I have a '56 Chevy with a stock 5.3L, LS6 manifold/fuel rails, Corvette FPR, using a stock tank (not baffled). I purchased the highest flowing pump from Tanks, Inc. and installed it in the stock tank.

I had significant leakage from my tank when I filled it up the first time. I dropped the tank, used copper washers around the sending unit and pump mounting bolts, and put it all back together. No more leaks. Dry as a bone.

I noticed after the repair, the pump was no longer as loud and sounded "different". It almost sounded like it wasn't getting enough power and was kinda sluggish when I first turned the key on. Can't explain but it didn't sound the same. Last week, I went out for probably a 10 mile ride. Toward the end I was coming to a stop light on a road with a slight decline and the pump started making this strange off and on sound. I can't describe it in words but it sounded like it was cycling on and off repeatedly. When I reached a stop, it stumbled and stalled. It started back right away but was kind of stumbling. It also seemed like the fuel gauge needle would show 1/4 tank and then Empty - back and forth.

I called a friend and he said since the sender and pump were acting erratic, it might be the ground. I took the common ground off, scrubbed the frame with 40 grit and put a star washer on it with the teeth. Put it back together and it fired right up. Pulled back out of the garage and as I was going down the slight decline, the pump started making that on and off again sound and it started to stumble. Pulled back in the garage and shut it off.

Thinking the tank might just be low on gas, I put about 8 gallons in the tank this week. The next day...strong gas stench in the garage and a nickel-sized gas leak on the ground under the tank.

This morning I took the car out for a drive again. Starts up with zero issues except the pump still doesn't sound right when it turns on. Drove around for about 10 minutes when I came to a red light and the pump started making that noise again. It tried to stall but the light turned green and I took off.

It doesn't seem to stumble when you're cruising along. It is also very responsive if you punch it. It only starts acting up after you've driven for 5-10 minutes. Coming to a stop seems to make it start acting funny then it doesn't go away. There is plenty of gas in the tank now so it shouldn't be starving for fuel. As I was pulling into the driveway, the noise with the pump was going on while going about 5 mph.

Very frustrating. The car has been driven about 40 miles so the pump is practically new. What would you do from here?

Jeff

 

I would call Tanks Inc and ask their opinion. Sounds kinda like you are getting low voltage at low engine RPM. Thanks for the copper washer tip on the leaks. I have the same problem, one of these days I will drop the tank and try the copper washers.

Pat

 

if the ECM controls the fuel pump relay, I would change the relay or double check all connections for that circuit

 

Is it possible that you have a tank venting issue? In other words, if there is no way for air to enter the tank, the pump would pump until it had formed a vacuum in the tank and then not be able to pump any more, it would likely pull a lot of current trying. If you think this might be the issue, remove the gas cap and see if it runs/pumps for longer than 5 or 10 minutes.

 

928, you're the second person that has thought of that as a possible problem. It sounds possible so I'll give it a try and drive it around with the cap off. However, on these old cars, the tank is vented at the cap. I bought a new, vented cap so it should be vented.

I'm also having leaking problems with the tank though so I don't know that it's completely sealed. I took the easy route today and bought a new tank and pump today. I know it's sealed and the pump should work. I'm just real frustrated.