It sounds ok at idle and and up to about 50 mph as long as I baby the throttle. If I ease into the throttle it starts to run rough and if I goose it it all but dies. On hills it is gutless. On long hills it eventually smokes grayish-white at I creep over the top.

Less than 100 miles ago, It did it and I changed the fuel filter. I thought I had it fixed. Then after sitting for a week, It is problematic again, making me suspect water in the fuel.

Other info. I ran bio in it through the summer, which makes me wonder about the diaphragm in the lift pump.

In the daylight I will draw some fluid out of the fuel filter and check for water, but other ideas will be helpful. Thanks.

 

check the oil level, it the LP died it will dump fuel in the oil.

 

I think you are right suspecting the lift pump. Rule that out as the culprit first. After changing your fuel filter again of course. Fuel supply rate sounds limited, whether LP is dead, filter is full, lines cracked, etc, etc.

 

Check the whole fuel supply system for leaks, I would bet you are sucking air.

 

I finally got a chance to look at this again. I found no leaks. I realize that if it is sucking air, there is probably nothing to "see".

I pulled a fuel sample from the bottom of the filter. It looked a tiny bit murkey, but there was no separate water. I put on a new filter and when I fired it up it ran beautifully.

I drove it about a mile, spun a few cookies in the snow, and then I had no power again.

SO, it was running fine and had good power for about 20 minuted (10 min at idle, ten minutes running). Now, as before the new filter, it idles fine and moves accross the flats fine, but at about half throttle, it loses power. If I bury my foot in it, I get white smoke.

Things I know:
1. The fuel cap did not fit tight (old style 1977, not behind a door)
2. Truck ran beautifully all summer(hot and dry), Started acting up after the rains came.
3. With a fresh filter, it runs great for a short time.

Should I drain the tank? It has about 15 gallons in it.
If it is sucking air, would the filter change effect it the way it does?

Got more snow coming. I want this thing on the road.

 

you might have water in it,
if you can drain the tank and lines and see whats there and refill with clean fuel, i dont know if the bio diesel mixes with water or stays seperate like diesel does

 

did you ever check the lift pump that bio fuel is hard on things!

 

Have you checked for a loose wire at the fuel shut off solenoid? Make sure they are snug. Do this first.
Could be the lift pump.
Might also be the suction line or crap in the bottom of the fuel pickup.

 

What's the fuel line pressure when it's doing this?

 

When you changed the filter you purged all the air out of the supply side. A few minutes of running and the air was back.

Check those lines...

 

I had the same problem with mine last year, turned out it was the add-on fuel/water seperator someone had put on. I tried to find a new filter element for it but could not, so i took it off. In doing so i found cracks in the globe that you could not see unless you took it out. Solved that problem. I've also heard that running Biodiesel will gum things up, it cleans the fuel system and i've heard of several people going through a ton of fuel filters before it straightens out. Either drain the tank or get a case of filters and change it when it starts running like crap.

 

yeah it will clean the crap out of your system. I would cut the bottom off your old filter and see whats in there.

 

Finally solved the problem. It wasn't that difficult. Replaced the 10" fuel hose between the steel line and the lift pump. As near as I can tell, it had a pinhole in it.

Thanks for all your ideas. And thanks Dave for being not only will ing, but also right.

 

good to hear, but the snows all gone

 

Might just have to go find some.