Ford 6700 fuel problem

[NHbalerman]

Having trouble starting my 6700 it has the two tanks and if the top tank is empty it will not start replaced the lift pump and can pump on it awhile and finally get it started even put a electric fuel pump on it and that didn't help but I put it on top of the bell housing can't figure out a good place to mount it. Probably better to mount it lower but can't find a good place where do y'all mount em at y'all who has done it. I got it at the parts store but it won't pump fuel up hill but if there is fuel in the tip tank starts fine. Some advice would greatly appreciated

 

[jhwis]

I have a 7700. I had problems with it feeding from bottom tank. There was a vacuum leak or pinched line somewhere. I just bypassed bottom tank by plumbing top tank right to lift pump or fuel rail...don't remember. It's gravity fed and never had a problem since. One tank more than enough for my uses.

 

[Bern]

I'm guessing that the screen in the bottom tank is plugged. It's not hard to remove and clean.

 

[NHbalerman]

Oh ok thanks I didn't know there was a screen in it I will chyit out. Thanks

 

[sotxbill]

There is.... a rubber line where it crosses over the transmission that connects to metal lines on both sides. Very common for this line to get cracks in it(45 years old)..... thus letting the fuel run back down and loosing prime... thus making it crank for a long time to start. Have seen this 3 times now. Starting through out the day is fine, but let it sit a couple of days, and it has to crank.... Also its always much worse when the top tank is empty, and not so bad when the top tank is full.
Also common for the first filter to fill up with fine red powder if your run the bottom tank low. Have done that several times now.

 

[NHbalerman]

I appreciate that you hit the nail on the head that is exactly what it is doing I will replace that line. Thanks a bunch

 

[RodinNS]

It could also be the steel line feeding the lift pump. I've had it wear thin behind the injection pump. Also worth checking and replacing all of the rubber seals on the various fuel line connections. Some of them use a flat quad ring that rots away. That's in addition to what the others have already mentioned...

Rod

 

[NHbalerman]

Ok thank you I will check that too