2024-03-09 Swap Pre-face Fuel Tank with Face-lift Fuel Tank
Since 2012 I've been running a Walbro 255lph pump in a pre-face fuel tank.
https://micra.org.uk/threads/pollymobiles-rebuild.35251/page-36#post-482610
The prefacelift pump motor/housing are larger than the Walbro pump, which was meant to fit smaller facelift tank housings, so for years I had to simply wrap the pump with rubber sleeve to fit the large opening and I'm concerned about durability of foam rubber.
I brought a spare facelift fuel tank to fix this
(left: preface tank, right: facelift tank)
So here's the old walbro pump wrapped in rubber and wedged into a preface mount (left)
vs the smaller enclosed facelift pump (right)
Comparing the larger, open-top early pre-face fuel pump surge-tank (left) to the smaller, enclosed face-lift surge-tank (right)
The preface surge-tank was very difficult to remove and had to break it out.
From the bottom view, note the fuel return pipe which features a narrow jet nozzle aimed at a small opening into the surge-tank, which uses the venturi-effect of the return flow to help force fresh surrounding fuel in the large tank into the surge-tank.
The surge-tank keeps the pump pickup submerged for few secs during any sudden sloshing (especially during low fuel) to reduce fuel starvation.
The preface has a larger surge-tank but the open-top design could let fuel slosh out the sides.
Whereas the facelift tank is smaller/shorter but fully enclosed, so more of the fuel inside will stay with the pump for longer during hard long accelerations
The surge tank bottom mounts are kinda similar (preface: left, facelift: right)
But the reason the preface surge tank was difficult to remove was due to this 1-way inaccessible latch (top)
while the facelift surge-tank has a rounded latch allowing the whole thing to easily removeable (bottom)
Comparing my current walbro pump to a facelift pump, I noticed a big issue.
The fuel pickup strainer that walbro supplied me in 2012 was actually upside down and wayy too long for the facelift tank
walbro is also 2mm longer than a facelift pump.
Only reason it worked on my preface tank is cos it had a longer surge tank & I could mount the motor upside down
To fix this, I removed both strainers
And fitted the facelift pickup onto the walbro pump.
It's a little squeeze fit with the longer motor
Surge tank complete
Next issue is swapping over the heat shield, where the facelift plastic mount was broken off
I simply tigersealed the thing on lol
All assembled and now has a strong buzzing sound during startup.
Ecu map may need a slight tweak cos there's an odd leanout during light throttle
(have to check if it's a mapping isse, wideband issue or fueling issue)
edit: I took out the sensor to just inspect and looked clean and now it doesn't randomly lean out. maybe just unscrew/screwing the thread made a better contact, does a wideband sensor ground via the manifold like a regular narrowband or does it have it's own ground within the 5pin plugs?