Hi all,

I need to ask a question which might seem a bit stupid but I am new to this fuel injection lark. With a large chunk of assistance from my friend (thanks Greg!) I managed to set up the fuel system yesterday. However there seemed to be a lot of air in the fuel that was returning to the tank. I am assuming that this is not a good thing. However I cannot see how it is getting so aerated unless there is a leak somewhere. Having pressurised the system and solved all the initial leaks I am at a loss. So my questions are - firstly is the aeration a problem and secondly any suggestions as to where to resolve the issue.

Thanks in advance...

Chris

r u running a swirl pot? this will reduce the amount of air in the fuel system.

Nope. No swirl pot just a tank with a baffled sump. The system is tank - filter - pump second filter - t piece feeding the rail (dead end) and the regulator on the other end of the t piece feeding the return line.

Done know what the state of the fuel reaching the rail is like but the aeration is clear on the return line. Could it be something to do with the regulator?

i take it you are running fuel injection on throttle boddies on your zetec, like your profile says, your fuel system should run

tank - low pres. filter - high pres. pump - high pres. filter - fuel rail - fuel pres. regulator - return to tank.

y are you running a t-piece before the fuel rail and the regulator before the fuel rail, the fuel pressure regulator should be situated after the fuel rail

My fuel rail is a dead end so the pressure reg in on the return line. So all the lines are at pressure on the engine side of the regulator and only the tank, the first filter and the return line are not at pressure. If that makes any sense.

Are you putting the return fuel back into the supply line? And not a seperate line bact to the tank?

Return line goes straight back to the tank.

return lines always look a bit odd, you sometimes get vapour bubbles as the fuel depressurises across the regulator.

If it runs ok, I wouldn't worry, if there's loads of air in it it will not run right, and if there's a leak, fuel will come out, not air in!

if the aeration is that bad then i would go with a swirl pot set up, you will have to install another fuel pump (low pressure) and the fuel pot itself

tank - L.P filter - L.P fuel pump - swirl pot - H.P fuel pump - H.P filter - fuel rail - pres. regulator. return line

Unfortunately it didn't run and I was wondering if this might have been an issue (probably should have mentioned that earlier!) However it might be something to do with the megasquirt. I am trying to eliminate all the issues one at a time.

My thinking with the leak issue was that if there was a leak in the low pressure section before the high pressure pump then it might draw air in with the fuel without much in the way of fuel coming out to show up a leak. Make sense?

I have to say I didn't think of the depressurising issue - could be a factor I hadn't counted on.

Its a bit like a coke bottle, no bubbles when under pressure, poor into a glass and bubbles galore.

High pressure side, ~4bar of pressure to nowt.

It can look bubbly.

Regards Mark

So I might be worrying about nothing?!?

u r running Megasquirt - now you've opened a can of worms

im confused now, have you ever had the car running whilst running MS, or r u still installing it?

im starting to think you might be worrying about nothing

where are you in the west mids?

[Edited on 5/4/09 by omega0684]

Its never run and I am just installing it. Myself and Greg just lashed it together to test out various parts of the system. Untried TBs/injectors, untried engine, untried pump, untried regulator etc but it didn't run so I was running through what might be causing to not start. In many respects it was a success as all the bits seem to work in isolation but just not as a system. I think I might be worrying about something that is 'normal'. It might be simply not starting as only bits of the MS were connected and the ecu might be a little confused. More work needed I think........

Thanks for the advice guys.......

Chris

Its called cavitation, just spaces in the liquid, can be a bit worrying to see though.

Steve.

Sorry forgot about the last bit - I am in Kenilworth.........

i have my engine up and running on MS now, its a pinto no zetec but your more than welcome to pop over and have a look if you want

im just off the eastern by pass down the road from tgi fridays and morrisons

Alex

When I get myself a bit further down the road I might well take you up on that offer thanks. You are about 10 minutes from me - small world and all that..........

Thanks

Chris

no worries