EXBP 10-15 psig w/ EBPV closed and not exceed 45 psig at WOT
*Note: EXBP showing low (3-5psi) that barley rises with acceleration indicates bad sensor or plugged tube.
IDM: 110 volt signal to the injectors. Grounds each injector as fuel is required for that cylinder. Fuel Pulse width is increased to deliver more fuel. The IDM sends a feedback signal to the PCM for fault detection.
IVS: 0 vdc at idle, 12 volts off idle. (off/on)
MAP: Frequency output; 111Hz / 14.7 psi, 130Hz / 20psi, 167Hz / 30psi.
IPR: Idle Warm: 8% - 14%, Idle Cold 10% - 15%, Electromagnetic Coil Test: OHMS = 10.2 - 10.6, Range: 0% - 65% (Not more than 20% Starting).
EPR: Exhaust Back Pressure Regulator, also EBP regulator Output: For quicker engine warm-up at cold temperatures. If the IAT is below 37°F (50°F some models) and the EOT is below 140°F (168° some models) the PCM sends a duty cycle signal to a solenoid which controls oil flow from the turbo pedestal. This causes a servo to close a valve at the turbo exhaust outlet. The PCM monitors the EBP input to determine if the EPR needs to be disabled to provide power for increased load, then reapplies the EPR as load demand decreases until EOT or IAT rises.
The Exhaust Back-Pressure sensor is a variable capacitor sensor that is supplied a 5-volt reference signal by the PCM and returns a linear analog voltage signal that indicates pressure. The Exhaust Back-Pressure sensor measures the pressure in the RH exhaust manifold. This sensor is used in conjunction with the exhaust back-pressure regulator to form a closed loop exhaust back-pressure control system.
The exhaust back-pressure is controlled by the PCM to provide more heat to the coolant for cab heating when ambient air temperature is below 7°C (45°F) and engine oil temperature is below 75°C (167°F) during low load, low speed operating conditions.
An open or short in the Exhaust Back-Pressure sensor wiring will result in a low out of range voltage at the PCM, and the PCM will disable Exhaust Back-Pressure control.
** NOTE: The Exhaust Back-Pressure sensor is not present on F-650 and F-750 models. **
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