Factoru 914-6 fuel pump with low pressure, Has anyone taken one apart and fixed them. Options

[toolguy]

I've got an original 6 with the factory fuel pump. . after sitting for 6 months, the pump runs but has low fuel pressure on the carb side. . Has great pressure on the tank return side. .no line obstructions. . . tested out of the car. . . won't lift fuel over level in the tank. . . anyone ever tried to adjust or repair one



Read down. . . Fixed !!!

[toolguy]

So the answer is, YES, they can easily be taken apart and the pump portion serviced. .
In my case, the motor ran fine, i just did not have sufficient pressure to lift the fuel to the level of the carbs. . meaning it was putting out less then 1 psi. In my mind I was looking for some sort of blockage. . Last picture is of the pump head apart. .

WARNING- As Dave D said, mark the pump, intermediate plate and head outlet before disassembling. . the intermediate goes back correctly in just one orientation, although you can put it back in 8 different variations.. The center hole that goes around the rollers is offset and must be in the proper place to coincide with the 3 outlet ports. . otherwise in could be out and suction could be pressure. .

Beside the center lobe and 5 rollers, there is a small crimped cover with a small o-ring inside and over the plunger port. I reused the o-ring and re-crimped the cover tightly. . .
Apparently the strength of the small spring regulates the outlet flow. . . the plunger is pushed toward the inward passage by the small spring. The plunger head then covers the inside port to the outlet tube. . the spring regulates the outlet flow. This plunger slides back and forth in the top cover, regulating gas flow either to the carbs, or back to the return port to the tank.

In my case the plunger was gummed up with varnish and debris, and helf in a mostly closed position. . j. . It was really tight and had no movement but some PB Blaster and a few dental tools took care of that . Once it was all the way out, a little cleaning and it was easily sliding in the bore of the passage.

First picture is the test arrangement i made, mostly to ensure no leaks and sufficient pressure. . On the initial test, the pump would not lift the fuel more that an inch above the pump level. . Now has plenty of pressure now, raised fuel 3 feet in elevation to the suspended can and I can stop it with my finger tightly held over the outlet port. . I plan on running an outlet pressure regulator and gauge to insure no pressure in excess of 4 pounds. .

So for posterity, they can be taken apart, cleaned and reassembled. . just be careful about exactly how it comes apart. I am still puzzled as to what actually controls the outlet pressure as the bypass plunger seems to be more related to flow rather than pressure. Maybe the strength of the little spring , but at this point , it works and that's good enough for now. . pressure could be a relationship of the motor speed and the roller dimensions. .