Saw him tonight at horse camp. He has 180k on it. Runs "ok" but has lost several mpgs.

Check the timing since they like to slip. Check all the filters. Check the fuel pressure as he might have a bad overflow valve. How does it start on a cold morning? Is it an auto tranny?

He told me it starts & dies a couple of times on a cold start. He's retired & doesn't use the truck a whole lot. Main use is hauling a 2 horse slant load gooseneck with living quarters. I think it is an automatic. We haven't seen much of them in recent years... they took my horse in (for free) when my ex kicked him out of the new barn I built. (So I would not loose him.) Later, they stood up for us at our wedding. (I did better the second time around.)

Have the rubber fuel and return lines been replaced?

I hung out with Tony for an hour this morning... Truck is 1997. He tells me when it starts up sometimes normal with no smoke, sometimes like it's starting one 3 cylinders with white smoke. Eventually it smooths out. He had to replace a solonoid in the transmission recently.

Replacing a solenoid in the transmission has nothing to do with the way the engine runs. It soulds like there is an air leak in the fuel system. Normally the rubber hoses behind the filter are the cause of the leak. You won't see fuel leaking, but the can suck air.

I let my friend know this information. It made sense to him. We appreciate the good advise. I included the transmission question because someone asked. No, I didn't think it would have anythiong to do with the complaint. Tx Russ

Replacing a solenoid in the transmission has nothing to do with the way the engine runs. It soulds like there is an air leak in the fuel system. Normally the rubber hoses behind the filter are the cause of the leak. You won't see fuel leaking, but the can suck air.

I let my friend know this information. It made sense to him. We appreciate the good advise. I included the transmission question because someone asked. No, I didn't think it would have anythiong to do with the complaint. Tx Russ

I am trying to figure out the original problem of bad mileage, that is why I ask about the tranny as an auto could have a bad converter or something. The lines could be the starting issue but I am not sure if they could be the mpg culprit. Supposedly what could happen is enough air bubbles form to where there is some cavitation in the fuel system and the air in the system creates injection issues which delay the timing, making it more retarded. Also causes some other issues and can even make the truck go into a run away condition. This is all "supposed" speaking as I read about this on a huge article on CF. I have done many things to my truck and have never seen anything touch my mileage so I never know what to think of people with mileage problems other than something like a weak overflow valve which I would think would cause hard starting since it isn't hardly getting any fuel into the plungers because of the period of time it has to go into the plungers before they are sealed off. At a low fuel pressure there wouldn't be as much fuel getting into them. When the engine is cold it takes more fuel to keep it/get it running. I have no way to test this theory unless I had a variable electric fuel pump but it makes sense to me.

... Or back to the basics of a fuel pressure gauge...

I had a return hose start leaking and boy did it drop my mileage!! I think I was down to about 2 GALLONS to the mile then, but fuel was pouring out something fierce!! Anyhow, I was thinking of the hard start with the lines sucking air. It very well could be an overflow valve problem too. Like Michael said, a fuel pressure gauge could be a good thing about now......... Is there any smoke of any kind that is not 'normal' for the truck weather cold or warm?