My 86 6.9 starts every time than chugs and dies. I've checked for leaks in the line and even checked the sending units but can't find where the airs getting in. Thinking the tank switch valve could be leaking internally? Still no leaks around the unit. Any advice or test procedure would be greatly appreciated. My truck is completely stock and the rear tank gives me problems while driving (chugs and even dies at times).

 

I'm having the EXACT same problem with my 86 Rollback! She fires up perfectly, turns over a several times and then dies. Takes a good bit of cranking, to get it restarted. After I get it running the second time, runs like a champ. Any suggestion why I'm not maintain fuel pressure before the pump (my guess) would be greatly appreciated.

AB

 

check the return lines

 

Go to the parts store and get an injector install kit. Replace the return line caps o-rings and lines. you will use everything in the kit except for the 8 copper washers. it takes about 30 min to do and you shouldnt have any more trouble.

 

So air intrusion from the return side would cause this kind of issue? I figured I was leaking down ahead of the pump somewhere....

 

Being the return lines are higher then the tank any air there causes the fuel to bleed back because it gets air behind it and that allows it to drain.

 

Mine are all brand new just installed em last summer. Like I said no visible leaks on any of the fuel lines.

 

Try putting a clear chunk of hose before the lift pump and see if your getting air bubbles in there. Does it do that on both tanks? Do you have the return line from the injectors running back to the filter? Alot for guys with this problem block off that line, buy you could put a clear hose on that to and check for bubbles.

 

It has to be a leak before the lift pump the pump is new. Both tanks are leaking somewhere the rear tank is worse. I'm sure there will be bubbles. It will run off the front tank but I can tell there's a loss of fuel. The return line is running back to the tank. How do you block it or return it to the filter.

 

You cant thats way too much fuel id think. I heard some guys having to replace the fuel lines running the lenth of the truck. if they look rusty and get thin especially under the hold down clips. Do any of the lines look wet any where? try the clear hose thing at the lift pump with the selector bypassed and see if you still get bubbles at least it might eliminate the selector valve