i am confused (help)
 

I have a 1991 e250 4.9.l . fuel system question dose ANY ONE know what a little gizmo on the frame just before the high pressure fuel pump and filter . the ford dealer cant tell me what is dose they did name it as the tank fuel reserve . . 2 hose in and 2 hose out looks like it runs fuel to the pump and then the return line comes back through it to the tank the number on it is FOUA-9K44-A then below there is a number 2610.
I have only one tank so its nothing to do with that

if you know what it is .can you tell me if it fails what are the symptoms

It is called a fuel reservoir. It's purpose is to make sure fuel is available should the vehicle wind up on a steep hill with a low fuel level in the tank to keep the vehicle running. Fuel does go from the in tank fuel pump to the reservoir and on to the filter, injectors etc. A return line comes from the engine , goes to the reservoir and back to the tank. They don't usually give any trouble. Is there some special reason why you are asking?

the van acts it is vapor locking (trice) 100 degree weather am looking for a reason .moved gas lines away from hot spots new filter, new pump, new coil ,
and I have no low end torq / new rebuild engine , transmission.
looking for anything that might help

you know when you step on the gas in a regular aspirated rig and you get a blast f gas
that's what I am missing it just don't have that . what can I do to fix that

There was a problem with the older 4.9 engines in hot areas that after parked a hot soaked period did allow the fuel system to develop a vapor lock condition. They corrected it by installing an electric motor fan to blow air over the engine after shutdown. I don't know if those are the conditions where you are, but 100+ seems to fit. It is not wise to go replacing parts based on some info I might offer without verifying there is a problem there. A throttle position sensor on the throttle body could have a bad spot in it and when the throttle is passing through that spot the signal drops out and a hesitation can be the result. If someone has played with the timing that could also affect performance. A fuel pump that is not producing sufficient pressure and volume or a restricted fuel filter could also get into the picture. Did the vehicle always have this problem or did some operating conditions change where this problem now appeared?

I bought this kinda dead hand engen rebuilt then installed by someone that shouldn't own a set of tools . he has bin in business for years anyway I am thinking these are due to him

If you are used to an 8 cyl, well the six will fall a little short, BUT they were a reliable engine when maintained well. We never know what is going on until we check. If for instance, the timing was set incorrectly , the engine just won't have the get up and go a six should have. If I might suggest it , try to read up on as much as you can what applies to this engine and start checking to confirm what you have learned. It may take a while, but you just might be surprised to find something the other fellow overlooked and it could be something small that might produce the results you are searching for. Why not give it a good shot and just maybe it could be something simple.

The reservoir canister was used with a DUAL circulating fuel system. There was a LOW pressure pump in the tank that fed the reservoir canister and returned to the tank. Then a frame rail mounted HIGH pressure pump that fed the fuel rail on the engine and returned to the reservoir. Where was the fuel pump located that you replaced?

on the frame drivers side it goes fuel tank ,fuel tank reserve gismo, high pressure pump, filter up to engine