Caterham fuel filler neck solved

[Alaskossie]

Caterham owners are too familiar with the car’s dreaded ”anti-fill” fuel filler system, caused by a minimally-inserted fuel nozzle, frequent automatic nozzle shut-offs, and pit stops that take four or five times longer than they should. One of the first bits of advice has been to remove the internal, spring-loaded flap in the Caterham’s steel fuel neck. However, this only slightly lessens, but does not solve, the basic problem – which is that the fuel nozzle, due to its curvature, cannot go far enough down into the Caterham’s fuel neck.

 

I have the Caterham “aero cap” for the fuel tank; the latest models have a larger recess machined out of the top quadrant of the outer aluminum ring, to supposedly give more clearance for the top-side of the curved fuel nozzle; but this alone does not solve the problem of minimal insertion of the fuel nozzle.

 

After my test run yesterday, I think I have the solution. First, I had to disassemble my fuel neck and cap because Caterham, in its wisdom, supplied a low-grade, non-fuelsafe section of hose to connect the fuel neck to the tank. After three years, this had split, and it leaked fuel onto the ground at each fill-up. Not good.

 

Then I bought a new steel fuel neck from Caterham. The new ones do not have that circular flange turned inward at the opening that the old ones had (the flange with two notches in it, presumably to latch a conventional gas cap). So the elimination of this flange gains an effective one-half inch increase in the effective diameter of the fuel neck – one-half of that increase coming at the point where the curved fuel nozzle meets the top part of the filler neck opening.

 

Next, I removed the spring-loaded flap from the new fuel neck, following conventional advice. Then I took a Dremel tool and ground out the spot welds that held the cone-shaped metal bracket to which the flap had been attached, and removed the bracket. This piece of metal had the effect of reducing the internal diameter of the neck at that critical point.

 

I smoothed out the Dremel cuts with Emery paper, and then had the fuel neck powder-coated. I assembled the whole shootin’ match with a short section of fuel-rated hose from NAPA (an RV accessory part, available in the proper diameter only as an 18-inch piece with a bend in it, for $28.00 – I only needed five inches of it) –

 

And to make a long story short, the fuel-pump nozzle now goes all the way into the fuel neck, and there are no more exasperating multiple shut-offs and hiccups and delays at the gas pump!

 

One continuing problem is that fuel sloshing in the tank and up the filler neck still weeps from around the aero flange and down the back body panel after hard acceleration or cornering (what, in a Caterham?!). Anybody solved this problem? Is there was a way to seal the point where the steel filler neck meets the aluminum aero-cap flange? Is there a fuel-rated silicone sealant, perhaps?

[bsimon]

Tom,

 

Hylomar Universal Blue

[scannon]

Tom,

 

I used a Hylomar sealant on the gasket for the fuel level sensor in the tank.

 

http://www.hylomarsealant.com/

 

It is fuel rated but is much thinner than the usual silicone sealants. It will depend on how large the gap is you are trying to seal.

 

Do you have pictures of the modifications you made?

 

Is powdercoat fuel resistant over time? I know it will peel off if exposed to hot engine oil such as the inside of a cam cover.

[Alaskossie]

Skip, I don't have photos of the mods. I'm not sure how a photo of the dark interior of a black filler neck would have shown up in a photo anyway.

 

Removal of the inner triangular cone in the fuel neck that once held the spring-loaded flap is pretty self-evident. It is a restriction that, when removed, allows the full diameter of the fuel neck to be available for insertion of the fuel nozzle.

 

As I mentioned, the new Caterham fuel necks do not have the internal rolled flange intended to latch a conventional gas cap. I suppose it would be possible to cut out this flange from inside an older-style fuel neck, to give the clearance advantage that the new fuel necks have.

 

I don't know how resistant powder-coating is to gasoline. I assume that it is at least as good as conventional paint. The original Caterham fuel necks appear to be powder-coated. I don't know what else could be used except paint or powder-coat -- chrome, perhaps?

 

Thans Skip and bsimon for the advice re Hylomar Universal Blue.

[jlumba81]

Tom, I just got 4 100g tubes of Hylomar universal blue off of ebay. If you have trouble finding any, just let me know and I can send you one. I got lucky and got them for about $12 each with free shipping.

[Alaskossie]

jlumba81,

 

Darn -- I just ordered one tube from the company, at $31.00.

 

I hadn't thought of looking on eBay. Thanks anyway.

[Croc]

Amazon is another cheap source for Hylomar.