fuel pressure
Turbo Mini Forums

Hi, ive got far too much fuel pressure at the carb (the gauge spins right round past 15psi!). Im using an mitsi evo fuel pump and malpassi regulator and wondering if i need to restrict the pump with a resistor? ive checked the return line and its not blocked. The return line is also bigger than the feed. Any thoughts?

Silly question, but you've not mentioned it.

Have you adjusted the pressure regulator?

Is the regulator in good order? Split diaphragm?

In the 13's at last!.. Just

yea ive screwed it fully in and out and still no change. its brand new from minispares

Explain how you've got it plumbed in, it sounds like you might have the return feed plumbed in to the float bowl of the carb.

hmmm....


I'd have the top off...

try sticking the return into a petrol can and see if its better.

carful though it'll fill up quick!

ive got it plumbed in as the instruction diagram shows. the bottom connection returns to the tank.

The diaphragm is almost certainly shagged then! Send it back for a replacement.

hang on.... dosent screwing in raise the pressure??

yes need screwing out

Done now needs redoing lol

yea i screwed it out first and made no difference. could the pump be too powerful?

what bar is the pump rated at?

Done now needs redoing lol

I cant see the pump being too big,

not sure what the pressure rating is of the evo pump. the regulator is supposed to handle 60 psi. im sure the pump wouldnt be that powerful.

ok, ive finally got the fuel pressure down to 3.5 psi. my fuel lines were too small, i upgraded them to 8mm ID. Now the problem is that fuel is leaking from the carb and the plenum is filling with fuel from the small hole beside the bolt holes. What could be causing this? Is a seal gone?

float valve knackered or full if shit?

needle valve is not sealing...either through damage, dirt or too much fuel pressure.

9.85 @ 145mph
202mph standing mile
speed didn't kill me, but taxation probably will

Thanks for the replies. Well today I took the carb off and looked at the float valve which seems ok. Might just replace it and the float anyway. Do you have to set the float height?

Did you check to see if it was the float valve that was leaking before removing the carb?

Also, you cannot normally see anything wrong with the valve other than a ridge on the point of the needle

Float height should be set...but really isnt that critical. Unless it was really bad.

Did you actually try blowing into the fuel entry to the carb to see if the valve was sealing ?

9.85 @ 145mph
202mph standing mile
speed didn't kill me, but taxation probably will

I blew into it and the valve seems to close it off when I push the float up ok. Further investigation required I think

All sorted now. Changed the needle valve and float. Holds pressure over 20 psi so good to go. Thanks to all that replied and helped out. Must get a build thread sorted sometime

Your needle valve holds 20psi ?? Holy moly.

I could never get one to hold past 5-6psi or so !

9.85 @ 145mph
202mph standing mile
speed didn't kill me, but taxation probably will

i was surprised also haha. just need to sort my trigger wheel on the pulley now and hopefully she'll fire.