Fuel pump safety cutout

[Oversize]

I believe the W116 fuel pumps should not run unless the engine is turning over. And that this was a safety measure should the vehicle become involved in a collision. However this feature does make it difficult to determine if the pump is working in the event of a fail to fire, as you can't hear it running over the noise of the starter.

The pump on Red Bull can be heard running with the just the ignition switched on and I believe it was modified to make diagnosis easier. Could anyone guess what's been bi-passed to achieve this? I'd like to return it to the standard system...

 

[Helmet]

Some versions of K jet had a switch on the air intake sensor plate that switched the fuel pump when the plate moves down (when air flowed over). If the plug is disconnected the pump runs all the time. On later models they used an ignition signal sensing fuel pump relay.

My guess yours has the plug off the air flow sensor

 

[Tony66_au]

Might have to check for the plug on the SE, its a 77 model and would make the initial diag much easier although i suspect the tank will have to come out for a clean and in tank filter.

Bloody LPG causes so much neglect

 

[Tony66_au]

BTW the issue is wont run on fuel under 2000 rpm, over that no probs but under that and its gone, cant even feather the throttle to get it back.

Car was run on LPG for years

 

[Oversize]

Is it possible Red Bull has a different relay and that's why the pump is running as soon as the ignition is on?

 

[SEL_69L]

Try to start the car in gear, or in reverse.
I won't start the engine of course, BUT the fuel delivery pump should get an electrical supply, and thus you should hear it, albeit faintly.