97 transport..new fuel pump..bad gas mileage

[stevgela]

I have a 97 transport. I had to get a new fuel pump and fuel filter installed. Now I get about 90 miles less to the tank full. It is getting about 17 miles per gallon now and used to get 22. What could be causing such a dramatic fuel consumption difference? I do not smell gas. How can I tell if they put the pump in correctly and it is not leaking around the seal. Any help is appreciated.

[LMP]

A possibility - other than fuel spillage - is that the car ran for quite a time with a much lower fuel pressure. THe computer has adapted (from the reading of the O2 sensor) and has adjusted injector opening time accordingly. THese values have adapted the "open loop " short and long time parameters . These values are kept and used when engine has not entered CLOSED LOOP operation.
Normally, it should detect the "rich" condition dependent of the higher pressure now available and then reduce the injector ON time...but for this the engine must enter the CLOSED LOOP condition, where the O2 values are infact read and used to readjust the parameters.
Closed loop is attained only after engine has attained normal operating temperature...and requires some time to adapt.
If you do only short treks, it will take sometime to adjust.
If you do one long run, it should recover to previous values...unless the O2 readings are not accurate ,( damaged O2 sensor.)

[LMP]

How did that condition evolve?

[stevgela]

It was not fuel spillage. I took it on a long run, three hours straight and 3 back...no better. I have had a mehanic look at it. Nothing seems to be wrong. It is still getting the poor gas mileage. I suppose it has something to do with the new fuel pump.

[LMP]

You would surely have noticed...but you have no doubts it shifts up to 4th gear and that TCC applies...? of course this would not have large effect on city driving though...but..just in case..
No CEL?

[stevgela]

no codes and it shifts fine. I suppose it is just the gas mileage I am stuck with.

[kb0nly]

Mine runs about 17-18mpg when its cold weather like this week, when its warm i average 22-25.. So i chalk it up to weather related, i wasn't about to start tossing parts at it for no reason. Starts and runs perfect, no codes, etc.