Need improved fuel delivery - BBC

[pismorat]

Within the last year I swapped my 383 SBC out for a 489BBC. I put a high volume mechanical pump on it and have always had an inline electrical pump for offroad situations that's controlled by a switch. With the bigger motor, if I hold the throttle open for more than 3 seconds, it basically runs itself out of gas cause it can't get enough fuel. If I leave the electric pump on it will keep it from happening, but seems like it still struggles. The truck has the larger 3/8" fuel line. Any ways you can think of to keep this from happening - without leaving the little electric pump on all the time?

 

[Fordum]

Well, those mechanical pumps are designed to handle that much flow. But they are not built to handle much suction.
Usually when you have that problem, the sock in the fuel tank is clogged up. But in this case, I'll bet its the electric pump.
Depending on the type, they range from restrictive to very restrictive when not running.

Not sure why you would need the electric pump for off road use, but I would put a temporary bypass on it to see if its the problem.
Just a piece of fuel hose or something to see if the engine will run right without it.

If it does, and you still want the pump, put a two way valve on the line.
In one position it will draw through the pump, in the other it will draw past it.

The mechanical pump could be bad also. They can develop problems where they will not pump what they are rated at.

But the electric pump is more likely.

 

[pismorat]

I'll bypass the electric pump and give it a try. I put it on as a backup years ago when my mechanical pump failed and left me stranded and I had to get towed out. Then I just started using it offroad to make sure I had pressure to the mechanical pump.

 

[folkenheath]

I agree with fordum, bypass the electric pump and it should fix the problem, assuming you have at least a 110 GPH (preferably 130 with external regulator) mechanical on there or so?

 

[Ned Kelly]

It may be your pump, or possibley the fuel line routed too close to the exhaust. I had dual exhuast put on my BBC K30 and then started having fuel starvation problems. It was very intermittent, and we always assumed it was a fuel delivery problem. Tried to solve it by changing mechanical pumps several times, and then switched to an electric pump. Still the problem persisted, but it was VERY intermittent. When we did a new pump swap, it always seemed the problem was solved. Then it would creep up on a hot day, slow moving 4x4, heavy traffic, etc. But it would disappear randomly too. Ended up being the new exhuast was too close to factory metal fuel line. Not obviously too close when you looked at though. We made some fuel line changes/ heat shielding and problem gone.

Two months later FourWheeler magazine did a BBC dual exhuast onto their truck and had the same problem, and they so also thought it was a fuel pump issue. They went through the same steps, then figured it was the new exhuast routing also.

Not saying that is the problem, but something to check.