volvo fuel pump setup

Jake Sternberg chickens at ccwf.cc.utexas.edu
Wed Oct 21 00:21:58 GMT 1998


Volvo discovered in 1976 that their cars were suffering from vapor-lock
and failed main pressure pumps under certain conditions, including low
fuel levels in the tank.

They were using a single pump, mounted under the back seat, and lower than
the bottom of the fuel tank, and they were relying on gravity to get the
fuel to the pump.  The pump was cooled by fuel flow through the system,
which was K-jetronic and kept the fuel pressure at a constant 65 PSI.
The return line dumped right back into the tank, no coolers.

Their solution for 1977 and onward was to put a second fuel pump in the
tank, which delivered fuel at about 4 PSI to the main fuel pump under the
seat.  It worked flawlessly.

The only downside is having two pumps to maintain, and that when the
in-tank pump stops working an owner can go through two or three main
pumps before they figure out what the problem is, since the main pump
has to work harder when it's alone.

The volvo 240 (their only car between 1975 and 1982 i believe) used a
cross-flow head during and after 1976, but surely vapor lock problems
were more common on the earlier engines with the exhaust manifolds
under the intakes.

Hope this helps someone,
-Jake




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