Still having fuelling issues!!
Turbo Mini Forums

Ok,

Recently started my engine for the first time, although it didnt run long it just died.

This was due to a "hi-flow" needle valve, flooding the engine even at really low fuel pressures.

The standard needle valve and seat was fitted, but the car wouldnt start. I had crudely set the fuel pressure with a boost gauge to 4 psi, and thought this might be the reason why it wasnt starting.

I had a search and found a way to set the fuel pressure manually, by winding the adjuster screw on the pressure regulator all the way out, then slowly back in until fuel would come out of the jet. I did this (although had to wind the adjuster screw nearly all the way in) and the car started and ran reasonably well without any problems.

I wanted to double check the pressure, Nic kindly sent me a proper fuel pressure gauge, upon hooking this up, I found that the pressure I had previously set to get the car running, was 12psi!!!!!

So I used the gauge and set the fuel pressure at the 4psi mark. Now the car wont start, no fuel comes out of the jet....

I took the carb off, the float chamber was full of petrol, the needle valve is free and not sticking and the jet is not blocked, but still no fuel comes out of the jet!!

I did the simple test of squirting fuel down the plug holes and it fired first time like that!!

Someone please help, i'm at my wits end now, the carbs been on and off about 20 times in the last week I have no idea what could be wrong with it!!!

There could be something obstructing the flow to the jet like dirt or debrit?

The float chamber was full when I took the cover off, so the needle valve is doing its job. The jet isn't/wasn't blocked.

There's nothing else that could be wrong? I dunno why the fooking thing wont work now.

there could be something blocking the jet, like the needle. have you adjusted the mixture?

Edited by Turbo Shed on 18th May, 2009.

I've set the top of the jet level with the bridge in the carb body, this is supposedly near enough the correct mixture for idle I heard.

I had the dashpot off when looking to see if fuel was coming out of the jet so the needle wasn't there blocking it.

it sounds like you nearly have it all correct so i would go with mixture, could be the needle set wrong or just needs the mixture screw wound in

Ahhhhh right.

Is that because, when a cylinder is on the "suck" stroke with the inlet valves open, that "venturi" effect off the piston going down sucks the fuel up from the float through the jet, past the needle and into the bore?

I guess it wouldnt do that with the dashpot off would it? As the vacuum created by the piston moving down wont be there??

I'll try starting it again with everything fixed back in place, but I cant see it magically working now as i've tried it before!!

I'll do as you say and set the jet lower but i've tried this before too hmm..

if you have set the fuel pressure high enough so it comes out the fuel pipe, but low enough that it does not force its way past the needle valve in the float chamber then you cant be far wrong. before you had too much fuel pressure so it was forcing past the needle vale and dumping uncontrolled amounts of fuel into the engine. if it ran before then chances are the mixture was set too lean. pulling the choke out lowers the jet just like adjusting the mixture

Brilliant, it runs really well now.

I had to lower the jet quite a bit to get it to run smoothly on idle but its there now.

Unfortunately the waterpipe take off on the end of the head pinged off when I was stood there and showered me in really hot water - ouch!!

And when I put my foot down on the clutch the revs dropped quite a bit - bugger :(

Will hook up my rev counter tomorrow to see how much the revs drop by, but from what i've read this cant be good!

What diaphram have you got fitted ?

WWW.TURBO-MINI.COM

Single grey, machined ultralite backplate, ultralight flywheel.

the single grey is quite a heavy clutch and will slow the engine slightly, but if your engine isnt running properly then the slow in engine speed will be exagerated, dont panic just yet

Ahhh ok thats relieving.

How should I treat it? Say something is wrong i'd rather do as little damage to the crank as possible.

Use it softly im guessing?