I have a 1990 F-350 7.3 IDI and when i fill one or both tanks up over a half a tank they leak real bad. are my lines leaking or is it something possibly with the tank. I try not to put much in each tank b.c it leaks all over my driveway and leaves black spots.

I also have a problem when i park the truck on a decline it dont want to start. It will turn over and over for a while before it will start. It starts right up if its parked flat or on an incline. Am i loosing prime somehow? Thanks for your help

 

As for tank leaking it could be in the area of the lines at the tank... there is a plate the lines go through it has a rubber seal that can leak. Other than that the lines have been known to rust at the plate too. Also the hoses can leak if they are cracked.

You need to get under there and check out the tanks...........

As for hard starting nose up and easy starting nose down...... that would relate to air intrusion into the fuel system (nose up) could be bad return lines and caps on the injectors. When nose down the air can't enter due to fuel pressure.

When air enters the fuel filter or IP then re filling is required thus the long cranking on the starter. Are there any wet spots on the return lines or caps.

 

when you say nose down i assume you mean front of truck facing down? If so it not hard starting when the nose is up its hard starting when the nose is down

 

I would guess the O-ring style seal where the pick up and return line meets the tank at the flange is leaking.

 

My guess on the tanks is rust right above the tank seam.
Dirt just lays on top of the seam, every time you drive wet roads the dirt just holds moisture to accelerate the rust process.

If you have a skid plate under the tanks, that is another dirt catcher, but then the tank bottom rots out.

A vacuum hold the fuel in the filter and fuel system.
When the front of the truck is up, the vacuum required to hold the fuel is higher since the engine is higher above the fuel level in the tank.
Likewise front down, less vacuum to hold the fuel since the tank fuel level is higher in relation to the motor.

A new set of return lines and O rings will fix the problem most likely.

Why yours is doing it backwards, I have no answer.

 

thanks for your help guys!

 

dave's right about the skid plate holding gunk and causing the rear tank to leak. been there done that. the only problem with mine was that there was a rock that had worn a hole through the tank that let some of the many pounds of dirt sandwiched in there to sift into the tank and cause worse problem than leaking. BTW, my tank didn't leak enough to get through all the dirt.
speedrdr