I bought a 1986 F-250 6.9L about a month ago, the gentleman I bought the truck from had dropped the front tank and had after market fuel lines running to the back tanks. he had bypassed the fuel selector valve and just run two lines from the back tank all the way to the engine, i was at a junk yard today looking for a fuel selector valve for this truck and noticed that ALL the trucks I crawled under had a small inline pusher pump between the selector valve and the engine. I was wondering if this is stock on these trucks, i mean i crawled under 10+ trucks today and they ALL had these things??? what was their function??? are they necessary, my truck now does not have one and i was not sure why others did and if i needed to get one for my truck, SECONDLY i pull the back tank off today to replace the fuel lines and I pulled the fuel sending unit out and noticed a check valve broken and sitting on the bottom of the tank. that made me think that it probably attached to the pick up tubes at one point, so i ask is this stock on all these trucks??? what is it's purpose and is it necessary??? i am sorry for having so many questions I am new to all this, I know you guys can help me though, THANKS for all your replies in advance.

 

Some members do have Holley red or a lesser named electrical pump installed. Can't believe every diesel you find would have one, were they all diesels. FSV were the same on gasser and diesel. The purpose was to screen fuel, but should it have become plugged the little valve above the screen would open and free flow fuel as required. You can use a length of fuel hose cut on a 45* angle on the lower end in place of the screen pickup.

 

the trucks were not all diesels, there were probably 6 out of the 10 that were diesels and had pusher pumps, why do members add them to their trucks, what are their functions?? i also do not understand what the check valve on the sending unit is for or if it is necessary, does anyone know what they are for or how necessary are they??

 

That check valve is a bypass valve, it sits at the 1/4 tank mark, its for if the pickup screen were to get cloged with ice or gelled fuel in the winter time you wount be left stranded as long as you had more than a 1/4 tank of fuel. its stated in the ford owners manual not to go below 1/4 tank in freezing temps

I fould my old ford supplement

heres a qoute from the 7.3 supplement manual
" due to diesel fuels affinity for water and waxing characteristics, your vhicle is equipped with a bypass relief valve on the in tank fuel sending unit.this valve provides fuel flow to the engine if the fuel pickup should become plugged by ice or wax

caution- to allow this bypass valve to function ans advoid engine fuel starvation - it is recommended that during cold weather operation (32F,0C or below) the fuel level in your tanks not be allowed to drop below 1/4 full ,to prevent air from entering the fuel system and stalling the engine"

 

what does the check/bypass valve connect to at the 1/4 tank mark??? i do not understand how it was set up in the first place??? does anyone have any suggestions about the pusher pump and its function??? thanks again for all your help.

 

the fuel system has a few weak spots that are known to let air into the system causing starting and running issures since the system will loose its prime . the older 6.9s have a water seperator on the firewall that is well known to let air in. people have added electric pumps to keep the system primed

 

thank you dieself250, that makes sense and i understand that, can you help explain the check valve/bypass valve issue in the fuel tank that i found, i do not understand where it once attached to or where to put another one at??

 

hey dieself250 i just saw your reply to the check valve/bypass valve, sorry i missed it, do you think that these 6.9's had the same bypass valve in them, i searched through my manual and could not find any such claim about the fuel systems. i even searched through the supplement guide and found nothing that said anything about a bypass valve in the fuel sending unit, this is DEFINETELY a check valve and i am not sure why it was in there or where it goes, thanks for all of yalls help, if anyone else has any suggestions i would appreciate it, thanks

 

I would assume they put it in with the 6.9s, on the pick up tube did you happen to see a hole in the tube a few inches up from the pickup screen or was your pick up in pices

 

well when i pulled the sending unit out all i saw were two metal lines running into the tank, i suppose one supply and one return, there were no rubber hoses or anything attached to these metal lines, i then cleared out the diesel and heard something rattling around in the tank and then proceeded to dump everything out, ALOT of undistinguishable plastic parts came out and a screen of some sort came out and then this check/bypass valve, none of these items were attached to anything, i am confused on how it all went together or how it was supposed to look, any help at all would be greatly appreciated, thanks again for all of yalls help

 

The check valve mounted on the pickup tube above the screen. It lets fuel into the tube without going through the filter screen on the bottom of the pickup tube.

When I used to drive long haul, running #2 fuel in very cold temps was always a fun trip. When you pulled the cap off the fuel tanks, they looked like the tank had icebergs floating around in them. That was the parrafin gelling out of the diesel at low temps. If you suck one of those icebergs into your fuel pickup tube, you will be walking to the closest warm place and staying there for a while. After a short nap in a Kansas rest area one morning I actually found out those electric hand blowers can keep you from freezing. Took two days to get the truck running again.