[T2] Fwd: Re: fuel pumps

[Jack Dinan]

>
>
>I'll try to round up some pumps and duplicate your experiment,,, and 
>give you my opinion,,
>might be a few days .. if that is ok
>
Jamie: I gave this a lot of thought today. I've studied the cut-away 
view of the vw fuel pump in Bentley fuel section. I've changed my 
mind about the usefulness of testing a pump by drawing vacuum on the 
two ports.

Input port. It is ok to draw vacuum on this port, but all it does is 
test the integrity of what Bentley refers to as the suction valve. If 
that valve holds properly, then the vacuum gauge will read a high 
number but no info on the diaphragm can be gotten from this.

Output port:  Drawing vacuum on this port will tend to open the 
"delivery valve" and draw air all the way to and through the input 
port. Again, no information on the diaphragm can be gotten. I tested 
this hypothesis by holding my finger on the input port while drawing 
vacuum with the mityvac on the output port. The gauge read 15 and 
held.

I repeated this on another pump. Same result.

So thank you for offering to test yours, but that might not be necessary.

On the other hand, my explanation might be totally wrong. :-(

jack