Fuel system woes - please help I'm crap at this!

[chodjinn]

For quite a while now I thought I has sorted out the fuel system in my head to how is was going to be. In practice its a hell of a lot different and now I can't seem to sort it! I would appreciate help with this because i am on the cusp of binning the whole project because I'm so damn pissed off about it and no company seems to be able to help!

So (deep breath) here's what I have;

1. MGB Fuel tank, modified with late fuel sender so I now have an 8mm feed and 8mm return (for the EFI).

2. Feed goes through a low pressure filter, to a Holley blue pump. Now i just found out the fittings on the holley are 10mm so I've just bought two adapters and two other fittings to convert to 8mm. No probs so far.

3. Holley is to feed a swirl pot; there are two 8mm fittings on the swirl pot (one for feed from holley, one for fuel return line) - Which one do I connect the pump feed to - top or lower?

4. There is a 13mm connector @ the bottom of the swirl pot to feed the HP Bosch pump. Except the Bosch pump is 14-16mm connection IIRC. HOw can I get round this without using reducers?

5. The HP side of teh Bosch pump has a (I think) M14x1.5 fitting (??) which currently has some adapter with screw fittings and some wierd valve. The problem i have is connecting the pump to the fuel rail (via the filter, which isn't a prob). The fuel rail has a half-pushon fitting with a wierd threaded nut???? I was under the impression I could use 8mm hose throughout but it doen't look like there is enough to use a jubilee clip on@ the fuel rail.

6. Return line from fuel rail is ok just need to know which of the two 8mm connectors to use (see 3 above).

7. Return to tank fitting on top of swirl pot is 6mm not 8mm like i thought. - again how can I get round this without using a reducer as the fitting on the fuel tank is 8mm.


Yeah I know lots of probs, but hopefully i'm just being a numpty. I did quite a bit of reading up on this and as I said, though it was sorted in my head in practice its not working out!

cheers in advance

[ihatesissycars]

Here's what I'd do.

Holley pump feeding the swirl pot via the bottom inlet of the pot.

Ref the possible 1 - 2 mm difference between the bosch pump and the swirl pot, well, I' have the same difference in mine. I just found some hose of a similar size to the two and did it up. 1 - 2 mm is a small amount and its low press if an so won't be a problem.

The bosch pump fittings I'm not sure, a pic of the pump would be good, some use a banjo fitting.

Now, the fuel rail needs an outlet to the fuel pressure regulator and then from the reg to somewhere. Some peopl in your situation have had the reg piped into the swirl pot however I've hear and know of people who have had problems with fuel over heating so I would put the return from the reg to the tank.

The remaining union on the swirl pot is obviously a return to the tank, It might be possible to tee the regulators return into this or it might not be but of the guys will clear this up.

So the fuel route is tank, holley, pot, tank and pot bosch, fuel rail, regulator, tank.

There is another option, a much simpler and neater one. Get the tank adapted for efi use that way there's less pipework, less pumps and less to go wrong and a more reliable setup!

Can you not get hold of a v8 specific tank?

[ian.stewart]

I dont use a lift pump to a swirl pot, I have run an extra pipe from the tank, this extends right to the rear of the tank to avoid fuel surge probs, ans a DeVilblis stem Paint filter attached to the end, Coming out of the tank its rund to an Audi V8 fuel filter, and then on to the pump, fuel lines are 8mm steel bundy tubing, and the return line uses the original fuel pipe in the tank,

[chodjinn]

Gav, I'm certain I have the fuel system plumbing set up as best as possible. The fuel regulator is at the end of the fuel rail (standard) so yes the return line comes from that. I'm really not fussed about heating thef uel at the moment ebcause the issue is so contencious - if it happens I will deal with it then.

I could pipe the return directly to the tank as you suggested, and then use the top connector on the fuel swirl pot for a breather, but from research the way I have it is the best: return to swirl pot, then from swirl pot to tank. Beside, I'd then have a spare connector on the swirl pot

The MGB V8 tanks are for carbs - if I wanted an EFI sepcific one I'd need one from an RV8 which are about 400 squids minimum if you can get them.

I modded my existing tank for £12.30 - the price of a new sender unit. Complete no brainer, no arguements! Beend one before and what I was recommended by some old MG geezers.

My problems aren't the layout of the system pre se, its getting it all hooked together that's causing me serious grief.

I can't seem to get 13mm braided hose, or anything similar to use between the swirl pot and HP pump.

[chodjinn]

there is also the issue of getting the hose fitted to the inlet at the fuel fail. As I said there is the push-on bit, but behind that there is a threaded bolt - does the standard fuel rail have some special fitting - I was thinking of just cutting the bolt off and using the HP push on fitting like I had planned?

[ian.stewart]

It may be nice to have 13mm/1/2" braded piping, but its not absoloutly nescarry as the area you are talking about should have no more pressure than the head of fuel from the swirl pot

[ihatesissycars]

Is your fuel rail a hotwire item?

[Ian Anderson]

Gav
It certainly sounds like it

On my set up I ook the angle grinder to the Nut on the inlet to the fuel rail and then used HP hose and a Jubilee clip

Works OK but not as pretty as it could be!

Ian

[stevieturbo]

For quite a while now I thought I has sorted out the fuel system in my head to how is was going to be. In practice its a hell of a lot different and now I can't seem to sort it! I would appreciate help with this because i am on the cusp of binning the whole project because I'm so damn pissed off about it and no company seems to be able to help!

