ion_four

OK OK, this post was ridiculously long...now shortened! Still a lot of info...

CAR:
1999 Base Model
JRSC
RC 440cc injectors
Hondata S200 w/P28 OBD1 ECU
B&M Adjustable FPR
Walbro 255lph in tank pump
New o2 sensor
New gas cap

The fuel system works fine under load (recent dyno AFR testing and fuel
pressure testing say so.) I don't have any noticeable leaks and no issues
when I have above 1/4 tank of gas.

When I have less than ~4 gal of gas, I start to have fuel starvation
problems, on the street. When I fill up, the car doesn't want to start without
giving it a bit of gas. After this initial start-up, everything is fine until I run
the tank down, again. This doesn't seem right, since I haven't ever been able
to get down to the fuel light level because of poor drivability.

My mileage is also not so great (IMO) at ~<19mpg city and gets worse if I
take a long time to go through a take (ie. go out of town), so some seems
to be evaporating.

The fuel pump sits in the very bottom of the tank, as it should. I'm at a loss,
except to possibly replace the fuel pump, despite it seeming fine, and/or build
a larger baffle around where it sits in the tank.

An thoughts on this?

ion_four

BUMP, shortened the post...there was a lot to read.

KraserK

Probably the pump. And maybe time to service your fuel filter too? Could be injectors? I suggest you do a full service on your fuel system

ion_four

Well, one might suspect the fuel filter, but the service manual specifies the filter only needs to be replaced IF idle pressure falls below a certain level, and mine hasn't. There is no replacement interval, indicating it could last forever. I also get enough pressure to have my AFR dip into the 10's at high rpm/high boost. The injectors only have <40k miles on them.

As long as I have more than 1/4 tank, the car runs/drives perfectly. So, I don't see how it could be the injectors or fuel filter. The only reason I might suspect the pump is if it is somehow drawing fuel in from higher than it should be, above the strainer?

Does anyone have pictures of the inside of a tank (from the fuel pump access hole)? I remember seeing some and that mine looked like that, but I'm wondering if some kind of baffling is missing? All mine has is a dinky little ash-tray looking thing the pump sits in.

ion_four

UPDATE!

I managed to fix at least one of these issues. I have no idea why this is the
case, but while it appeared that my fuel pump pickup was reaching the
bottom of the tank, it was actually only the far end (from the pump) of the
filter sock drooping down to contact the bottom of the tank. The pickup
tube, itself, was about an inch off of the bottom of the tank!

I modified the fuel pump bracket to make the pump sit about an inch lower, so
that the pickup is now fully on, or at least close to, the bottom of the tank!

I have no idea why the fuel pump was not sitting low enough in the tank. I
can only imagine that the tank or the bracket are not original, or that the
pickup/filter is not correct. The pump is the correct part number from Walbro,
and while the pickup looks correct, it has no part number on it.


In the following (huge!, sorry) picture, you can see there two bends in the
bracket. The higher one originally went out perpedicular to the pump and held
it in place. I bent this down and then bent a portion of it, further down,
back out to hold the pump and then added a hose clamp to assure it stays in
place. Note that the hose clamp is not very tight so as to not tweak the
internals of the rotary pump, but won't back off, since I secured the worm
gear screw on the other side by bending over the unused portion of the
clamp.