double relay buzzing

[Tempest455]

Hello,

My 80 FI spider developed an odd issue over the past couple days. At around 2500 RPMs the double relay makes a loud buzzing sound (not vibration). The unit also makes a single loud click when revving from idle. I replaced the unit with a used one I had lying around and it does the same thing. There are no adverse side affects that I have noticed, its just annoying. Any thoughts?

Thanks,
Brandon

[launieg]

I recall I had a buzzing noise on mine two summers ago. I think it was another relay right beside the double relay, or maybe the seat belt warning buzzer, but I do not recall exactly. Could it have been one that operates the wipers? Sorry I do not recall clearly (getting old, I guess)

In any case, I doubt it is the double relay, if you replaced it and have the same problem.

[htchevyii]

I think if the TPS is misadjusted it will cause a clicking. See page 9 of Brad Atrigue's guide:
http://www.mirafiori.com/faq/fiatFI_may2002.pdf
Some more sources of info:
http://bama.ua.edu/~darren/boschindex.html
http://www.hiperformancestore.com/Ljetronic.htm

[Tempest455]

ahhhh yes the old TPS! that makes sense. i will adjust/replace and see what happens.

Thanks!
Brandon

[Tempest455]

TPS was slightly out but issue remains. Replaced TPS with another one I had, issue remains.

Some additional research in Bradley Artigue's Fiat 124 Spider Engine Maintenance and Modification guide: He mentions a double relay chatter (clicking) condition when the rod connected to the AFM flap, which signals the double relay to power the fuel pump, gets out of adjustment. Funny thing is that i don’t have any adverse performance issues when the switch is making noise (the fuel pump keeps running) I am wondering if the double relay might still be receiving a signal from the AFM but the relay is bypassed somehow allowing the fuel pump to remain operational despite the AFM flap position....


More to come

[rlux4]

The dual relay will get 12V from the AFM whenever the flap is opened. This signals that air is going through and fuel is needed, so the fuel pump is energized. Does your fuel pump run when the key is in the "on" position, before it's in the "start" position? It shouldn't. Wired correctly, the dual relay needs (A) hot from the ignition switch, and (B) hot from the AFM when the flap opens.
Ron

[Tempest455]

The fuel pump wiring was recently restored so everything functions as it did from stock.

its been about 150 miles and she still runs strong despite the buzzing.

[rlux4]

Are you positive it's the dual relay? You've touched it when it's buzzing and it's the culprit? Launie has a valid point. The dual relay clicks when it makes contact on either side, which would be a chatter if it were making and releasing contact very quickly. It just seems like it could be one of the other relays on the plate that holds them, and the warning buzzer is a good candidate, because it does buzz.
Ron

[Tempest455]

Thanks for all the input folks. It was the double relay making the noise. I held it in my right hand and forced the condition by revving the motor with my left hand.

Now for the strange part:
I replaced the fuel injectors with a set of brand new ones i found on ebay for a price i couldn't pass up. Now, not only does the
car start much easier and run stronger, the clicking and buzzing in the relay stopped as well.

I am not going to look a gift horse in the mouth on this strange one.

[launieg]

I agree, accept it and be happy! But my bet is that the double relay was not making good contact on the portion that activates the positive line to the injectors. It is, after all, a small electromagnet that can be weak (or have a weak signal to it) and open and close rapidly (causing a buzz) and that in turn was sending a rapid fluctuating signal to the injectors. The relay is now working and the injectors are finally getting a consistent positive side. Just my guess, mind you...