So (deep breath) here's what I have;

1. MGB Fuel tank, modified with late fuel sender so I now have an 8mm feed and 8mm return (for the EFI).

if that feed is supplying any pumps, its far too small.

2. Feed goes through a low pressure filter, to a Holley blue pump. Now i just found out the fittings on the holley are 10mm so I've just bought two adapters and two other fittings to convert to 8mm. No probs so far.

3. Holley is to feed a swirl pot; there are two 8mm fittings on the swirl pot (one for feed from holley, one for fuel return line) - Which one do I connect the pump feed to - top or lower?

pump should always draw fuel from the lowest part of a tank...

4. There is a 13mm connector @ the bottom of the swirl pot to feed the HP Bosch pump. Except the Bosch pump is 14-16mm connection IIRC. How can I get round this without using reducers?

you cant....unless you sleeve and/or squeeze the pipe down. Neither of which is ideal either.
Or weld a new fitting onto the tank.

5. The HP side of teh Bosch pump has a (I think) M14x1.5 fitting (??) which currently has some adapter with screw fittings and some wierd valve. The problem i have is connecting the pump to the fuel rail (via the filter, which isn't a prob). The fuel rail has a half-pushon fitting with a wierd threaded nut???? I was under the impression I could use 8mm hose throughout but it doen't look like there is enough to use a jubilee clip on@ the fuel rail.

Probably M12x1.5. Chuck the non-return valve fitting in the bin.
The fact you are considering any form of push on hose, and jubilee clips on a high pressure fuel system, is a tad worrying. A lot of rubber hose available, is not rated for high pressure efi use, even if they claim it is. Some do hold...but its not good. If you must use this type, do ensure it really is good quality hose.

6. Return line from fuel rail is ok just need to know which of the two 8mm connectors to use (see 3 above).

7. Return to tank fitting on top of swirl pot is 6mm not 8mm like i thought. - again how can I get round this without using a reducer as the fitting on the fuel tank is 8mm.

return to top of tank, although its probably not that important.

weld a new fitting onto the tank.

Yeah I know lots of probs, but hopefully i'm just being a numpty. I did quite a bit of reading up on this and as I said, though it was sorted in my head in practice its not working out!

cheers in advance

sounds like you need new tanks !!!!

Buy this book, its very good.

http://www.amazon.co.uk/21st-Century-Performance-Julian-Edgar/dp/0947216901/ref=sr_1_1/026-5202340-9201263?ie=UTF8&s=books&qid=1183070698&sr=8-1

[chodjinn]

The 8mm feed from the tank is feeding the Holley. The original set up used carbs with the same size hose and the power hasn't gone up. 8mm is plenty enough to fuel 300bhp.

I meant which connector on the swirl pot to connect the feed FROM the holley. The HPO pump is gonna be fed from the bottom outlet on the swirl tank - i'm not that daft!

I'll have to sleeve/botch the HP feed, but no worries as its gravity fed and not under pressure at all. Gav's done it, so will I!

As for the hose and fittings - I'm using top quality high pressure hose with the best fittings you can get for push-on. I couldn't quite stretch to Aeroquip or similar - that would have doubled the budget! I bought from a well known company as well not some dodgy ebay shop!

Hopefully it should be sorted now, just me having garage-panic thats all!

will let oyu know how i get on

[stevieturbo]

The 8mm feed from the tank is feeding the Holley. The original set up used carbs with the same size hose and the power hasn't gone up. 8mm is plenty enough to fuel 300bhp.

After the pump, 8mm is plenty.
Before the pump, make it as big as you can. 8mm IMO is insufficient, especially given the pumps you are using, and the amount of fuel they will flow.

You will restrict the pumps, and cavitation will occur.

I meant which connector on the swirl pot to connect the feed FROM the holley. The HPO pump is gonna be fed from the bottom outlet on the swirl tank - i'm not that daft!

I'll have to sleeve/botch the HP feed, but no worries as its gravity fed and not under pressure at all. Gav's done it, so will I!

As for the hose and fittings - I'm using top quality high pressure hose with the best fittings you can get for push-on. I couldn't quite stretch to Aeroquip or similar - that would have doubled the budget! I bought from a well known company as well not some dodgy ebay shop!

Hopefully it should be sorted now, just me having garage-panic thats all!

will let oyu know how i get on

I used Earls Superstock stuff. Alloy fittings, with push on hose. Great stuff IMO...I hate braided stuff !!!

I think some of the hose people do these push on fittings in steel too, which would greatly reduce costs, but work equally as well.

[Ian Anderson]

On the Swirl pot
Starting at bottom
Output to HP pump
Next up is inlet from LP pump / Tank
Next up is return from fuek rail
That leaves the top which is return to tank

The way it works is the hot / warm fuel will rise so the hot returns to the tank (with any air), the warm fuel returned from the rail comes next (from the top and urthest from the HP outlet) and the cool fuel from the tank closest to the HP outlet

Seems to make sense to me

Ian

[chodjinn]

thanks Ian that's what I wanted to know.

[chodjinn]

http://www.sbdev.co.uk/Info_sheets/Fuel ... rl_pot.htm

that's what i have roughly based the fuel system on, except the LP filter is in a different place.