PollyMobiles Rebuild

[pollyp]

Didn't have much energy today but I managed to crimp the new relay wires together

Reassembled the loom & dash

Couldn't be bothered to correct the wideband wiring (connect 12v supply to the original O2 pink wire, add toggle switch to power-up wideband separately after cranking), check the ECU loom connectors are clean, and many other minor tasks cos it ain't essential yet and it still works ok.

Pump sounds abit stronger during cold priming with the higher voltage. She still drives like normal tonight, the odd rattle in the dash at specific rpm still there

 

[pollyp]

2025-02-15 Replace Walbro GSS250 255lph Fuel Pump

With approx 75% fuel level I removed the fuel pump assembly out of the tank.
Not a fun procedure, even with gloves

Opened the container & oh my god!

This clean face-lift fuel tank was swapped over 1 yr ago but now after filling it with mostly tesco / occasionally morrison fuel, there's soo much crap dirt in the tank/strainer

Poor pump strainer is covered in filth

Look at this tank!
I guarantee this tank was clean when it was swapped.
Non of this rust crap came from my car (old/new filler pipe wasn't rusty, pump itself ain't rusty).
It must certainly come from the old, badly maintained, cheapo supermarket fuel pumps

Old vs new Walbro GSS250 pumps

I flushed out as much of the debris off the strainer with can of carb cleaner

Fitted onto new pump

Pump, strainer & swirl pot all clean for now

Here's a comparison of how the pump sounds before/after.

First two clips were with fuel hose unplugged and fed freely into a fuel can with 0psi, while the last clip was with the hose connected onto fuel rail supplying 3 bar of pressure.

Old pump had a higher/faster/louder motor whine whereas the new pump (with fresh tighter tolerances?) has a lower pitch, especially once it's plumbed into the 3 bar fuel rail.

 

[Micra Paul]

Didn't have much energy today but I managed to crimp the new relay wires together

View attachment 89801

Reassembled the loom & dash

View attachment 89802

Couldn't be bothered to correct the wideband wiring (connect 12v supply to the original O2 pink wire, add toggle switch to power-up wideband separately after cranking), check the ECU loom connectors are clean, and many other minor tasks cos it ain't essential yet and it still works ok.

Pump sounds abit stronger during cold priming with the higher voltage. She still drives like normal tonight, the odd rattle in the dash at specific rpm still there

Loads of good work however may I suggest it would be advisable to replace all DIY temporary crimp joints with professional married electrical inline & tee joints soldered & sleeved?

Manifold fuel line/regulator pressures?

Married Electrical Inline & Tee Joints Soldered at DuckDuckGo

Keep up the good work!

 

[pollyp]

Loads of good work however may I suggest it would be advisable to replace all DIY temporary crimp joints with professional married electrical inline & tee joints soldered & sleeved?

Manifold fuel line/regulator pressures?

Married Electrical Inline & Tee Joints Soldered at DuckDuckGo

Keep up the good work!

Gradually working through my to-do list to replace all my nasty old weak solder with crimps
Next on my wiring list is to sort the wideband wiring.

 

[pollyp]

2025-02-17 Walbro GSS250 Fuel Pump Detailed Look

For a closer look at how the Walbro 255LPH internal gear type pump works and it's condition after 13yrs, I stripped it all apart

& 3D modelled it too

The port in the front plastic cover simply feeds fuel into the pump via this narrow slot.
The round hole at the bottom isn't used for output (maybe on a different model?) but instead it's just blocked off & keeps the front cover aligned

The pump unit separated from the motor casing, driven by these 4 prongs

This thin rigid backplate & brown slippery layer simply keeps the back of the gear pump sealed with minimal wear

The front brown gasket, which does most of the work sealing & controlling flow, seems quite worn.
Potentially the scoring marks maybe due to trapped debris from dirty supermarket fuel getting past the pump strainer

The gear pump face is also little worn. This will reduce sealing efficiency, less pumping performance, which may explain the higher motor pitch due to loose tolerance, less friction, less hydraulic pressure

In the model you'll see as the motor spins the pump clockwise, fluid enters the top slot as the gear teeth opens up.
At the bottom part of the cog, the closing teeth squeezes the fluid out (this additional loose brown 'tab' on the gasket might be used to smooth out the flow?)

Fluid then enters the casing via a narrow slot at the bottom. Seems like a kinda restrictive/rough path?

From that small slot, fuel flows through the motor casing, cooling the motor

The copper longitudinal commutator track, similar to the face-lift fuel pump, looks a little worn by 1mm.

Stator has a clear wrapping maybe for insulation & smoother fluid flow?

