2000 7.3L starting problems
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2000 7.3L starting problems
I'm new to the forum and new to owning a diesel. I have a 2000 7.3L SuperDuty 228k auto trans, not 4x4. If it sits overnight even in 80 degree weather, it takes about 20 minutes to start. White smoke, diesel smell. Once started, very rough idle for about 5 mins and drives rough for about 10 mins. If the block heater is plugged in overnight even in 80 degree weather, it starts right up with no hesitation and no issues driving. Once warm, I can start it up with no problems all day long, even if it has been sitting for 3-4 hours. I replaced the GP relay. Same problem. Plz help.
Post Fiend
Joined: Nov 2001
Posts: 6,748
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From: Tallassee, ALabama
Sounds like your glow plug relay is bad or you have multiple glow plugs bad or the valve cover wiring harness is bad. Since you have replaced the glow plug relay, I would consider replacing the glow plugs and valve cover harness.
First check the Black and Orange wire on the GP relay. See if it has 12v even with the key off. If no voltage, trace the B/O wire back and see if the 2 gray fuse links are blown. If so, replace them and see if the truck starts ok. Check to make sure the there is voltage on the red wire on the GP relay to energize the GP relay.
If they are ok, you need to check the circuits coming out of the relay for conductivity to the valve cover harness. If connectivity, check the valve cover harness to the glow plugs. And it that is ok, I think maybe glow plugs.
Theory of operation.....
The 7.3L diesel engine uses a glow plug system that preheats air in the combustion chamber to improve cold engine starting.
The system consists of:
intake manifold glow plugs (12A342).
glow plug relay (12A343).
powertrain control module (PCM) (12A650).
engine oil temperature (EOT) sensor.
barometric pressure sensor (BARO sensor) (12A644).
The glow plug system is electronically controlled by the powertrain control module. If the temperature is below 55°C (131°F) the powertrain control module will energize the glow plugs immediately after the key is placed in the ON position. Then, depending on the readings from the engine oil temperature (EOT) sensor and the barometric pressure (BARO) sensor, the powertrain control module determines how long the glow plugs will be on.
Glow Plugs — PCM-Controlled
The intake manifold glow plugs are located in the cylinder heads (6049), under the valve covers (6582).
The glow plugs are self-regulating. If the engine oil temperature is above 55°C (131°F), the powertrain control module will bulb-check the WAIT TO START lamp but not energize the glow plug relay.
The powertrain control module protects the glow plugs by energizing them for short durations if the battery voltage is abnormally high.
The glow plug ON time varies from 0-120 seconds depending on battery voltage, engine oil temperature and barometric pressure.
On California vehicles the glow plug monitor system is part of the On-Board Diagnostics II (OBD II) System.
The glow plug monitor (GPM) system is designed to find failed glow plugs or failed wiring in the glow plug system.
The GPM system uses a low resistance shunt to conduct current to the left and right bank glow plugs.
Three sensing wires measure the voltage drops across the shunt when the glow plugs are operating. A failure in the glow plug system will set a diagnostic trouble code (DTC).
First check the Black and Orange wire on the GP relay. See if it has 12v even with the key off. If no voltage, trace the B/O wire back and see if the 2 gray fuse links are blown. If so, replace them and see if the truck starts ok. Check to make sure the there is voltage on the red wire on the GP relay to energize the GP relay.
If they are ok, you need to check the circuits coming out of the relay for conductivity to the valve cover harness. If connectivity, check the valve cover harness to the glow plugs. And it that is ok, I think maybe glow plugs.
Theory of operation.....
The 7.3L diesel engine uses a glow plug system that preheats air in the combustion chamber to improve cold engine starting.
The system consists of:
intake manifold glow plugs (12A342).
glow plug relay (12A343).
powertrain control module (PCM) (12A650).
engine oil temperature (EOT) sensor.
barometric pressure sensor (BARO sensor) (12A644).
The glow plug system is electronically controlled by the powertrain control module. If the temperature is below 55°C (131°F) the powertrain control module will energize the glow plugs immediately after the key is placed in the ON position. Then, depending on the readings from the engine oil temperature (EOT) sensor and the barometric pressure (BARO) sensor, the powertrain control module determines how long the glow plugs will be on.
Glow Plugs — PCM-Controlled
The intake manifold glow plugs are located in the cylinder heads (6049), under the valve covers (6582).
The glow plugs are self-regulating. If the engine oil temperature is above 55°C (131°F), the powertrain control module will bulb-check the WAIT TO START lamp but not energize the glow plug relay.
The powertrain control module protects the glow plugs by energizing them for short durations if the battery voltage is abnormally high.
The glow plug ON time varies from 0-120 seconds depending on battery voltage, engine oil temperature and barometric pressure.
On California vehicles the glow plug monitor system is part of the On-Board Diagnostics II (OBD II) System.
The glow plug monitor (GPM) system is designed to find failed glow plugs or failed wiring in the glow plug system.
The GPM system uses a low resistance shunt to conduct current to the left and right bank glow plugs.
Three sensing wires measure the voltage drops across the shunt when the glow plugs are operating. A failure in the glow plug system will set a diagnostic trouble code (DTC).
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