I have the "normal"/cheap facet pump (I think it's called the Silver Top?) and there are a couple of things i noticed I would just like to get straight in my head. 1. Is it meant to be that loud? On start up it makes a very loud rattling noise like a machine gun. 2. Is it meant to be intermittent? The rattling sound goes away within a couple of minutes of starting up but comes and goes seemingly randomly. 3. Is the fuel pressure meant to drop? While the rattling is going on the fuel gauge only reads about 0.1psi but once it stops it shoots up to 3psi... Which I would have thought is a little counter-intuitive, unless when the pump is "rat-a-tat-tattling" it's not actually pumping.. In which case (4) what is it doing? 5. There's no need for a red top pump if I'm running under 150bhp, right?
1. Yeah, I just bought a brand new one and it does that 2. As for yours rattling intermittently I'm not sure but wouldn't worry if the fuel pressure is staying on the mark. 3. The pressure is low because as it primes because the pump isn't actually pumping fuel at this point, just creating the pressure change in the vapours to draw fuel into it, once the vapours are out the way the pressure goes up. 4. The reason it rattles is that there is a solenoid and valve (I think), the rattling is the solenoid alternating, the reason it's loud is that initially there is vapour inside the pump, as it primes this is pushed out the way and the pump assembly picks up fuel instead, this dampens the noise it makes. 5. No, I don't think so, you'd know if your pump wasn't good enough as you'd be booting it and the power would suddenly die as the float chamber in the carb got too low for it to work properly. 6... Have you got the rubber mounts on the fuel pump? they should go between the pump and the car body, without them the vibration of the pump will resonate through the cars shell and amplify the rattle!
1. That's normal. It's because the fuel drains out the pump when it's not working. It rattles until there is fuel in there. 2. No, it shouldn't. If it's rattling like on start up, it's running out of fuel. 3. Not sure, but I would have thought you should have constant fuel pressure. 4. Sounds like it's running out of fuel. 5. No idea.
I'm confused now... Once it's primed up and running it shouldn't "run out of fuel" and have to prime the vapours again while it's running, right? The pressure doesn't stay on the mark, it drops once the rattling/priming starts. Haven't had a chance to investigate this while the car is moving (for obvious reasons) but it does happen. Haven't really noticed anything happening to the running of the car though. Yes it's on the rubber mounts so there's no real vibration, just a lot of noise. Oh is 3.0psi too high for DHLA 40s?
3psi is fine... My red top has always been noisey, i think they all are - but its never caused problems. IIRC they stop pumping when they go against a certain pressure?
I've actual had my red top apart last year when it stopped working the rattling is once it able build up pressure, the pump is a diaphragm which pumps the fuel which is linked to the contacts which operate the magnetic field the diaphragm if you run it without fuel if will constantly rattle until the diaphragm has resistance, very much like controlled relay in design I run one on my mk1 TDI as a lift pump, on start up it will 'rattle for seconds the a progressive slow click , as it gets hot it runs std fuel block off/pressure build up in the supply of fuel when it gets hot and the fuel line have no resistance in the system it will just rattle constantly, which was part of my contacts heating up and seizing on So sounds like its working fine
OK it's doing that thing where it won't stop rattling and doesn't build up pressure again. I'm trying to understand this conceptually, does the pump draw fuel out of the tank or is there a lifter pump that pushes fuel up to the engine bay and then the facet pump gives it another push towards the carbs? At the moment it sometimes randomly decides to keep rattling continuously and I can see no fuel flowing through the inline filter which sits just before it. Now is this indicative of an air leak somewhere before the facet or a problem with the lifter pump not getting fuel up to the engine bay or a problem with the facet pump itself? I would've thought that if it were an airleak the problem would be constant not intermittent and most of the time it primes/pressurizes in a couple of seconds. Could it be having the same problem as your red top Crispy where the contacts overheat and sieze? Even so and the diaphragm continued to operate it should still draw fuel in, right? Could the facet pump be mounted too high?
if it runs constsntly as you say it's not building pressure (resistance) in the fuel pipe. when it's rattling, try squeezing the outlet pipe to see it slows down as it's building pressure (fuel no where to go) you can use the same method thoughout the piping to try to isolate to loss of pressure
Normally yes. Usually when the pump itself is running properly. When it keeps rattling/pressurising and no fuel comes through then it won't start. It's random when it happens and how long it lasts for, can be off a cold or warm start, and can lead to stalling.
Hmmm. Seems my pump is actually a Red Top not a Silver Top considering it has the 1/4 threads... I actually expected one of the ends to be red. I'm not really downgrading by switching to a Silver Top if I'm making less than 150bhp anyway, right? I also have no idea what size fuel hose I have so I just went with the smallest barb size, 6mm. Will that be a problem?
DOes orientation of the pump matter? Tried rotating it today cos it kept rattling for 20 minutes and filter king bowl filled immediately.
are you running any type of fuel reg. valve ? where is your return hose to tank in relation to the carb?
Um I don't know what a fuel regulator valve is. As far as I'm aware there is no need for a fuel return hose, right? That's what it says in Jolfa's bike carb thread. The pump is mounted on the inside OS/drivers wing and it was mounted vertically with the inlet on the bottom and out on top. The FPR is mounted on the suspension turret behind and above the pump but below or level with the carbs. I certaintly don't have any flooding problems. Quite the contrary. This morning I rotated the pump (it's only attached on one side) so it's now almost flat with the inlet towards the bulkhead and the out towards the front and further from the fpr. As soon as I rotated it the fpr bowl filled.
An advantage of having a return line would be that you'd have a circulation of cool fuel into/warmed fuel out of, the engine bay. Not sure how it would work with your set-up; does the pressure regulator not have a return-line facility?
nope just in and out. this isn't a temp related problem though... It wouldn't start this morning when it was cold. And it has also happened when warm.