After cooling the motor, fuel goes to the rear section through these two holes & gaps in the graphite brush holder

In the rear section, most of the fuel flows through the regular output, which has a 1-way check valve to maintain fuel pressure after shutdown.
For non-return fuel systems, there's also an over-pressure relief valve which bleeds excess pressure back into the tank

The graphite brushes has plenty of life left

I believe these conductive end-caps are press-fitted into the rear section at the last-stage of manufacture so it's easy & fast to assemble the graphite brush springs and test the motor circuit simultaneously

Overall an interesting design to check out

Here's a look at the pre-face & face-lift pump for comparison
https://micra.org.uk/threads/pollymobiles-rebuild.35251/page-203#post-884005

 

[pollyp]

Recently noticed hearing a slight rubbing noise once-per-wheel turn only at low speed, shortly after applying brakes and after driving for few mins.
I suspect it might be the caliper rubbing on the edge of the discs (considering they were rebuilt recently)

Looking under the passenger caliper, not much signs of rubbing, just some brake pad dust

But the drivers caliper definately has some rubbing from the disc edge

I tried to shift the whole brake carrier further outward slightly but it still rubs after warming up the brakes from few mins driving

May have to remove the carrier cage and mill the hub upright bolt hole slightly oval to install the whole thing further outwards by 1mm till the top of pads sit flush with the disc edge and caliper has a larger gap from the disc

 

[pollyp]

The caliper carrier has upto 2mm gap from the disc edge

Whereas the caliper sits abit closer upto 1mm gap from the disc

notice the top of the pads have always sat 2mm too low from the edge of the disc

I drilled the bolt hole slightly further outwards to shift the carrier approx 0.5mm from the disc

Can see the top of the pads now sit past the old line on the disc

Went to heat the brakes up in country roads and Nope it still rubs
It sounds more like a rubber seal noise than a metal to metal sound,
Gets louder when cornering right,
& mostly under slight brake pressure but quieter under hard braking

The last time I experienced a similar thing was a loose wheel bearing due to the LSD.

I lifted the front on axle stands, run it on 3rd gear, apply slight braking and listening to the brakes for any rubbing, nope they're both quiet so they're definately not rubbing.

Both wheels don't show much side-side or vertical play but let's check the passenger shaft nut (which historically tends to loosen with the vibration off the LSD),
& sure enough the driveshaft nut was only loose by 5-10deg

Tightened the nut hard as I can and went for another drive and that's finally fixed the rubbing noise

 

[Micra Paul]

The caliper carrier has upto 2mm gap from the disc edge

View attachment 89842

Whereas the caliper sits abit closer upto 1mm gap from the disc

View attachment 89843

notice the top of the pads have always sat 2mm too low from the edge of the disc

View attachment 89845

View attachment 89846

I drilled the bolt hole slightly further outwards to shift the carrier approx 0.5mm from the disc

View attachment 89844

Can see the top of the pads now sit past the old line on the disc

View attachment 89847

Went to heat the brakes up in country roads and Nope it still rubs
It sounds more like a rubber seal noise than a metal to metal sound,
Gets louder when cornering right,
& mostly under slight brake pressure but quieter under hard braking

The last time I experienced a similar thing was a loose wheel bearing due to the LSD.

I lifted the front on axle stands, run it on 3rd gear, apply slight braking and listening to the brakes for any rubbing, nope they're both quiet so they're definately not rubbing.

Both wheels don't show much side-side or vertical play but let's check the passenger shaft nut (which historically tends to loosen with the vibration off the LSD),
& sure enough the driveshaft nut was only loose by 5-10deg

View attachment 89848

Tightened the nut hard as I can and went for another drive and that's finally fixed the rubbing noise

Quote; “carrier cage and mill the hub upright bolt hole slightly oval”

Well investigated however needs comparison of discs outside diameter dimensions equality & compared to OEM discs?

Milling/drilling out mounting holes on critical brake components would not be advisable & may introduce parts movement together with stress fractures in future?

Good luck

 

[pollyp]

Quote; “carrier cage and mill the hub upright bolt hole slightly oval”

Well investigated however needs comparison of discs outside diameter dimensions equality & compared to OEM discs?

Milling/drilling out mounting holes on critical brake components would not be advisable & may introduce parts movement together with stress fractures in future?

Good luck

Cheers
All of the GTIR discs I've ever brought have the same dimensions but the main problem is that the carrier cage and/or K11 hub bolt holes on mine makes the whole assembly sit 1-2mm too close to the disc until it rubs at high temp
But I remember other owners with same brakes didn't have this issue?

Yrs ago I had new discs machined smaller before fitting, but was uneconomical.
Then I later grinded the bottom of calipers 1mm to clear the disc, but couldn't grind too much out.
This last option here was to just slot 0.5mm of the hole to nudge the assembly out just enough to clear the disc, but given the remaining 10-15mm of thick steel around the hole I doubt it'll affect overall strength enough to worry about for daily driving unless i start fitting extremely oversized racing brakes and increase the stress loads on those bolt holes from more trackdays

 

[Micra Paul]

T

Cheers
All of the GTIR discs I've ever brought have the same dimensions but the main problem is that the carrier cage and/or K11 hub bolt holes on mine makes the whole assembly sit 1-2mm too close to the disc until it rubs at high temp
But I remember other owners with same brakes didn't have this issue?

Yrs ago I had new discs machined smaller before fitting, but was uneconomical.
Then I later grinded the bottom of calipers 1mm to clear the disc, but couldn't grind too much out.
This last option here was to just slot 0.5mm of the hole to nudge the assembly out just enough to clear the disc, but given the remaining 10-15mm of thick steel around the hole I doubt it'll affect overall strength enough to worry about for daily driving unless i start fitting extremely oversized racing brakes and increase the stress loads on those bolt holes from more trackdays Many

Many thanks for your interesting experience based response.

May I suggest shape overrides minimal material removed in order to equally distribute stress lines in circular lacuna compared to oval lacuna stress concentration of the resulting critical brake mounting stress ellipsoid.

Stresses At Elliptical Holes

Good luck