Fuel supply modifications to a TC

1 Sep

Having grown tired of attempts to get his SU petrol pump working reliably, Steve Priston decided to fit a Facet pump. Here’s what was involved….

Having had the standard AUA 25, SU fuel pump fail on my TC, I tried to cure its reluctance to keep going by fitting some new contacts; but the best that I could get from it was something that must have sounded like a WW2 airborne dog fight, in the distance. Unfortunately for me, despite hours of persevering with the diaphragm positions, the guns kept stopping briefly, as the SU tried to save its ammo!

The pump had caused problems before, by the tell-tale chewed-up screw heads, so it was time for a replacement; but rather than blindly fitting the same thing, it was time for some research to see what other people had been doing to their cars.

A Riley man, a friend of a friend, had fitted a modern, American made Facet fuel pump, by his tank, with a return fuel line, back from the engine bay, connected to the tank’s filler neck. This worked for him, despite not having a regulator or even a flow restrictor on its return line.

A very good friend, a V8 Morgan owner, had fitted his Facet pump, also close to the fuel tank, but this time a pressure regulator, made by Malpassi was used. This was able to regulate the supply pressure, having a range of between 1.5 & 5 psi, easily adjusted, via a top mounted screw, with a lock nut. He had seen the fuel boiling, in the glass filter bowl on his regulator, whilst positioned under the bonnet, so had moved it to the rear of his car, near the pump!

This second version seemed to be the way to go, not having to worry about a return line to the tank, but just requiring a means of mounting the two major components close to the TC’s tank; however not too close, in the case of the regulator, which was not going to have a filter.

I don’t like drilling extra holes in anything, if it can be avoided, so after much head scratching, with the new pump being offered about, I decided that I would use the nearside rear axle bump stop fixing holes. I then cobbled-up an alloy bracket, from a piece of off cut angle, mounting it under the top of the chassis rail to be held in place by the nuts of the bump stop bracket.

In this picture you can see the alloy bracket (shown in the previous picture) secured in position by the nuts of the bump stop bracket. Once secured, it acts as the mounting bracket for the pump.

An overhead view of the arrangement.

Apparently there is a preferred way to mount this type of pump, to avoid any issues with cavitation, which is for the flow to be upwards and for the pump to be at a 45 degree angle. So that was my target, proving to be ideal for connecting to the existing copper line, from the tank, which travels along the outside of the nearside chassis rail.

The pump in question is listed as negative earth, as I believe are all of their pumps, but this could be overcome by using rubber mounting blocks, along with plain, non-conductive rubber tubing. In fact, this model has a plastic outer casing and when I put a meter across the inlet filter/outlet hose tails, there was no continuity.

The regulator comes with its own bracket, which requires bending so that it remains horizontal when screwed to the plywood as shown; the use of a 90 degree hose tail, making for a good alignment, with the copper fuel line, which needs about 18 inches cutting out under the axle, with a little bending to suit.

The pressure regulator screwed to the ply behind the lower part of the seat back backrest.

Of course, it will need wiring and a 5-amp fuse, which to me is not my bag but had to be done whilst laying on my back, when an ice cream would have struggled to melt quicker than I was!

Having altered the float chamber tops some time earlier (see later text), it raised concerns over the possibility of rupturing part of the fuel supply system after the pump, especially above that damned exhaust, should the car be involved in a frontal impact, so I have fitted a second-hand inertia switch, from a Rover. I think that the same model is used on many cars but I doubt they are fitted just up the back of the dash, on the passenger’s side.

I remember hearing about the position used by Ford, in their early Mondeo estate cars, not enjoyed by a friend, with a fully loaded boot, when he stalled it so violently, that the switch was activated, in heavy traffic, on a motorway!

I would say that this is all straight forward work, best undertaken when the weather is a little cooler so the sweat doesn’t fill the lenses of your glasses! 

Sourcing the parts

Once again ‘good old’ eBay again came into its own to find what I needed cheaply and to get it quickly. Surprisingly, the cost of all this lot is similar to or cheaper than, that of an original type SU pump but the Facet was only £32 including postage, rated at 6,000 hours.

A Facet PRO243-K pump.

A Malpassi FSEFPR008B regulator, with 8mm hose tails.

A pair of Syntec FPA rubber mounts, although longer ones would be an advantage.

A pair of Syntec NPT Fine, 90 degree, 8mm hose tails.

Some 8mm / 5/16″ bore non-overbraided fuel hose and clips.

Prior to this pump replacement, I had already decided to see what I could do to improve matters with hot fuel under the bonnet. The fuel hoses to the twin carburettors were re-routed by swapping the float chamber tops over. This enabled me to run the feed to the front float chamber around the back of the air cleaner, so that being nearer the bonnet louvres, it was away from being directly above the exhaust manifold.

Re-routing of the fuel hoses to keep the carb to carb hose as far away as possible from the exhaust manifold.

I also wondered why the hoses from the SU pump and between the float chambers, were such a large bore size, when later cars employing a similar SU set-up, had either 1/4″ or 3/16″ bore tubing. So, I made some new hoses in 6mm bore, reducing the hose stored fuel volume, by around 40% per inch, but now with a further reduction as a result of removing the contents inside the SU pump as well.

Ed’s note: The old fuel hoses which were replaced using new hoses of a 6mm bore had a bore size of 8mm. Steve now has a 35 inch length of fuel hose under the bonnet, instead of a 29 inch length.

The above, to my mind could only but help with the problem of vapour lock, caused by so much fuel being heated under the bonnet, as its volume has been reduced. The smaller bore hoses also increase the fuel velocity from the pump so it is not exposed to the heat for so long either; at least that is my view!

To finish off, I saw the original mounting position for the SU pump, to be where logically, the coil should now be mounted, no longer tucked partially behind the rocker cover and in a position that nicely disguises the missing pump from the bulk head, and also nearer to the louvres.

The coil now re-positioned to where the SU pump was originally located.

Since this work, I have adjusted the fuel regulator a couple of times, now being just two turns up, from being fully home, having only five turns of adjustment.

The engine idles beautifully, especially when hot and I have now adopted a way of starting the car, after it has been parked for as long as it takes to eat a nice cake and ‘down’ a decent coffee. This is to simply to pull the starter, then let it idle for a few moments, whilst the oil pressure goes up, before driving away, hopefully now without any drama or embarrassment.


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