Temperature, Pressure vs Voltage - Troubleshooting
#1
07-10-2014, 09:13 AM
Temperature, Pressure vs Voltage - Troubleshooting
I have seen many Posters who rely solely on Temperature and/or Pressure readings to rely on for diagnostics. Especially since the ambient temperature is rising rapidly across the country as we’re into mid-summer.
Relying on gauge Temperature, Pressure is fine for the daily driver who wishes to monitor variations in hopes of identifying issues early before they become larger issues. But, for example: A rise in Oil Temperature, is it actually rising or is there a sender issue? I have attached some notes from classes I’ve taken over the years which I hope will be of some value to you Guys and Gals to ensure “what you’re seeing is – what you’re getting” on the Gauge and help you choose a path for troubleshooting.
When we’re troubleshooting issues, we need to explore alternative tests to ensure the system is functioning correctly and provide a way to ensure “what we see is what we’re getting”.
These are easy tests which using a simple DVOM will assist in your choosing the shortest path in diagnosing a possible issue. And, hopefully save you some money and time.
Tom
Oil-pressure, pulse width and timing. Supply 5.0V +/ - 0.5V, signal 0.5–0.7V at idle, 4.5V at wide open throttle.
The ECM uses the BARO signal to adjust fuel timing, fuel quantity, and glow-plug on-time during high altitude operation. Supply 5.0V +/_ 0.5V, signal 4.6V at sea level, decreasing at higher altitudes.
CMP Camshaft position sensor The ECM uses the CMP signal to monitor engine rpm and TDC for No’s. 1 and 4 cylinders. This Hall-effect sensor generates a digital voltage signal of 12.0V high, 1.5V low.
The ECM uses the EBP signal to control the exhaust pressure regulator (EPR). Supply 5.0V +/- 0.5V, signal 0.8–1.0V @ 14.7 psi at idle, increasing with engine speed and load, decreasing with altitude.
EOT Engine oil temperature sensor The ECM uses the EOT signal to control glow-plug on time, EPR, idle rpm and fuel delivery and timing. Supply 5.0V +/-0.5V, signal 4.37V @ 32°F, 1.37V @ 176°F, 0.96V @ 205°F.
EPR Exhaust back pressure regulator The EPR operates hydraulically from oil taken off the turbocharger pedestal mount. When intake air temperature is less than 37°F (50°F on some models) and the engine oil temperature is less than 140°F (168°F on some models) the ECM energizes a solenoid valve that causes oil pressure to close a butterfly at the turbo exhaust outlet. The valve opens under load and as the engine warms.
The ECM turns the “wait to start” lamp “on” for 1–10 seconds, depending on engine oil temperature and barometric pressure.
IAT Intake air temperature sensor The ECM uses the IAT signal to regulate exhaust backpressure. Supply 5 V+/- 0.5V, signal 3.90V @ 32°F, 3.09V @ 68°F, and 1.72V @ 122°F.
IPC Injection pressure control sensor The ECM uses the IPC signal to match fuel delivery with load and to stabilize idle rpm. Signal 1.00V @ 580 psi, 3.22V @ 2520 psi.
IDM Injector driver module. The IDM receives cylinder-identification and fuel-demand signals from the ECM, and generates a 115 VDC, 10A signal for the appropriate injector, varying pulse width as required.
IPR Injection pressure regulator The ECM varies the duty cycle of the IPR to control oil pressure and the volume of fuel delivered. 0% full return to sump (open valve), 100% full flow to injectors (closed valve). Functioning is monitored by the Injector pressure control sensor going to glow plugs is hot when the relay is energized. One of the 18-gauge wires (usually red with a light green tracer) is the signal wire, energized by the lube-oil temperature sensor. This wire must have battery voltage for the relay to function. Depending upon the circuit, the “wait-to-start” lamp may signal when the glow plugs energize or merely count off seconds. Individual glow-plugs should have a resistance of about 0.1Ω to ground when cold and 2Ω or more after cylinder temperatures normalize.
Check fuel pressure while cranking for 15 seconds. If pressure is less than 50 psi, replace the fuel-filter element, remove any debris on the fuel screen and on the screen protecting the IPR deceleration orifice. See the “IPR” section for more information.
Check injector-oil pressure during cranking. A pressure of 500 psi must be present to enable the injectors. Expect to see 960–1180 psi at high idle and 2500+ psi during snap acceleration. If the computer senses that the IPR has malfunctioned, it holds idle oil pressure at a constant 725 psi.
Trouble code 1280 means low IPR signal voltage, 1281 high signal voltage, and 1212 abnormally high (at least 1160 psi) oil pressure with engine off. See “Low oil pressure” below.
While cranking, check for the presence of an rpm signal. A failed CMP can hold oil pressure below the 500-psi injector-enabling threshold. Refer to “Camshaft position sensor” section below.
Check power at the injector solenoids with an appropriate scan tool. Zero pulse width on all injectors means a bad CMP sensor or IDM. Failure may trip trouble code 1298. The high power levels—10A at 115 VDC—put severe demands on the injector drive module. In addition, modules on Econoline 7.3L vans built before 4–11–96 have problems with water intrusion.
Electronic management systems, The IVS is an on-off switch that signals the ECM when the engine is idling. Signal 0V at idle, 12V off-idle.
