ECOTEC Fuel System

Supplying fuel to the Ecotec required a special delivery system.  Unlike the system we had in place for the V6, the Ecotec is a “returnless” design.  I’ll get back to that, but first let me describe what we had before with the V6.

The V6’s fuel rail required a “loop” for the fuel to flow in.  So a special made aluminium tank was made to fit the stock fuel tank location.  Since we wanted to extend the range, the tank was made larger.  This tank has two bungs, one is an output and the other a return.  The output was connected to an external high pressure fuel pump and plumbed to supply fuel to the fuel pressure regulator and ultimately the fuel rail up front on the engine.  A return line was also plumbed and this dumped unspent fuel back to the tank.  This is a “return” fuel system.

There are advantages to this design.  The pump can be easily serviced and replaced if needed.  However, these high pressure pumps are getting a little expensive these days.  Another advantage is that the fuel returns back to the tank and ensures a fresh supply of “cool” fuel – no vapour lock.  The big disadvantage and something that really screws up folks doing conversions is the tank must be modified (unless specifically designed like mine) to have a return line bung.

The Ecotec however, is part of the new design that does not use a return line.  With this system, there is a single line going to the fuel rail constantly supplying high pressure fuel to the injectors.  This posed some challenges for us.  Since we had made that nice alumimium tank, we did not feel like pulling it out and making a new one with only one output instead of the two used by the return system.

This is what it looks like now:

Whoa!  This looks busy.  Well, let me explain what is going on.  The fuel tank is covered with the black carpet.  At the very bottom, on the extreme right is the former “return” line input.  On the bottom of the tank you see another line feeding the small box on the left.  That is now the supply line into the small box holding the high pressure fuel pump (see picture below).  The fuel pump box above has two lines going up ending in blue fittings.  They supply high pressure fuel into the new fuel pressure regulator and combined fuel filter.  So you see, excess fuel goes back directly to the pump box.  The silver braided line coming out of the regulator feeds a stainless line that runs on the frame and feeds the fuel rail up front with high pressure fuel.  Very neat, and only one line goes forward.

This is what the fuel pump looks like.  The pump has a “sock” that mounts to the input side.  This is a pre-filter.  The rest of the bits are the rubber isolation tube on the left and the wiring adapter.  This is all GM as fitted to Corvettes.

OK – there is a reason for all this.  If you look closely at the tank you see a protrusion at the very bottom.  Even though the tank is baffled, when doing heavy cornering fuel has a tendency to starve the pump.  We solved that by making a special lower compartment that will not allow that.  Kinda like a windage tray on an oil pan.

The fuel pump tank (the small box) as described previously contains a submerged GM high pressure fuel pump.  The box has a “lid” held by several screws and machined to hold Vitrol “O” rings to keep fuel from leaking.  This is a tight seal.  The rubber line at the top of the fuel pump box allows air to escape, allowing the box to always be full of fuel.

The tank holds about 15 gallons and the small box holds about another gallon (give or take).  The beauty of all this is the fuel pump box always contains fuel.  When taking turns at high speed this all now ensured no fuel starvation.

Of course all this comes at a price.  All this has taken up precious space in the trunk but then again, I don’t carry a bunch of wrenches and spare parts like many other owners of “originally” restored cars do.  Furthermore, the extra fuel capacity offers a much more respectable driving range:  I have already been able to get 350 miles of city driving from a tankfull and still had some fuel left in the tank before filling it back.  I am hoping that once I get bowtie6 on a long trip on an interstate, I can reach the 400 mile mark.  Not too bad huh?

One more picture showing the custom made aluminium battery box housing an Optima Red Top battery.  Behind the battery box is the Triumph “bleed” tank that is plumbed to the fuel tank filler neck and allows fumes to be routed back to the intake side of the engine.


4 thoughts on “ECOTEC Fuel System

  1. Dick Olds

    Can you tell me what pressure the LE5 injectors are designed for? I’m using the same engine in a TR4A and would like to install an in-tank pump and level sender assembly. I’m considering a 2003 or so Silverado pump, which has the height needed to reach to the bottom of the stock Triumph tank, but I don’t know what pressure it runs at, and I don’t know what pressure the LE5 needs. Also, that pump was never specified by GM for smaller engines. Is that a problem? I see you are using a Corvette pump, which must also be intended for much larger engines…
    Thanks again for the great blog. I’m learning a ton.

    1. bowtie6 Post author

      The LE5 Ecotec calls for 50-60 PSI.

      Having said that, I have no idea what the 2003 Silverado pumps delivere. If that pump fed a Vortec engine, I would imagine that should be sufficient pressure and volume (Ecotec is half the cylinders and half the displacement – more or less), but you will need to research all this. Silverado’s did use different sized Vortec engines though. You want to make sure you get something that can deliver not only the appropriate pressure but the appropriate volume. Pressure is only half the equation. You will then need to run the appropriate FPR – remember the LE5 uses a returnless fuel rail.

      Good luck using the “stock Triumph tank”. You will need to cut that tank to accept the mount to hold the pump, and then make some sort of hermetical “cap” to seal everything back up. Also remember you will need to run a B+ signal (using a relay controlled by the ECM’s pump controller circuit) as well as a ground to the pump and last but not least welding on a previously used fuel tank is not exactly “safe”.

      Finally, Stock TR tanks don’t have baffles. The GM pumps expect a sizable amount of fuel and if the pump sucks anything but fuel (ie., air) it will cause the engine to stumble (been there, done that) especially under cornering. This will become more evident when the tank is low on fuel. By the time you “modify” the tank, you will have as much (or more) than if you had spent on having a custom tank designed for EFI.

      Fuel delivery is absolutely essential for an EFI engine to perform properly. Carb engines run very low fuel pressure. EFI fuel injectors will have a serious issue unless you provide the appropriate pressure and volume especially at WOT. Finally, just because a given pump works for me it does not mean it will for you – in my case the fuel system was designed from the ground up specifically for my needs.

  2. Jordan

    Very nice fuel system write up! I do have one thing to fix though. The 2 fitting at the FPR, the middle fitting is the return back to the surge tank and the outside fitting is the pressure feed. Other than That, Very nice setup. I basically have the same thing other than I used an external High pressure pump. Love the updates!!!!

    1. bowtie6 Post author

      Thank you for the feedback.

      The fuel pressure regulator (FPR) has a built in fuel filter and three tubes sticking out of it.

      On the left hand side are two blue fittings. They are both plumbed with special fuel-resistant rubber hoses. The one coming from the top of the fuel pump tank (the one next to the red plug) is high pressure fuel that the pump has retrieved. The other line is the “bleedoff” line and basically returns fuel back to the fuel pump tank. I put the red plug there for a reason: that is where the B+ lead from the fuel pump relay is attached. I did this because I don’t want any accidental sparks back there. This is something I’m not 100% happy with yet, and will require some further tweaking.

      OK – the other line on the right side is braided steel with a Teflon liner. This is the line where high pressure fuel is routed to the front of the engine. This braided line is short and basically goes through a hole we drilled on the floor of the trunk. On the other side is the hard stainless line that goes forward.

      Finally, the fuel sending unit is inside the large fuel tank. It is NOT in the little tank pump – duh! I’ll try to pick the car up on a lift soon and have some better pictures of all the plumbing underneath the car.


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