Loss of fuel pressure
Turbo Mini Forums

Hello
First of all, had a good look through the search thingy and could not find an answer.

My problem is that I set the brand new regulator to just above 6psi. Fine if I drive at about 30-40, but anything above that and the pressure starts to dwindle away. I can see it happening on the lamda sensor gauge. Then it just runs out of fuel. Leave it for a minute or two with the pump running and the pressure starts to return. I have a new pump that discharges fine and when I looped it onto the return pipe it went round and round no prob. I blew out all the fuel lines with compressed air just in case.
The regulator is defo plumbed in correctly, with a pressure gauge in the line to the carb to see whats going on.
It happens every time and is driving me potty cos something is wrong but I can`t see it.
I think it may happen when it go`s into boost. The boost is set to only 8 pound as I am running it in gently.
Any Ideas please

What pump have you got?

Bought the pump from ebay. Flow rate of 3 bar

Yes, but what pump is it? An efi pump? A redtop? etc

Not being very good on this pc thing, best I can do is if you pump in this number on ebay, the pump I have will pop up.
281034141976
Ta

Should be fine.

Maybe you have cavitation in the tank?

If something is worth doing, it's worth doing half of.

Looks to be up to the job to me, maybe it's faulty?

I have also fitted a race type air vent in the tank neck to make sure that its not a vacumn (spelling?) causing the prob. Allows air in to replace fuel use.

Im having the exact same problem at the mo. Mine seems to go lean on boost then when i back off the fuel builds up again and it runs fine. I have a foam filled tank and it seems to do this more when the fuel is low (ish). Im gonna try and remove my foam filling and see if that does the trick.
Im not totaly convinced this will work though as when i boot it and hit the boost somtimes it just completly dies and almost chcuks me outer the front window, so this is making me think maybe its somthing else?...

What size fuel lines have you got between the pump, regulator and the return to the tank?

8mm feed and return
6mm regulator to carb
on mobile at work now so bit slow to reply. sorry

Firstly, the pressure should be set to 3-4psi.

Is the pressure rising with boost?

If you set the reg to 3psi, at 10psi boost the gauge should show 13psi.

In the 13's at last!.. Just

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

http://www.turbominis.co.uk/forums/index.php?p=vt&tid=2103

Was going to say that colin, the excellent article wrote by turbodave

A very useful bit by turbo dave, will follow right through that. As for the lambda sensor thing. When the pressure starts to drop, there is a lack of fuel to the engine and therefore this is indicated by the gauge, just like it was going very lean. It just lets me know it`s gonna pack up and I need to find somewhere to pull over! The fuel pressure gauge near the carb confirms this
I will today go though all turbo daves points and let you know.
Thanks for the help so far .

Fuel pressure won't effect AFR until the float bowl runs dry.

Is the pressure on the fuel pressure gauge dropping?

In the 13's at last!.. Just

This is my plumbing drawing as requested .

Attachments:

60.35kb

Hello theoneeyedlizard,
Yes the pressure gauge drops to near nothing. But after a minute or so ,slowly climbs back up. After dropping off, it just gives enough pressure to crawl along at about 30mph

Is this a new problem or a new build? Has this fuelling setup previously worked OK or have you recently changed it all and it never worked right?

Just one little point maybe worth considering - in your sketch it says Estate tank.....

They seem to have reputation of problems because they are so shallow so the pump easily loses suction.

Have you been testing with it fairly full or fairly empty ???

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

I don't like the idea of the fuel filter before the pump, unless it is a specific filter for fitting in the suction of the pump.

filters in the suction of pumps are usually more of a strainer to catch the big crud that could easily damage the pump and have a relatively low pressure drop across them. The filter would normally go after the pump and before the carb or fuel rail.

The main reason for this is that a filter has a reasonibly large pressure drop across it even when new. This will cause the pump suction to drop into a vacuum. some pumps just don't like running with a negative pressure suction.

Compound that with some shit in the filter and the greater the problem.

Also, on the estate tank you have no head of fuel, as the outlet is piped to near the top on the front side of the tank. Thus the pump has to pull it from the tank. Compared to a saloon tank where the outlet is at the bottom so you get a gravitational head of fuel to the pump inlet.

Have you tried it without the pressure gauge in line? And make sure the filter is the correct way round, and as Sprocket says it would be better off after the pump.

Hi
gonna try with out the filter in then,anythings worth a go.