Walbro Pump - Cause - Alternator Overcharging!!!!

[sbyder]

Hi all,

I have a Walbro 255 intake pump in my GT starlet and although it is fairly noisey standard, it has started to become very noisey, but only when the car gets hot. If its a hot day, as soon as the car heats up enough (or i drive a bit hardcore), the pump starts to make some pretty loud wirring noises. I have experienced noisey pumps before so i know what to expect, but for some reason mine will actually change the tone and pitch of the sound constantly when hot. If i pull over and let it cool down, its goes back to the normal quieter sound, until it heats up again. If its a cold night, i never have a problem.

I am also having the battery charge light flash on and off when the pump makes the really high pitch noises. I thought this was just a loose connection on the back of the dash cluster, but I have noticed it to only happen when the pump starts to sound like a small orchestra!

I have called auto electricians and performance shops who all are telling me different stories. Some listed below.

1. The pump is on the way out.
2. The alternator is having issues causing the pump to get too much charge.
3. The fuel pump relay is stuffed.

What i cant work out is why it happens ONLY when it heats up. The alternator has been replaced a few months ago and the pump works fine when cold, so im tending to lean towards 1 or 3.

What are your thoughts suggestions?

If i take it to a electrician, they said they can only test some of the things, then all they can do is start replacing things to see what fixes it. Not a cheap option in my opinion.

Any help would be great! Thanks peoples!
Ben

[Hypo]

Check the voltage at the pump when cold and then check it when hot.

This will tell you if its drawing more power when hot.

You will need a volt meter and will need to remove the back seat and open the inspection panel.

On a side I note I wired my fuel pump directly to battery and used two relays. The original one to kick in the new relay to get the fuel pump to function.

[oldcorollas]

your pump is unlikely to draw enough current to make ligths come on (around 40-50amp alternator?)

i would be checking your alternator again. is the pump mounted low enough? are you running with a low tank of fuel all the time (so does not have as much fuel cooling it etc)

[sbyder]

Checking the voltage is on my to do list for tomorrow

Maybe the battery light is a seperate issue

Its an intake pump, mounted like a stock one. I usually have at least half a tank of fuel and try not to run it below 1/4 tank.

[JustCallMeOrlando]

I've had a similar thing with my Walbro over the time i've had my car, and Peewee is experiencing the same with his. I've run new wiring to my pump and now have barely any voltage drop, but she still does it from time to time. I've just learnt to live with it.

[ProjectSleeper]

I had a similar problem with mine...

whilst mine is uber quiet in tank, it started to scream like a F1 car. If I let it sit for a while, it was fine. if I kept it running, the pump just died..

I didn't take any chances and just replaced the pump.. I can't afford to have a lean out with my car. I still have a walbro 255lph in-tank pump, but it will shortly be feeding an under car mounted surge tank that has an external Bosch 044 pump to supply the rail...

[camrygt?]

my walbro 255 does same thing no voltage issues and no drop in pressure just screams loudly sometimes on really hot days when the tank is below about 1/2. been doing it for about 2 years and 50,000km

[TurboRA28]

My Bosch 044 pump does the same thing.

[chris davey]

internal or externally mounted 044?

From the short amount of driving I have done with my car I haven't noticed an increase in noise. It is just bloody noisy the whole time! This is an 044.

[nick.parker]

I have a Walbro 255 in my AW11, and though its always louder than the stock pump, sometimes, maybe its when it hot, it does gets maybe twice as loud as normal, I usually notice this after driving for say 30mins. At first I though there was something very wrong, then I thought maybe the pump was moving a bit in the cradle and touching metal to metal and transferring more vibration on something....but its still works fine. I am glad to here other people having the same issue. Means its probably not a fatal thing.
Cheers, Nick

[sbyder]

but does everyones change the sound to a high pitch sound, then low pitch then high pitch, etc...? Mine does not stay constantly louder, unless i cool it down.

[Andrew162]

I've experienced a similar problem when I had my RAV, but this happened when I had the external fuel pump (Bosch 500hp) running on a low tank of fuel, first sign that I needed to refill it. I also had a Walbro 255L/h fuel pump from a GT-Four put into my tank but it never made this noise, not even on hot days.

I have a bit of a theory on this, but I don't know how solid it is, so feel free to shoot holes in it. My theory is that when the fuel gets hot enough it loses density and the fuel that doesn't get delivered (ie. returns through the return line into the tank) is less dense and causes the fuel pump to act up and make a lot of noises because the fuel isn't as dense as it's expecting to deliver. I'm guessing that 91RON fuel would be most susceptible to this as it's more prone to changes in density than say 98 or 100RON fuel would be, which wouldn't cause the pump to go crazy with these noises.

Again, this is just a theory, but the logic is there, and I'm hoping that it can make sense.

[pilot]

I have an external 255 HP and it is a pain in the ass! it makes a very high noise and it keeps changing the sound and pitch. I really hate it...

[nick.parker]

Maybe there is something in that fuel density idea. What is the relationship between petrol density and petrol temperature? Does anyone know?
Another silly idea I have is this, I wonder if the pump is trying to move so much fuel, that it is on the edge on cavitating and operating conditions (fuel temp) sometimes push it past the edge...?? Cavitation would explain the increase the noise somewhat.
Nick.

[oldcorollas]

Another silly idea I have is this, I wonder if the pump is trying to move so much fuel, that it is on the edge on cavitating and operating conditions (fuel temp) sometimes push it past the edge...?? Cavitation would explain the increase the noise somewhat.
Nick.

it's more likely to do with vapour pressure than the density.. density doesn't change much with temperature, but vapour pressure changes significantly.

if the pump sucks up the tiniest bit of air.. or cavitates slightly, it will run faster for a short time, and raise the pitch.

this could be an issue if you are using one of the small fuel strainers, esp if there is any crap in ther clogging it up.

a larger strainer/prefilter, which has an internal expander so it doesn't collapse, might make all the difference.
although i only ran it for a few months, my walbro 190 was always quiet, never changed pitch (and this was peak of summer)