Bosch -6 rotory fuel pump plumbing

[todd230]

Putting the last fuel pieces together on my car and wanted to ask for confirmation on the plumbing hook up for this pump.

Right now I have the follow -
A - 5/16 line to fuel tank
B - 5/16 line to pressure regulator (carbs)
C - 3/8 line to fuel tank

Is this right? Thx

[Dave at Pelican Parts]

On the -4 pumps, there are labels embossed or engraved on the cover: S, D, R. S for "suction", D for "druck" (pressure), and R for "return". Are there any labels on this one?

The port next to the silver cap has to be the return port. In the -4 system, that goes to a Y fitting; one leg of that goes to the tank and the other goes to the return port on the fuel pressure regulator. There is pretty much never any fuel coming out of the R port on the pump, but it's there just in case.

If the other two ports also follow the -4 pump example, the middle is the pressure outlet (which would go to the carbs or the injection), and the one on the right is the suction inlet, which would come from the fuel filter which would in turn hook up to the tank.

--DD

[todd230]

Thanks Dave, yes my pump is labeled. I wasn't smart enough to figure out that "D" stands for druck! I assumed "drain" which was the cause for some of my doubt in hooking it up to the carbs. After rebuilding/cleaning out the pump I'm over pressurizing the carbs and pushing fuel out of the float caps. I've purchased a fuel pressure regulator and gauge so I can tune the pressure. Thought it might have been a mix up in the lines. I've got my SS lines in the tunnel and just need to hook up the new tank. Other cause for the pressure issue might have been the short run to the external tank 2 feet from the pump (?). Figured I'd run the regulator and see where I am.

[Steam Driver]

As an ex -6 owner I have a question (just to satisfy my curiosity). Back when the cars were new those pumps had a propensity to begin leaking fuel out of the electrical connection! Because of that I changed to another brand of pump. Do the one available now still do that? I had three in two years.

[todd230]

wow, I can see how that would happen now that you mention it. The large portion of the pump is the electric motor. The rotary pump parts are just a machined eccentric at the end of the motor that has an o-ring to seal the wet and dry portions. If the oring were to degrade or the seal on the shaft leak then fuel could get inside the electric pump housing and drain out the electrical connector because the pump is clocked such that the connector is the lowest point as it is mounted in the car. I will look at this after I get my car running - thanks for the info and hopefully others will chime in.

[Dave at Pelican Parts]

Originally Posted by todd230

After rebuilding/cleaning out the pump I'm over pressurizing the carbs and pushing fuel out of the float caps.

Double-check the part number to make sure it's not a four-cylinder pump. Those put out way too much pressure and volume for any carbs, and it is nontrivial to choke them back to the point where they provide the proper low pressure for carbs.

You can also check the pressure--probably a good idea anyway. If it's over 30 PSI, you've got the wrong pump.

--DD