I haven't used by back tank in a while and one day last week decided to put some fuel in it. Well the next day, the wife switches over to the back tank and runs for a good 3 miles. Then the truck started acting like it was missing and was running out a fuel. We I got to her on the side of the freeway, I switched it over o the front tank. When it craked it ran rough, but after about 45 sec. it cleared up. Well, I switch over to the back tank again and sure enough, after about 10 min of of idil and then about 3 miles down the road it statrted all over again. But i switch to the front and it goes away. I have check for water when I drain the fron the seperator, but don't see anything noticable.

 

Is the fuel in the back tank gasoline, perhaps? (It doesn't mean you pumped gas in there by mistake; it could have been the station got its tanks filled wrong. Wouldn't be the first time!)

I'd think you could get a good idea by opening the tank and smelling the filler pipe.

Duncan

 

It is diesel.

Could it be the "fuel relay valve" that is between the two tanks?

 

Could be the valve. Is it possible that there's some crud clogging the pickup on the back tank, and you're actually getting little or no fuel flow from there?

Duncan

 

Almost sounds like a bunch of sediment collecting around the in tank pick up screen, plugging off the fuel supply, then falling off when you switch to the front tank, and plugging up again when going back to the rear. but if this was the case, it should plug up the fuel filter. Do those truck have the low pressure in tank pump, and then the HP pump upstream of the relay valve? if so, maybe the rear tank pump is not kicking on? Does your fuel gage switch also when you switch tanks? just a few random thoughts to maybe start with.

 

i think it could be that there is a little crack in the fuel line somewhere between the back tank and the fuel switch-um-abobber whatever you call it it could also be that the ickup tube in the back tank is not right, sometimes the little plastic thingy breaks up and it wont run under a 1/4 tank

 

well, 89ford73, that is exactly what is happening. I have filled it up and it runs fine until just below 1/4 tank then it starts up. Just like it's running out of fuel. So you think it might be the pick up tube in the tank, might be cracked?

 

thats exactly what hapened to mine biesel diesel, i heated up my inlet tube and bent it down to get it all the way to the bottom, but you can put a 6" piece of fuel hose on the end of this tube, 3/8's what will fit i think and put a good hose clamp on it and that should do the trick also... remember to get a rag and clean up all the little pieces of cracked plastic floating around in the tank, (im sure there will be some)so it doesn't clog the fuel line later on, if you pull the bed off to do this it is easier and you can do the same thing to the front tank also as a preventive measure. and if you take the big hose off the filler neck, there is another smaller hose in side of it, cut the rubber small rubber hose off and drill a hole in the to metal part of the fill neck like about a 3/8 or so it will make filling with diesel at the pump much easier.