Tampa 928s

I found an accumulator 0 438-170-025 in my bin off of a 80
The 78 is a 0 438-170-022 the difference is the top that nothing connects to, is this interchangeable?

Tampa 928s

Any way to bench test the accumulator?

ROG100

On the 78 the single connection faces upwards and was purely for leakage if the accumulator overflowed. They changed in late 78 and removed the hose connection from the top and left just a small bleed screw in its place.
So yes they should be interchangeable.

Jadz928

I've seen a late style accum on an early. Only difference is there is nothing which connects to the port on-top on later.
The later expansion tank has different fittings (3 instead of 2, IIRC)... 3rd fitting for vapor/fuel evac.

Short of it is you can plug the early fuel evap for use on later, or plumb it out of the car.

ROG100

Just for clarity ----
Four accumulators fitted to USA/CAN (78 to 79) & ROW cars (78 to 83).
928 110 197 04 - Bosch not known
928 110 197 05 - Bosch 0438170022
928 110 197 06 - Bosch 0438170026
928 110 197 07 - Bosch 0438170026

Bosch 0438170026 is just about NLA OEM but still a few sitting in Germany from Porsche for circa $425 each.

As already said in the above post the single male fitting on the early accumulators with three connections is purely a drain and had a hose connected that allowed a drain to the floor. This was eliminated on the 043817026 and replaced by a simple screw drain. Fuel can escape either side of the screw head.

With the demise of the 043817026 we have found an alternative which needs a couple of adapters to make it work on our cars.

Tampa 928s

Thanks roger!
So the new adaptors what does that include and do you know where the pricing will be.
I still am not sure if the used one I have is good guess I need to install it and see what the leak down looks like. The original is shot, gas is leaking out of the top when turned upside down, and top hole is filled with old fuel and crud. I could not find info on bench testing it blowing in each inlet allows air to pass in either direction not what I expected. Both maybe bad but with out knowing what I should observe the test is useless. I assumed it would act as a one way valve allowing fuel to travel in one direction only but the air test does not prove this.

ROG100

I am thinking that if fuel comes out of the drain then the unit has failed. The diaphragm has ruptured.
The accumulator acts as a damper to attenuate noise from the fuel pump. It also maintains fuel pressure in the system for some time after the engine is turned off for easier starting - particularly when the engine is hot.

James Bailey

I believe that the top needs to be vented to allow the diaphragm to move expand so the vent or third fitting should only be partially blocked to limit the amount of fuel which will leak out if the diaphragm fails ...