Sometime after after getting on the road today I noticed my EGT's are up about 200 degrees on the average. Flat roads around 60mph I was around 800 degrees, those conditions in the close past has usually been a little under 600. This is on a truck with no fueling mods (sold the pup), only airflow has been modded. I haven't hand calculated the mpg lately, but just looking at the fuel level guage it seems I am burning more than usuall. It don't smoke any more than normal, runs fine, power is there, idles smooth. All seems normal with the exception of the EGT's being higher now for some reason, and this seemed to just start over night. Anyone have any gueses as to what's going on?

 

Possibly a dirty air filter? If the filter is good, while you are there check the turbo for freedom of movement, visual abnormalities and end play. If all that looks good next guess would be a restriction in the exhaust. This of course is after ruling out a bad gauge/connection. Then there are things beyond the engine, like dragging brakes etc. Good Luck!

I just checked your sig., try turning down the stereo

 

Cooler weather = thicker air. Winter blended fuel?

I woudn't give it another thought.

 

dirty fuel filter will cause that too.

 

"dirty fuel filter will cause that too."

No, it won't.

The 3rd gens have a common rail fuel system. As long as the fuel pump and filter have enough flow to keep the CP3 reasonably fed and as long as the fuel rail pressure stays within the commanded limits, ie no check engine light, a dirty fuel filter will have NO effect on operating performance. None.

It might have some effect on the longevity of the low pressure fuel pump and on the CP3, but as long as the rail pressure is where it needs to be, the engine will run the same.

 

I will respectfully disagree that a plugging fuel filter will not cause these problems. Please see the below thread for why. I should add that no code was set for this situation.

https://www.dieseltruckresource.com/...ht=fuel+filter

 

That's interesting.

Well the strange EGT's are gone as fast as they came. Left the hotel this moring to find the EGT's are back to their norm. 70 mph on a flat interstate was 600 degrees.

Some other little tid bits. Boost was normal that I didn't mention earlier (went back to analog guages, Outlook was sold too) Water temp same as always, and I changed the oil and fuel filter before I left for Cincy last weekend. So I only have around 1500 miles on this fuel filter. Also the EGT's came back to normal while running the same fuel as yesterday when the EGT's were flakey. The last place I got fuel was at the Pilot about 15 miles North of Lexington, Ky. We'll see what tomorrow brings in the EGT department.

 

Could just be the guage. My FP guage shows higher pressure when I turn the lights on..

 

"I will respectfully disagree that a plugging fuel filter will not cause these problems. Please see the below thread for why. I should add that no code was set for this situation."

I dunno if I believe that.

If those guys are seeing enough fuel starvation to the CP3 that it can't keep the fuel rail full, thus affecting fuel economy, then the CP3 isn't getting any lubrication flow either. They are wrecking their CP3s.

I don't know if I believe everything I read.

 

how would cooler thicker air cause higher exhaust temps and I agree with Superduty about the fuel filter.
Jim O

 

Not trying to be disrespectful, but the thread I linked was my personal experience. I also had the exact same symptoms (high EGT and Boost) when my thermostatically controlled fuel heater wasn't working and my filter plugged up. See this thread https://www.dieseltruckresource.com/...ht=fuel+filter and this from page 4

"Yesterday afternoon I was barely able to limp my truck home. Engine was sputtering and unable to maintain 45 mph up some hills. I think I've diagnosed what' s going on, and it isn't the lift pump . . .

Issue #1.) I've been filling up at a truck stop and at the diesel island each fill up spot has two pumps labeled #2 and #1. I assumed the #2 was blended, but turns out it's straight #2 according to the station. This way the semi drivers can blend whatever % they want. So my last several tanks have been pretty much straight #2.

Issue #2.) We've had a cold snap recently as well. Yesterday morning was in the low teens and stayed cold until later in the day when it got up to ~32. I'm pretty certain my fuel was starting to gel (the morning drive was fine as my garage stays >45).

Issue #3.) The thermostate which controls the fuel heater doesn't work. When I got home I drained my fuel filter and examined the fuel. It was thick, cloudy and cold. I thought this was odd since my fuel heater should be warming the fuel. Put a thermometer in the diesel and it registered ~35 degrees. Got out the shop manual and on page 14-63 under "Diagnosis and Testing - Fuel Heater" it says that "A malfunctioning fuel heater can cause a wax build-up in the fuel filter/water separator ... this build up can cause engine starting problems and prevent the engine from reving up. It can also cause blue or white fog-like exhaust. If the heater is not operating in cold temperatures, the engine may not operate due to fuel waxing." This is exactly what my truck symptoms were.

