Fuel pump Hi/Lo pressure circuit and where's that fuel pump DIY thread?
 

Does anyone know what the high and low fuel pressures are? How does the hi/lo pressure circuit work? I'm assuming the PCM just controls a pressure regulator or does it control the pressure regulator and increase the fuel pump voltage?


I've searched and searched with the RX-8 club search engine and with Google site:rx8club.com and I can't seem to find the thread where someone takes out their fuel pump and disassembles it. Looking at the fuel pump assembly I have it looks like the plastic is melted together or there's some kind of glue being used?

There were couple of thread that ppl disassemble their fuel pump.

I kinda want to replace the fuel pump myself, but I made an appointment at a very good dealership, so Im going to bring it there and see what they say first. Next wednesday.

From the service manual, it does not seem hard to replace the pump urself. Its just that u better be sure that you secure them back to the way it was.

I know how to install/remove the pump no problem, but I want to know how people are opening up the assembly. Do you have the links to those threads or remember parts of the titles?

To open it, you have to cut it. Cuz its not designed to be a serviceable part.

nothing really that interesting inside, its just pump with a filter with crap on it.

^Love the details.

The only thing you have to cut are the hoses/clamps...

I used a thin, flathead screwdriver to seperate the two tabs holding the swirl tank and filter housing together. Everything else will take very little effort to disassemble.

http://img60.imageshack.us/img60/448...umps006ue7.jpg

I've measured it after both fuel rails at idle and it reads ~59psi.

Straight from the Service Manual:
http://img366.imageshack.us/img366/4484/fpxi0.png


The pump speeds are controlled between two relays, one with a resistor for idle and low load and bypassing it for higher load. This resistor is located under the airpump FYI.

http://img366.imageshack.us/img366/1462/fpresaq0.png


A lot of info can be found at http://smrmicro.com/rx8servicemanual/

To find info here, you're going to have to dig a little deeper...

isnt it true tho, there is nothing really interesting inside, its a fuel pump, wow :lol2:

I have a new pump, I probably blind and missed the tab on it. I will go relook it tonight. lol

my pump is having issues, it works but like most other people's problem pump, its not pushing enough pressure under rapid acceleration.

So does the fuel pressure ever actually change? It has to pass through a static pressure regulator regardless of whether the fuel pump is slugging about or spinning like a turbo, right?

Could you eliminate the pressure circuit stuff, which I assume is there only to preserve fuel pump life/overheating, and run a bigger pump at constant speed with a 60psi regulated return system while still on stock engine management?

Its a dead-end system. There is no regulator. It is self-regulating.
I've got a set of return rails sitting here, but I haven't had any real motivation to install them.

BTW - Thanks, GTAW, for giving away the secret. I was hoping to keep that one from Team and OD just a little while longer.
Oh well...

I know it's a dead-end system, I was thinking maybe there was some kind of regulator in the fuel system similar to the pressure regulators on air tanks. I guess not though...

Are there only two pressure ranges that the fuel system operates at? First, being the 54.4-65.2psi and then what's the high pressure range?

I'm trying to figure out how you would use an aftermarket pump and still have it work on stock mapping.

...uh, what secret? Must be ma mad skillz wit da flathead...oops, sorry.

okay, so there is a regulator in the system. It's the little metal regulator looking thing beneath the fuel filter in the picture. It maintains ~60psi by just dumping the excess fuel out, I guess that's kind of what should've been assumed in the first place, but the whole High/Low pressure circuit thing kind of threw me off.

Exactly.
I caught a bunch of heat a few months back when I took mine apart.
Apparently, its not possible to take it apart without breaking it.http://www.mazdamaniac.com/portal/smiles/icon_shrug.gif

Seriously though, what kind of scam is Mazda trying to pull? That fuel pump assembly is easily disassembled, they just put a drop of glue on each side and now it becomes some kind of one-piece expensive repair that everyone will eventually have to buy once theirs clogs up...

^^ Do you have a link, I would love to see what the pros had to say...

Its actually pretty cheap - about $130 for the whole unit.

It was in one of the Pre-Mix threads.
Lemme look...

^Can/do you change when the high speed relay turns on?

"What you talking about" He hasnt given away any secrets. We were talking about taking the FILTER out. THAT cant be done without wrecking the housing the filter is in. Therefore making replacing the filter a "cant do"job.
OD

Hey, quote that part of the thread if you could, please.

Obviously, you can take the filter out without wrecking the housing I've done it twice now and this is what GTAW is talking about (but you guys simply wouldn't hear it).

I tried explaining to you how to do it, but you and some of your Georgia buddies wouldn't listen (and some took to just calling me names and such), so I relented.
It only takes a small screwdriver...

so does that mean you can clean the filter and reassemble without buying a new pump ?

Uh, once again, yes.

Cool - i'm up to 95,000 kms on mine so it is due for a new pump . Any pointers on how to clean the filter ?

Unless your dealer is taking you for a ride, just replace the whole thing.
Its cheap and you get the added insurance of a new pump, not just a clean filter.

If you say you can , I guess you can. but I tried with 2 different pumps and couldnt without cracking the housing the filter is in. The ones i dealt with were sealed all the way around. Mo power to ya Bro--i must have missed that inservice:).
i know if I could I would clean my filter.
OD

Just buy a new pump, 130 bux wont hurt. :)

installation was much easier than I first expect (with the right tool, of course)