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Patrick 13th November 2005 16:40

Fuel system
I've been thinking about the fuel system before I put it together, could someone please confirm I've got these components in the right order?

Tank -> Bottom Connector -> Fuel Filter -> Pump -> Engine

Engine -> One way valve -> Top Connector -> Tank

Thanks, Patrick :)

peterux 13th November 2005 20:54

Hi Patrick,
I think the one way valve provided is for the breather tube?

I have a diagram of the fuel sytem drawn by Mark using two pumps and a swirl pot provided by Marlin.

I'll send you a diagram by email from a guy called John on the Marlin Owners forum.



Patrick 14th November 2005 14:04

Thanks for the email :) Only thing is I'm not using a swirl pot (not something Marlin ever mentioned me needing)

peterux 14th November 2005 23:00

Hi Patrick,
according to Mark, if you don't use a swirl pot, you get fuel starvation when you go round a corner and all the fuel moves to one side of the tank.
( I took his word for it and ordered both pumps and swirl pot from Marlin.)

You'll need a low pressure pump at the back of the car to pump the fuel from the tank up to the swirl pot mounted next to the battery at the front. You then need a high pressure pump from the swirl pot to the engine EFI. The return pipe from the EFI fuel rail goes back to the swirl pot and the return from the swirl pot goes back to the tank.

The swirl pot keeps a constant fuel supply to the engine. It's actually just a small square tank with four connections. I'll send you a picture to your email address.

best regards


Patrick 14th November 2005 23:13

Thanks Peter got your email, its quite a bit smaller than I thought it would be!

Patrick 15th November 2005 10:34

I have asked Terry about using the swirl pot / two pump layout and she's come back to me with this:


Yes this is a good way to go as it ensures you will never have a fuel surge
but not necessary.
I would guess the swirl pot is a good idea if your going to be doing a lot of track days?

peterux 15th November 2005 22:55


That's not what Mark told me when I picked up my kit. I still have his hand written diagram somewhere.

I wonder if any owners with completed cars would like to comment?


MartinClan 16th November 2005 13:20

Swirl Pot
Although Marlin call it a swirl pot I think it would be better described as a surge tank. The problem is that there are no baffles in the fuel tank. So if you tank is say only half full and you pull away quickly the fuel all goes to the back of the tank and the engine is sucking air. Of course if you never plan to pull away quickly or always have a full tank it wont be a problem :biggrin:

For how much it is and the pain of retrofitting I think it is worth fitting from the start.

I beleive some of the early fuel tanks did have baffles so probably wouldn't need a surge tank.

BTW - still having problems mounting my AFM - I am on to the MkIII bracket now. Someone told me that mounting it direct to the engine (which was easy and I had done) is not good as the AFM contains a very fragile thermocouple arrangement that would not last long with the vibration from the engine.

BR Robin

Patrick 16th November 2005 19:22

I've got a nice fuel pump someone gave me already which is why I'm a little hesitant of going for the "swirl pot" option. I suppose if the tank is always 1/2 it would be less of an issue but I see what you mean about pulling away quickly and the fuel sloshing to the back. Might have to dig into my pockets again...

Strolls 17th November 2005 14:01

Re: Swirl Pot

Originally Posted by MartinClan
...The problem is that there are no baffles in the fuel tank.

That's disappointing. Surely the fuel tank should have baffles? I understood that a single plate (with cutouts) down the middle of the tank was adequate for this, so it's not like it'd cost much to factory fit.


holgate86 17th November 2005 22:14

fuel surge
Hi guys,
I have a sportster i built in 1997 with sierra cosworh engine. I have standard large fuel tank. I do get a problem with fuel surge once the tank gets below a 1/3 if i accelerate hard. I was going to modify it but never got round to it and it doesn't cause too many problems. I thought about the special foam they use in race car tanks which prevents surge, the only problem would be the float would need clearance. I suppose if you haven't put fuel in the tank yet it could be fitted with baffles.

best regards Brian

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