Still trying to figure out dramatic drop in fuel mileage since cold weather showed up.

I had someone go over the fuel pump and intake lines, injection lines... pretty much looked over everything and could find nothing to show a fuel leak. What he did notice was that the temp gauge barely moved off the C even well after it was warmed up and blowing heat. The truck makes plenty of heat but he thought maybe the thermostat was opening to soon to allow it to run hot enough to burn correctly and we just never had an issue during warmer weather. Is this possible or is there some other place we should look? Would there be a sensor or something that would allow it to run cold? Could the gauge be the issue and there's another reason for the lousy mileage???

 

first thing is what are you calling horrible milleage? but these stock gauges are not accurate and normally show it running cool, heck mine only barely moves, but you can put a 203* stat in it to make it run warmer

 

That's what we put in tonight. It's what the parts store said the book called for from the factory. Mileage dropped from 12+ to 7 or 8 literally overnight

 

what year is your truck??

 

95 F350 Psd, Cc, Drw

 

You may want to scan EOT ,,,might be off a bit.....(alot)....

 

Whats eot???

 

The fuel milage drop very well could be due to the winter blend diesel your buying.
Everyone will have their milage drop when the winter fuel starts being delivered.

 

Winter fuel seems to burn faster for some reason,and the cold weather also activates the EBPV which will give you terrable milage,if the truck is blowing heat it is running normal like already said the stock gauges suck,there would be a problem if after it had been running a while and was still blowing cold air this would give poor milage

 

Engine Oil Temp. its the only engine temp the PCM cares about.

 

And you alway go start your truck 10-15 mins before ya make your trip.

 

Fuel, warm-up.. all stuff I'm aware of as I've either been in a big truck or my pick-up for the last 22 years. Still, this is the 3rd 7.3 I've had and I've never had this issue before so one would think that there is a logical explanation. A slight drop is one thing, a 35% cut is another. Don't you think?

Maybe I'll disconnect the ebpv and see if that makes a difference.

 

Wonder if this temp would play havoc on a map sensor. Its just a thought. Its a easy check too. Have another thing that people commonly overlook is tire air pressure. Although you say it happened overnight, it can still get you 1 to three, depending. Have you cleaned the FPR screen? Maybe its plugged? Fuel Filter? Just a few of the basics I am throwing out there. you will see it drop 3 mpg just from the switch in fuels. another thing a lot of guys do, is try dumping a qt of tranny fluid into the fuel. 1/2 in front tank, 1/2 in rear on a fill up. Then check your FPR and filter after you run those tanks out. It will loosen a lot of the junk that kills mileage, plus its lubes injectors and such. You have no wetness in the enine valley, correct?? Hope you find it.....

 

EBPV stuck closed?

 

If the PCM is getting signal from the EOT sensor that the motor is always cold ,, your mileage will suffer,, Low fuel pressure can hurt milage as well (from what I read)...

Scan Eot ,& see how it compares to ambient air temp,, check the fuel pressure ,, See what up....

If the EBPV was stuck , it would effect milage , but also performance....