No power to fuel pump - W116 M110 280SE

[Norm126]

I am not getting any power to the fuel pump of my 1977, 280SE, W116. I have only one relay in the fuse box with two numbers on it - 0015422219 and 0332205001, so I assume that controls the fuel pump? Anyway, I tried to bridge terminal 30 and 87 but the pump still won't run. Then tested to see if I get any voltage at terminal 30 or 87 with a multimeter and it doesn't seem to be getting any power.

Other electical things are working though, such as lights, blower motor, etc.

Wondered if anyone has any ideas for me?

Thanks
Norm

 

[Norm126]

Ok, so I bridged terminals 30 and 87a with a wire and the fuel pump runs... then I bought a new relay... but it's won't run with that in place, only with the wire bridge.
And also the blower motor fan always blows full blast when I turn the ignition on and I cannot turn it down/off.
I'm stuck :-(

 

[grober]

http://handbook.w116.org/ETM\77s.pdf

 

[grober]

http://handbook.w116.org/ETM\77s.pdf

If you scroll down to to the third page you will see this you might have a faulty sensor plate safety switch?

 

[Norm126]

Thanks for the reply. That sounds quite possible doesn't it. Would that be difficult to replace do you know?

 

[Norm126]

Interestingly, with the relay in place, igntion on, when I tap down on the throttle plate the pump buzzes. So what does that mean? Surely the pump should buzz simply with the ignition in position 2 for a few seconds? So maybe this sensor plate safety switch is indeed the culprit then?

 

[grober]

to test this try isolating/earthing pin 5 [ 85] of the relay- one of these will cause the pump to run. If earthing it causes the pump to run you can run a temporary wire to earth with an interrupter switch till you repair the airflow plate switch. The explanation on the circuit diagram is counter intuitive to me [ might have suffered in translation??] but will depend on whether the relay is normally closed [ position shown] or normally open when powered