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| Author: | cumminspilot [ Wed Jul 25, 2007 12:43 am ] |
| Post subject: | how does fuel temp sensor work |
and how does it effect performance and why do we need one? |
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| Author: | onthehunt [ Wed Jul 25, 2007 1:23 am ] |
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Which one? There are several. |
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| Author: | cumminspilot [ Wed Jul 25, 2007 10:23 am ] |
| Post subject: | |
oops sorry' How does the fuel temperature sensor that is attached to the fuel filter housing next to the fuel heater work? |
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| Author: | dgeist [ Wed Jul 25, 2007 2:09 pm ] |
| Post subject: | Re: how does fuel temp sensor work |
cumminspilot wrote: and how does it effect performance and why do we need one?
From the manual: An negative temperature coefficient (NTC) resistor integrated in the fuel temperature sensor alters it’s electrical resistance in line with the fuel temperature (the resistance drops as the temperature rises). The ECM uses this reading to calculate optimum engine performance under all driving conditions. If the fuel is to warm, the rail pressure in the system is lowered. The controlled quantity of the fuel rail pressure solenoid is reduced and the fuel temperature is lowered ... I even included the factory grammatical errors for authenticity... That what you were wondering? Dan |
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| Author: | Cowcatcher [ Wed Jul 25, 2007 3:58 pm ] |
| Post subject: | Re: how does fuel temp sensor work |
dgeist wrote: [ ... I even included the factory grammatical errors for authenticity... That what you were wondering? Dan I did!  I wonder how this can happen Quote: The controlled quantity of the fuel rail pressure
solenoid is reduced and the fuel temperature is lowered |
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| Author: | dgeist [ Wed Jul 25, 2007 4:52 pm ] |
| Post subject: | Re: how does fuel temp sensor work |
Cowcatcher wrote: I wonder how this can happen Quote: The controlled quantity of the fuel rail pressure solenoid is reduced and the fuel temperature is lowered Exactly, I'd like to know what "to warm" is 
Regardless, I'll like to get a functional unit on an ohmmeter and measure resistance at some specific temperatures (and perhaps plot a curve) or find someone's OEM coolant sensor or something. |
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| Author: | cumminspilot [ Wed Jul 25, 2007 6:21 pm ] |
| Post subject: | |
so what setting does it default to if it has no signal? Hopefully it is the max pressure setting as that is what we need all the time. A recent study found that 125f. was the optimum fuel temp. for diesel in otr trucks |
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| Author: | RFCRD [ Wed Jul 25, 2007 9:53 pm ] |
| Post subject: | |
cumminspilot wrote: so what setting does it default to if it has no signal? Hopefully it is the max pressure setting as that is what we need all the time.
A recent study found that 125f. was the optimum fuel temp. for diesel in otr trucks Hope this isn't like the Detroit Diesel DDEC logic, computer goes wackey and the engine won't run. Was a common problem to get a small air pocket at the sensor while priming a system after changing filters. Would default to injector closed (no fuel delivery) if it can't read a fuel temp. Could crank the engine over all day long, simply wouldn't start. |
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| Author: | cumminspilot [ Wed Jul 25, 2007 11:23 pm ] |
| Post subject: | |
It seems to work just fine with it unplugged. I did ehm and orm and unplugged the fuel heater and temp sensor. Took it around the block and ok so far. Will report back later. |
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| Author: | DZL_LOU [ Thu Jul 26, 2007 9:43 am ] |
| Post subject: | |
The fuel temperature sensor is integrated into the fuel filter housing, along side of the fuel heater. The sensor detects the temperature of the fuel and supplies that information to the ECM. The sensor ranges from - 40°F (- 40C) to 284°F (140°C). If the engine is cold, the actual value sent will read ambient temperature. The value rises after the engine has been started. The fuel temerature sensor IS NOT SERVICED separate from the housing assembly. The element inside the heater assembly is made of a Positive Temperature Coefficient (PTC) material, and has power applied to it by the fuel heater relay anytime the ignition key is in the “on” position. PTC material has a high resistance to current flow when its temperature is high, which means that it will not generate heat when the temperature is above a certain value. When the temperature is below 7°C (45° F), the resistance of the PTC element is lowered, and allows current to flow through the fuel heater element warming the fuel. When the temperature is above 29°C (85° F), the PTC element's resistance rises, and current flow through the heater element stops. Voltage to operate the fuel heater is supplied from the glow plug module, through the fuel heater relay, when the ECM senses the ignition (key) switch. |
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| Author: | dgeist [ Thu Jul 26, 2007 5:40 pm ] |
| Post subject: | |
DZL_LOU wrote: The fuel temperature sensor is integrated into the fuel filter housing, along side of the fuel heater. The sensor detects the temperature of the fuel and supplies that information to the ECM.
