Foam in Fuel Tank

[crafty]

I am experiencing a fuel pressure issue. One of the possibilities that was raised by Jeff is the fuel feed.

I have a tank balance on the rear two fittings and the front two are also linked, with a Tee for fuel feed.

Jeff suggested that one possibility is that the foam is cleared around the rear fitting, but not the front fitting, and that the pump is sucking the foam against the hole and losing pressure.

Anyone out there with a new tank on their bench that can have a look at it for me and tell me if the foam is cleared around the rear fitting and not the front fitting.

[ROWDYRENAULT]

Sir: I do not think thats your issue, but that's not what you asked. The foam is right up against the front fitting. Rowdyrenault

[crafty]

Thanks for the response..... is the foam also hard up against the rear one?

We are theorizing over a number of possibilities, this is one of them... all theory until I get time to go and try a few things.

#1 suspect is electrical.

[steve_d]

Both fittings enter the tank at the same level which is not at the bottom of the tank.
The rear fitting has a pickup pipe on the inside that points down to almost the very bottom of the tank so this is the one the pumps should be connected to. The other should either be a balance pipe or a return.

Steve

[crafty]

steve_d said:

Both fittings enter the tank at the same level which is not at the bottom of the tank.
The rear fitting has a pickup pipe on the inside that points down to almost the very bottom of the tank so this is the one the pumps should be connected to. The other should either be a balance pipe or a return.

Steve

Thanks Steve,

I actually recall someone mentioning that before and I thought I'd checked mine before installing the tanks and found that mine didnt have the pipe inside....I have -12AN fittings and I thought that they may not have installed a pipe because of the large diameter. In retrospect this was at a time when I was having nightmares about rivets and exploding foam so I may have imagined checking but didnt actually check.... will check again.

[steve_d]

crafty said:

....I have -12AN fittings.....

Is that where the petrol tanker connects up?
What made you put in that size?

Steve

[crafty]

steve_d said:

What made you put in that size?

The devil made me do it.

Nah....I didnt want to have to fill from both sides.

[andygtt]

I used a 12- for the balance bar.... but you are not using this to suck your fuel but the rear -6 one?

You do need to make sure the one you are using sucks from the bottom of the tank via the bent pipe.... if you don't have this then you are also loosing about 10litres capacity from each tank.

Edited by andygtt on Tuesday 13th March 09:35

[peterpsg]

Was your pump designed for a -12 fitting?

Maybe it likes the narrower gauge pipes to help with getting the pressure up higher?

On the carb, I have to restrict the flow thru the fuel regulator before the pressure rises...

But I guess you have 2 stages? A low pressure, hi volumne to a swirl pot, then a hi pressure, lower flow volume fuel rail pump???

[gtrclive]

-12 is fine for a balance but maybe alittle overkill for a fuel pickup.... -8 would have been fine... pumps maybe having problems drawing that amount of fuel on the suction side...

Is the suction line to the pumps -12, if so you could fitt a reducer on the tanks to -8 and change the lines that should get over the problem...

[crafty]

peterpsg said:

Was your pump designed for a -12 fitting?

Maybe it likes the narrower gauge pipes to help with getting the pressure up higher?

On the carb, I have to restrict the flow thru the fuel regulator before the pressure rises...

But I guess you have 2 stages? A low pressure, hi volumne to a swirl pot, then a hi pressure, lower flow volume fuel rail pump???

I have a -12 link with a tee and a -8 from the tee to the pump.... reduced to -6 on the pressure side of the pump.

The pump is a Walbro 255 mounted horizontally on the bulkhead, its level with the top of the tank. I have since read that the pump should be as low as possible as these pumps like gravity feed. This however does not explain the eratic pressure problem that I have... electrical is suspect #1, the foam is currently suspect #2.

I will probably move the pump anyway, but suspects #1 and #2 are quicker to check and eliminate as suspects.

I was also considering a swirl pot.... but I dont have room for one... and most of the LS engines I have seen dont bother with one...

Jeff is running 2 x Walbro 255's - no swirl pot. Pre-turbo he was running one only - again with no swirl pot.

Edited by crafty on Tuesday 13th March 10:28

[xtr2turbo]

These pumps do draw alot of current and need a good electrical supply.

I would focus on this and temporarily double up the earth and supply to check.

[crafty]

I have a mate with a multimeter that can datalog.... he's gonna help me trouble shoot on a road test.

[CanAm Dave]

Apart from any electrical issues you may have the mounting postion of your pump explains completely why you have fuel pressure problems. As you say yourself these pumps must be gravity feed as they are not designed to suck.

Regards Dave

[Alan 2]

[quote=crafty]

The pump is a Walbro 255 mounted horizontally on the bulkhead, its level with the top of the tank. I have since read that the pump should be as low as possible as these pumps like gravity feed.[quote]

Grant. I'm with CanAm Dave on this one. I suspect that your pump is mounted too high. I have two Walbro 255 pumps mounted like this :-

[pic][URL=http://imageshack.us][/URL][/pic]

[builder]

CanAm Dave said:

As you say yourself these pumps must be gravity feed as they are not designed to suck.

This was the pump I was going with as well. What in-line filters do you suggest? Do you have two filters (per pump); one before and one after the pump? And, looking at Alan's setup, if the pump doesn't suck well, how well does it pull fuel through the filter? Could the filter(s) also be effecting Grant's setup?

Edited by builder on Wednesday 14th March 15:52

[crafty]

I finally got back to the car again today.

Recapping, I had the pump hooked up to the front two fittings and the tanks linked using the rear fittings. I set out to change this.

Before doing anything I had to empty the tank. I got a bucket ready under the car and disconnected the fuel line before the filter.... drip ... drip... drip. AHAH! The foam was affecting the flow.

I switched em around... also found a bit of crap in the fuel filter....and badaboom badabang......fuel pressure under load.

So, I experienced my first drive with the boot into it today.... Im still shaking.... its absolutely NUTS and still havent given it all it's got as I was on narrow winding roads.

Yippeee!!

[steve_d]

Good result.
Did you poke anything into the holes when you had the fittings apart to see if you did have a bent pipe? If you don't have the pipe then you will never get to use the max capacity of the tank.
Your other issue is that if the fuel was not flowing when you released the pipe then it won't work as a balance pipe either making your -12 fittings a waste of money.

Steve

[crafty]

1. Yes, it does have the bent pipe in the rear fittings.

2. I havent tackled the balance pipe issue yet.... I was thinking of making an insert for the front fittings to push the foam away from the outlet and see if it flows better that way.

[steve_d]

crafty said:

.....2. I havent tackled the balance pipe issue yet.... I was thinking of making an insert for the front fittings to push the foam away from the outlet and see if it flows better that way.....

With -12 fittings you should be able to get in there with a pair of long nose pliers or better still forcepts (OOOO matron) and rip out a few chunks of foam aroung the holes.

Steve