EFI fuel system

[chris davey]

Was going to post in the FAQ section but looks like I can’t so will ask here

I can attest to the problem of sucking air in when using an EFI pump in a non EFI tank. I am using a bosch EFI fuel pump and I have a 40L fuel tank. Because of the way the pump is mounted I effectively only have 30L of fuel to use before I reverse down my driveway (steep) and I can hear the pump sucking air. This is the time where I get petrol (guage doesn’t work).

I can’t remember if I have an 040 or an 044 but it was rated at 600hp. (I know that doesn’t mean shit ) but would this be ok to use as a lift pump to a surge tank or would the fact that it is high pressure mean that I cannot use it? If so, I would have to get a lift pump fitted in the tank and sell the intank bosch pump and get an external pump.

Thanks

Chris

[TurboRA28]

I understand that EFI pumps dont like to suck much.. Where lift pumps are ok with sucking .. But that being said.. I've seen plenty of fuel systems setup this way. I guess it's just not ideal.

[The Witzl]

you DO NOT want a high pressure pump feeding your surge tank - get an external, low pressure, hi flow pump like what i pictured in the FAQ to draw fuel from the main tank and fill the surge tank...

if you use an high pressure EFI pump to fill the surge, you would have massive fuel pressure backing up against the return from the FPR on your fuel rail and pushing into your external EFI high pressure pump that the surge tank is feeding - NOT COOL!

The option im going to be taking with the '28 is to build some baffles inside the tank and create a little "swirl pot" of sorts from which the in-tank Walbro pump I have can draw.

I'll try to make a little dodgy pic for you later today

[o_man_ra23]

I ran an in tank pump in my RA23 for a while. The tank in these however is upright, and has a small area on the bottom of the tank. I loosely mounted an in tank skyline pump using just flexible fuel line, and it moved about the bottom quite well, and sucked from wherever the fuel moved to. never had a problem with surging, even driving around with low fuel most of the time. From this experience however, i would be going with the witzl. use a low pressure lift pump etc. just make sure you put a low pressure fuel filter before the pump (like a standard RA40 filter etc) and a high pressure filter after the EFI pump (dont wanna get any crap in those injectors).

Cheers, Owen

[chris davey]

Thanks guys.

At present it works fine until the fuel is low so I will just live with it but in the future if I need more fuel I might go the surge tank and dual external fuel pumps later with twin lines and a collector point but still run the stock fuel rail.

[gianttomato]

if you use an high pressure EFI pump to fill the surge, you would have massive fuel pressure backing up against the return from the FPR on your fuel rail and pushing into your external EFI high pressure pump that the surge tank is feeding - NOT COOL!

Not necessarily true depending on how the surge tank is configured. If the fuel rail return port is at the top of the surge tank and the surge tank overflow to fuel tank port is a little way below and of large enough calibre to cope with any excess flow, then pressure build up is a non issue.

However, the use of a high pressure EFI pump as a lift pump remains a logic error. It still will intermittently suck air (depending on where it is mounted), overheat and eventually fail.

The correct option is to have a low pressure lift pump or fit an intank EFI pump with a nice little swirl pot.

If your high pressure pump is low enough below the tank then the siphoning action may help. I have done this on a few conversions now and works OK.

[o_man_ra23]

dont forget the efi pump also draws more electrical current and wreaks havoc with your alternator when you have 2 of em.

Cheers, Owen

[thechuckster]

can you modify the way the pump is mounted in the tank so the inlet is lower? e.g. something like the pump in a Supra (pump attached vertically to a hanger and sideways-facing inlet sock-filter).

[Nim]

You might find ripping the whole fuel tank out, and putting in an EFI tank could be a better option. Dunno what car you have, but MA61 EFI tanks fit into Carby AE86s... sorta.

[chris davey]

It is an xt130 corona which AFAIK never came out EFI. Don't know much about Coronas actually as there isn't much standard left in mine

Thanks guys, all good info.

[o_man_ra23]

Try an RT142 avante tank,
I know they look to fit RA60.

Cheers, Owen