Fuel Pressure Problems.
Turbo Mini Forums

Well i went to set up my fuel pressure today, fitted the pressure gauge inline with the output of the regulator and put the pump on, the gauge was only showing about 1 bar.

So i wount the screw right in an it didnt effect the gauge a great deal, so to get it to wind it further i took the lock nut off and went a bit further the the gauge shot up and i had about 6 bar, this caused fuel to start coming out the bottom plenum take-off, so i would it out about half a turn and this gave me 3.5bar.

But im still left with no way of locking off the bolt...

I then turned the pump off and let the pressure drop off, then put the pump back on an the pressure was only at 1 bar again! So i undid the lock nut and moved the bolt not even 1/8 of a turn and the pressure shot back to 3.5bar. But everytime i turn the pump off i have to move the bolt to get the pressure to go up...

The pressure regulator has had a brand new diaphragm fitted...

Are you using a carb'd car with a metro turbo regulator and an EFI pump? If so, your target fuel pressure at idle is between 3 and 5 psi. (14.5psi equals 1 Bar, or something close to that). The boost take-off takes care of the fuel pressure rise and maintains fuel pressure at the set value above boost pressure. i.e. if you set pressure to 4 psi and run 10psi boost, fuel pressure at that time will be 14psi (10+4)

On 12th Nov, 2009 Paul S said:

I think Gary OS has taken over my role as the forum smart arse

Are you sure you are reading pressure in bar ???

There is a fifteen times difference (as Gary says) and an injection pump will easily do 6 bar but that is about 90 psi, not the 3 to 4 psi (plus boost pressure) you are looking for with a carb.

Edited by Rod S on 14th Apr, 2010.

Schrödinger's cat - so which one am I ???

Dam looks like iv cocked that up haha, yes i was reading in bar, so am i looking to set the pressure at 3-4psi not bar?

Will i now need to get a lower pressure fuel pump or will my EFI pump still be ok?

yep the pump will be ok.

Perfect, alot lower pressure than i was thinking then haha. I did get i bit concerned when fuel spurted out the plenum take off.

when you have set the pressure to the 3-5psi, when you are driving its handy to be able to see the gauge whilst boosting to see if it goes up properly, as gary said if you set to 4psi at idle and your running 10psi of boost then when your driving and its at 10psi of boost your fuel pressure gauge should be reading 14psi

And now that you have basically filled your entire intake system with fuel...time to strip it all down to clean out, including removal of any fuel dumped into the cylinders, and possibly also past the rings and into the sump.

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

What seal ?

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

Iv had another go with the regulator today, but it only seems to show any pressure on the gauge when the middle bolt is near enough completely in, is this normal? as it doesnt look like there is enough in the thread to fit the lock nut...

The diaphragm could be wanked after seeing such high pressure

On 12th Nov, 2009 Paul S said:

I think Gary OS has taken over my role as the forum smart arse

I dont think thats happened, but its a possibility.

I stripped down the regulator and it seems om my regulator that the middle screw must be bolted in the majority of the way so the rubber seal off the diaphragm can start to offer resistance of return take off.

I have taken some pictures of my regulator stripped down to make sure there are no parts missing...

Top half of the casing removed, with the center bolt in place and the spring.



The bottom half of the regulator with the diaphragm in position.



The bottom of the diaphragm showing the rubber seal, that located in the return to give resistance thus giving the fuel pressure to the carb.



So the question is am i missing something or is the middle bolt supposed to be bolted so far into the casing?

Well i think iv now found my problem, after spending ages searching on google i came accross this image:

http://www.superchargedmorrisminorblog.com/fuel.png

And it shows the spring seats on a cap off the adjuster bolt, but my spring is searing on the casing.

So now the question is, is this cap supposed to be secured to the adjuster bolt or does it just sit on the nipple on the end of the bolt and is held in place by the pressure of the spring?

Anyone got any idea where do i get a the part from? if it just sits in place on the end of the adjuster im sure ill be able to make one up if i cant source one, but i just cant see it being very secure balancing there.

Just openned one up.....
The cap is not secured to the adjuster bolt - probably because they don't want the cap to rotate with the adjuster bolt - it just has a small hole in the middle to match the pip on the end of the adjuster bolt, and is dished to be an accurate fit around the spring.
It's identical to the one rivetted to the diaphragm so if you can find a scrap regulator just remove the one from the diaphragm (or copy the one on the diaphragm but make sure you copy the lip around the edge).

EDIT - it will be stable unsecured because the adjuster has a fairly large flat end and the spring is a properly ground affair with perfectly flat ends and the lip around the cap keeps it central.

Edited by Rod S on 17th Apr, 2010.

Schrödinger's cat - so which one am I ???

Thanks for having a look at one for me. Iv just had a look at mine, and did a quick test with a 5 pence coin as it seemed to be near enough the same diameter as the locating disk on the diaphragm.

So to just see if it solve my problems i drilled a hole in the middle of the 5p and put it all together. So i fitted it up to the car and it seems to be working perfectly now.

So ill make up a better locating disk for the top now.

Thanks for the help.