I am new to diesels and need help. I bought my truck a year ago it is a used 02 7.3 F-250 165000 miles. When the air temp got to 100 deg. last summer i lost about 3 miles per gal. and never regained it. I was getting 17 around town 21 hwy now getting 14 to 17 then this winter i noticed that when the truck sat for 3 or 4 days that it would not start the first time i would have to turn key off and try again then it would start but gray smoke would roll when it first started. Any ideas app.

 

OK, first of all from now on you should post your questions in the 99-03 7.3 forum, as you'll get answers there a lot faster. I'm not sure where in the country you're at, but some stations might have been late in swapping over to the new USLD (ultra low sulfur diesel) which caused ALL of us to lose about 1-3 mpg. It sucks but nothing we can do about it. And you hard starting is more than likely due to a burned out glow plug solenoid. That powers the glow plugs in the engine combustion chamber to help assist in heating the air for proper combustion. Without them, the engine will take a considerably longer time to compress the air and make it hot enough to ignite the fuel that's injected into the cylinder. And of course once it does start, the glow plugs are supposed to stay on for at least 90 seconds, but usually more like 3 minutes. However, yours arent, and that is causing the fuel / air mixture to not completely burn, thus causing the gray smoke. So all you need to do to test it, it run a jumper wire across the heavy leads of your GPR (glow plug regulator) or solenoid as it's also called, and then start the truck. You should then see no, or a whole lot less smoke on a cold day. The GPR is located behind, and toward the passenger side of the fuel bowl. Hope this helps! And stay around, and read as much as you can- this site has saved me literally THOUSANDS of dollars on repairs 'cause I learned to do it here. And the 7.3 forum is a pretty tight family. Look forward to seeing you there!