The sensor ranges from - 40°F (- 40C) to 284°F (140°C). If the engine is cold, the actual value sent will read ambient temperature. The value rises after the engine has been started. The fuel temerature sensor IS NOT SERVICED separate from the housing assembly. The element inside the heater assembly is made of a Positive Temperature Coefficient (PTC) material, and has power applied to it by the fuel heater relay anytime the ignition key is in the “on” position. PTC material has a high resistance to current flow when its temperature is high, which means that it will not generate heat when the temperature is above a certain value. When the temperature is below 7°C (45° F), the resistance of the PTC element is lowered, and allows current to flow through the fuel heater element warming the fuel. When the temperature is above 29°C (85° F), the PTC element's resistance rises, and current flow through the heater element stops. Voltage to operate the fuel heater is supplied from the glow plug module, through the fuel heater relay, when the ECM senses the ignition (key) switch. Ummm, that's the sensor AND the heater.... right? |
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| Author: | DZL_LOU [ Thu Jul 26, 2007 7:39 pm ] |
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dgeist wrote: Ummm, that's the sensor AND the heater.... right?
Yes, I was trying to describe the operation of both. First the sensor then the heater. Did I omit something? |
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| Author: | RFCRD [ Thu Jul 26, 2007 8:21 pm ] |
| Post subject: | |
DZL_LOU wrote: dgeist wrote: Ummm, that's the sensor AND the heater.... right? Yes, I was trying to describe the operation of both. First the sensor then the heater. Did I omit something? Consider this concept: What good is a temp sensor if its located in the same physical space as the heater element? Seems like it would distort the temp data being sent to the ECM and give you wacky performance. Would make more sense to have this closer to the pump and/or in the common rail. |
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| Author: | DZL_LOU [ Thu Jul 26, 2007 8:41 pm ] |
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RFCRD wrote: DZL_LOU wrote: dgeist wrote: Ummm, that's the sensor AND the heater.... right? Yes, I was trying to describe the operation of both. First the sensor then the heater. Did I omit something? Consider this concept: What good is a temp sensor if its located in the same physical space as the heater element? Seems like it would distort the temp data being sent to the ECM and give you wacky performance. Would make more sense to have this closer to the pump and/or in the common rail. Understood, but that's where DCX unfortunately located them right next to each other in the fuel filter head. Here's a quick diagram. #7 Fuel Temp Sensor, #4 Fuel Heater 
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| Author: | cumminspilot [ Fri Jul 27, 2007 12:01 am ] |
| Post subject: | |
when temp sensor is unplugged it seems to default to a lower rail pressure setting thereby reducing performance. My wife reports that since I unplugged the sensor and heater and did the orm performance has gone down and it does not have the same get up and go. Since my housing is leaking I am going to replace before plugging back in. As I now understand it the fuel temp sensor moderates rail pressure depending on temp input to ecm Unplugging defaults to hot fuel which lowers rail pressure so i guess we need to keep it plugged in until we find a way to defeat it. |
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| Author: | dgeist [ Fri Jul 27, 2007 10:23 am ] |
| Post subject: | |
RFCRD wrote: DZL_LOU wrote: dgeist wrote: Ummm, that's the sensor AND the heater.... right? Yes, I was trying to describe the operation of both. First the sensor then the heater. Did I omit something? Consider this concept: What good is a temp sensor if its located in the same physical space as the heater element? Seems like it would distort the temp data being sent to the ECM and give you wacky performance. Would make more sense to have this closer to the pump and/or in the common rail. That's why I like the design of the Racor units (heater in bottom of bowl). Not sure if the bungs in the top of the units are on the inflow or outflow side, but regardless, it's got to be better than being right next to the heater in a pocket of AIR 
Lou, I was just giving you a hard time for the formatting of the copy-paste
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