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Old 07-07-2008, 10:47 AM
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Positive Ground Charging Systems

I need a bit of help.

The postive ground charging systems like the old 6 volt Mopars have.

My father owns a '41 Dodge pickup. We found out recently the electric fuel pump a neighbor installed for him a couple years ago wasn't operating. Thanks to help on here we purchased a new 6 volt pump from Speedway Motors and I installed it on the truck for him.

While trying to get the engine running, I found the new pump wasn't sucking gas through the inlet side but the outlet side. I figured since the truck is positive ground instead of negative ground system, this was the reason. But the pump was made for either type of charging system. So hopefully no damage was done to it?

But I swapped the inlet and outlet hoses of the pump so it now pulled gasoline out of the tank and sent it to the carburator. This was yesterday. I got the truck running and we drove it a very short distance. Till I realized the pump was forcing gas out of the carburator. So I got it parked back in the barn and shut it off.

A cousin who works for NAPA and has every bit of 30 years suggested the new pump is being doubled grounded. I'm into '57 Chevies and Monte Carlos so I'm not real sure if this is the case here or not?

He said since the pump has a metal mounting bracket plus you ground the (+) side of the pump to the frame, this is the reason the pump wants to work in reverse. That the pump needs to be isolated from the frame like with a rubber pad or something, so then when I use the (+) wire from the pump as a ground wire, the inlet side of the pump will now draw gasoline from the tank. Unlike now where the outlet side of the pump is drawing the gasoline from the tank.

My cousin also thinks the leaking from the carburator is due to the needle/seat being dirty? Which could very well be? The truck has sat for close to 2 years without being started. That the pump isn't producing TOO much pressure for the carb to handle. It's just showing a weak point that the dirty needle/seat are causing.

Can anyone help me here?

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Old 07-07-2008, 11:59 AM
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Well, I'm not sure about "double grounding", it sounds like the pump is working just fine. An electric fuel pump can very easily develop more pressure than the needle and seat in your carb will hold, it sounds like it's flooding the carb, overfilling the fuel bowl and running out. Get a rebuild kit for the carb, replace the needle and seat, and put a pressure regulator in the line. 2lbs is probably all the carb will handle, and lots of those pumps will develop 6+. Why not just rebuild the original fuel pump and use it? They are rebuildable and work fine, provided your tank isn't full of crud. Filters fore and aft of the pump!

Brian
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Old 07-08-2008, 11:34 AM
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Thanks for advice Brian.

I'm not sure what became of the pump that was on the truck? It was either replaced and the old one discarded or the truck has an electric pump on it to begin with and it was getting weak? That's why it got replaced?

I talked with Speedway Motors yesterday about the pump we bought from them. Their tech guy said to just run the wiring for the pump in reverse of the diagram Carter supplied with it. They felt it would not damage the pump in any way doing this. So now the inlet port of the pump is once again the inlet and not the outlet side like it is now.

I too thought installing a pressure regulator was a good idea. But my cousin does not feel it's nessesary?

If this new pump is creating more pressure then the system needs, then using a regulator shouldn't be out of the question?

I'll be the first to admit I have no idea what the stock pressure of the system on the truck should be? Two pounds? Four pounds? Perhaps 4.5 pounds? I'm not sure?
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Old 07-08-2008, 12:10 PM
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No problem. Your cousin, desite his parts store job, is wrong. If it's flooding the carb, it's pushing the needle off the seat, too much pressure. Clean e'thing, new needle and seat, pressure regulator dialed down to 2lbs, you'll be good to go.
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