Fuel Pump (Early, Tall model) - Impellor to Cover Plate clearance

[Steven A]

Hi

I am trying to find out the specification for the clearance between the impellor and the cover (end) plate.   With wear (and abrasion) over the years,  fuel pump has been losing performance (have a modern aftermarket pump in temporarily, but want to get the original pump back up to performance and re-installed (1964 230SL).    The fuel pump is the "early (tall)" pump as described in the fuel pump section of the Pagoda SL Group web-site.    I can skim cover/clean up face of the impellor, hence seeking the correct clearance.

With thanks

Steven

[Benz Dr.]

I have attempted this repair before and I didn't get very far. The cover plate has to be perfectly smooth and the bottom of the pump housing should be as well. I put a piece of sticky backed sand paper on a piece of glass and then I swirl the part around unil all of the high areas are removed. This should give you a very flat surface for the impeller to ride on.

There are two problems you will need to address; the impeller will be worn and the pump housing will also be worn. If you can remove all of the parts from inside of the pump you should be able to true up the bottom parting surface. You should also do both sides of the impeller so that they're as smooth as you can make them.

Place the impeller on the pump main shaft and use a depth micrometer to measure the difference between the thickness of the impeller and the pump housing. I would think you would want around .001 - .0015 clearance. Gasoline is a very thin and it will easily leak by very small gaps. Maybe Rolf can give us an idea on tollerances since he once worked around stuff ike this.

The end play on the impeller blades is what you will have to work with because I doubt you can do anything about that. I once found a new impeller and I still couldn't get enough pressure with this new part. You need at least 10 PSI to make the pressure relief valve work although it may be possible to reduce the regulator pressure a bit.

[Rolf-Dieter ✝︎]

Sahern and Dan

I send you both a PM
 

[Steven A]

thanks for advice, and thanks to Rolf....appreciated.

Regards

Steven