[ROVERNET - UK] Re: 3500S intermittent power loss

Christopher Smith csmith at ssl.berkeley.edu
Thu Sep 20 22:43:44 BST 2007

I removed the fuel pump on my 3500S and have a question concerning its internal 
setup if anyone has taken one of these apart before. The screen was a little 
dirty but not too bad, so I figure I am left with three possible causes at this 
- Fuel pump doesn't work efficiently (I know it runs)
- fuel lines are clogged between the tank and pump
- the pickups in the tank are clogged

I don't have any way of measuring the pressure output of the pump so all I can 
do is look at is. When you take it apart there are two reddish brown valves on 
the solenoid piston assembly. The one on top is spring loaded and allows fuel 
into the cylinder as the solenoid withdraws. There is a second valve at the top 
of the piston itself that I assume would do the opposite. Mine is just kind of 
lying in there and is not spring loaded. The only thing that would close it 
would be momentum or back pressure from the fuel on the other side. Seems wrong 
to me but I can't seem to take the piston apart anymore to look at it. Has 
anyone played with these before? Should that second valve be spring loaded?
Also can anyone recommend a replacement fuel pump that is available from a 
regular auto parts store?

1970 3500S
Northern California, USA

Christopher L. Smith
Thermal Engineer
Space Sciences Lab - U.C. Berkeley
Addition, Room #235
Phone: 510-642-2461
Cell: 510-301-7541
Fax: 510-643-4478
Email: csmith at ssl.berkeley.edu
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