Okay, here are my symptoms:

Full tank of gas, car runs great!

As the tank empty's, there becomes a bog when you floor it.

Additionally, the tank seems to build pressure and purges gas fumes back into the cab.



Is there a vacuum diaphragm on/ around/ in the tank that might go bad and cause a vacuum or pressure problem on the FD's?



Thanks

"bog" may not be the right word. It is more like a "studder" as the rpms spin up...

No one knows anything about the evap system on the FD?

The fumes should be directed through the charcol cannister, back into the UIM through the Purge Control System. Do you notice the gas fumes inside the cockpit while the car is idling or driving? If it while idling, your charcol cannister could be filled with fuel. If it's while you are driving, it could be a failed aluminum check valve between the UIM and the Purge Control solenoid.



As for the low tank problem, open the top of the fuel tank and verify nothing has broken away in the tank which could get in the way when the fuel is low.

Yeah, its not the charcol cannister. You can hear it purge pressure from the top of the gas tank into the cab during hard excelleration. I am thinking there has to be a vaccume valve/ diaphragm that controls pressure and vaccume in the gas tank. Any ideas?

check the fuel sock on the fuel pump itself, had a similar problem on my fd.



it could be clogged up which cause the pump to not output the volume it should.



kevin.

Thanks, I will do that. I recently changed the fuel pump, sock and filter. It had some rust on it from sitting. I should do it again.



Additionally, I spoke with my friends Mike and Ivan this weekend. We concluded, it may also include the purge valve on the rats nest (consequently wouldn't regulate the pressure in the tank...)

That was one of the things I suggested that you check/test days ago.

" it could be a failed aluminum check valve between the UIM and the Purge Control solenoid."



You did! I am sorry! I missed that! I really appreciate you following up. I still haven't had the time to check it. But I will this weekend. https://www.nopistons.com/forums/pub...IR#>/blush.gif

Okay, I took apart the entire evap system, checked all the 1 and 2 way valves. Checked the solenoids, and blew compressed air through the entire system. The only thing I found odd was the charcoal cannister.



Has any heard of a charcoal cannister going bad? There was charcoal pieces all throughout the system. in the valves, the solenoid, in the catch tank, etc.. I was able to blow it all out and air seems to flow much better. But, I am afraid to put that cannister back on. Would bypassing the cannister affect anything? I know it absorbs vapors while at idle, but wouldn't they simply recirculate and get burned off during acceleration?



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