[ROVERNET - UK] Fuel Pump woes

Lance La Certe lacpsyd at earthlink.net
Tue Aug 2 04:36:43 BST 2005

Hi Gang,

Need help with fuel pump and discovered some info that may be helpful to
others on the list.

1) 1970 3500S ----I'm in need of a new fuel pump.  Any suggestions for a
state-side source (I will be contacting Ruth Burgess in Canada)

2) I need to know if anyone can give me the specs on the OEM fuel
pump----specifically what are the upper and lower pressure limits (e.g.,
2.5 psi to 4.5 psi, etc).

3) For several months I have struggled with the car not being able to idle
once the engine was at normal operating temperatures (especially in the
summer when it has become especially hot).  After many helpful suggestions
from the listers (e.g. blow out the return fuel lines; check the
circulating coolant line which runs directly into the intake manifold;
check your timing, etc)-----I discovered that when cold and just starting
that my fuel pump was putting out only about 3 psi-----this was adequate to
keep things running smoothly, but after several minutes of running, as the
fuel pump becomes warm it actually becomes less efficient (apparently most
all fuel pumps operate this way----hence the listed range on the specs). 
As it turns out, when warm (and this has nothing to do with the engine
temperature, but the pump temperature), it was only putting out 1 psi.  At
this pressure there is not enough flow into the carb bowls to overcome the
tendency for the gas to vaporize, especially when the engine is warm/hot. 
With a properly operating pump which is keeping the pressure up, it should
overcome the tendency to vaporize and allow the engine to continue to idle.

4) My mechanic is suggesting that I find a pump that will put out about 7
psi when cold, so that when it heats up it will still be putting out about
3 psi to overcome the vaporizing problems.

Any help with this would be appreciated.

Lance La Certe,  Denver, CO

Lance La Certe
lacpsyd at earthlink.net

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