Fuel delivery issues.....

[Saskredneck]

So my million miler went down last Tuesday and because of ****** weather and spring goose hunting I didn't get much time to work on it until today. The truck randomly died on the highway heading to work showing just under 1/4 tank, ok so I thought either the gauge in the cluster I installed that has a tach was off, put 20L of fuel in and cranked and cranked and cranked eventually killing the starter. Installed a new starter on the side of the highway on Tuesday and cranked some more, nothing... So we hooked up my buddies cummins and dragged it over 3 miles down the grid roads with the hood up and me watching the bleeder trying to get fuel to fuel filter and nothing.... So I changed the lift pump even though it seemed fine when I pulled it off, now I'm getting random fuel flow when cranking but more times than not it's just pumping air.... So after screwing with it for a couple hours today and disconnecting the lines from the FSV to check them for blockage, both of which were good, I took the wife's car to town to get more fuel and filled the tank thinking it might be a broken pick up. Well still nothing is happening with a full tank, so my question here is can the FSV somehow malfunction to the point that even if I have only been running one tank (rear one has a huge hole...) can they malfunction if the switch is never used? I can hear it when I move the switch but don't know if its working or if its just trying to switch and somehow got stuck closed between the two tanks when I never touched the switch. This is frustrating me and I've replaced all the lines from the tank to the lift pump and the lift pump. Never heard of FSV randomly moving to the dead spot between tanks, but it seemed to of happened. The only way I could get some fuel to flow was while the truck was running off of the fuel I put into the filter and played with the switch in the cab flipping from front to rear tank. Need some input before I rip the FSV out of my dead 4x4 and throw it into the 2wd.

 

[79jasper]

FSV can be stuck.
Could've sucked up something, and be between the pickup and the FSV.
Or just in the FSV, as it has tiny passages and makes a sharp turn or two.


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[OLDBULL8]

You ran out of fuel with a quarter of a tank. That means your shower head pickup is broke off.

Filled the tank. Changed the lift pump, still no fuel. Could be the suction in the tank is plugged, or the FSV is plugged, both of those can happen. Since you didn't switch the FSV after you ran out of fuel, I wouldn't blame the FSV being switched half way. Take the front tank 3/8" line off the FSV, blow some air back into the tank, re-hook it up and try to start, 20 second cranks and 2 minutes between cranks. Try that.

You can pull the unit out of the tank without dropping it, since it's an 86, might be difficult to do if it's rusted pretty good.

 

[icanfixall]

I agree with what Bill has posted above. At this point you need to either blow air back thru the suction lines or remove the sender with the suction and return lines on it. Clean out the crap that plugged up the line. If you going to blow air back thru the lines do this. Unplug the suction line at the tank switching valve and plug it. then add just a few lbs to the line at the filter head. then check the line under the truck for wet places. If none found then unplug the line and blow the fuel thru it but catch it in something. your wanting to see what the problem was. If noting is found then blow air thru the sender unit suction line after its removed from the tank. I also would bypass the tsv so nothing gets messed up again if thats where the plug happens to be. Probably would bypass it anyway seeing you run off one tank cause of a leak in the other tank. For me this is the simple easy way of insuring the line has no leaks and your sucking air or the line is clear.

 

[Saskredneck]

I pulled the lines off it yesterday and blew through all the lines no problems there and can hear it bubbling in the tank when I checked the line from the FSV to tank. Tinkered on it a bit today in between Easter things and it runs great with the supply line in a full jerry can, so going to pick up some new fuel line to run from the water separator to the tank and find a fitting to join the return lines at the FSV location. Fuel gauge isn't working now either, what wires are for the front tank so I can get my gauge working