Electric Fuel Pump for a Carb’d Engine : Saving Pumps By Moving It To The Rear

I drive an old car, to be exact, I drive a 1987 (model year) Mitsubishi Lancer (A173) SL, which is colloquially known as a “Boxtype” Lancer. Around the house, we refer to it as “Dad”, much for the fact that it’s pretty old, officially I named her “Aska”, after who’s arguably the best girl in the Evangelion franchise (until Mari came along) just because I thought I wanted a Japanese name to connote the car’s lineage.

This is one of the last photoshoots Aska appeared in. Originally, it was supposed to be for our club’s planned 2013 photo calendar. Yes, that’s a NERV sticker there.

It runs with a very bone stock 4G33 Saturn engine, a 4 speed transmission, front discs, rear drums, no ABS. Everything about her is very basic, conventional and delightfully mechanical, which leaves a lot of things open for the average guy who wants to get down and dirty, to be able to do a lot of work on her with their bare hands.

When she arrived, she was no longer using her mechanical fuel pump. See, this kind of car uses a mechanical fuel pump driven off the engine through a spring loaded lever. This is located on the left side of the block, just below the distributor. It brings fuel to the carburetor by siphoning the fuel from the tank, into the pump’s diaphragm, into the carb’s bowl.

This is how a mechanical pump looks like. The part with the lever is attached to the side of the cylinder head.

 

A stock photo of the Maruzen pump I used. This same type of design is what I’d been using since I got Aska.

This is pretty reliable in itself, but has a couple of drawbacks (as far as I can see) in terms of function. Since the pump is driven off the engine’s power, if the carb’s bowl becomes empty (wholly possible especially if the car is stored for a long period of time) by the gasoline evaporating, the engine will have to crank for a long period of time in order for the fuel pump to bring the gas from the tank up to the carb. Do this long enough, and you will be draining your battery’s power really quick, and shorten the life of your starter.

Another thing is that if the engine is running for long periods, and it had gotten really hot, the fuel within the pump and possibly the line close to the engine will evaporate due to the heat, causing loss of pressure which in turn will hinder the pump’s ability to pump the fuel. This phenomenon is called vapor lock and you can read more about it here.

A very distant third is that it causes parasitic losses in terms of power generated by the engine, but this is very, very small – it can be easily offset by friction from anything else.

An electric fuel pump offsets these cons effectively. Since it’s electrically driven via a pump motor, you don’t have to crank the engine til kingdom come for the fuel to reach the carb. And when mounted correctly on the vehicle, it is pretty much immune to vapor lock. Since it feeds off electrical power from the car, it will tend to draw from your electrical system, but this loss is very, very small, and again can easily be offset by anything else feeding off your electrical system.

So back to Aska’s electric fuel pump.

When I got her, the electric fuel pump was initially placed within the engine bay, right beside the A/C compressor. I drove it around loads until about a year later when I found that fuel pumps (brand new Mitsubishi replacements, and they’re not cheap) would fail, one after the other, within a span of months. Early on, I was given advice by a good friend of mine, Phil (check out his mechanical meanderings) that this was happening because of vapor lock. The extreme heat of the engine bay is literally killing my pump, which wasn’t meant to operate in such a harsh environment and giving me vapor lock while it’s being destroyed. Truth be told, I didn’t quite believe that at the time because I was thick headed.

After a third pump failed while my father and sister were in a heavy downpour at night miles from home, I had to seriously rethink my line of thought. To get my father home, one of his friends gave him a Maruzen brand fuel pump, which they installed (still in the engine bay) to get them home. The Maruzen pump looked exactly the same as the ones I used so they were pretty much pro with it, dumped it in the car and they were able to drive home.

The following morning, I thought back to Phil’s advice, and sought ways to have it moved into the rear. I had a track day coming up, and I just could not afford any sort of trouble on the track nor on the way there.

I knew had to move the fuel pump to the rear, but exactly where?

Phil’s car was pretty much rebuilt from the ground up, so it had a custom fitting for his fuel pump. My father and I decided to MacGyverize stuff to work for Aska. He went out to buy flat pieces of steel that would serve as mounts for the pump. Luckily, these were locally available near our place. Holes were drilled at pre-determined spots, and luckily the fuel tank itself had holes that matched the length of the bars.

Remember my father’s friend who gave us the Maruzen pump? He made us a mount made of a thin piece of metal plate – it was this piecethat held the pump, and it mated to the steel bracket pieces.

This shows the bracket that my old man rigged, and the fabricated mounting plate for the pump. The pump itself is secured by wing nuts.

**Before attempting to work on your vehicle, make sure it is properly jacked by having the jack lift that car at a rigid point, like in my case, the differential housing. Make sure the car will not move around by blocking off the wheels.

Now we have the pump in place, but it’s so far to the back that we had to run wires to the back where the pump is. That was an easy job on its own, and we also housed the wires in flexible hoses to protect it from stuff under the car, and fixed the whole thing in place with zipties. A relay was also installed to make sure that the current to the pump remains stable (very important considering how far it is from the battery) which can also act as an anti-theft device of sorts.

Oh, I forgot to mention. Having an electric pump in the rear makes its job much, much easier – because it’s close to the tank, it has an easier time sucking up the fuel and pushing it towards the carb. If the pump is still within the engine bay, it will have a hard time sucking in the fuel from way back there, and then pushing it to the carb.

The whole set-up looks very ghetto, but is proven and reliable. The Maruzen pump had far outlived all the other pumps (Mitsubishi) that I had for Aska. I’d taken her on trackdays, autocross events, joined carshows, driven hours and hours away from home, in all weather conditions. It’s only just over the past few days that the pump is showing signs of it weakening because I’m encountering fuel starvation issues.

The new pump installed.

Comparison of the now 4 year old Maruzen pump, and a brand new Mitsubishi replacement.

If you have become interested with the set-up, and have questions, feel free to comment, and I will try to answer them.

 

 

 

 

 

 

 

 

 

 

 

 

 

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