Alarm buzzing upon start up

[ahsan127]

Hi,

I was wondering if it is normal for the alarm to sound when the key is inserted into the ignition to have the fuel pump come on? My alarm sounds but then immediately goes off when the motor turns on. Is that normal for a 2400 coupe?

Thanks

Syed

[GaryS]

Normal, no .. but it happens. Happened to me a few years ago. Sound was easily traced to fuel pump relay wired to oil pressure binary sensor switch. The purpose of this circuit is to prevent the fuel pump from operating in condition that the engine has stopped, but the ignition is still 'live' in the Run position (possible accident). There is the position in the ignition switch between starter motor and run position that engages the fuel pump through the circuit with relay. Disconnect the blue(?) wire at the relay and your fuel pump will now prime under the run position. I have not determined the cause, but have swapped another relay in place without altering the buzz. As a precaution, by accepting the risk associated with this minor modification, double down on all efforts to prevent barrel rolling the car onto its roof, But perchance this were to happen Please (1) return the key to Garage or full off position to reduce the risk of possible barbecue, and then (2) get yourself and others foolish enough to be your passegers removed safely and with all necessary haste.

[ahsan127]

Thanks! It sounds like its more of a safety mechanism, correct?
Just curious. Did you decide to wire yours back to stock form? If so, why?

Regards,

Syed

[GaryS]

A safety mechanism, precisely - yes. In cars fitted with mechanical diaphragm fuel pumps on the engine block when the engine stops so does the fuel flow. With the electric fuel pump you need a 'smart' solution to prevent unecessary mishap by maintaining a 'communication' with the powerplant. FIAT's of the 70's with electric fuel pumps hava a peculiar but (hopefully) effective solution. Were your car to flip over there is an inline switch that would operate on gravity (upside down) and 'break' the electrical connection to avoid the possibility of an unrestricted fuel flow streaming from carb or damaged fuel line/filter/etc.
Personally I prefer the fuel pump priming away with the key in the run position. Just be aware, however improbable that something may happen, that a previously automatic safety feature is now under your control. Were I to find the cause and eleminate the buzzing I would use the system as designed - maybe -.
Gary

[Tobi]

I still wonder what you mean with alarm. The buzzing sound may be the Dinoplex that you can hear as long as engine sound does not drown it out.

[ahsan127]

Thank you for your informative reply Gary. I think I'm inclined to leave it alone at this point.

Tobi, by buzzing I mean I hear a buzzing sound from within the cabin when I turn the key to the first position. Its not a subtle sound, literally sounds like a alarm buzzing. But the sound goes away as soon as the key is turned to the second position to start the car. Maybe I'll post a sound clip when I have a little time.