MAP Manifold absolute pressure sensor The MAP measures manifold pressure to limit turbo boost, optimize timing, and reduce over-fueling and smoke. Signal frequency: 111 Hz @ 14.7 psi, 130 Hz @ 20 psi, 167 Hz @ 30 psi.
Relying on gauge Temperature, Pressure is fine for the daily driver who wishes to monitor variations in hopes of identifying issues early before they become larger issues. But, for example: A rise in Oil Temperature, is it actually rising or is there a sender issue? I have attached some notes from classes I’ve taken over the years which I hope will be of some value to you Guys and Gals to ensure “what you’re seeing is – what you’re getting” on the Gauge and help you choose a path for troubleshooting.
When we’re troubleshooting issues, we need to explore alternative tests to ensure the system is functioning correctly and provide a way to ensure “what we see is what we’re getting”.
These are easy tests which using a simple DVOM will assist in your choosing the shortest path in diagnosing a possible issue. And, hopefully save you some money and time.
Tom
Oil-pressure, pulse width and timing. Supply 5.0V +/ - 0.5V, signal 0.5–0.7V at idle, 4.5V at wide open throttle.
The ECM uses the BARO signal to adjust fuel timing, fuel quantity, and glow-plug on-time during high altitude operation. Supply 5.0V +/_ 0.5V, signal 4.6V at sea level, decreasing at higher altitudes.
CMP Camshaft position sensor The ECM uses the CMP signal to monitor engine rpm and TDC for No’s. 1 and 4 cylinders. This Hall-effect sensor generates a digital voltage signal of 12.0V high, 1.5V low.
The ECM uses the EBP signal to control the exhaust pressure regulator (EPR). Supply 5.0V +/- 0.5V, signal 0.8–1.0V @ 14.7 psi at idle, increasing with engine speed and load, decreasing with altitude.
EOT Engine oil temperature sensor The ECM uses the EOT signal to control glow-plug on time, EPR, idle rpm and fuel delivery and timing. Supply 5.0V +/-0.5V, signal 4.37V @ 32°F, 1.37V @ 176°F, 0.96V @ 205°F.
EPR Exhaust back pressure regulator The EPR operates hydraulically from oil taken off the turbocharger pedestal mount. When intake air temperature is less than 37°F (50°F on some models) and the engine oil temperature is less than 140°F (168°F on some models) the ECM energizes a solenoid valve that causes oil pressure to close a butterfly at the turbo exhaust outlet. The valve opens under load and as the engine warms.
The ECM turns the “wait to start” lamp “on” for 1–10 seconds, depending on engine oil temperature and barometric pressure.
IAT Intake air temperature sensor The ECM uses the IAT signal to regulate exhaust backpressure. Supply 5 V+/- 0.5V, signal 3.90V @ 32°F, 3.09V @ 68°F, and 1.72V @ 122°F.
IPC Injection pressure control sensor The ECM uses the IPC signal to match fuel delivery with load and to stabilize idle rpm. Signal 1.00V @ 580 psi, 3.22V @ 2520 psi.
IDM Injector driver module. The IDM receives cylinder-identification and fuel-demand signals from the ECM, and generates a 115 VDC, 10A signal for the appropriate injector, varying pulse width as required.
IPR Injection pressure regulator The ECM varies the duty cycle of the IPR to control oil pressure and the volume of fuel delivered. 0% full return to sump (open valve), 100% full flow to injectors (closed valve). Functioning is monitored by the Injector pressure control sensor going to glow plugs is hot when the relay is energized. One of the 18-gauge wires (usually red with a light green tracer) is the signal wire, energized by the lube-oil temperature sensor. This wire must have battery voltage for the relay to function. Depending upon the circuit, the “wait-to-start” lamp may signal when the glow plugs energize or merely count off seconds. Individual glow-plugs should have a resistance of about 0.1Ω to ground when cold and 2Ω or more after cylinder temperatures normalize.
Check fuel pressure while cranking for 15 seconds. If pressure is less than 50 psi, replace the fuel-filter element, remove any debris on the fuel screen and on the screen protecting the IPR deceleration orifice. See the “IPR” section for more information.
Check injector-oil pressure during cranking. A pressure of 500 psi must be present to enable the injectors. Expect to see 960–1180 psi at high idle and 2500+ psi during snap acceleration. If the computer senses that the IPR has malfunctioned, it holds idle oil pressure at a constant 725 psi.
Trouble code 1280 means low IPR signal voltage, 1281 high signal voltage, and 1212 abnormally high (at least 1160 psi) oil pressure with engine off. See “Low oil pressure” below.
While cranking, check for the presence of an rpm signal. A failed CMP can hold oil pressure below the 500-psi injector-enabling threshold. Refer to “Camshaft position sensor” section below.
Check power at the injector solenoids with an appropriate scan tool. Zero pulse width on all injectors means a bad CMP sensor or IDM. Failure may trip trouble code 1298. The high power levels—10A at 115 VDC—put severe demands on the injector drive module. In addition, modules on Econoline 7.3L vans built before 4–11–96 have problems with water intrusion.
Electronic management systems, The IVS is an on-off switch that signals the ECM when the engine is idling. Signal 0V at idle, 12V off-idle.
MAP Manifold absolute pressure sensor The MAP measures manifold pressure to limit turbo boost, optimize timing, and reduce over-fueling and smoke. Signal frequency: 111 Hz @ 14.7 psi, 130 Hz @ 20 psi, 167 Hz @ 30 psi.
#2
07-11-2014, 05:56 PM
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