Testing one of the benefits to having two fuel pickups.....

[dcdoug]

As most of you probably know, the original cobras had both a mechanical fuel pump and twin electric fuel pumps with separate pick-ups. I have been told that one of the purposes for this set-up was to provide drivers with a fuel "reserve" since they only had a fuel pressure gauge and not a fuel level gauge. (I'm sure the other was the additional fuel pressure that the electrics provide over the mechanical for sustained WOT driving).

The CSX 4000/6000 cars are set up the same way. So I decided to test it this AM (unintentionally). I was driving up a hill this AM when my motor sputtered and died (maybe the mechanical pick-up is in the front of the tank, I don't know). I knew I was low on gas (I actually have a fuel level gauge ), but figured I'd get gas where I was going as the gauge was showing about 1/4 tank (yes I know they are not accurate). I had a friend that was going to meet me who would be coming the same way, so I figured he could give me a ride.

As I sat there waiting and hoping no idiot would hit me (very small shoulder on the road), a light bulb went on and I remembered the electric fuel pumps and the theory about the lower pick-up and the "reserve". (I normally drive on just the mechanical pump). So I flicked the switch, waited a few seconds and fired it right up and drove straight to the closest gas station.

So now I know that it works and I don't plan on testing it again.....but thought I'd share, just in case anyone wondered about it.

[mickmate]

6025 has been tested also and works good.

[ERA Chas]

And do the valve covers still leak massively when going up that steep incline???

[Shelby Cobra]

Doug, almost the exact same thing happened to me in my CSX6000 car shortly after I acquired it, but mine sputtered for a couple miles before finally quitting. I thought it was bad gas or debris in the carb. The electric pumps fired it right up and let me get to the nearest station.

The story goes is that originally with the S/C cars, since they were basically race cars, the thinking was that a fuel gauge was not needed, so only a fuel pressure gauge existed, and the way that the driver could tell he was low on fuel in a race was when the fuel pressure dropped on the gauge, and then the driver would flip the switch for the electric pumps (which had a lower pickup on the tank than the mechanical pump) and would give the driver another lap or so to come in for fuel. Since the CSX4000/6000 cars are set up like the original S/C cars, we have the same mechanical/dual electric fuel pump system with higher/lower pickup points on the tank. Pretty cool.

Alan

[dcdoug]

Originally Posted by ERA Chas

And do the valve covers still leak massively when going up that steep incline???

They never leaked massively, just a tiny bit. But I would prefer no leaks (I think I'm there on the oil pan). But maybe I'll let them leak a bit longer just to torment you.

[ERA Chas]

GGGGGrrrrrrrrrrrrrrrr.

[patrickt]

Doug, that OG grease is the key -- it's like magic. Plus, when I was doing my valves a few weeks ago, some of those nuisance stink bugs that have inundated our area flew in, and when the fumes from that grease hit them, they dropped right out of the air, dead as doornails. Now that's the mark of good grease.

[Trueoo7]

How do you hook up a mechanical as well as an electric pump at the same time? Is it two separate lines or is there a tee somehow in the line. Would like to see a schematic of how this is done.

[mickmate]

There are two separate lines and a tee. One line goes from low pickup in tank through trunk and electrics to a tee right after the mechanical pump. The other goes to the mechanical pump. They both run along the drivers side as that's where the mechanical is.

[dcdoug]

Originally Posted by mickmate

There are two separate lines and a tee. One line goes from low pickup in tank through trunk and electrics to a tee right after the mechanical pump. The other goes to the mechanical pump. They both run along the drivers side as that's where the mechanical is.

What he said.

Hey Nick, do you remember if the pick up for the mechanical is in the front or back of the tank? I'm wondering if the hill I was on exacerbated the problem. Certainly seemed like it did.

[Trueoo7]

Originally Posted by mickmate

There are two separate lines and a tee. One line goes from low pickup in tank through trunk and electrics to a tee right after the mechanical pump. The other goes to the mechanical pump. They both run along the drivers side as that's where the mechanical is.

So you have two pickups coming out of the tank (2 separate that tee's back to one up at the front) or just one that is split into two and then tee's back together( one going to electric and one to mechanical) ?

[damdfw]

Originally Posted by Trueoo7

So you have two pickups coming out of the tank (2 separate that tee's back to one up at the front) or just one that is split into two and then tee's back together( one going to electric and one to mechanical) ?

Two separate lines coming from the tank (one is deeper than the other). The shallower line is the input for the mechanical fuel pump. The deeper line is the input for the twin electric fuel pumps in the trunk. From the electric fuel pumps a line comes to the front of the car and is tee'ed to the output of the mechanical pump.

BTW. I "tested" mine on my first drive....

[mickmate]

Both pickups are at the front of the tank but the tank floor slopes down to the front so it should run down to the pickups. Unless you're accelerating hard and tossing it all to the back.

[dcdoug]

Originally Posted by mickmate

Both pickups are at the front of the tank but the tank floor slopes down to the front so it should run down to the pickups. Unless you're accelerating hard and tossing it all to the back.

OK, possibly the hill I was on was steep enough to allow the gas to move away from the pickup. Good to know anyway. Not that there will be a next time.

[Trueoo7]

What do you do for a fuel filter?

[damdfw]

Originally Posted by Trueoo7

What do you do for a fuel filter?

Inline filter after the mechanical pump output tee.

[dcdoug]

Originally Posted by damdfw

Inline filter after the mechanical pump output tee.

Same here.

[Trueoo7]

Are there any one way check valves needed in the system? Sorry to ask so many questions.

[damdfw]

Originally Posted by Trueoo7

Are there any one way check valves needed in the system? Sorry to ask so many questions.

No check valve needed. I read a post about just that question and the consensus among the experts was that there was not enough pressure in the system and if I remember correctly the electric pumps would not allow the fuel to run back into the tank.

It's been a number of years since I looked into this so I may be fuzzy on the details.

[mickmate]

Its in the mechanical pump. One only lets it in the other lets it out. The tee is after the out valve so that works as a check. You only learn by asking questions and we love to talk about em here.