I followed the diagnostic procedure (which involves using an ice pack to force the thermostate below 45 degrees) and determined the heating element was OK, but the thermostate which allows current to flow to the heating element was not turning on. The thermostate is not connected to the ECM or PCM so if it goes bad the computer does not know. So I hard-wired around the thermostat until I can get a new one.

As a side note: The pre-filter pressure gauge does let you know when the filter is plugging. The pressure will not pull down at WOT when it's plugged. At least that's what it did on my truck when the filter waxed up.
"

 

I doubt you were seeing diesel jell at those temps, even straight number 2. As soon as the engine starts the fuel lines and filter assembly and engine compartment get warm and cold fuel ceases to be a problem.

I dunno what is going on with your truck, but I doubt that it is fuel related. The first sign of fuel starvation is a check engine light when the CP3 can't keep the rail pressure up.

I'd pull codes on your engine.

 

I did scan for codes with my reader and there weren't any. The only variable changed in these cases was the filter. For example, in the first link my test isolated the filter as the only variable being changed because: Same fuel, same outside temp, some time (within 10 mins as I took the truck back out after changing the filter), same truck, etc. The only variable was the filter and that single item changed the whole behavior of the truck.

"I doubt you were seeing diesel jell at those temps, even straight number 2. As soon as the engine starts the fuel lines and filter assembly and engine compartment get warm and cold fuel ceases to be a problem."

Cold soaking at 13F from 6am to 12am with lots of wind, then slightly warming temps until 2pm when I left, could definitely cause CFPP problems with straight #2. The fuel I drained out of the filter housing was definitely thinker than normal. Of course I may have gotten a bad load of fuel? However, cold fuel does not instantly warm up and "cease to be a problem" once the truck is turned on, especially if the fuel filter heater isn't working.

Both of these cases were last year. Since I've been changing the fuel filter more often and got my fuel filter heater fixed I've had no problems since with low fuel pressure or low mpg or abnormal EGT's and boost. Was just trying to help this guy possible diagnosis a problem.

"The first sign of fuel starvation is a check engine light when the CP3 can't keep the rail pressure up.
"

I don't believe the truck will necessarily throw a code in all cases if the rail pressure doesn't agree with the desired set pressure. For example, numerous people have reported that while dynoing with the TST (or other boxes) the rail pressure can't keep up and reads several 1000's of psi below the requested value. Not all of these trucks set codes. Also in these conditions when the rail can't maintain pressure and "falls on its face" they see less hp and torque being made, higher EGT's, and darker exhaust due to fuel not being atomized as well. This is why many people make more hp on the TST at lower settings than they do at the highest settings.

It would be an interesting test for those people who have rail pressure gauges (not talking about lift pump gauges) to see how much difference between requested and actual is required to throw a code, or if there are some other conditions needed to cause the code to occur (does the difference in pressures have to occur for a certain period of time, etc.). If this can be tested it could support Superduty's position that the truck will throw a code when the filter is plugging.

 

"The first sign of fuel starvation is a check engine light when the CP3 can't keep the rail pressure up."

"I don't believe the truck will necessarily throw a code in all cases if the rail pressure doesn't agree with the desired set pressure. For example, numerous people have reported that while dynoing with the TST (or other boxes) the rail pressure can't keep up and reads several 1000's of psi below the requested value."

The reason that doesn't show a code is because the TST box is sitting between the rail sensor and the ECM and its feeding the ECM the correct pressure ! Geesh !


"Not all of these trucks set codes. Also in these conditions when the rail can't maintain pressure and "falls on its face" they see less hp and torque being made, higher EGT's, and darker exhaust due to fuel not being atomized as well. This is why many people make more hp on the TST at lower settings than they do at the highest settings."

Once again don't infer stock behavior from running a box. The other thing is that the TST is modifying the injection duration and timing.

"It would be an interesting test for those people who have rail pressure gauges (not talking about lift pump gauges) to see how much difference between requested and actual is required to throw a code, or if there are some other conditions needed to cause the code to occur (does the difference in pressures have to occur for a certain period of time, etc.). If this can be tested it could support Superduty's position that the truck will throw a code when the filter is plugging."

All one has to do is monitor the rail pressure sensor voltage with a voltmeter and do some math. The ECM doesn't just look at the difference between requested and actual pressure, it also looks at the fuel actuator duty cycle to get that pressure.

If your filter was really plugged, the duty cycle to the fuel actuator would have been 100% and your rail pressure would have dropped. That would set a code. If you want to check this, just pull the fuse for your fuel pump and let the engine starve a bit.

BTW: adding a mechanical gage to the fuel rail is a bad idea.

 

Thicker (more dense) air has more oxygen in it and will result in higher egt's.