[Rovernet] Sd1 fuel pump woes

[Michael Pellow]

series 1 SD1 have a 3 terminal oil light sender that switches on the oil 
light when there is no pressure. ie engine not running. however once the 
engine is running it switches over to power up the petrol pump.While the 
engine is cranking over on the key ,this is bypassed to power up the 
pump till the oil pressure has come up.These oil light senders give 
trouble so on the later cars they changed back to a normal single 
terminal sender and added a relay behind the speedo to do the 
switching.This is as a safety measure to stop the pump running after a 
crash to stop fuel being pumped into the engine bay.There was an 
additional benefit for the 2nd version in that if the sender goes flty 
,all that is needed to get the pump working ,is to disconnect the sender 
,and the pump is permanently on while the ignition is on.
Have no idea why this should affect the speedo.Hope this may help
Michael.

On 5/01/2017 12:39 p.m., Jess Rainey via Rovernet wrote:
> Any help out there would be appreciated.
> Electrical problem to fuel pump for carbureted engine. Pump is in tank, not external like efi
> No fuel to carburetors, but can apply current to pump and then fuel gets to carburetors. But when in this arrangement and attempt to crank engine, speedo goes to 145 km and then breaker opens and speedo goes to zero. Engine does not crank. Without external power to pump engine cranks, but of course does not start as no fuel.
> Electrical to pump is grounding out. Question: with these presenting symptoms any ideas as to where short is located?
> Car is 1985 sd1 2600
> Thanks is advance
> Jess Rainey
>
> Sent from my iPhone
>
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